Anti-Stokes signal conversion in the higher-order modes of photonic crystal fiber

With the photonic crystal fiber (PCF) with the zero dispersion wavelengths of second-order and third-order mode around 775 nm and 770 nm designed and fabricated in our lab, the anti-Stokes signals at 575 nm and 570 nm are efficiently generated in the second-order and third-order mode by Ti: sapphire laser with working wavelength of 845 nm and pulse width of 200 fs. In the experiment, most of pump energy is coupled into the higher-order modes by adjusting the angle between input pump and principal axis of fiber to be 25° and 30°, and the phase-matching four-wave mixing (FWM) takes place remarkably.