Generation of anti-Stokes pulses through phase-matched four wave mixing in birefringent photonic crystal fibers

An analysis into the phase matching condition of four-wave-mixing in highly birefringent photonic crystal fiber is presented to yield twelve independent processes combining the nonlinear terms with those of linear terms. The pump wavelength, power and pump pulse incident angles effects on the anti-Stokes frequency shifts are analyzed. The results show that the incident polarization angles along the slow-axis of the PCF, anti-Stokes wavelength is shorter than the case of along the fast-axis. In the case of a divided pump polarization, the frequency shifts decrease gradually with the increase of the incident angles. The pump wavelength is much more important factor in the phase-matched processes, but not sensitive to change of power. Experimental results link power, incident angles and phase-matched wavelengths are presented. Experiments demonstrate that the variation of the pump pulse parameters results in the anti-Stokes lines generation at 550 and 620 nm, which is in good agreement with the theoretical analysis. Furthermore, there exists the polarization-, power-independent anti-Stokes emissions.