Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Response to Arguments
Applicant’s arguments with respect to claim(s) 1, 13 and 17 have been considered but are moot because the new ground of rejection does not rely on any reference applied in the prior rejection of record for any teaching or matter specifically challenged in the argument. Necessitated by amendments, the office now relies on new reference Guan (CN 114400499 A), that teach the newly added limitations of claim 1, 13 and 17 as explained below.
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claims 1-3, 6-7, 10-12, 21 and 29 are rejected under 35 U.S.C. 103 as being unpatentable over Deppe (US 20050063440 A1) in view of Guan (CN 114400499 A) and further in view of Koerner (US 20230006423 A1).
Re: Independent Claim 1 (Currently amended), Deppe discloses a method of forming a laser structure, the method comprising:
growing a bottom distributed Bragg reflector (DBR) (Deppe, Fig. 1A, ¶ [0039], lower DBR 110) and a first part of a cavity on a substrate to form a bottom structure comprising a plurality of layers (Deppe discloses a substrate layer 100 on which lower DBR mirror layers 110 are epitaxially grown, followed by an active region 120 (spacer and active layers 130) and layers 140 which is a first part of cavity grown on the bottom DBR);
Regarding the limitation “etching subwavelength anisotropic grating features on an upper layer of the bottom structure to produce a patterned growth interface, the anisotropic grating features being configured to induce a polarization-dependent effective refractive index in the cavity”, Deppe teaches, in ¶ [0039], that on the upper part of the cavity, a final layer is formed and patterned using lithography to form shallow mesa layer 150, and the subsequent epitaxial growth covers shallow mesa 150. Thus, Deppe teaches the base process of etching a pattern feature on an upper layer of the bottom structure to produce a patterned growth interface for epitaxial regrowth. Deppe is silent regarding the etched patterned feature being subwavelength anisotropic grating features and regarding the grating features being configured to induce a polarization-dependent effective refractive index in the cavity.
However, Guan teaches a VSCEL polarization-selection structure including a sub-wavelength grating. Guan teaches, in Fig. 2 description, that the sub-wavelength grating has a form birefringence effect, can be equivalent to a uniform uniaxial film layer, and can cause the grating layer to obtain an effective refractive index by adjusting the grating duty ratio. Guan further teaches that, by designing the grating period, duty ratio, and depth, only polarized light having a polarization direction parallel to the grating strips is transmitted, thereby realizing single-polarization output.
Deppe is further silent regarding “wherein the anisotropic grating features define a birefringence strength determined by a ratio of grating ridge width to grating period”. However, Guan teaches, in Fig. 2 description, that the sub-wavelength grating has a form birefringence effect and that the grating layer obtains an effective refractive index by adjusting the duty ratio of the grating. Thus, Guan teaches that the birefringence/effective refractive index behavior of the anisotropic grating features is determined by the ratio of grating ridge width to grating period.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify Deppe’s etched pattern growth interface, i.e., shallow mesa 150 formed on the upper layer of the partially grown VSEL/bottom structure, so that the etched patterned feature is implemented as subwavelength anisotropic grating features as taught by Gaun, in order to provide polarization control and single-polarization output in the VCSEL using form birefringence and a polarization-dependent effective refractive index. Deppe already teaches forming an etched patterned interface in the VCSEL cavity and overgrowing that interface, while Guan teaches that subwavelength grating geometry provides polarization-dependent optical behavior through form birefringence and effective refractive index control.
Regarding the limitation “overgrowing a remaining part of the cavity and a top DBR on the patterned growth interface to form an epitaxial structure”, Deppe teaches, in ¶ [0040], that "a subsequent epitaxial growth covers the shallow mesa 150 and forms two distinct but nearly identical cavity regions, a first cavity region 160 and a second cavity region 170 and that these cavity regions 160 and 170 are formed by covering the semiconductor layers 140 and 150 with additional semiconductor layers 180 to complete or partially complete the upper DBR". Deppe also states, in ¶ [0037], that "the shallow etched mesa is formed in the upper region of the lower semiconductor mirror, so that remaining layers of the lower mirror, active region, and upper mirror are formed in the second epitaxial regrowth over the mesa". Accordingly, the "remaining part of the cavity" is the portion of the resonant cavity above the first part (additional cavity/mirror layers included in layers 180), and the "top DBR" is the completed upper DBR formed by layers 140 and 180 grown during the second epitaxial step. Thus, Deppe teaches overgrowing a remaining part of the cavity and a top DBR on the patterned growth interface (mesa 150) to form an epitaxial structure including bottom DBR 110, cavity 120/160/170, and upper DBR 140/180.
Deppe is further silent regarding forming one or more apertures in the epitaxial structure.
However, Koerner teaches forming one or more apertures in the epitaxial structure (Deppe teaches a VCSEL structure formed by epitaxial growth on a substrate 100, including a bottom mirror 110, an active region 120, and upper mirror/cavity layers 140, 180, i.e., an epitaxial VCSEL stack. Deppe, however, is silent regarding any specific process step that actually forms an aperture in that stack. However, Koerner teaches, in Figs. 1-2 and ¶ [0010], a method of forming an optical aperture of a VCSEL. Koerner discloses providing a layer stack of semiconductor layers which includes, on a substrate 12, a first DBR 14, an active region 16, a second DBR 18, and an intermediate layer 50 comprising a semiconductor material suitable to be oxidized. Koerner then oxidizes the intermediate layer 50 to an oxidation width so as to form an oxidized outer region and a non-oxidized center region in the intermediate layer, thereby forming an optical aperture 24 in the VCSEL layer stack).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to apply Koerner’s known oxidation-aperture process to a suitable oxidation layer within Deppe's epitaxially grown VCSEL structure (layers 110/120/140/180) in order to reduce mechanical stress in the final VCSEL layer stack (Koerner, ¶ [0031]).
Accordingly, Deppe teaches the claimed VCSEL growth, etched patterned growth interface, and overgrowth process; Guan teaches modifying the etched patterned interface to subwavelength anisotropic grating features configured to induce a polarization-dependent effective refractive index and having birefringence/effective refractive index controlled by grating duty ration; and Koerner teaches forming one or more apertures in the epitaxial structure. Therefore, the combination teaches or renders obvious all the limitations of claim 1
Re: Claim 2 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Deppe further teaches wherein the first part of the cavity comprises a plurality of active region quantum wells (Deppe discloses, in ¶ [0039], active region 120 consisting of a spacer layer and active layers 130 made of either bulk, quantum well, quantum wire, or quantum dot semiconducting materials. Deppe further provides an explicit example, in ¶ [0061], in which multiple quantum wells are used in the cavity, stating that quantum wells are placed at the center of the undoped full-wave cavity spacer and separated by GaAs barriers. Thus, "the first part of cavity" in claim 1 corresponds to Deppe's initial grown cavity portion including active region 120 and its quantum well active layers 130, which comprise a plurality of active region quantum wells).
Re: Claim 3 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Deppe further teaches wherein the etching is one of dry etching and wet etching ((Deppe, ¶ [0061]) Deppe teaches that the mesa is formed by photolithography and wet etching).
