Bài báo khoa học

Supercontinuum generation in highly birefringent fiber infiltrated with carbon disulfide is numerically studied with a linearly polarized femtosecond laser (1560 nm wavelength, 90 fs pulse duration) as a pump source. The fiber has two polarized modes (x- and y-polarized LP01) with different dispersion characteristics, meaning all-normal dispersion for the y-polarized mode and anomalous dispersion for the x-polarized mode. We build a numerical modeling for nonlinear propagation including Kerr effects and Raman effects with positive and negative nonlinear refractive. Our results point out that spectral bandwidth, flatness, and coherence of supercontinuum generation depend on the input polarized angle (an angle with respect to the x-axis) of the laser pulses. In particular, the input pulses polarized near slow-axis (x-axis) provide 1.5 octave-spanning soliton-induced SC generation with bandwidth from 1000 nm to 3300 nm via 10 kW input peak power, while input pulses polarized near the fast-axis (y-axis) create octave-spanning all-normal dispersion supercontinuum generation (from 1200 nm to 2500 nm). Modification of the input angle enables controlling spectro-temporal properties of supercontinuum generation, such as polarization state, coherence, spectral bandwidth, and flatness. In addition, the use of highly birefringent fiber also enables suppression of polarization modulation instability; therefore coherence solely depends on effects of modulation instability and it is possible to tailor via changing the input angle.