High-power narrowband mid-IR laser based on pulsed difference-frequency generation in PPLN

A compact difference-frequency laser for spectroscopic applications using a diode-pumped pulsed Nd:YAG laser at 1064 nm as pump and a cw diode laser around 1540 nm as signal source is reported. With 240-muW signal and 4.6-kW pump power incident oil an uncoated 50-mm-long PPLN crystal, the novel mixing scheme exhibits a 65-times higher conversion efficiency than its allow-pumped counterpart resulting in a mid-infrared peak power of 0.22 W. The freuquency conversion process is discussed in detail including effects like optical parametric amplification. Continuous tunability in the 3-4-mum wavelength region and a laser linewidth of only 280 MHz combined with >600-W mid-IR peak (17-mW average) power are obtained when 4-mW signal (tunable from 1500-1620 nm) and 6.1-kW pump power are incident on an antireflection-coated 50-mm-long PPLN crystal.