Widely tunable in the mid-IR BaGa_4Se_7 optical parametric oscillator pumped at 1064  nm

Abstract

A BaGa₄Se₇ nanosecond optical parametric oscillator (OPO) shows extremely wide idler tunability in the mid-IR (2.7-17 μm) under 1.064 μm pumping. The ∼10 ns pulses at ∼7.2 μm have an energy of 3.7 mJ at 10 Hz. The pump-to-idler conversion efficiency for this wavelength reaches 5.9% with a slope of 6.5% corresponding to a quantum conversion efficiency or pump depletion of 40%.

Widely tunable (2.6–10.4μm) BaGa4Se7optical parametric oscillator pumped by a Q-switched Nd:YLiF4laser

“…The threshold pump energy is extrapolated to be E p,th =250 μJ. This threshold is about 25× lower than that reported in the previous BGSe-OPO employing a 5× larger pump beam diameter [27]. The intensity threshold of a singly-resonant, critically phase-matched, nanosecond OPO can be expressed as [28,29],…”

“…However the tunable 3-5 μm idler wavelength did not exceed the ∼5 μm limit of oxide-based ferroelectrics and the downconversion idler pulse energy (<1.4 mJ at 20 mJ pump) was quite modest despite the sample length used (dimension 6×6×30 mm 3 ). With a similarly cut but shorter BGSe sample (dimension 10.33×11.95×14.57 mm 3 ), a 1064-nm pumped BGSe OPO was reported in [27], demonstrating a considerably improved output performance in terms of both idler MIR tunability (2.7-17 μm) and output pulse energy (∼3×). Using a wide pump beam diameter (2w=5 mm) to accommodate for the available high-energy from the Nd:YAG laser (up to E p =250 mJ for 8 ns pulse at f=10 Hz), 3.7 mJ at 7.2 μm from 63 mJ of pump pulse energy without any significant saturation in the observed 40% quantum conversion efficiency was obtained.…”

“…In this article, we report on a BaGa 4 Se 7 nanosecond OPO pumped for the first time by a Q-switched Nd:YLiF 4 (Nd:YLF) at 1053 nm, the shortest OPO pump wavelength used for this crystal. Contrary to [27], the pump laser has not only a slightly shorter wavelength but also much lower pulse energy (maximum energy 1.3 mJ). Low threshold of oscillation (E p,th =0.25 mJ) was achieved by reducing the pump beam diameter to 2w∼1 mm, thus the reported performance corresponds to the operation of the OPO far below parametric gain saturation (and damage threshold).…”

Long-wave infrared generation from femtosecond and picosecond optical parametric oscillators based on orientation-patterned gallium phosphide

“…1 as it has a very low nonlinear figure of merit, it was chosen in [36] for its thermal conductivity, high damage threshold and favourable phase matching). A newly developed material, barium gallium selenide, has been used with a nanosecond 1-µm pump laser to generate between 2.7 and 17 µm [37]. These materials, as well as others, can be used for DFG in the long-wave mid-IR, however, they are less versatile than OPGaAs and OPGaP due to the lack of suitable quasi-phasematching techniques, meaning that the maximum nonlinear coefficient cannot always be exploited.…”

Temperature-Dependent Sellmeier Equations of IR Nonlinear Optical Crystal BaGa4Se7

“…It possesses intriguing overall properties for IR NLO applications including wide transparent range (0.47 to 18 µm), suitable birefringence, large nonlinear optical coefficients, and high laser damage threshold [8][9][10][11][12]. The outstanding properties of BaGa 4 Se 7 have been exemplified by some recent laser experiments [13][14][15][16][17]. Given the outstanding NLO properties and the preliminary laser experiment results, BGSe may have attractive applications in three aspects: (1) realizing mid IR output using the conventional 1 µm laser as the pumping source; (2) the generation of IR laser in the long wavelength, especially the 8-15 µm range; (3) the second-harmonic generation the CO 2 laser.…”