9-13 July 2012
Mid-Infrared doubly-resonant Optical Parametric Oscillator based on ZnGeP2
Presented by Mr. Wayne KOEN on 13 Jul 2012 from 09:00 to 09:20
Type: Oral Presentation
Track: Track C - Photonics
Laser sources emitting in the 3-5 micron wavelength region is of particular interest for applications in medicine (tissue ablation), remote sensing (LIDAR) and the military (directed infra-red countermeasures). However; while solid state laser sources in the 1 micron region (Neodymium based lasers) are well established and sources in the 2 micron region are maturing (Holmium and Thulium based lasers); sources in the 3 to 5 micron region are still limited. An efficient path to obtain coherent light in the 3-5 micron region is by converting light from a 2 micron laser source, such as a solid-state Ho:YLF laser, through the use of an optical parametric oscillator (OPO). Here we present a high-power mid infra-red optical parametric oscillator (OPO) based on ZnGeP<sub>2</sub> (ZGP). The ZGP crystal was pumped with an in-house developed Ho:YLF slab laser. The OPO consisted of a linear cavity, double passing the pump light through the ZGP crystal with the use of an output coupler mirror that was highly reflective at 2 micron. The input coupler mirror was highly reflective for both the signal and the idler while the output coupler mirror was partially reflective for both, thus making a doubly-resonant OPO. The OPO had a slope efficiency of 30% from incident power to the combined signal and idler output power (from the ZGP OPO) when operating at a pulse repetition rate of 5 kHz. Through rotation of the ZGP crystal, output could be obtained from as short as 3515 nm, and as long as 4993 nm. A maximum output power of 1 W was measured when limiting the incident pump power to 7 W. The OPO exhibited a good beam quality.