High-peak-power long-wave infrared BaGa4Se7 optical parametric oscillator with 6.7-13.9†µm widely tunable range.

A high-peak-power, widely tunable range long-wave infrared optical parametric oscillator (OPO) based on the BaGa4Se7 (BGSe) crystal is demonstrated in this Letter. Pumped by a 1064 nm Nd:YAG laser, a high-peak-power of 0.15 MW was achieved at 9.8 µm with a pulse width of 5.0 ns. At 11.0 µm, a high beam quality of M2x = 4.1 and M2y = 3.3 was achieved. By rotating the BGSe crystal, a broad tuning range of 6.7-13.9 µm was realized. Furthermore, a theoretical analysis was conducted to elucidate the reasons behind the improvement in beam quality in the x-direction as the wavelength of the idler wave increases.

Evolution properties of a Laguerre-Gaussian correlated Schell-model beam propagating in uniaxial crystals orthogonal to the optical axis.

Analytical expressions for the cross-spectral density function and the second-order moments of a Laguerre-Gaussian correlated Schell-model (LGCSM) beam propagating in uniaxial crystals orthogonal to the optical axis are derived. Based on the formulas derived, we study the propagation properties, such as beam irradiance, beam diameters, and the spectral degree of coherence, of a LGCSM beam inside uniaxial crystals in detail. The effect of the initial beam parameters (mode order and spatial coherence length) and the parameters of the uniaxial crystals on the evolution properties of a LGCSM beam is revealed through numerical examples. The uniaxial crystals provide one way to modulate the properties of a LGCSM beam.