DETAILED ACTION
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 Amendment
Examiner acknowledges the amendments to the specification, abstract, and claims 1-8 submitted on March 15th, 2015.
Claim Rejections - 35 USC § 112
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION.—The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claim 8 is rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
Regarding claim 8:
The claim recites the phrase, “are similar to an asymmetric Mach-Zehnder interferometer array structure.” MZMI array structures occupy a range of specific geometries and layouts, and the degree of similarity is difficult to ascertain without a standard with respect to which we can ascertain them to. There are many facets of an MZM which may be compared with – the geometry, the phase response, transfer function, topology – and the degree of separation must also be quantified or qualified.
As there is a term of degree with no established standard for comparison, appropriate correction is required to address the uncertainty of the claim’s scope.
Claim Rejections - 35 USC § 103
Claim(s) 1 and 3-8 is/are rejected under 35 U.S.C. 103 as being unpatentable over Takada (US 8406580 B2) in view of Bischel (US 20190101392 A1), and further in view of Vivien (“42 GHz PIN Germanium photodetector integrated in a silicon-on-insulator waveguide”, 2009), Velasco (“High-resolution Fourier-transform spectrometer chip with micro photonic silicon spiral waveguides”, Optics Letters, 2013), and Huang (“Coupled-mode theory for optical waveguides: an overview”, 1994).
Regarding claim 1:
Takada teach an on-chip Fourier transform spectrometer (Abstract, discloses a planar Lightwave Fourier transform/spatial heterodyne spectrometer implemented on a PLC platform – this establishes the spectrometer concept), comprising:
A waveguide input coupler (Figure 1, input coupler),
1xN optical splitter (Figure 1, white boxes indicate a 1xN array of 3-dB couplers),
N waveguide Y-branch structures (Figure 1, the waveguide paths being a Y-branch structure is apparent),
N waveguide Y-branch structure arranged in opposite directions (Figure 1, Figure 2A both show that the Y-branch structures are arranged in opposite directions),
wherein an output end of the waveguide input coupler is connected to an input end of the 1xN optical splitter (Figure 1, Figure 2 show this flow for an MZI-array spectrometer);
N output ends of the 1xN optical splitter are respectively connected to an input end of the N waveguide Y-branch structures (Figure 1, Figure 2 show this flow for an MZI-array spectrometer);
output ends of the N waveguide Y-branch structures are connected to input ends of the N waveguides (Figure 1, Figure 2 show this flow for an MZI-array spectrometer);
output ends of the N waveguides are connected to input ends of N waveguide Y-branch structures arranged in opposite directions (Figure 1, Figure 2, this design is apparent in the waveguides and how they are coupled to the MZI arrays);
one output end of the N waveguide Y-branch structures arranged in opposite directions is connected to an input end of the N detectors (Cover Image, Figure 1 both show that the output coupler is reference labeled for p(N-1), indicating a variable number from 1 to N, this reads on the limitation that one output end is connected to an input end and it would only require routine design oversight to choose one connection over N many connections);
Takada does not teach a spiral waveguide, or that the waveguides are “double-layer”, or a Germanium-silicon composition.
Bischel teaches a multilayer waveguide, wherein the waveguides are a stacked (hence, double layer) of spiral waveguide coils (Figure 1, coils 112 and 114).
‘double layering’ the waveguides results in a waveguide that experience less loss due to optical crosstalk and with improved phase stability and symmetry (among other benefits).
It would have been obvious to one having ordinary skill in the art at the effective filing date of the invention to make N spiral double layer spiral waveguides, since it has been held that mere duplication of the essential working parts of a device involves only routine skill in the art. St. Regis Paper Co. v. Bemis Co., 193 USPQ 8.
Bischel also teaches that the two layers of waveguides (112, 114) of each double-layer spiral waveguide are parallel to each other ([0009] “In one implementation, an optical gyroscope includes a substrate; a multilayer waveguide rotation sensor disposed on the substrate and comprising a plurality of waveguides that overly each other”),
Bischel does not expressly disclose that the width and height of each double-layer spiral waveguide are consistent with the width and height of the corresponding Y branch structure of the waveguide Y-branch structure. However, a skilled artisan would have found it obvious to make consistent the dimensions of the waveguides with that of the Y-branch structure, as a mismatch between the two would result in signal loss and render less-useful the device.
