Excimer laser

The excimer laser emerged from Cold War research on high-energy light sources, evolving from a Soviet laboratory curiosity into the precision tool that would give millions of people perfect vision. The technology developed through an international relay race of discoveries, each building on the last until it became the foundation of modern eye surgery and semiconductor manufacturing.

The adjacent possible required understanding of "excited dimers"—molecules that exist only in an excited state. Fritz Houtermans first proposed the concept in 1960. In 1971, Nikolai Basov and colleagues at the Lebedev Physical Institute in Moscow observed spectral line narrowing at 176 nm using liquid xenon excited by electron beams. H.A. Koehler provided better evidence of stimulated emission in 1972 using high-pressure xenon gas.

The definitive demonstration came in March 1973 when Mani Lal Bhaumik at Northrop Corporation in Los Angeles achieved clear xenon excimer laser action at 173 nm using high-pressure gas at 12 atmospheres. This was the first unambiguous proof that excimer lasers could produce coherent ultraviolet light.

The real breakthrough came in 1975 when multiple groups discovered noble gas halide excimers. Using combinations like xenon bromide (XeBr), argon fluoride (ArF at 193 nm), and krypton fluoride (KrF at 248 nm), researchers at Avco Everett, Sandia, the Naval Research Laboratory, and Los Alamos achieved much more practical lasers. These wavelengths would prove transformative: deep in the ultraviolet, precise enough to ablate tissue and etch semiconductors.

The cascade to medicine began at IBM's T.J. Watson Research Center in 1980-1983, when Rangaswamy Srinivasan, Samuel Blum, and James Wynne discovered that ultraviolet excimer lasers could precisely remove biological tissue without thermal damage. In 1983, Stephen Trokel demonstrated that the ArF excimer laser could safely reshape corneas in calf eyes. In 1989, Marguerite McDonald performed the first excimer procedure on human eyes—photorefractive keratectomy (PRK). LASIK followed in the USA in 1991.

Path dependence favored the ArF 193 nm wavelength for eye surgery. Early success with this wavelength created an installed base of approved equipment, trained surgeons, and safety data that alternatives couldn't match. The same wavelength became essential for semiconductor lithography—the patterns on modern chips are etched by ArF excimer lasers.

By 2026, excimer lasers have corrected the vision of over 40 million people worldwide through LASIK and PRK. They etch the transistors in every advanced microprocessor. The technology that began with Soviet observations of glowing xenon became one of the most consequential light sources in modern medicine and manufacturing.