[OPTICAL REVIEW Vol. 4, No. 6 (1997) 675-682]

Accurate Stabilization of a 3 mW Single-Mode Output He-Ne Laser by Intermittent Frequency Offset Locking to an Iodine Stabilized He-Ne Laser

Takeshi YASUI,1 Tsutomu ARAKI2,* and Norihito SUZUKI3

1Department of Mechanical Engineering, University of Tokushima, Jousanjima, Tokushima, 770 Japan, 2Department of Systems and Human Science, Graduate School of Engineering Science, Osaka University, Toyonaka, 560 Japan, 3Department of Precision Engineering, Osaka Electro Communication University, Neyagawa, 572 Japan

(Received September 17, 1997; Accepted October 22, 1997)

A high-power, unmodulated frequency standard laser light with low running cost is a powerful tool for industrial measurement involving laser calibration and interferometry in length and shape. To obtain such a laser light, we developed an intermittent frequency offset locked laser (IFOL laser). This laser system, composed of an iodine stabilized He-Ne laser (I2SL) and a high-powered symmetric three-mode He-Ne laser (HP-3ML, optical output=5 mW), provides two stabilization operational modes: (1) independent mode (I-mode) and (2) slave mode (S-mode). Utilizing the frequency pulling effect, HP-3ML is stabilized at the condition of symmetric three-mode oscillation, and a 3 mW single-mode light with frequency instability of 10-12 is obtained (I-mode). When the optical frequency deviates from the allowed limit during I-mode, HP-3ML is temporarily offset-locked to I2SL (S-mode) with frequency resettability of 10-10 and frequency instability of 10-12. After completion of the drift reset in S-mode, HP-3ML is stabilized in I-mode again, and then I2SL is turned off. In a typical case of allowed drift in ±1 MHz, repetitive operation of I-mode for 10 days and S-mode for 5 min was satisfactory. Such an intermittent operation reduces the working time of I2SL dramatically, resulting in low running cost that enables long-term use in industrial measurement.

Key words : frequency stabilized He-Ne laser, frequency standard laser, iodine stabilized He-Ne laser, single-mode laser, frequency offset lock, frequency pulling, high accuracy

*araki@me.es.osaka-u.ac.jp

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