# Silver gallium selenide, AgGaSe2 (AGSe)

AgGaSe2, often abbreviated as AGSe, is a ternary I-III-VI2 chalcogenide compound known for its exceptional nonlinear optical properties. It crystallizes in a monoclinic structure and has a broad transparency range that extends from the visible to the mid-infrared regions of the electromagnetic spectrum. One of the standout features of AgGaSe2 is its high nonlinear optical coefficient, which makes it especially useful in applications requiring frequency conversion, such as second-harmonic generation (SHG), sum-frequency generation (SFG), and parametric down-conversion. The compound is commonly employed in optical parametric oscillators (OPOs) and other tunable laser systems designed for mid-infrared applications. Its properties are highly anisotropic, which necessitates precise crystal orientation during device fabrication. While AGSe offers many advantages in terms of its optical characteristics, it is also sensitive to thermal and mechanical stresses, making careful handling and environmental control crucial for maintaining its performance. Overall, AgGaSe2 is a pivotal material in the field of nonlinear optics, and it continues to be the focus of extensive research aimed at better understanding its properties and potential applications.

## External links

- GaAgSe2 - Materials project
- I-III-VI semiconductors - Wikipedia