Search

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]

3–5, 8–14 μm mid-far infrared (MF-IR) coherent lights generated by nonlinear optical (NLO) crystals are crucial for many industrial and military applications. AgGaGe5Se12 (AGGSe) is a promising NLO candidate because of its good optical performance. In this paper, the large AGGSe single crystal of 35 mm diameter and 80 mm length was obtained by the seed-aided Bridgman method. The crystalline quality was characterized with X-ray diffraction, rocking curve, transmission spectrum. The FWHM of the (210) peak was about 0.05° and the IR transmission was about 60% (1–10 μm, 6 mm thick). Additionally, it performed well in 8 μm frequency doubling, with a maximum output power of about 41 mW, corresponding to an optical-to-optical conversion efficiency of 3.2%. The laser induced damage threshold (LIDT) value was about 200 MW/cm2 (1.06 μm, 20 ns, 1 Hz). [ABSTRACT FROM AUTHOR]