Frequency-locked He-Ne laser system: stability measurements

An iodine-stabilized He-Ne laser and a short external-mirror laser operating in single-longitudinal-mode were used to form a master-slave laser system at 633 run wavelength. As compared to the beam from the master laser the beam of the slave laser is frequency-modulation-free and has a higher power. Also, the slave laser oscillation frequency is offset-locked in iodine-stabilized He-Ne laser by using a fast phase-lock loop (PLL) circuit. The fluctuations of the frequency offset between the master and the slave lasers were less than 5 parts in 10(13) with a 100 s gate time (the relative standard Allan variance was determined measuring the beat frequency between the master laser and the slave laser for different gate times while the iodine-stabilized laser was locked to different lines from the group d, e, f, g). The system proved a fast response and allows for a frequency offset of up to 300 MHz.