Properties of a He-Ne laser at λ = 612 nm, stabilized by means of an external iodine absorption cell

Abstract
A He-Ne laser at λ = 612 nm, stabilized to saturated absorption features of l27I2 in an external cell (and with no cell inside the laser), shows an uncertainty of the laser frequency due to variations of power or of the external beam geometry of less than 5 kHz. Pressure, modulation, power, and pushing effects as well as linewidth and asymmetry of the peaks have been studied. Also, the frequency differences of 20 hyperfine components have been determined by using an acoustooptic modulator (AOM) that shifts the frequency of the laser radiation by ±250 MHz.