BACKCONVERSION IN A PULSED OPTICAL PARAMETRIC OSCILLATOR - EVIDENCE FROM INJECTION-SEEDED SIDE-BAND

A pulsed optical parametric oscillator (OPO) is pumped at 355 nm and i njection seeded at two distinct idler wavelengths at similar to 855 nm ; these are separated by a frequency interval a falling within the 350 -GHz free-running OPO bandwidth. Above-threshold operation of this dua l-frequency seeded OPO causes sidebands to be observed at multiples of ii in the spectrum of the 607-nm signal radiation. The sideband spaci ng varies smoothly as Delta is tuned (with the injection-seeded OPO ca vity misaligned to reduce its effective finesse), and corresponding si debands are observed on the transmitted 35-nm pump radiation. This is interpreted as direct evidence of backconversion of signal and idler w aves in a pulsed OPO, consistent with previous temporal observations a nd other aspects of OPO performance. Signal-wave sidebands are observe d well beyond the regular free-running OPO gain profile, which is unde rstood in terms of the different phase-matching conditions for the var ious OPO pump and idler (seed) frequencies that are involved. (C) 1997 Optical Society of America.