Broadband midinfrared from fiber laser difference frequency generation in OP-GaP

摘要

We generate 52 mW of broadband pulses at 8 μm wavelength by difference frequency generation (DFG) in orientation-patterned GaP (OP-GaP). Pumping by fiber lasers is possible because of the wide transparency range of GaP. An Er fiber oscillator at 1.5 μm wavelength and 90 MHz repetition rate provides pulses for direct amplification and shifting to 1.9 μm followed by amplification in Tm doped fiber. The two beams are mixed in OP-GaP with up to 20% photon conversion efficiency. The wavelength is tunable from 5 to 11 μm by changing the crystal period or the degree of wavelength shifting. With coherent broadening, we can also generate midinfrared frequency combs with tunable carrier envelope offset frequencies.