Re: Claim 6 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Deppe further teaches wherein the overgrowing produces a layer having a different material refractive index than the etched layer of the bottom structure (Deppe teaches, in ¶¶ [0039] - [0040], DBR mirrors formed from alternating semiconductor layers with different refractive indices, e.g., AlxGa1-xAs/AlyGa1-yAs. In Deppe, the shallow mesa 150 is etched in the upper semiconductor layer of the first grown mirror/cavity stack (part of region 140, i.e., bottom structure), and a second epitaxial regrowth then deposits additional mirror layers 180 above that mesa to complete the upper DBR. Because the DBR is expressly made of alternating high-index/low-index semiconductor materials, at least one of the overgrown DBR layers 180 necessarily has a different refractive index than the etched mesa-forming layer in 140).
Re: Claim 7 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Deppe further teaches wherein the one or more features are transferred to a profile of the top DBR (Deppe teaches, in ¶ [0040], forming a shallow mesa 150 in the upper semiconductor layer of the first -grown mirror/cavity and then performing a subsequent epitaxial growth that covers the mesa 150 and surrounding regions with additional semiconductor layers 180 to complete or partially complete the upper DBR. Deppe further explains, in ¶ [0061], in the GaAs/AlAs implementation, that the subsequent epitaxial overgrowth of GaAs/AlAs DBR pairs preserves the shallow mesa step height after regrowth. A person of ordinary skill in the art would understand that preserving the mesa step height means the thickness difference created by the etched mesa is maintained through the regrown DBR stack, so that the top DBR has a step or thickness profile corresponding to the underlying mesa feature. This corresponds to "the one or more features are transferred to a profile of the top DBR).
Re: Claim 10 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Koerner further teaches wherein the forming one or more apertures comprises growing an oxidation layer above the patterned growth interface as part of a top growth of the epitaxial structure (As discussed for claim 1, Deppe teaches forming a patterned growth interface by etching a shallow mesa 150 in the upper semiconductor layer of the first-grown mirror/cavity stack (the bottom structure including layers 110/120/140), and then performing a subsequent epitaxial growth that covers the mesa 150 and the surrounding regions with additional semiconductor layers 180 to complete or partially complete the upper DBR. Accordingly, this subsequent epitaxial growth of the layers 180 constitutes a "top growth of the epitaxial structure" above the patterned growth interface (the mesa surface). Koerner teaches, in ¶ [0064], forming an optical aperture in a VCSEL by providing a layer stack of semiconductor layers in which the stack includes an intermediate layer comprising a semiconductor material suitable to be oxidized, and then oxidizing the intermediate layer to form an oxidized outer region and a non-oxidized central region in that intermediate layer. Koerner’s oxidizable intermediate layer is grown as part of the VCSEL semiconductor layer stack and is specifically used as the layer that is laterally oxidized to define the aperture).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to incorporate Koerner's oxidizable intermediate layer into the second epitaxial growth of Deppe (i.e., into the layers 180 that are grown above the mesa-patterned interface), so that an oxidation layer is grown above the patterned growth interface as part of the top growth of the VCSEL epitaxial structure. Doing so would simply place Koerner's known oxidizable aperture-forming layer in the regrown portion of Deppe's structure, allowing the aperture to be formed by laterally oxidizing that layer in the completed epitaxial stack, in order to achieve the benefits for current confinement (Koerner, ¶ [0072]).
Re: Claim 11 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Koerner further teaches wherein the forming one or more apertures comprises growing an oxidation layer below the patterned growth interface as part of the bottom structure of the epitaxial structure (As discussed for claim 1, Deppe teaches forming a bottom surface on substrate 100 (including lower DBR 110 and cavity/active region 120, with upper region 140) and then defining a patterned growth interface by etching a shallow mesa 150 in the upper semiconductor layer of that first grown stack. Layers below the mesa 150 are part of the "bottom structure", and layers grown in the second epitaxial step 180 are part of the top growth. Koerner teaches, in ¶ [0010], that an optical aperture in a VCSEL can be formed by providing, within the semiconductor layer stack between the mirrors, an intermediate layer of oxidizable semiconductor material and laterally oxidizing that layer so that an oxidized outer region surrounds an unoxidized central region, thereby defining an aperture in the VCSEL. Koerner's oxidizable intermediate layer is grown as part of the epitaxial stack and is not limited to any particular vertical position beyond being located where the aperture is desired).
In view of Koerner, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention, when implementing Deppe's structure, to grow such an oxidizable intermediate layer as one of the layers in the first grown stack 110/120/140, i.e., as part of the bottom structure below the mesa-patterned interface 150, and to laterally oxidize that layer to form the aperture in the completed epitaxial structure. Accordingly, this corresponds to forming one or more apertures comprises growing an oxidation layer below the patterned growth interface as part of the bottom structure of the epitaxial structure in order to achieve the benefits for current confinement (Koerner, ¶ [0072]).
Re: Claim 12 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Deppe further teaches wherein the method comprises introducing a patterned vertical-cavity surface-emitting laser (VCSEL) cavity with a tunnel junction lithographic aperture (Deppe teaches, in ¶¶ [0060] - [0061], the VCSEL cavity (between the bottom and top DBRs) includes a tunnel junction region, and a mode-confined cavity is formed by defining a shallow intracavity mesa using photolithography and etching. Deppe explicitly describes that "photolithography and wet etching are used to define a mesa by selectively etching the tunnel junction layers outside a shallow mesa, with the mesa diameter ranging from 6 to 10 micro meter", so that only a selected-junction region remains in the mesa area while the tunnel - junction layers outside the mesa are removed. Accordingly, the VCSEL cavity that remains in the mesa region, whose lateral extent is set by the lithographic pattern, is a "patterned VCSEL cavity", and the remaining tunnel-junction region inside the lithographically defined mesa is a "tunnel junction lithographic aperture" (a tunnel junction aperture defined by lithography/etch)).
Re: Claim 21 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Deppe further teaches wherein the bottom DBR has a lower reflectivity compared to the top DBR, thereby enabling a bottom emission configuration (Deppe teaches a VCSEL structure having bottom and top DBR mirrors formed from GaAs/AlAs (or similar) quarter-wave pairs, and explains that the DBR reflectivity is determined by the number of layer pairs and their refractive indices. In the specific example, Deppe uses a larger number of mirror pairs in the bottom DBR than in the top DBR, so that the bottom mirror has higher reflectivity and the top mirror has lower reflectivity, corresponding to a top emitting configuration. POSITA would recognize that this is asymmetric DBR design is a routine VCSEL design parameter, and that a bottom emitting configuration is obtained simply by choosing the opposite asymmetry, i.e., by providing fewer mirror pairs (lower reflectivity) in the bottom DBR and more mirror pairs (higher reflectivity) in the top DBR, while keeping the rest of the cavity structure unchanged. Thus, in view of Deppe's explicit teaching that DBR reflectivity is set by the number of DBR pairs and that mirror asymmetry is used to control emission, it would have been an obvious design choice for a skilled artesian to adjust the DBR pair counts so that the bottom DBR has lower reflectivity than the top DBR when a bottom-emission configuration is desired. Accordingly, this corresponds to "the bottom DBR has a has a lower reflectivity compared to the top DBR, thereby enabling a bottom emission configuration).
