Tunable midinfrared source by difference frequency generation in bulk periodically poled KTiOPO4

We demonstrate quasi-phase-matched difference frequency generation in perio dically poled KTiOPO4. A midinfrared (3.2-3.4 mu m) idler with a power leve l of 0.17 mu W is generated by mixing a Nd:YAG laser and tunable external c avity laser near 1550 nm which is amplified by an erbium-doped fiber amplif ier. The wavelength, temperature, and angle tuning characteristics of this device are determined. The experimental results are used to derive a Sellme ier equation with improved accuracy in the midinfrared range for the extrao rdinary refractive index of flux-grown KTiOPO4. (C) 1999 American Institute of Physics. [S0003-6951(99)04007-3].