# Thallium arsenic selenide, Tl3AsSe3 (TAS)

Thallium arsenic selenide (Tl3AsSe3, often referred to as TAS) is a mixed crystal compound known for its nonlinear optical properties and high electro-optic coefficients. Its large transparency range, spanning the mid-infrared spectrum, makes it a valuable material for infrared detectors, parametric oscillators, and other optoelectronic devices. TAS is especially useful in applications that require fast response times due to its high-speed electro-optic effect. However, handling and processing TAS should be approached with caution, as both thallium and arsenic are highly toxic.