Re: Claim 29 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends.
Deppe further teaches wherein the remaining part of the cavity comprises a plurality of active region quantum wells (Deppe discloses, in ¶ [0039], between a lower DBR (e.g., 110) and an upper DBR, an active region 120 that consists of a spacer layer and active layer 130 made of quantum well semiconductor material. The active layers 130 are plural and are disposed in the cavity region between the DBRs, i.e., the remaining part of the cavity comprises a plurality of active region quantum wells).
Claims 4-5, 8-9 and 24 are rejected under 35 U.S.C. 103 as being unpatentable over Deppe (US 20050063440 A1) in view of Guan (CN 114400499 A) further in view of Koerner (US 20230006423 A1), and further in view of Amann (US 20100128749 A1).
Re: Claim 4 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends. Deppe, Guan and Koerner are silent regarding wherein the one or more features are subwavelength features defined via lithography.
However, Amann teaches wherein the one or more features are subwavelength features defined via lithography (Amann teaches, in ¶ [0017], integrating a periodic structure 80 within a VCSEL resonator "for example in the form of a subwavelength grating (SWG)", and explicitly states that the period of the periodic structure is at most one, preferably at most half an emission wavelength .lambda, or more generally at most λ/n, preferably at most λ/2n, n being a function of the index of refraction, and gives concrete feature sizes as web and pit widths of about 200nm, in ¶ [0021]. Amann further teaches, in ¶ [0037], that this periodic subwavelength structure is formed by defining a mask on semiconductor layer 70 using nanostructure lithography techniques and then transferring the pattern to the semiconductor by dry-chemical etching).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement the lithographically defined features of Deppe (e.g., mesa or cavity-patterning features) as subwavelength features, using standard lithography and etch techniques as taught by Amann in order to obtain known benefits such as better polarization stability (Amann, ¶ [0021]).
Re: Claim 5 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends. Both Deppe and Koerner are silent regarding wherein the one or more features are linear gratings.
However, Amann teaches wherein the one or more features are linear gratings (As discussed in claim 1, Deppe teaches forming features on the upper layer of the partially grown VCSEL structure by photolithography and etching to create shallow mesa 150. Deppe is silent regarding the patterned features are linear gratings. Amann teaches (Amann, Figs. 2 and 3C, ¶ [0037]) forming an optical grating inside a VCSEL resonator as a periodic structure 80. In Amann, structure 80 if formed by patterning a semiconductor layer with lithography and etching so that the surface consists of alternating raised "web" regions and recessed "pit" regions that repeat with a period P. In top view, this is a set of parallel web and pit stripes repeating in one direction. Such a pattern of parallel, periodically repeating lines is a linear grating).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement the lithographically defined features on Deppe's patterned interface (e.g., the mesa region used for mode control) as linear grating features, as taught by Amann, in order to obtain known benefits such as better polarization stability (Amann, ¶ [0021]).
Re: Claim 8 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends. Deppe, Guna and Koerner are silent regarding wherein the method comprises controlling a birefringence strength according to a selection of one or more features.
However, Amann teaches wherein the method comprises controlling a birefringence strength according to a selection of one or more features (As discussed for claim 1, Deppe in view of Koerner teaches the method of forming the VCSEL structure, including etching one or more features (e.g., mesa/grating type features) on the upper layer of the bottom structure and then overgrowing the remaining cavity and top DBR. These etched or patterned structures correspond to the claimed "one or more features". Amann describes, in ¶ [0010], a VCSEL in which a periodic structure 80 is arranged within the resonator as an optical grating made of semiconductive material and dielectric material, with a defined orientation, geometry and index-of-refraction profile. Amann teaches, in ¶ [0019], that this periodic structure has sufficiently high index of refraction contrast to define a preferred polarization direction by means of birefringence, and states that the invention presents a polarization-stable VCSEL. Amann further discloses, in ¶ [0017], that geometric parameters of the periodic structure are chosen and adjusted. Taken together, Amann therefore explicitly teaches using birefringence of the periodic semiconductor/dielectric structure to define a preferred polarization direction, and selecting structural features of that periodic structure - such as period, web/pit ratio, etch depth, and layer thickness).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement Deppe's lithographically defined features (e.g. mesa or grating features on the patterned growth interface) with dimensions and shapes selected as taught by Amann so as to obtain a desired level of cavity birefringence and polarization stability, with predictable results, as taught by Amann in ¶ [0017].
Re: Claim 9 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends. Deppe, Guan and Koerner are silent regarding wherein:
the one or more features comprise a grating that is characterized by a grating ridge width and a grating period, and
the method comprises controlling a birefringence strength according to a ratio of the grating ridge width and the grating period.
However, Amann teaches wherein:
the one or more features comprise a grating that is characterized by a grating ridge width and a grating period (As applied to claim 1, Depe in view of Koerner teaches forming a VCSEL Structure and etching one or more lithographically defined features (e.g., mesa/grating-type features) on the upper layer of the bottom structure before overgrowing the remaining cavity and top DBR. These etched patterns correspond to the "one or more features". Amann describes, in ¶ [0010], a periodic structure 80 arranged within the VCSEL resonator "as an optical grating made of semiconductor material and dielectric material" with a defined orientation and geometry. In the manufacturing description,¶ [0041], Amann explains that the grating is formed as a "diffraction grating-like periodic structure" having a period length P and a web/pit ration of 1:1, where web widths L2 correspond to pit width L1, and Fig 4 shows this is a set of parallel web ("ridge") and pit ("groove") stripes repeating with period P. Accordingly, the web (ridge) width L2 is a grating ridge width, and period P is a grating period, so structure 80 is a grating characterized by ridge width and period),and
the method comprises controlling a birefringence strength according to a ratio of the grating ridge width and the grating period (Amann further teaches, in [0019], that this periodic semiconductor/dielectric structure has a "sufficiently high index of refraction contrast to define a preferred polarization direction by means of birefringence", and that the device is a polarization-stable VCSEL. Amann explicitly discloses, in ¶¶ [0041] - [0042], that geometric parameters of the grating are chosen and varied, including the period P of the structure, the ratio of web width and pit width, and the etching depth H. Thus, Amann teaches (i) a grating whose ridge (web) width and period P are defined, and (ii) that geometric ratios are chosen in connection with achieving stable polarization behaviors, where the polarization selection is explicitly attributed to birefringence of the grating structure.
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement lithographically defined featured of Deppe (e.g., the intracavity patterned region on the growth interface) as the optical grating taught by Amann, and to select the width and grating period (and thus their ratio) as Amann described in order to obtain a desired birefringence-based polarization behavior (Amann, ¶ [0023]).
Re: Claim 24 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends. Deppe, Guan and Koerner are silent regarding wherein the one or more features are anisotropic features.
