Red light diode lasers

Diode lasers that operate from the near ultraviolet to well into the infra-red region are common place and used, among others, in optical fibre communication, optical memories and compact-disc players. Until a few years ago, the only lasers producing visible light were He-Ne lasers. Some of lhe He-Ne lasers emit a deep red light at a wavelength of 632.8 nm, that is in the visible light region, while others operate at 1.15 µm or 3.39 µm. In spite of the fact that they are (relatively) large, require apower source of kilovolts, cannot be modulated and are highly sensitive to mechanical phenomena, these gas lasers have become very popular because they are inexpensive and easy to manage.