Ultrashort optical pulse interaction with fibre gratings and device applications

grantor: University of TorontoThe linear interaction between (coherent) ultrashort broadband optical and fibre gratings, referred to as the ultrashort pulse response of fibre gratings, is theoretically and experimentally investigated. The reflected and transmitted pulses of an ultrashort pulse incident upon a fibre grating are calculated using coupled-wave theory. The effects of different grating characteristics, such as grating strength, phase response (dispersion), chirp, and apodization on the ultrashort pulse response are examined. A symmetric transform-limited 1-ps Gaussian pulse is assumed as the ultrashort broadband input to the gratings; the reflected and transmitted pulses take on significantly different shapes and vary in duration. The prominent features observed are qualitatively explained in order to gain physical insight into the dynamics of the ultrashort pulse response. To experimentally verify the theoretical calculations, the temporal response of transform-limited picosecond pulses reflected and transmitted from a fibre Bragg grating is measured using a surface-emitting nonlinear semiconductor multi-layer waveguide as an optical correlator. The results of the theoretical study indicate that there is the potential for a new class of devices and applications for optical communications by combining ultrashort broadband pulses and fibre gratings. In particular, a multiple-grating fibre device structure that can decompose an ultrashort broadband pulse simultaneously in both wavelength and time domains is designed, demonstrated, and its uses in optical communications are outlined. Other applications, including temporal pulse shaping and the implementation of optical code-division multiple access are also discussed.M.A.Sc