However, Amann teaches wherein the one or more features are anisotropic features (Amann discloses, in ¶ [0010], a periodic structure 80 arranged within the VCSEL resonator "as an optical grating made of semiconductor material and dielectric material", with a defined orientation and geometry. In the fabrication description (Figs. 3A-3D and ¶ [0041]) Amann explains that this structure is a diffraction grating-like periodic structure having a period length P and a web/pit ratio of 1:1, where the web widths L2 correspond to pit widths L1, and Fig 4 (plan view of the grating plane) shows parallel web ("ridge") and pit ("groove") stripes repeating with period P in one lateral direction. Thus, along the direction of the stripes the structure is essentially uniform, while in the perpendicular direction the surface periodically alternates between web and pit regions. Accordingly, such a grating - with a geometry that is different along one in-plane direction than along the orthogonal direction - is an anisotropic feature in the lateral plane).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement the lithographically defined features on Deppe's patterned growth interface as such directionally oriented grating features taught by Amann, so that the "one or more features" are anisotropic features (Amann, ¶ [0041]).
Claims 27-28 are rejected under 35 U.S.C. 103 as being unpatentable over Deppe (US 20050063440 A1) in view of Guan (CN 114400499 A) further in view of Koerner (US 20230006423 A1), and further in view of Graham (US 20180090909 A1).
Re: Claim 27 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends. Deppe, Guna and Koerner are silent regarding wherein the one or more apertures comprises implantation.
However, Graham teaches wherein the one or more apertures comprises implantation (Graham, in ¶ [0014], teaches a VCSEL in which the current/optical aperture is defined by an ion-implantation process (an "implant-regrown VCSEL"). In particular, Graham discloses forming a blocking region and one or more conductive channel cores from a conductive layer "by implanting a region of the conductive layer that becomes the blocking region and where one or more regions devoid of the implanting becomes the one or more conductive channel cores". Graham further teaches, in ¶ [0061], an aperture of a VCSEL (the conductive channel core/conductive aperture 129) that is defined by and formed using an implantation process, with the aperture region bounded by an implanted blocking layer 127. Thus, Graham teaches one or more apertures comprises implantation).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify the VCSEL aperture of Deppe as combined with Koerner so that the one or more apertures are formed using an implant-defined conductive channel core surrounded by by an implanted blocking region as taught by Graham. Graham's implant-defined aperture is simply a known alternative way to achieve lateral current and optical mode confinement in VCSELs, and substituting this known implant-based aperture structure for the oxide or other apertures of Deppe/Koerner would have been a routine design choice, made in order to obtain predictable current-confinement benefits using a familiar implantation process (Graham, ¶ [0083]).
Re: Claim 28 (Original), Deppe, Guan and Koerner disclose all the limitations of claim 1 on which this claim depends. Deppe, Guan and Koerner are silent regarding wherein the one or more apertures comprises implantation.
However, Graham teaches wherein the one or more apertures comprise a blocking layer lithographic aperture (Graham teaches, in ¶ [0013], VCSEL that includes "a blocking region over or under an active region, the blocking region having a first thickness; one or more conductive channel cores in the blocking region, the one or more conductive channel cores having a second thickness that is larger than the first thickness, wherein the blocking region is defined by having an implant and the one or more conductive channel cores are devoid of the implant, wherein the blocking region is lateral the one or more conductive channel cores, the blocking region and one or more conductive channel cores being an isolation region". Graham further teaches that "the method can include forming the blocking region and one or more conductive channel cores from a conductive layer by implanting a region of the conductive layer that becomes the blocking region and where one or more regions devoid of the implanting becomes the one or more conductive channel cores" and that "the method can include: coating one or more regions of the top of the conductive layer with a photoresist that inhibits implantation and etching where the one or more regions with the photoresist define the one or more conductive channel cores and the region without the photoresist defines the blocking region; and implanting the region without the photoresist to form the blocking region". Thus, Graham expressly teaches (i) a blocking region that is defined by having an implant and is lateral to one or more conductive channel cores that are devoid of the implant; and together form an isolation region, and (ii) that the conductive channel cores and blocking region are defined by patterning a photoresist on the conductive layer, where regions with photoresist define the conductive channel cores and the uncoated region defines the blocking region, followed by implantation of the uncoated region. Accordingly, the conductive channel cores correspond to apertures for current and optical flow in the VCSEL, the implanted blocking region corresponds to a blocking layer, and the use of a patterned photoresist to define the conductive channel cores and blocking region corresponds to formation of a lithographic aperture. Thus, Graham teaches "one or more aperture" that "comprise a blocking layer" and that are defined by a lithographic (photoresist) pattern, matching the additional limitation of claim 28).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement, in the VCSEL method of Deppe in view of Koerner, the aperture structure of Graham - namely, a lithographically defined conductive channel core surrounded by an implanted blocking region-as a known alternative aperture and current-confinement scheme in order to obtain predictable current confinement using a blocking layer defined by standard lithographic patterning and implantation (Graham, ¶ [0052]).
Claims 13, 17 and 22-23 are rejected under 35 U.S.C. 103 as being unpatentable over Deppe (US 20050063440 A1) in view of Bour (US 20040076209 A1) and further in view of Guan (CN 114400499 A).
Re: Independent Claim 13 (Currently amended), Deppe discloses a method of forming a laser structure, the method comprising:
growing a bottom distributed Bragg reflector (DBR) and a first part of a cavity on a substrate to form a bottom structure comprising a plurality of layers (Deppe teaches (Fig. 1A, ¶ [0039]) a substrate 100 on which a lower DBR mirror 110 is epitaxially grown, followed by an active region 120 consisting of a spacer layer and active layers 130, and first upper mirror/cavity 140, together forming a bottom structure of multiple layers on the substrate);
generating a lithographic aperture on the bottom structure (Deppe teaches forming a shallow intracavity mesa 150 by forming a final layer of thickness delta.t on the partially grown cavity (110/120/140) and patterning it using lithography and etching; Deppe describes this mesa as a mode-confining region defined using a lithography process, which corresponds to a lithographic aperture on the bottom surface);
overgrowing a top DBR on the patterned growth interface to form an epitaxial structure (Deppe teaches that a subsequent epitaxial growth covers the shallow mesa 150 and the surrounding regions, forming cavity regions 160 and 170 and additional layers 180 that complete or partially complete the upper DBR, and in Fig. 9A/9B teaches subsequent epitaxial growth of layers 740 over the etched mesa and surrounding surface layer 700, which corresponds to overgrowing a top DBR on the patterned growth interface to form the final epitaxial VCSEL structure).
Deppe is silent regarding:
overgrowing a spacer layer on the lithographic aperture; etching one or more features in the spacer layer to form a patterned growth interface.
