Enhancement of four-wave mixing via stimulated emission in a Yb-doped photonic crystal fiber

We present a novel photonic Crystal Fiber (PCF), designed for degenerate four-wave mixing (FWM), with a Yb-doped core to amplify the FWM pump light via stimulated emission. Using a 1030 nm Q-switched microchip laser as the FWM pump, the generation of anti-Stokes light at 691 nm was enhanced by using a 976 nm CW laser diode to create a population inversion in the Yb-doped core of the PCF, which amplifies the 1030 nm pulses. For a 1030 nm incident average power of 15 mW (4 kW peak power), the 691 nm anti-Stokes power generated increased from 0 to 1.15 mW when the incident 976 nm power was increased from 0 to 287 mW. FWM was not observed for this 1030 nm input power level in a similar length of a conventional PCF with the same phase-matching properties. Hence, we demonstrate that amplification of the FWM pump pulse through stimulated emission boosts the generated anti-Stokes power, providing a promising route to increasing the pump to anti-Stokes conversion efficiency beyond what is possible with non-rare-earth-doped FWM PCFs.