Polarization-controlled vectorial spectral transformations of femtosecond pulses in a birefringent photonic-crystal fiber

Abstract

Polarization analysis reveals the vectorial nature of nonlinear-optical spectral transformations of femtosecond Cr:forsterite laser pulses in a highly birefringent photonic-crystal fiber. The birefringence in this fiber is induced by elliptical shape of the core of the size of 2.0 μm by 5.7 μm. We demonstrate the possibility of polarization control of the blueshifted radiation at the fiber output originating from the Cherenkov emission of dispersive waves induced by solitons that are generated by input 1.25⁢ μm laser pulses. Polarization-sensitive, two-color nonlinear-optical processes in such a fiber, pumped by the fundamental-frequency radiation of the Cr:forsterite laser and its second harmonic, are shown to allow the generation of a broadband spectrum covering the range from 430 to 660 nm.