However, Bour teaches
overgrowing a spacer layer on the lithographic aperture (Deppe further teaches, in ¶ [0040], returning the partially grown structure with the etched mesa to the growth chamber and performing a subsequent epitaxial growth step that covers the mesa: "a subsequent epitaxial growth covers the shallow mesa 150 and forms two distinct but nearly identical cavity regions, a first cavity region 160 and a second cavity region 170. The two cavity regions 160 and 170 are formed by covering the semiconductor layers 140 and 150 with additional semiconductor layers 180 to complete or partially complete the upper DBR". Bour teaches, in ¶ [0038], that it is conventional in VCSEL design to provide explicit "cavity spacer" layers between the DBRs and the active regions, such as lower cavity spacer layer 122 and upper cavity spacer layer 140 of InP, and that "The lower cavity spacer layer 122, the active region spacer layers 124, 128, 134 and 138, the active regions 126, 132 and 136, and the upper cavity spacer layer 142 form an asymmetric optical cavity 152". Accordingly, these "cavity spacer layers" are "spacer layers" within the laser cavity);
etching one or more features in the spacer layer to form a patterned growth interface (Bour further discloses, in ¶ [0043], forming current/optical confinement regions by incorporating a specific material (e.g., AlInAs) within the active region spacer layers and then selectively etching that material laterally. In particular, Bour describes confinement structures 164, 168, 174 formed in active region spacer layers 128, 134,138 by "forming a layer of, for example, aluminum indium arsenide (AlInAs) in the active region spacer layers 128, 134 and 138 during fabrication" where "a layer of AlInAs is formed partway through the formation of the active region spacer layer 128" and "The active region spacer layer 128 is then completed; he AlInAs is then selectively etched in a lateral direction so that the confinement region 162 is formed and the etching removes a portion of the AlInAs material, resulting in the confinement region 162". Accordingly, laterally etching portions of the AlInAs inside spacer layer 128 to form confinement region 162 is "etching one or features in the spacer layer". In view of Deppe's teaching of performing a subsequent epitaxial growth over a previously patterned intracavity surface (mesa 150), the etched confinement structures of Bour would present a "patterned" interface upon which later growth can occur. Thus, the combination of Deppe (regrowth over a patterned intracavity surface) and Bour (etching features within a cavity spacer layer) teaches and suggests "etching one or more features in the spacer layer to form a patterned growth interface".
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify Deppe's epitaxial VCSEL process - which already uses a lithographically defined intracavity mesa 150 and a subsequent epitaxial regrowth to complete the top DBR- to incorporate the well-known cavity spacer and confinement structures taught by Bour in the region above the lithographically defined aperture and providing dedicated cavity spacer layers (122, 142) and confinement regions (e.g., 162) formed by selectively etching within spacer layers in order to improve control of cavity length, optical confinement, and device performance (Bour, ¶ [0043]).
Deppe is further silent regarding wherein the one or more features comprise subwavelength anisotropic grating features configured to induce structural birefringence in the cavity; and wherein a birefringence strength is controlled by a ratio of grating ridge width to grating period.
However, Guan teaches wherein the one or more features comprise subwavelength anisotropic grating features configured to induce structural birefringence in the cavity (Guan teaches a VCSEL polarization selection structure including a sub-wavelength grating. Guan teaches, in Fig. 2 description, that the sub-wavelength grating has a form birefringence effect, which can be equivalent to a uniform single-axis positive crystal film layer, and obtains effective refractive index by adjusting the grating duty ratio. Guan further teaches that, by designing the grating period, duty ratio and depth, making only the polarization direction parallel to the polarization light of the grating bar, so as to realize the single polarization output. Guan also teaches, in step S40, etching the sub-wavelength grating using EBL/photoetching and RIE.
Guan further teaches wherein a birefringence strength is controlled by a ratio of grating ridge width to grating period (Guan teaches that subwavelength grating has a form birefringence effect and that the effective refractive index of the grating layer is adjusted by the duty ratio of the grating. Guan further teaches designing the grating period, duty ratio, and depth to obtain polarization-selective transmission and single-polarization output. Therefore, Guan teaches that the birefringence strength is controlled by a ratio of grating ridge width to grating period (duty ratio)).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify the spacer-layer etching of Bour, as incorporated into Deppe’s regrowth process, so that the etched features in the spacer layer are subwavelength anisotropic grating features as taught by Guan, in order to induce structural/form birefringence in the VCSEL cavity and thereby provide polarization control/single-polarization output.
Re: Claim 22 (Original), Deppe, Bour and Guan disclose all the limitations of claim 13 on which this claim depends.
Deppe further teaches wherein the bottom DBR has a lower reflectivity compared to the top DBR, thereby enabling a bottom emission configuration (Deppe teaches a VCSEL structure having bottom and top DBR mirrors formed from GaAs/AlAs (or similar) quarter-wave pairs, and explains that the DBR reflectivity is determined by the number of layer pairs and their refractive indices. In the specific example, Deppe uses a larger number of mirror pairs in the bottom DBR than in the top DBR, so that the bottom mirror has higher reflectivity and the top mirror has lower reflectivity, corresponding to a top emitting configuration. POSITA would recognize that this is asymmetric DBR design is a routine VCSEL design parameter, and that a bottom emitting configuration is obtained simply by choosing the opposite asymmetry, i.e., by providing fewer mirror pairs (lower reflectivity) in the bottom DBR and more mirror pairs (higher reflectivity) in the top DBR, while keeping the rest of the cavity structure unchanged. Thus, in view of Deppe's explicit teaching that DBR reflectivity is set by the number of DBR pairs and that mirror asymmetry is used to control emission, it would have been an obvious design choice for a skilled artesian to adjust the DBR pair counts so that the bottom DBR has lower reflectivity than the top DBR when a bottom-emission configuration is desired. Accordingly, this corresponds to "the bottom DBR has a has a lower reflectivity compared to the top DBR, thereby enabling a bottom emission configuration).
Re: Independent Claim 17 (Currently amended), Deppe discloses a method of forming a laser structure, the method comprising:
growing a bottom distributed Bragg reflector (DBR) and a first part of a cavity on a substrate to form a bottom structure comprising a plurality of layers (Deppe teaches (Fig. 1A, ¶ [0039]) a substrate 100 on which a lower DBR mirror 110 is epitaxially grown, followed by an active region 120 consisting of a spacer layer and active layers 130, and first upper mirror/cavity 140, together forming a bottom structure of multiple layers on the substrate);
generating a lithographic aperture on the bottom structure (Deppe teaches, in ¶ [0039], forming a shallow intracavity mesa 150 by forming a final layer of thickness delta.t on the partially grown cavity (110/120/140) and patterning it using lithography and etching; Deppe describes this mesa as a mode-confining region defined using a lithography process, which corresponds to a lithographic aperture on the bottom surface);
overgrowing a top DBR on the patterned growth interface to form an epitaxial structure (Deppe teaches that a subsequent epitaxial growth covers the shallow mesa 150 and the surrounding regions, forming cavity regions 160 and 170 and additional layers 180 that complete or partially complete the upper DBR, and in Fig. 9A/9B teaches subsequent epitaxial growth of layers 740 over the etched mesa and surrounding surface layer 700, which corresponds to overgrowing a top DBR on the patterned growth interface to form the final epitaxial VCSEL structure).
Deppe is silent regarding:
growing a spacer layer on the lithographic aperture; defining the lithographic aperture via etching through the spacer layer; etching one or more features in the spacer layer to form a patterned growth interface.
