APPLICATIONS THE HeNe LASER

     Until the 1990s, was the only option for many pointing, alignment, and scanning applications. Not long ago, many supermarket bar-code scanners and even some high-end handheld scanners used HeNe lasers, as did the original (early 1980s) CD and laser disk players. Today, most applications have migrated toward more compact (and inexpensive) semiconductor laser diodes. However, in some applications where beam quality, beam collimation, and coherence length are important, HeNe lasers are still used extensively. For holography, the HeNe laser is still the laser of choice because of its good coherence length compared to other types of lasers. The same is true for many precision measurement applications that utilize interferometry to measure tiny distances. Access to the gain medium and the ability to use unique cavity configurations (e.g., a ring) allows the HeNe laser to be used as the basis for instruments such as laser gyroscopes for aircraft. Finally, the HeNe laser is indeed the de facto standard laboratory laser, with uses ranging from alignment of optics to testing of optical components.