Tunable MID-IR Optical Parametric Oscillator Using Periodically Poled Rubidium Titanyl Arsenate

摘要

Tunable sources of coherent radiation are needed for a variety of military and commercial applications, including infrared countermeasures and atmospheric remote sensing. This research investigates a tunable mid-infrared coherent source using periodically-poled rubidium titanyl arsenate (PPRTA) as a quasi-phase matched (QPM) optical parametric oscillator (OPO). The advantages of PPRTA over periodically poled lithium niobate (PPLN) are presented. Quasi-phase matching and periodic poling theory are discussed, along with some important historical results and current developments. Experimental setups for determining threshold, conversion efficiency, pump depletion, and beam quality are presented along with experimental results. The research effort is focused on characterizing PPRTA through the generation of tunable midinfrared laser radiation in the 1.4 to 4.0 micron region. Results successfully demonstrate PPRTA conversion in the 1.5 um range with a 173 mJ oscillation threshold and a beam quality (M2) value of 9.0. Slope efficiency of PPRTA is shown to be 24%, compared to slope efficiency of 15% for PPLN in an identical system setup. The high slope efficiency, high pump conversion (approximately equal 60%), absence of damage at pump levels in excess of 300 MW/ sq cm, and large aperture scaling possibilities suggest that PPRTA is well suited for higher power applications.