The experimental and theoretical investigation of the generation of an ultra broadband optical pulse in a microstructure fiber

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The aims of this project were 1)the generation of an ultra broadband optical pulse in a microstructure optical fiber by the use of induced-phase modulation and 2)the comparison between theory and experiment to understand the mechanism of the spectral modulations in a microstructure fiber. The research results are summarized as follows.1)The phase and amplitude of an ultra broadband optical pulse generated by propagating an optical pulse from a Ti : Sapphire laser oscillator in a taper fiber were measured by a cross-correlation frequency-resolved optical gating apparatus. The experimental results were compared with calculations obtained by a finite-difference in the frequency domain method. These results agreed well and the calculations showed that a fundamental soliton pulse was generated in a taper fiber by the fission of the optical pulse inputted in a fiber.2)The spectral broadening of a second-harmonic pulse was observed when a fundamental pulse and its second-harmonic pulse from a Ti : Sapphire laser oscillator were co-propagated in a microstructure fiber by the use of induced-phase modulation. Especially, the generation of an ultra broadband pulse from 380 nm to 1000 nm was observed when these pulses were co-propagated in a 1.0-μm-core-diameter photonic crystal fiber. The dependence of the spectral broadenings on the delay times of the second-harmonic pulse was measured and compared with calculations. From the calculations, it was found that the timings of the generation of a fundamental soliton pulse created by the fission of a fundamental pulse and the spectral peak position of the fundamental soliton pulse were strongly modified by the delay times of the second-harmonic pulse.