However, Bour teaches:
growing a spacer layer on the lithographic aperture (Deppe further teaches returning the patterning structure with mesa 150 (or mesa 720/730 in the lower-mirror embodiment) to the growth chamber and performing a subsequent epitaxial growth of layer 180/740 that covers the mesa and surrounding regions. Bour teaches that VCSEL cavities conventionally include explicit spacer layers (e.g., active region spacer layers 124, 128, 134, 138 and upper cavity spacer 142) between the DBRs and active regions. Accordingly, a person of ordinary skill in the art would understand that in view of Bour, a dedicated cavity spacer portion of the regrowth stack 180/740 would be grown on the lithographically defined mesa/ aperture in Deppe, corresponding to growing a spacer layer on the lithographic aperture);
defining the lithographic aperture via etching through the spacer layer (Bour teaches forming a lateral confinement region 162 inside active region spacer layer 128 by incorporating and AlInAs layer partway through formation of the spacer, completing the spacer layer, and then selectively etching the AlInAs laterally so that a confined region 162 is formed within the spacer; the etching removes portion of internal AlInAs within the spacer layer to define the confinement region that limits currents and optical-mode, which corresponds to defining the lithographic aperture via etching through the spacer layer);
etching one or more features in the spacer layer to form a patterned growth interface (Bour further discloses, in ¶ [0043], forming current/optical confinement regions by incorporating a specific material (e.g., AlInAs) within the active region spacer layers and then selectively etching that material laterally. In particular, Bour describes confinement structures 164, 168, 174 formed in active region spacer layers 128, 134,138 by "forming a layer of, for example, aluminum indium arsenide (AlInAs) in the active region spacer layers 128, 134 and 138 during fabrication" where "a layer of AlInAs is formed partway through the formation of the active region spacer layer 128" and "The active region spacer layer 128 is then completed; the AlInAs is then selectively etched in a lateral direction so that the confinement region 162 is formed and the etching removes a portion of the AlInAs material, resulting in the confinement region 162". Accordingly, laterally etching portions of the AlInAs inside spacer layer 128 to form confinement region 162 is "etching one or features in the spacer layer". In view of Deppe's teaching of performing a subsequent epitaxial growth over a previously patterned intracavity surface (mesa 150), the etched confinement structures of Bour would present a "patterned" interface upon which later growth can occur. Thus, the combination of Deppe (regrowth over a patterned intracavity surface) and Bour (etching features within a cavity spacer layer) teaches and suggests "etching one or more features in the spacer layer to form a patterned growth interface").
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify Deppe's epitaxial VCSEL process- which already uses a lithographically defined intracavity mesa 150 and a subsequent epitaxial regrowth to complete the top DBR- to incorporate the well-known cavity spacer and confinement structures taught by Bour in the region above the lithographically defined aperture and providing dedicated cavity spacer layers (122, 142) and confinement regions (e.g., 162) formed by selectively etching within spacer layers in order to improve control of cavity length, optical confinement, and device performance (Bour, ¶ [0043]).
Deppe is further silent regarding wherein the one or more features comprise subwavelength anisotropic grating features configured to induce a polarization-dependent refractive index within the cavity; and wherein the anisotropic grating features introduce a difference between refractive index parallel and perpendicular to the grating.
However, Guan teaches
wherein the one or more features comprise subwavelength anisotropic grating features configured to induce a polarization-dependent refractive index within the cavity (Guan teaches a VCSEL structure including polarization selection structure 3 having sub-wavelength grating. Guan teaches that the sub-wavelength grating is etched, has a form birefringence effect, which can be equivalent to a uniform single-axis positive crystal film layer, and enables the grating layer to obtain effective refractive index by adjusting the duty ratio of the grating. Guan further teaches that by designing the grating period, duty ratio, and depth, only polarized light having a polarization direct parallel to the grating strips is transmitted, thereby realizing single- polarization output. Thus, Guan teaches that subwavelength grating features induce polarization-dependent effective refractive-index behavior);
and wherein the anisotropic grating features introduce a difference between refractive index parallel and perpendicular to the grating (Guan teaches that polarization selection structure 3 may be a sub-wavelength grating etched on the upper surface of glass substrate 201, and that the sub-wavelength grating has a form birefringence effect, which can be equivalent to a uniform single-axis positive crystal film layer. Guan further teaches that the grating layer obtains an effective refractive index by adjusting the duty ratio of the grating, and that by designing the grating period, duty ratio, and depth, only polarized light having a polarization direction parallel to the grating strips is transmitted. Guan also teaches that TE and TM linear polarization modes having polarization direction parallel or vertical to the polarization selection structure realize polarization regulation. Therefore, Guan teaches or at least suggests that the subwavelength grating introduces different effective refractive index for orthogonal polarization direction, including directions parallel and perpendicular/vertical to the grating strips).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify the etched spacer-layer feature of Bour, as incorporated into Deppe’s regrowth process, so that the etched features in the spacer layer are subwavelength anisotropic grating features as taught by Guan, in order to provide polarization control and single-polarization output in the VCSEL by using the form birefringence of a subwavelength grating. Deppe already teaches regrowth over a patterned intracavity interface. Bour teaches forming/etching features in VCSEL spacer layers for optical/current confinement, and Guan teaches that subwavelength grating features provide polarization-selective behavior through form birefringence, effective refractive-index control, and different behavior for TE/TM polarization modes parallel or vertical to the polarization selection structure.
Re: Claim 23 (Original), Deppe, Bour and Guan disclose all the limitations of claim 17 on which this claim depends.
Deppe further teaches wherein the bottom DBR has a lower reflectivity compared to the top DBR, thereby enabling a bottom emission configuration (Deppe teaches a VCSEL structure having bottom and top DBR mirrors formed from GaAs/AlAs (or similar) quarter-wave pairs, and explains that the DBR reflectivity is determined by the number of layer pairs and their refractive indices. In the specific example, Deppe uses a larger number of mirror pairs in the bottom DBR than in the top DBR, so that the bottom mirror has higher reflectivity and the top mirror has lower reflectivity, corresponding to a top emitting configuration. POSITA would recognize that this is asymmetric DBR design is a routine VCSEL design parameter, and that a bottom emitting configuration is obtained simply by choosing the opposite asymmetry, i.e., by providing fewer mirror pairs (lower reflectivity) in the bottom DBR and more mirror pairs (higher reflectivity) in the top DBR, while keeping the rest of the cavity structure unchanged. Thus, in view of Deppe's explicit teaching that DBR reflectivity is set by the number of DBR pairs and that mirror asymmetry is used to control emission, it would have been an obvious design choice for a skilled artesian to adjust the DBR pair counts so that the bottom DBR has lower reflectivity than the top DBR when a bottom-emission configuration is desired. Accordingly, this corresponds to "the bottom DBR has a has a lower reflectivity compared to the top DBR, thereby enabling a bottom emission configuration).
Claims 14 and 20 are rejected under 35 U.S.C. 103 as being unpatentable over Deppe (US 20050063440 A1) in view of Bour (US 20040076209 A1) further in view of Guan (CN 114400499 A), and further in view of Wong (US 20180241177 A1).
Re: Claim 14 (Original), Deppe, Bour and Guan disclose all the limitations of claim 13 on which this claim depends.
