Overview

The helium-neon laser probably is the most familiar of all lasers. The least-expensive gas laser, it has long been the standard choice to demonstrate laser physics in schools, colleges, and museums. In its most familiar form, the He Ne emits a fraction of a milliwatt to tens of milliwatts (mW) of red light at 632.8 nanometers (nm). As such, it has long been the most common and most economical visible laser.

The helium-neon laser was among the first lasers demonstrated, and was the first gas laser (Javan et al., 1961). Initial versions emitted at 1153 nm in the infrared, but other researchers soon found that the same gas mixture could lase in the red (White and Rigden, 1962). Other lines were produced in the laboratory, but the strong 632.8-nm red line has long been the most important because it made up to about 50 mW available at a visible wavelength. Sales have climbed over the years, and were nearing the half-million mark in 1990 ( Lasers & Optronics, 1990).

However, important changes are in the offing. Red semiconductor lasers were developed in the late 1980s. Although they cost more than near-infrared semiconductor lasers, the prices of red semiconductor lasers are dropping, and they have become competitive with red heliumneon lasers. Semiconductor lasers have important advantages, including smaller size, higher efficiency, and no need for the high drive voltage used in gas lasers. They cannot replace all red helium-neon lasers because the gas lasers have better coherence and beam quality,...