We propose a new configuration for a high-resolution heterodyne interferometer that employs a two-longitudinal-mode He-Ne laser with an intermode beat frequency of 600–1000 MHz. The high beat frequency is downconverted to 5 MHz such that the phase change of the interferometer output is precisely measured with a displacement resolution of 0.1 nm. A thermal control scheme is adopted to stabilize the cavity length of the He-Ne plasma tube such that a frequency stability of 2 parts in 10<sup>9</sup> is obtained by suppression of frequency drifts caused by the phenomena of frequency pulling and polarization anisotropy. This two-longitudinal-mode He-Ne laser yields a high output power of 2.0 mW, which permits multiple measurements of as many as 10 machine axes simultaneously.
© 2002 Optical Society of America
(040.2840) Detectors : Heterodyne
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.3940) Instrumentation, measurement, and metrology : Metrology
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(140.3460) Lasers and laser optics : Lasers
Min-Seok Kim and Seung-Woo Kim, "Two-Longitudinal-Mode He-Ne Laser for Heterodyne Interferometers to Measure Displacement," Appl. Opt. 41, 5938-5942 (2002)