Deppe, Bour and Guna are silent regarding wherein the lithographic aperture is a tunnel junction.
However, Wong teaches wherein the lithographic aperture is a tunnel junction (As set forth in the rejection of claim 13, Deppe teaches the method steps of claim 13, including forming a VCSEL structure with a lithographically defined intracavity mesa 150 on a partially grown cavity and overgrowing the top DBR on this mesa, which corresponds to the claimed "lithographic aperture". Deppe also discloses embodiments in which an n+/p+ tunnel junction is provided within the mesa so that electrical current is confined to the mesa region, but does not expressly state that the lithographic aperture itself is implemented as a tunnel junction aperture. Wong, however, explicitly teaches VCSELs in which a buried tunnel junction forms the aperture. Wong describes, in Fig 1 and ¶¶ [0022] and [0026], a VCSEL with a buried tunnel junction aperture in which a tunnel junction 19 is formed within the mirror stack and used as a current and mode confining aperture, and explains that buried tunnel-junction VCSELs offer advantages because the aperture dimensions are defined precisely by lithography, providing highly uniform lithographically defined apertures. Thus, Wong teaches a tunnel-junction lithographic aperture).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement the lithographic aperture of Deppe's mesa defined VCSEL in view of Bour and Guna using the tunnel junction aperture structure of Wong - i.e., to configure the lithographically defined aperture region so that it is realized as a buried tunnel junction- because both Deppe and Wong address current and mode confinement in VCSELs using intracavity tunnel junctions, in order to achieve the benefits of lithographically defined tunnel junction apertures like improved uniformity and reliability over oxide apertures as taught by Wong in ¶ [0022].
Re: Claim 20 (Original), Deppe, Bour and Guan disclose all the limitations of claim 17 on which this claim depends.
Deppe, Bour and Guna are silent regarding wherein the lithographic aperture is a tunnel junction.
However, Wong teaches wherein the lithographic aperture is a tunnel junction (As set forth in the rejection of claim 17, Deppe teaches the method steps of claim 17, including forming a VCSEL structure with a lithographically defined intracavity mesa 150 on a partially grown cavity and overgrowing the top DBR on this mesa, which corresponds to the claimed "lithographic aperture". Deppe also discloses embodiments in which an n+/p+ tunnel junction is provided within the mesa so that electrical current is confined to the mesa region, but does not expressly state that the lithographic aperture itself is implemented as a tunnel junction aperture. Wong, however, explicitly teaches VCSELs in which a buried tunnel junction forms the aperture. Wong describes, in Fig 1 and ¶¶ [0022] and [0026], a VCSEL with a buried tunnel junction aperture in which a tunnel junction 19 is formed within the mirror stack and used as a current and mode confining aperture, and explains that buried tunnel-junction VCSELs offer advantages because the aperture dimensions are defined precisely by lithography, providing highly uniform lithographically defined apertures. Thus, Wong teaches a tunnel-junction lithographic aperture).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement the lithographic aperture of Deppe's mesa defined VCSEL in view of Bour and Guna using the tunnel junction aperture structure of Wong - i.e., to configure the lithographically defined aperture region so that it is realized as a buried tunnel junction- because both Deppe and Wong address current and mode confinement in VCSELs using intracavity tunnel junctions, in order to achieve the benefits of lithographically defined tunnel junction apertures like improved uniformity and reliability over oxide apertures as taught by Wong in ¶ [0022].
Claims 15-16, 18-19 and 25-26 are rejected under 35 U.S.C. 103 as being unpatentable over Deppe (US 20050063440 A1) in view of Bour (US 20040076209 A1) further in view of Guan (CN 114400499 A) and further in view of Amann (US 20100128749 A1).
Re: Claim 15 (Original), Deppe, Bour and Guan disclose all the limitations of claim 13 on which this claim depends.
Deppe, Bour and Guna are silent regarding wherein the lithographic aperture is a tunnel junction.
However, Amann teaches wherein the method comprises controlling a birefringence strength according to a selection of one or more features (As discussed for claim 13, Deppe teaches the method of forming the VCSEL structure, including etching one or more features (e.g., mesa/grating type features) on the upper layer of the bottom structure and then overgrowing the remaining cavity and top DBR. These etched or patterned structures correspond to the claimed "one or more features". Amann describes, in ¶ [0010], a VCSEL in which a periodic structure 80 is arranged within the resonator as an optical grating made of semiconductive material and dielectric material, with a defined orientation, geometry and index-of-refraction profile. Amann teaches, in ¶ [0019], that this periodic structure has sufficiently high index of refraction contrast to define a preferred polarization direction by means of birefringence, and states that the invention presents a polarization-stable VCSEL. Amann further discloses, in ¶ [0017], that geometric parameters of the periodic structure are chosen and adjusted. Taken together, Amann therefore explicitly teaches using birefringence of the periodic semiconductor/dielectric structure to define a preferred polarization direction, and selecting structural features of that periodic structure - such as period, web/pit ratio, etch depth, and layer thickness).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement Deppe's lithographically defined features (e.g. mesa or grating features on the patterned growth interface) in view of Bour and Guan with dimensions and shapes selected as taught by Amann so as to obtain a desired level of cavity birefringence and polarization stability, with predictable results, as taught by Amann in ¶ [0017].
Re: Claim 16 (Original), Deppe, Bour and Guan disclose all the limitations of claim 13 on which this claim depends.
Deppe, Bour and Guan are silent regarding wherein: the one or more features comprise a grating that is characterized by a grating ridge width and a grating period, and the method comprises controlling a birefringence strength according to a ratio of the grating ridge width and the grating period.
However, Amann teaches wherein: the one or more features comprise a grating that is characterized by a grating ridge width and a grating period (As applied to claim 13, Deppe teaches forming a VCSEL Structure and etching one or more lithographically defined features (e.g., mesa/grating-type features) on the upper layer of the bottom structure before overgrowing the remaining cavity and top DBR. These etched patterns correspond to the "one or more features". Amann describes, in ¶ [0010], a periodic structure 80 arranged within the VCSEL resonator "as an optical grating made of semiconductor material and dielectric material" with a defined orientation and geometry. In the manufacturing description,¶ [0041], Amann explains that the grating is formed as a "diffraction grating-like periodic structure" having a period length P and a web/pit ration of 1:1, where web widths L2 correspond to pit width L1, and Fig 4 shows this is a set of parallel web ("ridge") and pit ("groove") stripes repeating with period P. Accordingly, the web (ridge) width L2 is a grating ridge width, and period P is a grating period, so structure 80 is a grating characterized by ridge width and period);
and the method comprises controlling a birefringence strength according to a ratio of the grating ridge width and the grating period (Amann further teaches, in [0019], that this periodic semiconductor/dielectric structure has a "sufficiently high index of refraction contrast to define a preferred polarization direction by means of birefringence", and that the device is a polarization-stable VCSEL. Amann explicitly discloses, in ¶¶ [0041] - [0042], that geometric parameters of the grating are chosen and varied, including the period P of the structure, the ratio of web width and pit width, and the etching depth H. Thus, Amann teaches (i) a grating whose ridge (web) width and period P are defined, and (ii) that geometric ratios are chosen in connection with achieving stable polarization behaviors, where the polarization selection is explicitly attributed to birefringence of the grating structure).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement lithographically defined featured of Deppe (e.g., the intracavity patterned region on the growth interface) in view of Bour and Guna as the optical grating taught by Amann, and to select the width and grating period (and thus their ratio) as Amann described in order to obtain a desired birefringence-based polarization behavior (Amann, ¶ [0023]).
