The wavelength of laser radiation is usually constant and changing it is extremely hard, which is why, in practice, parametric light generators are used, which allow to continuously change radiation wavelength in a wide spectral range. Currently, the parametric generators are created with ultrashort (less than 100 ps) and long (more than 1 ns) pulse durations, however subnanosecond pulse (less than 1 ns and more than 100 ps) generators have not yet been invented. This is due to certain physical limitations - in the case of subnanosecond pulses, the damage threshold of many nonlinear media is lower than the parametric generation threshold [1-3].
The goal of this research was to construct and investigate an optical parametric generator/amplifier (OPG/OPA) system, which uses 15 mm LBO crystal as a nonlinear medium and Nd:YAG MOPA laser as a seed. Here, 3rd harmonic of laser (355 nm) was used as pump radiation, and fundamental harmonic (1064 nm) – as pump source for seed radiation. OPG/OPA seed was supercontinuum generated in a photonic crystal fiber (PCF).
The supercontinuum radiation used as OPG/OPA seed extended from 650 nm to 1600 nm at maximum pump pulse energy. The maximal seed energy was measured to be 5 mW over the entire spectrum. We achieved signal wave generation via optical parametric amplification of idler wave. Further on, we measured spectral and energy characteristics of OPG/OPA. Signal wave tunning range was from 456 nm to 670 nm and was limited by idler wave tunning range which depends on seed radiation spectrum extension. Signal wave power was of the order of microwatts over the whole wavelength tuning range due to the fact that during this work, we used a single-pass OPG/OPA configuration. The measured generation threshold was similar for most of the OPG/OPA tunning range.
The results of this work will be used for further development of more effective subnanosecond OPG/OPA systems.
