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We report on a cascade nanosecond CdSe optical parametric oscillator with an output energy of 0.54 mJ at 100 Hz, temperature tuning within 9245–9285 nm, and a narrow (∼6 cm−1) spectral width achieved by a volume Bragg grating acting on the first stage. The CdSe crystal is pumped intracavity by the signal wave from the PPKTP-based first stage, and both stages operate under noncritical phase-matching conditions. The simple, compact, and robust setup produced the highest overall conversion efficiency for an all-solid-state laser system based on CdSe with 1-μm pumping, and the corresponding quantum conversion efficiency exceeded 13%. [ABSTRACT FROM AUTHOR]

In this study, the Cr2+ :CdSe and Fe2+ :CdSe crystals were successfully grown by the Mo-crucible sealed Bridgman method using a vacuum single-crystal furnace with two zones developed by ourselves, and the crystal size reaches φ51 mm x 110 mm. Cr2+ :CdSe and Fe2+ :CdSe crystals demonstrate obvious absorption in the bands of 1 400 ~ 2 400 nm and 2 500 ~5 200 nm, respectively. The transmittances of Cr2+/Fe2+ doped CdSe crystals are close to the transmittance limit of CdSe crystal (~70%) in the 7 ~ 15 μm band, and the converted absorption coefficient is about 0.005 cm-1. The Cr2+/Fe2+ : CdSe crystals grown by the Mo-crucible sealed Bridgman method have the advantages of the controllable doping concentration of transition metal ions, uniform doping and high crystal quality. The Cr2+/Fe2+ : CdSe crystals could be used as both midinfrared laser crystal and far-infrared nonlinear optical crystal material. [ABSTRACT FROM AUTHOR]

CdSe crystals are one of the most potential far infrared (IR) nonlinear optical (NLO) materials due to their excellent overall performance. However, it is difficult to prepare a large-size and low absorption CdSe component, which limits laser output power. In this work, a CdSe crystal was grown using a capsuled Mo-crucible method to maintain a stoichiometric melt composition in the process of crystal growth. A high-quality CdSe crystal with the largest size to date of Φ40 × 100 mm3 along the (100) direction was successfully obtained using this method combined with a seed directional technique. The as-grown CdSe crystal demonstrated low absorption coefficients of <0.005 cm−1 at 2.05 μm and 10.6 μm, good crystallinity, and optical homogeneity. An 11 mm × 11 mm × 78 mm CdSe crystal element with = 73.5° ± 0.2°, and ϕ = 0° was fabricated to meet the requirement for type-II phase match (PM), the average idler output power of 1.8 W was obtained corresponding to a pulse energy of ∼0.36 mJ at 10.2 μm using signal-resonate optical parametric oscillator (SR-OPO) technology. Besides, the seed directional technique could provide reference for preparing other NLO crystals, and the capsuled Mo-crucible method could also be used to grow other chalcogenide crystals that have high melting points. [ABSTRACT FROM AUTHOR]

The Dy3+:PbGa2S4 crystal with low phonon energy has been used to achieve direct lasing of 4.3–4.7 μm lasers. High quality PbGa2S4 crystals are difficult to fabricate due to component volatilization. In this work, the influence of component condition on the intrinsic defects and optical absorption in the Dy3+:PbGa2S4 crystal was investigated through first-principles calculations and crystal growth experiments. We found that PbGa2S4 was prone to decompose into Ga2S3 at its growth temperature, usually resulting in PbS-rich (Ga2S3-deficient) growth conditions. The calculated results of defect formation energy indicate that the PbGa and VGa defects play a dominant role in PbGa2S4 under PbS-rich growth conditions. The Ga2S3-rich growth conditions can increase the defect formation energy and may lower the defect density. Our post-growth annealing and crystal growth experiments proved that the Ga2S3-rich conditions did improve the optical quality of the Dy3+:PbGa2S4 crystal. The structure and composition of PGS were analyzed by XRD and EDS. The XRC result showed the crystal has a high crystalline quality. The changes of bond length were studied through XPS characterization and DFT calculations. The VGa and PbGa defects result in different XPS peaks of PbGa2S4 crystals fabricated under PbS-rich and Ga2S3-rich growth conditions. [ABSTRACT FROM AUTHOR]