Injection-seeded optical parametric oscillator for efficient difference frequency generation in mid-IR

The design and performance of an injection-seeded pulsed parametric oscilla tor (OPO) is described for efficient difference frequency generation (DFG) in AgGaSe2 and AgGaS2 crystals. A LiNbO3 OPO with unstable-resonator is inj ection-seeded by another LiNbO3 OPO of narrow linewidth having a grating in cavity. The resulting narrow bandwidth, low divergent signal and idler wav es are mixed in AgGaSe2 and AgGaS2 crystals to produce difference-frequency tunable from 5 to 18 mu m and 5 to 12 mu m, respectively. The maximum DFG conversion efficiency with a 2-cm-long AgGaSe2 crystal obtained is 3.6% (16 % quantum efficiency) at around 7.5 mu m. (C) 1999 Elsevier Science B.V. Al l rights reserved.