Non-Final Rejection
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA . By preliminary amendment, claims 1-15 were cancelled and claims 16-46 added. Claims 16-46 are pending.
Claim Rejections - 35 USC § 103
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 16-23, 25-26, 30-45 are rejected under 35 U.S.C. 103 as being unpatentable over Klenke et al., Coherent combination of spectrally broadened femtosecond pulses for nonlinear compression, Optics Letters Vol. 39 No. 12 (2014) (“Klenke”) in view of Benedetti et al., Plasma wakefield excitation by incoherent laser pulses: a path towards high-average power laser-plasma accelerators, AIP Conference Proceedings 1777 (2016) (“Benedetti”).
Regarding claim 16, Klenke discloses a method for providing an ensemble of pulsed laser beamlets having a defined envelope, comprising the steps of:
(a) providing a beamlet pattern comprising a plurality of spatially distributed laser beamlets, (Fig. 2, input pulse is split into separate beamlets by beamsplitter, going to fiber 1 and fiber 2)
(b) separating the beamlets in time by introducing different temporal delays to each of the beamlets, (p. 3521 first full par., one beamlet is delayed)
(c) spectrally broadening the beamlets, and (via broadening fibers 1 and 2)
(d) incoherently combining the beamlets in space and time to provide the ensemble of beamlets.
The beamlets are combined, but they are coherently combined and not incoherently combined, see title. Benedetti teaches that while coherent combination of beamlets is common, incoherent combination can also be done and can also be useful for many of the same applications, like laser plasma accelerators. P. 1-2, conclusion. It would have been obvious to a person of ordinary skill in the art to use incoherent combination instead of coherent because the requirements are simpler and more relaxed, as taught by Benedetti.
Regarding claim 17, the steps are done in order a to d as in Fig. 2.
Regarding claim 18, the beamlet pattern is from splitting a single beam.
Regarding claim 19, the initial beam source does not seem to be important to Klenke, so whether the multiple beams are formed by a single source that is split or by multiple sources in an array is no more than a substitution of art recognized equivalents to serve the same purpose. MPEP 2144.06.
Regarding claim 20, there is further the step of fine-tuning spatio-temporal properties of at least one of the beamlet pattern and individual beamlets via the QWP and piezo mirror.
Regarding claim 21, there is further the step of modifying optical properties of the beamlets prior to the step of spectrally broadening, as they go through HWP.
Regarding claims 22-23, in Klenke the optical path length of a respective beamlet is controlled by the QWP and piezo mirror, with feedback from the HC. P. 3521 left col. This will at least indirectly control any combination that occurs.
Regarding claims 25, 44, and 45, the method and arrangement of the independent claims for creating the combination of beamlets was deemed obvious over Klenke and Benedetti as above. Benedetti additionally suggests that such an ensemble of beamlets is useable in driving a plasma wave in a plasma wakefield of a laser plasma accelerator. It again would have been obvious to use the combined beam as Klenke provides femtosecond pulses that may be useful for such application, and Benedetti suggests that incoherent combination would work for laser accelerators and has simpler requirements than coherent combination. Any remaining limitations of these claims are just to the normal operation of a laser plasma accelerator (particles injected into wakefield, accelerated by wakefield, particles extracted).
Regarding claim 26, Klenke discloses in Fig. 2 an optical arrangement, comprising:
a beamlet generating device providing a beamlet pattern of spatially distributed laser beamlets, (input is split into different beamlets that go to fiber 1 and fiber 2)
a first optical device for spreading spatially distributed laser beamlets in time by introducing a different temporal delay to each of the beamlets, (p. 3521 first full par., one beamlet is delayed by QWP and piezo)
a spectral broadening device, and (broadening fibers 1 and 2)
a combining device for incoherently combining the beamlets in space and time to provide an ensemble of beamlets having a defined envelope.
A combining device (from second splitter to the end at compressor) combines the beamlets, but they are coherently combined, see title. This is not in Klenke but would have been obvious for the same reasons as the like limitation of claim 16 above.
Regarding claim 30, there is further a beam splitter after the fibers for temporally combining the beamlets.
Regarding claim 31, a step optic is not shown. The examiner takes official notice that step optics are known in the art to introduce temporal delay. It would have been obvious to a person of ordinary skill in the art to use such optics as they may perhaps be simpler than using the QWP+piezo mirror set up of Klenke.
Regarding claim 32, the combining device is a beam splitter and therefore has at least a reflective optical element for spatially combining the beamlets.
Regarding claim 33, the combining device is just shown as a beam splitter. Lens arrays are of course known in the art. It would have been obvious to a person of ordinary skill in the art to include a lens array to ensure that the beams are located as appropriate so that they may be combined as wanted.
Regarding claim 34, Fig. 2 shows a spatial beam splitter for splitting a single-aperture laser beam into the beamlet pattern.
Regarding claim 35, the laser beam is provided by a fiber based CPA system. P. 3521-22.
Regarding claim 36, the beam splitter is at least reflective as seen in Fig. 2.
Regarding claim 37, there is QWP when the delay is introduced.
Regarding claim 38, prior to the broadening there is half wave plate, beam splitter, quarter wave plate, and piezo mounted mirror, i.e. an imaging system having one or more of at least one of refractive and reflective optical elements configured for modifying optical properties of the beamlets when imaging the beamlet pattern into the spectral broadening device.
Regarding claim 39, the examiner takes Official Notice that it is known in optical systems to include optics for aberration and wavefront control. Optical systems often need to be very precise and could be inoperable if there are imperfections, so it would have been obvious to a person of ordinary skill in the art to correct for such things.
Regarding claims 40-41, step optics would have been obvious as discussed above re: claim 31. Klenke also already includes a QWP and polarizing beam splitter as part of changing the delay, and thus would also include them if a step optic were used.
Regarding claims 42-43, there is an actuated mirror (piezo mirror) for fine tuning the delay between the beamlets.
Claims 27-29 are rejected under 35 U.S.C. 103 as being unpatentable over Klenke and Benedetti as applied to parent claim 26, and further in view of US 2017/0125964 (“Russbueldt”).
Klenke uses fibers for spectral broadening, not a multi-pass cell that is a Herriot cell. Russbueldt teaches that spectral broadening of laser pulses can be by a Herriot cell. [0001], [0023]. It would have been obvious to a person of ordinary skill in the art to use this spectral broadening configuration as Russbueldt recognizes that it overcomes various limitations of known broadening techniques, such as pulse power limitations. [0013]-[0014], [0024]. The Herriot cell provides non-linear effects for the broadening and will provide amplitude filtering.
Allowable Subject Matter
Claims 24 and 46 are objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
There is not taught or disclosed in the prior art the method of claim 22 wherein a figure of merit of an application being driven by the ensemble of beamlets is used as control input for controlling the incoherent combination. There is not taught or disclosed in the prior art the laser plasma accelerator of claim 45 further comprising at least one of at least one laser sensor and at least one electron diagnostic sensor for outputting a control signal controlling the incoherent beamlet combination in the optical arrangement. There is no indication of controlling the incoherent combination by an application being driven by the beamlets. Again the only feedback suggested is before the combination, so before the application, and there is no reason to do it from the application other than hindsight.
Conclusion
The prior art made of record and not relied upon is considered pertinent to applicant's disclosure. Other laser plasma accelerators are cited.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to James Menefee whose telephone number is (571)272-1944. The examiner can normally be reached M-F 7-4.
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/JAMES A MENEFEE/Primary Examiner, Art Unit 2828