Vivien discloses a SOI Germanium photodetector (Title), teaching the use of Ge-Si photodetectors integrated with waveguides (Figure 1a, shown below, indicates that a germanium detector is taught).
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Vivien does not teach incremental lengths in spiral regions of waveguides.
Velasco teaches on-chip arrays of silicon spiral waveguides, wherein:
the N spiral waveguides are composed of N spiral waveguides with linearly incremental lengths (Figure 1 below, p. 707, “The FT spectrometer was designed with 32 MZIs and with spiral lengths increasing across the array”);
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the teachings of Velasco would allow a skilled artisan to define Li such that it is the length of an ith spiral waveguide.
Velasco does not teach even and odd modality of the waveguides, even if odd and even modes as well as structures which propagate them efficiently are well known in the art.
Huang teaches coupled-mode theory, which details the underlying physics of mode coupling in optical waveguides as well as many practical scenarios in which it is applied.
Specifically, Huang derives that two coupled waveguides support symmetric (even) and antisymmetric (odd) modes when the coupled mode equations are diagonalized (eqs. 3.37-3.38). The composite modes have different propagation constants because the propagation constants are different. The group index therefore varies for the odd and even modes. The natural physical conclusion of this is that the even and odd modes accrue different phase and group delays per unit length.
Huang thus teaches that the double-layer spiral waveguides have even modes and odd modes with different group index refraction laws so that the output ends have different optical path differences (OPD),
O
P
D
i
=
L
i
(
n
g
o
-
n
g
e
)
, wherein ngo, and nge, are group indices refraction coefficients of the odd mode and even mode excitations in the double-layer spiral waveguide respectively.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in Takada under the teachings of Bischel, Vivien, Velasco and Huang to utilize the 1xN waveguide and branch input/output structures to include spiral waveguides instead of those disclosed in Takada, connected to optical paths wherein the modality of the signal determines the OPD. The benefits and theory underlying OPDs are well understood in the art. These modifications may be accomplished using components, materials (Ge-Si, standard chip materials), methods (lithography, etching), design oversight (standard use of arrays and Y-junctions) and design objectives (decreasing the footprint/volume of spectrometers, reducing noise and crosstalk) known in the art, and would predictably result in a device which further reduces the volumetric footprint of on-chip spectrometers through the use of spiral waveguides, while maintaining signal integrity.
Regarding claim 3:
Takada in view of Bischel, Vivian, Velasco, and Huang teaches the on-chip Fourier transform spectrometer based on the double-layer spiral waveguide according to claim 1, wherein:
The waveguide input coupler adopts a butt-coupling structure (the disclosed planar Lightwave circuit spectrometer is intended for coupling with external optical signals via standard interfaces; butt-coupling to optical fibers is a conventional coupling method for PLC devices)
Takada does not teach a grating structure.
Velasco explicitly discloses grating couplers at the input facet for coupling light between optical fibers and the on-chip waveguide (p. 707, “Efficient subwavelength grating couplers [14] were included at the input and output facets of the chip for optimized fiber coupling”),
And an optical spectral signal to be measured is input into the chip by an optical fiber (Figure 1 text, Velasco explicitly teaches fiber-to-chip coupling using optical fibers in conjunction with grating couplers.)
Takada similarly contemplates fiber-fed planar waveguide spectrometers as part of standard PLC measurement setups, but this is not as direct of a teaching.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Velasco to include a grating structure for fiber-to-chip coupling in the device. This may be accomplished using methods and materials known in the art, and would predictably result in a device which compactly processes a signal spectrum as part of a spectrometric process while retaining signal integrity with low loss and cost efficiency.
