Mid-infrared radiation in the 5–18-μm range has been obtained by difference frequency generation in a AgGaSe<sub>2</sub> crystal by pumping with the output of a type I LiNbO<sub>3</sub> optical parametric oscillator (OPO). Here we suggest the use of a LiTaO<sub>3</sub> retarder to achieve an orthogonal state of polarization between OPO outputs that are necessary for efficient pumping of a AgGaSe<sub>2</sub> crystal. Several tens of kilowatts of peak power near 8 μm and continuously tunable operation in the above range have been obtained.
© 1998 Optical Society of America
Kazi Sarwar Abedin, Sajjad Haidar, Yuji Konno, Choichi Takyu, and Hiromasa Ito, "Difference Frequency Generation of 5-18 μm in a AgGaSe2 Crystal," Appl. Opt. 37, 1642-1646 (1998)