Browsing by Author "Shu, SF"

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Electro-optic characterization of nonlinear-optical guest-host films and polymers
(1996-09-01)
Khanarian, G
;
Sounik, J
;
Allen, D
;
Shu, SF
;
Walton, C
The Pockels coefficients r(33) of four dyes for electro-optic applications are reported, including ones with stilbene, butadiene, ate, and hexatriene linkages between the charge donors and accepters, with the charge donor being the amino group and the acceptor groups being the nitro and dicyanovinyl groups. r(33) are reported for dyes as guest-hosts in poly(methyl methacrylate) and 50/50 copolymers with methyl methacrylate. The largest r(33) is observed for the copolymer containing the amino donor, hexatriene linkage, and the dicyanovinyl acceptor group with a value of r(33) = 18 pm/V at 140 V/mu m at a wavelength lambda = 1.3 mu m. We also find evidence that the dicyanovinyl hexatriene dyes in the copolymer are interacting with one another, causing a relative decrease in the copolymer's electro-optic efficiency compared with its value as a guest-host in poly(methyl methacrylate). The Pockels coefficient is measured by the ellipsometric reflection technique. We derive approximate analytic equations to analyze the reflected intensity and verify the validity of these approximations when the analyzing wavelength is far from the absorption of the dye. We also derive an approximate analytic expression for the optical retardation as a function of the ratio of the off-diagonal to the diagonal components of the Pockels coefficients r(13)/r(33) and also the finite birefringence of the poled film. We show that accurate knowledge of the ratio r(13)/r(33) is critical to obtaining accurate values of r(33). (C) 1996 Optical Society of America.
Learning evolution design of multiband-transmission fiber Bragg grating filters
(2003-10-01)
Shu, SF
;
Lai, Y
;
Pan, CL
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光電工程學系
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Department of Photonics
A composite fiber Bragg grating (FBG) structure with several apodized sections is utilized for designing dense wavelength division multiplexing (DWDM) multiband transmission filters. A learning genetic algorithm (LGA) is also developed to determine the optimum design parameters of these filters. By taking advantage of a knowledge base (KB) that stores the FBG parameter sets and the corresponding transmission profile feature sets, our LGA can generate a suitable initial population and perform evolutionary optimization starting from it. This has made the LGA evolve more quickly to more accurate results than the methods without using the KB. The LGA can also store new results into the KB according to its decision procedure and improve its precision of initial prediction as it works through more and more examples. (C) 2003 Society of Photo-Optical Instrumentation Engineers.
Population-split genetic algorithm for phase retrieval of ultrafast laser pulses
(2005)
Chen, CW
;
Shu, SF
;
Lee, CK
;
Pan, CL
;
光電工程學系
We report a new population split genetic algorithm for phase retrieval of femtosecond pulses from interferometric autocorrelation traces. After 200 GA generations, pulse width, phase, and chirp could be determined with a convergence error of 6 x 10(-3).