ABSTRACT
For many readers, perhaps their first sight of laser radiation was from a helium–neon lasers, the subject of Alan White and Lisa Tsufura’s chapter (Chapter 22). The helium–neon laser was first demonstrated in 1961; it was the prototype of all gas lasers, and the first laser of any kind to be operated continuous-wave (cw), first in the near-infrared (IR) at 1.15 µm and then—by White and Rigden—at the familiar red wavelength of 633 nm. Production of the helium–neon laser peaked in the 1980s at more than 750 000 units per annum, for applications from holography to printing and barcode scanning. Since then it has been displaced in many areas by semiconductor diode lasers (see Chapter 11) but still has sales exceeding 200 000 each year, more than for any type other than the diode laser.
