3D model (Jmol)
Key: QNWMNMIVDYETIG-UHFFFAOYSA-N Y
960 °C (1,760 °F; 1,230 K)
2.1 eV (indirect)
Refractive index (nD)
P63/mmc, No. 194
Gallium(II) oxide, Gallium(II) sulfide, Gallium(II) telluride
Zinc(II) selenide, Germanium monoselenide, Indium monoselenide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Gallium(II) selenide (GaSe) is a chemical compound. It has a hexagonal layer structure, similar to that of GaS. It is a photoconductor, a second harmonic generation crystal in nonlinear optics, and has been used as a far-infrared conversion material at 14-31 THz and above.
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It is said to have potential for optical applications but the exploitation of this potential has been limited by the ability to readily grow single crystals  Gallium selenide crystals show great promise as a nonlinear optical material and photoconductor. Non-linear optical materials are used in the frequency conversion of laser light. Frequency conversion involves the shifting of the wavelength of a monochromatic source of light, usually laser light, to a higher or lower wavelength of light that cannot be produced from a conventional laser source.
Several methods of frequency conversion using non-linear optical materials exist. Second harmonic generation leads to doubling of the frequency of infrared carbon dioxide lasers. In optical parametric generation, the wavelength of light is doubled. Near-infrared solid-state lasers are usually used in optical parametric generations.
One original problem with using gallium selenide in