Narrow Bandwidth Tunable Optical Parametric Generator

摘要

The output of a periodically poled lithium niobate (PPLN) optical parametric generator (OPG) is filtered using an off axis Fabry-Perot etalon. The filtered output is then parametrically amplified in the same PPLN crystal resulting in a tunable narrow-band infrared source. The PPLN OPG is pumped with a 10 nsec pulse duration, 1.064 urn single-frequency pump laser, with an output signal and idler determined by the PPLN periodicity. The polarization of the pump laser is rotated so that only a portion of it is phase matched on the first pass through the PPLN crystal. The portion that is phase matched generates a signal that is directed to an off-axis Fabry-Perot etalon, which, in the off-axis configuration has a narrow bandwidth reflection. The pump beam is transmitted through a quarter wave plate and reflected with a mirror so that when passed back through the PPLN crystal, its polarization is rotated 90 degrees with respect to the input. Hence the portion of the pump not phase matched on the first pass is now phase matched for the second pass. The reflected and filtered signal is co-aligned with the pump resulting in a narrow bandwidth amplified signal. This system is capable of generating narrow bandwidth over the tuning range of the PPLN crystal and is only restricted by the etalon reflectivity range. We demonstrate tunability in the 1.4 μrn -1.6 μm signal range (3.0 μm-4.4 μm idler range), which is restricted by our etalon reflectivity.