Widely wavelength-tunable ultrashort pulse generation using polarization maintaining optical fibers

Characteristics of widely wavelength tunable ultrashort pulse generation using several types of polarization maintaining fibers have been experimentally analyzed. Using the diameter reduced type of polarization maintaining fibers, the wavelength tunable soliton pulse is generated from 1.56 to 2.03 μm. It is confirmed that the almost transform-limited 340-fs soliton pulse is generated at a wavelength of around 2 μm using a frequency-resolved optical gating method. When low-birefringence fibers are used, it is observed that the orthogonally polarized small pulse spectrum is trapped by the soliton pulse and is also shifted toward the longer wavelength side in the process of soliton self-frequency shift. The wavelength of the orthogonally polarized pulse spectrum is 40-50 nm longer than that of the soliton pulse, and the birefringence of the fiber is compensated by the chromatic dispersion. Finally, a polarization maintaining highly nonlinear dispersion-shifted fiber is used as the sample fiber. When the fiber input power is low, the wavelength-tunable soliton and anti-Stokes pulses are generated. As the fiber input power is increased, the pulse spectra are gradually overlapped and the 1.1-2.1 μm widely broadened supercontinuum spectra are generated by only 520 pJ pulse energy