Highly-nonlinear polarization-maintaining As2Se3-based photonic quasi-crystal fiber for supercontinuum generation.

We propose an As 2 Se 3 -based photonic quasi-crystal fiber (PQF) with high nonlinearity and birefringence. By optimizing the structure parameters, a nonlinear coefficient up to 2079 W −1 km −1 can be achieved at the wavelength of 2 μ m; the birefringence reaches up to the order of 10 −2 due to the introduction of large circular air holes in the cladding. Using an optical pulse with a peak power of 6 kW, a pulse width of 150 f s, and a central wavelength of 2.94 μ m as the pump pulse, a mid-infrared polarized supercontinuum is obtained by using a 15 mm long PQF. The spectral width for x - and y -polarizations covers 1 μ m–10.2 μ m and 1 μ m–12.5 μ m, respectively. The polarization state can be well maintained when the incident angle of the input pulse changes within ±2°. The proposed PQF, with high nonlinear coefficient and birefringence, has potential applications in mid-infrared polarization-maintaining supercontinuum generation. [ABSTRACT FROM AUTHOR]