Midinfrared optical parametric oscillator based on the wide-bandgap BaGa_4S_7 nonlinear crystal

Abstract

The orthorhombic biaxial crystal BaGa(4)S(7) has been employed in a 1064 nm pumped optical parametric oscillator generating <6 ns long idler pulses with energies as high as 0.5 mJ at 6.217 μm and average power of ~50 mW at 100 Hz. Notwithstanding the relatively low nonlinearity, ~3 times above threshold operation has been achieved at pump intensities more than 5 times below the crystal surface damage limit.

High-energy 1064-nm pumped optical parametric oscillator for the 6 µm spectral range based on HgGa2S4

“…This makes it difficult to achieve few times above threshold operation before surface damage occurs. Here we demonstrate that HGS presents a perfect combination of properties that enable such operation with type-II phase matching, reaching idler energy of 3 mJ at 6.3 µm which is an improvement of more than 6 times compared to previous best results with CdSiP 2 and BaGa 4 S 7 based OPOs [4,5].…”

Progress in 1-μm Pumped Mid-IR Optical Parametric Oscillators Based on Non-Oxide Nonlinear Crystals

“…The measured temporal shapes are shown in Fig. 9c, however, the idler pulse duration was affected by the detector response and the actual value should be <6 ns [54]. The idler M 2 value measured for this OPO was ~10, better than for HGS probably related to spatial confinement of the signal beam through the parametric gain.…”

“…Thus, the main challenge for LGS is the availability of longer samples to reduce the OPO threshold. However, at present the development of the related BGS seems faster (in terms of sizes and reduction of residual losses) and some results with such a SRO are presented below [54].…”

“…7a for LISe-2 at axial pump fluence exceeding 377 mJ/cm 2 or peak intensity >27 MW/cm 2 ). Thus, this shifted our interest to LGS [53] and BGS [54] which exhibit the largest band-gaps (Table I) and are colourless (Fig. 2).…”

“…Decreasing d eff and parametric gain alone cannot account for the strong drop in the conversion efficiency at long idler wavelengths. In this particular case the decreasing angular acceptance might play a role, an effect that could be easily suppressed by improved alignment of the pump telescope [54].…”