IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0299161
(2005-12-08)
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발명자
/ 주소 |
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출원인 / 주소 |
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대리인 / 주소 |
Lumen Intellectual Property Services, Inc.
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인용정보 |
피인용 횟수 :
4 인용 특허 :
19 |
초록
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Quasi-phasematching design to provide an approximation to a desired spectral amplitude response A(f) is provided. An initial phase response φ(f) corresponding to A(f) is generated. Preferably, d2φ(f)/df2 is proportional to A2(f) . A function h(x) is computed such that h(x) and H(f)=A(f) ex
Quasi-phasematching design to provide an approximation to a desired spectral amplitude response A(f) is provided. An initial phase response φ(f) corresponding to A(f) is generated. Preferably, d2φ(f)/df2 is proportional to A2(f) . A function h(x) is computed such that h(x) and H(f)=A(f) exp(iφ(f)) are a Fourier transform pair. A domain pattern function d(x) is computed by binarizing h(x) (i.e., approximating h(x) with a constant-amplitude approximation). In some cases, the response provided by this d(x) is sufficiently close to A(f) that no further design work is necessary. In other cases, the design can be iteratively improved by modifying φ(f) responsive to a difference between the desired response A(f) and the response provided by domain pattern d(x) . Various approaches for binarization are provided. The availability of multiple binarization approaches is helpful for making design trades (e.g. , in one example, fidelity to A(f) can be decreased to increase efficiency and to increase domain size).
대표청구항
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What is claimed is: 1. A method for designing a quasi-phasematched optical frequency converter, the method comprising: a) specifying a non-negative real target spectral amplitude response A(f), wherein A(-f)=A(f); b) providing a real initial phase response φ(f) associated with A(f), wherein
What is claimed is: 1. A method for designing a quasi-phasematched optical frequency converter, the method comprising: a) specifying a non-negative real target spectral amplitude response A(f), wherein A(-f)=A(f); b) providing a real initial phase response φ(f) associated with A(f), wherein φ(f)=-φ(-f); c) calculating a real function h(x) such that h(x) and H(f) =A(f) exp(iφ(f)) are a Fourier transform pair; d) binarizing h(x) to provide a domain pattern function d(x), wherein d(x) is a real constant-amplitude approximation to h(x). 2. The method of claim 1, wherein said providing a phase response comprises providing φ(f) such that d2 φ(f)/df2 is proportional to A2(f). 3. The method of claim 2, wherein said providing a phase response comprises providing φ(f)∝∫0 f(∫0z2A2(z1 )dz1)dz2. 4. The method of claim 3, wherein φ(f)=K∫ 0f(∫0z2A2 (z1)dz1)dz2 and wherein K is selected to minimize a standard deviation of h2(x) divided by an average value of h2(x). 5. The method of claim 1, wherein h(x) and H(f) are a discrete Fourier transform pair. 6. The method of claim 1, wherein h(x) and H(f) are a continuous Fourier transform pair. 7. The method of claim 1, wherein said binarizing comprises setting d(x) substantially proportional to sgn(h(x)). 8. The method of claim 1 further comprising: e) calculating a function D(f)=B(f) exp(iψ(f)) such that D(f) and d(x) are a Fourier transform pair, wherein B(f) is real and non-negative and wherein ψ(f) is real. 9. The method of claim 8, wherein said binarizing comprises setting d(x) substantially proportional to sgn(g(x)-m(x)), wherein m(x) is a modulating waveform and wherein g(x) is an average of h(x). 10. The method of claim 9, wherein m(x) is periodic with period T, and wherein 11. The method of claim 9, wherein g(x) is a moving average of h(x). 12. The method of claim 8, wherein said binarizing comprises setting d(x) substantially proportional to sgn(h(x)-m(x)), wherein m(x) is a modulating waveform selected such that D(f) is substantially proportional to H(f) over a predetermined range of f. 13. The method of claim 12, wherein said modulating waveform is a triangle wave or a sawtooth wave. 14. The method of claim 12, wherein said modulating waveform is random or pseudorandom. 15. The method of claim 14, wherein a power spectral density of said modulating waveform is determined by passing said waveform through a filter. 16. The method of claim 14, wherein said modulating waveform has an amplitude that is uniformly distributed within a predetermined range. 17. The method of claim 8, wherein said binarizing further comprises: processing said function D(f) to provide a modified function F(f); computing a function f'(x) such that f'(x) and F(f) are a Fourier transform pair; binarizing f'(x) to provide a domain pattern function f(x), wherein f(x) is a real constant-amplitude approximation to f'(x). 18. The method of claim 17, wherein said processing comprises low pass filtering, whereby a minimum domain size in f(x) is increased compared to a minimum domain size in d(x). 19. The method of claim 18, wherein said processing comprises filtering to reject quasi-phasematching harmonics. 20. The method of claim 17, further comprising repeating said processing, said computing and said binarizing f'(x) in sequence until a termination condition is satisfied. 21. The method of claim 20, further comprising monitoring a convergence rate of said repeating and resetting said repeating if a condition of slow convergence is detected. 22. The method of claim 8, further comprising: f) modifying said phase response φ(f) responsive to a figure of merit depending on A(f) and B(f). 23. The method of claim 22, further comprising g) iteratively repeating said steps (c) through (f) in sequence until a termination condition depending in part on said figure of merit is satisfied. 24. A quasi-phasematched optical frequency converter comprising: a quasi-phasematched active region having a real constant-amplitude domain pattern function d(x); wherein a function D(f) and the pattern function d(x) are a Fourier transform pair; wherein a non-negative real amplitude response A(f) and a real phase response φ(f) of the active region are defined via D(f)=A(f) exp(iφ(f)); wherein d2φ(f)/df2 is substantially proportional to A2(f). 25. The optical frequency converter of claim 24, wherein a relation φ(f)∝∫0f(∫0 z2A2(z1)dz1)dz2 substantially holds between A(f) and φ(f).
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