Dependency of injection seeding and spectral purity of a single resonant KTP optical parametric oscillator on the phase matching condition

For spectroscopic and remote sensing applications injection seeded optical parametric oscillators (OPOs) are well established. In this paper we study the dependencies of signal resonant injection seeding of an OPO on its resonator length, phase matching angle and pump power in detail. The quality of the seeding process is assessed by stabilising the seed laser on a molecular absorption line of water vapour and using a water vapour absorption cell as a narrow bandwidth filter for the injection seeded radiation. A reduction of the acceptance of injection seeding is observed with increasing pump power. For small phase mismatch injection seeding with a spectral purity of 99.7% was observed at 13-fold OPO threshold. A signal pulse energy of 38 mJ with 50% pump depletion was achieved with a beam parameter M² of about 6. PACS 42.65.Yj; 42.79.Nv; 42.79.Qx