Abstract
We reported a type-I difference-frequency generator (DFG), based on erbium doped GaSe (Er:GaSe) crystals as a coherent infrared source tunable from 2.4 μm to 28 μm. The two mixing beams used for the DFG are a tunable near infrared output (1.1-1.8 μm) from an optical parametric amplifier (OPA) and the fundamental beam of a picosecond Nd:YAG laser at 1.064 μm. The system can produce a maximum output pulse energy of 5 μJ at wavelength of 3.5 μm, corresponding to a photon conversion efficiency of 8% at a pump intensity of 1.7 GW/cm 2 . The nonlinear coefficient (d eff ) of 0.5 atom% erbium doped GaSe crystal was found to be 55.3 pm/V or 24% higher than that of a pure GaSe crystal. The improvement of d eff is attributed to the substitutive and interstitial doping of Er ion in GaSe unit cell. The optical properties of GaSe influenced by the erbium doping are also presented. © 2006 Optical Society of America.