Abstract

Pulsed intra-cavity OPO-DFG (OPO-iDFG) using two periodically poled lithium niobate (PPLN) crystals and cascaded mid-infrared generation was demonstrated using AgGaSe₂,. The OPO-PPLN crystal operated in the usual manner by converting pump photons (ω_p) into signal (ω_s) and idler (ω_i) photons (ω_p = ω_s + ω_i). The DFG-PPLN crystal was designed to phase match the signal and idler waves to produce a difference frequency photon (ω_d = ω_s − ω_i = 2ω_s − ω_p) and an additional idler photon. Since the signal photon is generated in the OPO, but consumed in the nonlinear DFG process, back conversion is minimized and pump depletion is improved.^1,2 The output of the OPO-iDFG (ω_i and ω_d) is used to generate inter-cavity DFG radiation (ω_D = ω_d − ω_i) using an AgGaSe₂ crystal. By changing the temperature of the PPLN crystals, the wavelength of the OPO-iDFG radiation (ω_i and ω_d) changes, and consequently changes the wavelength of the inter-cavity DFG radiation (ω_D). The experimental setup and energy diagrams of each process are shown in Fig. 1.

© 2002 Optical Society of America