Regarding claim 4:
Takada in view of Bischel, Vivian, Velasco, and Huang teaches the on-chip Fourier transform spectrometer based on the double-layer spiral waveguide according to claim 1, wherein:
the 1xN optical splitter achieves an equal division of the incident optical power by using a cascaded 1x2 splitter structure of log2N stages, or using 1xN multi-mode interference structure
Takada teaches distributing optical power to N output channels using cascaded 3-dB splitters (Figure 1). In a binary splitter architecture, each splitter stage doubles the number of outputs. Therefore, achieving N equal-power outputs necessarily requires log2N stages. The 1x2 splitter structure cannot adopt another log-base, as it splits in two, so this feature is disclosed by Takada as a natural result of the 1x2 splitter design.
Takada also teaches multimode interference couplers (“The minimum bend radius is 2 mm. White boxes indicate 3-dB couplers consisting of either directional couplers or multimode interference couplers”).
Regarding claim 5:
Takada in view of Bischel, Vivian, Velasco, and Huang teaches the on-chip Fourier transform spectrometer based on the double-layer spiral waveguide according to claim 4, wherein:
The 1x2 splitter structure is a Y-branch, directional coupler (Figure 1, Figure 2a) or
multi-mode interferometer (MMI) structure (“The minimum bend radius is 2 mm. White boxes indicate 3-dB couplers consisting of either directional couplers or multimode interference couplers”).
Regarding claim 6:
Takada in view of Bischel, Vivian, Velasco, and Huang teaches the on-chip Fourier transform spectrometer based on the double-layer spiral waveguide according to claim 1, wherein:
The N-double layer waveguide Y-branch structures and the N double-layer waveguide Y-branch structures arranged in opposite directions are both composed of N double-layer waveguide Y-branch structures with the same structure (Figure 1, multiple/repeated identical splitter/recombiner units are disposed across the interferometer array);
Takada does not teach the upper/lower waveguide and thickness variation, or the merging of waveguides.
Bischel teaches a multilayer spiral waveguide, wherein:
upper and lower waveguides (Figure 1, 112, 114) with the same width and thickness and are parallel to each other ([0009] “In one implementation, an optical gyroscope includes a substrate; a multilayer waveguide rotation sensor disposed on the substrate and comprising a plurality of waveguides that overly each other”) at a beam combination position, and the double-layer waveguides together constitute a beam combination end (when two waveguides are stacked, parallel, and close enough, a skill artisan recognizes that these conditions are the physical conditions necessary for waveguides to be coupled – this is a consequence of the underlying physics of waveguides); and
The upper and lower vertical waveguides are gradually separated at the branch in the horizontal direction, each becoming a single-layer waveguide, achieving the splitting of incident light and the conversion of the waveguide from a double layer to a single layer
Bischel teaches regions where the waveguides are stacked/coupled, and also regions where it is apparent that the waveguides are routed to separate outputs, and they can clearly be seen as non-overlapping (Figure 11A, for example). This independent spiral routing of the same waveguides reads onto a separation.
A skilled artisan understands that abrupt vertical separation would cause excess loss and mode mismatch (standard physics), to preserve mode and reduce loss, adiabatic (gradual) separation is needed. The purpose of such a device is to propagate the signal into the output regions, and doing so with minimal loss and mode conservation is paramount to proper function.
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Bischel et al., to include a multilayer spiral waveguide which has a gradual transition from double layered to two single layered waveguides. This may be accomplished using routine design oversight when constructing the waveguides, and would predictably result in a compact waveguide operated device which propagates signals in a dual layer initially (to minimize loss) and then separates the layers adiabatically (to maintain signal and mode integrity).
Regarding claim 7:
Takada in view of Bischel, Vivian, Velasco, and Huang teaches the on-chip Fourier transform spectrometer based on the double-layer spiral waveguide according to claim 1.
Takada does not teach germanium silicon PIN structures.
Vivien explicitly teaches N germanium-silicon detectors convert optical power signals into electrical signals by germanium-silicon PIN structures (Figure 1, a PIN germanium-silicon detector is taught).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Vivien, to compose the detectors to be germanium-silicon PIN structures as disclosed in Vivien. The Ge-Si detector is a choice of implementation, not a new detection principle, may be implemented using methods and materials known in the art. Predictably, this would impart the benefit of material compatibility with SOI photonic circuits for easy manufacturing, high responsivity at near-IR wavelengths (a skilled artisan recognizes the advantage over pure silicon), and high bandwidth with low loss.
