ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 microm source.

A tandem optical parametric oscillator (OPO) is used to convert radiation from 1.064 microm to the mid-infrared. Spectral bandwidth narrowing close to 80 times compared with a conventional cavity was achieved by using a bulk Bragg grating as an outcoupler in a near-degenerate periodically poled KTiOPO(4) OPO. The narrowed 2,008 nm radiation was subsequently used for pumping the ZnGeP(2) OPO, which was tunable between 3.3 and 5.2 microm. Pulse energies of 170 microJ and pump depletion close to 70% were obtained in the ZnGeP(2) OPO. To our knowledge this is the first time the output from a near-degenerate type I PPKTP OPO has been used for ZnGeP(2) OPO pumping.