Excimerlaser

An excimer laser is a gas-discharge ultraviolet laser whose gain medium is an excimer, a short-lived diatomic molecule such as ArF, KrF, or XeCl. These excimers exist only in excited states; when they decay to dissociated products they emit a photon in the deep ultraviolet region. The name excimer comes from "excited dimer." The laser is powered by pulsed electrical discharge of a gas mixture, typically noble gas halides, in a sealed or flowing cavity. Output consists of short, high-energy UV pulses with very narrow spectral width, enabling precise photochemical ablation with minimal heat diffusion.

Common wavelengths include 193 nm (ArF), 248 nm (KrF), and 308 nm (XeCl). Pulse durations are typically in the tens of nanoseconds, and repetition rates range from a few to tens of hertz in many industrial systems, though higher-rate variants exist for specialized tooling.

Major uses include photolithography for semiconductor manufacturing, where the short-wavelength UV light allows fine patterning beyond visible-light limits; ophthalmic applications such as refractive surgery (LASIK and PRK) using 193 nm pulses to remove tissue with high precision; and micromachining and materials processing where clean ablation is required.

Advantages of excimer lasers include high photon energy and precise, photochemical ablation, which reduces the heat-affected zone relative to longer-wavelength lasers. Limitations include complex and costly equipment, maintenance of UV optics, and safety concerns due to UV exposure and ozone generation.

Safety and handling: require appropriate shielding, interlocks, and eye/skin protection; the UV output is hazardous to tissue and some materials.