Re: Claim 18 (Original), Deppe, Bour and Guan disclose all the limitations of claim 17 on which this claim depends.
Deppe, Bour and Guan are silent regarding wherein the lithographic aperture is a tunnel junction.
However, Amann teaches wherein the method comprises controlling a birefringence strength according to a selection of one or more features (As discussed for claim 17, Deppe teaches the method of forming the VCSEL structure, including etching one or more features (e.g., mesa/grating type features) on the upper layer of the bottom structure and then overgrowing the remaining cavity and top DBR. These etched or patterned structures correspond to the claimed "one or more features". Amann describes, in ¶ [0010], a VCSEL in which a periodic structure 80 is arranged within the resonator as an optical grating made of semiconductive material and dielectric material, with a defined orientation, geometry and index-of-refraction profile. Amann teaches, in ¶ [0019], that this periodic structure has sufficiently high index of refraction contrast to define a preferred polarization direction by means of birefringence, and states that the invention presents a polarization-stable VCSEL. Amann further discloses, in ¶ [0017], that geometric parameters of the periodic structure are chosen and adjusted. Taken together, Amann therefore explicitly teaches using birefringence of the periodic semiconductor/dielectric structure to define a preferred polarization direction, and selecting structural features of that periodic structure - such as period, web/pit ratio, etch depth, and layer thickness).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement Deppe's lithographically defined features (e.g. mesa or grating features on the patterned growth interface) in view of Bour and Guna with dimensions and shapes selected as taught by Amann so as to obtain a desired level of cavity birefringence and polarization stability, with predictable results, as taught by Amann in ¶ [0017].
Re: Claim 19 (Original), Deppe, Bour and Guan disclose all the limitations of claim 17 on which this claim depends.
Deppe, Bour and Guna are silent regarding wherein: the one or more features comprise a grating that is characterized by a grating ridge width and a grating period, and the method comprises controlling a birefringence strength according to a ratio of the grating ridge width and the grating period.
However, Amann teaches wherein: the one or more features comprise a grating that is characterized by a grating ridge width and a grating period (As applied to claim 17, Deppe teaches forming a VCSEL Structure and etching one or more lithographically defined features (e.g., mesa/grating-type features) on the upper layer of the bottom structure before overgrowing the remaining cavity and top DBR. These etched patterns correspond to the "one or more features". Amann describes, in ¶ [0010], a periodic structure 80 arranged within the VCSEL resonator "as an optical grating made of semiconductor material and dielectric material" with a defined orientation and geometry. In the manufacturing description,¶ [0041], Amann explains that the grating is formed as a "diffraction grating-like periodic structure" having a period length P and a web/pit ration of 1:1, where web widths L2 correspond to pit width L1, and Fig 4 shows this is a set of parallel web ("ridge") and pit ("groove") stripes repeating with period P. Accordingly, the web (ridge) width L2 is a grating ridge width, and period P is a grating period, so structure 80 is a grating characterized by ridge width and period);
and the method comprises controlling a birefringence strength according to a ratio of the grating ridge width and the grating period (Amann further teaches, in [0019], that this periodic semiconductor/dielectric structure has a "sufficiently high index of refraction contrast to define a preferred polarization direction by means of birefringence", and that the device is a polarization-stable VCSEL. Amann explicitly discloses, in ¶¶ [0041] - [0042], that geometric parameters of the grating are chosen and varied, including the period P of the structure, the ratio of web width and pit width, and the etching depth H. Thus, Amann teaches (i) a grating whose ridge (web) width and period P are defined, and (ii) that geometric ratios are chosen in connection with achieving stable polarization behaviors, where the polarization selection is explicitly attributed to birefringence of the grating structure).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement lithographically defined featured of Deppe (e.g., the intracavity patterned region on the growth interface) in view of Bour and Guna as the optical grating taught by Amann, and to select the width and grating period (and thus their ratio) as Amann described in order to obtain a desired birefringence-based polarization behavior (Amann, ¶ [0023]).
Re: Claim 25 (Original), Deppe and Bour disclose all the limitations of claim 13 on which this claim depends.
Deppe, Bour and Guna are silent regarding wherein the wherein the one or more features are anisotropic features.
However, Amann teaches wherein the one or more features are anisotropic features (Amann discloses, in ¶ [0010], a periodic structure 80 arranged within the VCSEL resonator "as an optical grating made of semiconductor material and dielectric material", with a defined orientation and geometry. In the fabrication description (Figs. 3A-3D and ¶ [0041]) Amann explains that this structure is a diffraction grating-like periodic structure having a period length P and a web/pit ratio of 1:1, where the web widths L2 correspond to pit widths L1, and Fig 4 (plan view of the grating plane) shows parallel web ("ridge") and pit ("groove") stripes repeating with period P in one lateral direction. Thus, along the direction of the stripes the structure is essentially uniform, while in the perpendicular direction the surface periodically alternates between web and pit regions. Accordingly, such a grating - with a geometry that is different along one in-plane direction than along the orthogonal direction - is an anisotropic feature in the lateral plane).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement the lithographically defined features on Deppe's patterned growth interface in view of Bour and Guna as such directionally oriented grating features taught by Amann, so that the "one or more features" are anisotropic features (Amann, ¶ [0041]).
Re: Claim 26 (Original), Deppe and Bour disclose all the limitations of claim 17 on which this claim depends.
Deppe, Bour and Guna are silent regarding wherein the one or more features are anisotropic features.
However, Amann teaches wherein the one or more features are anisotropic features (Amann discloses, in ¶ [0010], a periodic structure 80 arranged within the VCSEL resonator "as an optical grating made of semiconductor material and dielectric material", with a defined orientation and geometry. In the fabrication description (Figs. 3A-3D and ¶ [0041]) Amann explains that this structure is a diffraction grating-like periodic structure having a period length P and a web/pit ratio of 1:1, where the web widths L2 correspond to pit widths L1, and Fig 4 (plan view of the grating plane) shows parallel web ("ridge") and pit ("groove") stripes repeating with period P in one lateral direction. Thus, along the direction of the stripes the structure is essentially uniform, while in the perpendicular direction the surface periodically alternates between web and pit regions. Accordingly, such a grating - with a geometry that is different along one in-plane direction than along the orthogonal direction - is an anisotropic feature in the lateral plane).
It would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to implement the lithographically defined features on Deppe's patterned growth interface in view of Bour and Guna as such directionally oriented grating features taught by Amann, so that the "one or more features" are anisotropic features (Amann, ¶ [0041]).
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/BIPANA ADHIKARI DAWADI/Examiner, Art Unit 2898
/JESSICA S MANNO/SPE, Art Unit 2898
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