Selenides for nonlinear optical applications

The authors have developed several binary, ternary, and quaternary selenide crystals for nonlinear optical (NLO) applications. The authors present an overview of the crystal growth and characterization of bulk and quasi-phase matched (QPM) crystals for their applications in mid-wave infrared (MWIR) and long-wave infrared (LWIR) regions. The authors have summarized the crystal growth, fabrication, and performance of gallium selenide and ternary and quaternary selenide compounds, silver gallium selenide, thallium arsenic selenide, and silver gallium germanium selenide crystals. Large crystals are grown by Bridgman method from the melt. These crystals transmit up to 16 μm wavelength, have high value of nonlinear conversion merit (d²/n³, d is the NLO coefficient, n is the refractive index) and have the lowest absorption coefficient compared to arsenides, phosphides, and other NLO materials. In addition to bulk crystals, the authors have developed ZnSe-based QPM materials for the MWIR and LWIR regions. The authors present their recent progress in the development of optical parametric ZnSe (OPZnSe) devices. Transmission measurements for these QPM film of thickness exceeding 1 mm show low-optical loss from 1 to 12 μm wavelength region. Nonlinear frequency conversion experiments were performed, demonstrating the vast spectral range of this material. Near-infrared wavelength conversion at 0.8 μm was obtained by frequency doubling a 1.6 μm wavelength beam with these devices.