Alignment-free He–Ne laser with folded cavity

To solve out of operation induced by the disarrangement of cavity mirrors in half intra-cavity He–Ne lasers, a new structure of alignment-free He–Ne laser with folded cavity is invented. A corner cube prism (CCP) is used to structure a folded cavity. This novel laser can work conveniently without any adjustment. Both intensity curves of solid and hollow CCPs are studied, which indicate that it is a finely robust and stabile, and has a large changeable range (approximately, 60 mm) of cavity length. Bright prospect in applications improving the nanometer laser ruler invented by our group before is also shown.