Frequency doubling of 100-fs pulses with 50% efficiency by use of a resonant enhancement cavity

Abstract
The use of a resonant cavity for efficient second-harmonic generation with 100-fs pulses is demonstrated. With 2-nJ pulses from a mode-locked Cr:forsterite laser, 53% conversion efficiency to the second harmonic at 625 nm is achieved while ~100-fs duration is maintained. This is an order-of-magnitude improvement over the conversion efficiency obtained directly with the laser output.