Abstract

The near-infrared region is of importance in areas such as photochemistry, optical communications, and optical pumping; yet it remains relatively uncovered by strong coherent sources of radiation. The CO₂ laser is an efficient and tunable source of mid-IR radiation, and as a result frequency conversion of CO₂ lasers in nonlinear materials is an attractive method for generating new IR sources. Thallium arsenic selenide (TI₃AsSe₃) (TAS) is a biréfringent ternary chalcogenide salt with many properties that are useful for CO₂ harmonic generation. It is a member of the space group R3m, possesses a large nonlinear coefficient (d_eff = 40 X 10⁻¹² m/V), has a fairly high damage threshold (1.7 J/cm²), and is transparent and phase-matchable throughout the IR. Under type I phase matching, high second harmonic conversion efficiencies of CO₂ laser radiation have been measured in the present study, and conversion of the CO₂ fundamental into its third, fourth, and fifth harmonic has been achieved for the first time.

© 1988 Optical Society of America