Regarding claim 8:
Takada in view of Bischel, Vivian, Velasco, and Huang teaches the on-chip Fourier transform spectrometer based on the double-layer spiral waveguide according to claim 1, wherein:
the N double-layer waveguide Y-branch structures, N double-layer spiral waveguides with incremental lengths and N double-layer waveguide Y-branch structures arranged in opposite directions are similar to an asymmetric Mach-Zehnder interferometer array structure with incremental optical path differences that function as a Fourier transform spectrometer (Abstract, Figure 1, explicitly teaches an array of asymmetric Mach-Zehnder interferometers used for the Fourier-transform spectroscopy);
the double-layer spiral waveguide array constitutes an array of interferometer a structure with different optical path differences (Col 4, Ln. 15-24, “The number of Mach-Zehnder interferometers (MZIs) is N and the optical path differences between the two arms of the individual MZIs are designed to increase at equal increment of
n
*
Δ
L
”);
Takada does not teach that the optical path difference variation is introduced by variation of the spiral waveguide length.
Velasco teaches that the optical path difference variation is introduced by variation of the spiral waveguide length (Figure 1, p. 707,
Δ
L
description regarding the change in spiral lengths).
Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Velasco to introduce optical path difference using variation of the spiral waveguide length. This may be accomplished using known physical principles and routine design oversight during the manufacturing process of waveguides, with known methods (etching, deposition, lithography). This would predictably result in a spectrometer wherein the waveguide adopts a spiral structure to achieve known design objectives (OPD variation) with a much smaller volumetric footprint than previous designs, while maintaining signal integrity amid low loss.
Claim(s) 2 is/are rejected under 35 U.S.C. 103 as being unpatentable over Takada (US 8406580 B2) in view of Bischel (US 20190101392 A1), and further in view of Vivien (“42 GHz PIN Germanium photodetector integrated in a silicon-on-insulator waveguide”, 2009), Velasco (“High-resolution Fourier-transform spectrometer chip with microphotonic silicon spiral waveguides”, Optics Letters, 2013), Huang (“Coupled-mode theory for optical waveguides: an overview”, 1994), and Nie (“CMOS-compatible broadband co-propagative stationary Fourier transform spectrometer integrated on a silicon nitride photonics platform”, Optics Express, 2017).
Regarding claim 2:
Takada in view of Bischel, Vivian, Velasco, and Huang teaches the on-chip Fourier transform spectrometer based on the double-layer spiral waveguide according to claim 1, wherein:
the waveguide input coupler, the 1xN optical splitter, N dual-layer waveguide Y-branch structure, N dual-layer spiral waveguide, N dual-layer waveguide Y-branch structures arranged in opposite directions (Figure 1, Figure 2a show that the system level structure is arranged such that the components are arranged in opposite directions as claimed),
Takada does not disclose that detectors are integrated in a silicon-on-insulator material, or that the waveguides are made from a silicon nitride material.
Vivien teaches a SOI germanium photodetector (Title), but not a Silicon Nitride waveguide.
Nie teaches Silicon Nitride waveguides (Title, “silicon nitride photonics platform”, also shown in Figure 1 below).
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Before the effective filing date of the claimed invention, one of ordinary skill in the art would have found it obvious to modify the invention described in the rejection of claim 1 above under the teachings of Vivien and Nie, to compose the waveguides of Silicon Nitride (Si3N4) and the detectors on a SOI material (germanium-silicon). This may be accomplished using materials well known in the art, and through methods (lithography, etching, vapor deposition) well understood and commonly practiced in the art. This would predictably result in a device which receives and processes signals with minimal loss on devices that can be manufactured using efficient and known methods.
Conclusion
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/PREET B PATEL/Examiner, Art Unit 2874
/THOMAS A HOLLWEG/Supervisory Patent Examiner, Art Unit 2874