Development of Optical Crystals for High Power and Tunable Visible and Infrared Light Generation.

摘要

Lithium based chalcogenides 6LiInSe2 semiconductor has recently get much attention due to its possible application in neutron detection. It has a high resistivity and wide band gap 2.8 eV which makes it an attractive candidate for semiconductor radiation detector. Due to high reactivity of Li, stoichiometric amount of starting materials are grown as a red crystal with an absorption edge around 2.2 eV due to the intrinsic defect induced donor acceptor pair recombination. In this investigation we have introduced excess Li from stoichiometry 4% during synthesis of the 6LiInSe2 Charge materials with an intention to greenish yellow crystal by reducing the intrinsic defects. This award has extended our experimental capabilities and enabled us to consolidate past strengths to allow us to perform state-of-the-art research in the area of nonlinear optical crystals. These classes of infrared materials have high second and third order optical nonlinearities which are essential for second harmonic generation, optical parametric oscillation, optical switching, and wavelength conversion. In spite of being known and studied for a long period of time, the knowledge of the properties, figures-of-merit and ultimately their incorporation in useful devices has been hampered by compositional variations due to a combination of stoichiometry and extrinsic impurities. These characterization techniques are infrared absorption and Raman microscopy, emission spectroscopy, differential scanning calorimetry/thermogravimetric analysis, measurements of thermal diffusivity, scanning electron microscopy/energy dispersive X-ray analysis, atomic force microscopy and electrical charge carrier transport studies. We are focusing on the purification and growth of crystals belonging to the class of materials of the type Li-III-VI2 . We intend to achieve improvements through better purification and stoichiometry control during the crystal growth process.