Title :
Enhancement of CW THz Wave Power Under Noncollinear Phase-Matching Conditions in Difference Frequency Generation
Author :
Ragam, Srinivasa ; Tanabe, Tadao ; Saito, Kyosuke ; Oyama, Yutaka ; Nishizawa, Jun-ichi
Author_Institution :
Dept. of Mater. Sci., Tohoku Univ., Sendai, Japan
Abstract :
We investigated methods for improvement of continuous-wave (CW) terahertz (THz) output power by laser diode (LD) pumping in noncollinear phase-matched difference frequency generation (DFG). The effects of interaction length and beam spot size of input lasers (near-IR) in GaP crystals were studied. The THz wave power dependence on various sizes of GaP crystals was investigated and it was observed that an output power of 4 nW was obtained with a 20 mm long GaP crystal at 1.5 THz. Also, the THz wave absorption coefficient was dominant for longer GaP crystals at high frequencies (above 2.5 THz). The THz wave power dependence on beam spot size (1.2 mm-300 mum) of near-IR lasers at 1.62 THz was studied, and an improvement of THz wave power being seen with a 500 mum beam spot size, while the beam divergence effect was dominant for beam spot sizes below 500 mum.
Keywords :
III-V semiconductors; gallium compounds; laser beams; optical frequency conversion; optical materials; optical phase matching; optical pumping; terahertz wave generation; CW terahertz wave power enhancement; GaP; difference frequency generation; frequency 1.5 THz; frequency 1.62 THz; gallium phosphide crystal; laser beam divergence effect; laser diode pumping; near-IR laser; noncollinear phase-matching condition; power 4 nW; size 10 mm; size 500 mum; wave absorption coefficient; Continuous-wave (CW); GaP; difference frequency generation (DFG); phase matching; terahertz (THz);
Journal_Title :
Lightwave Technology, Journal of
DOI :
10.1109/JLT.2009.2022340
