Iodine-stabilized diode laser at 633 nm: effects of optical feedback

The frequency of a diode laser has been stabilized to the hyperfine spectrum of molecular iodine at 633 mm. A frequency stability and a (day-to-day) reproducibility of 4×10^-12 and 5×10^-11, respectively, were obtained. In particular, we have investigated the effect of optical feedback on the locking point frequency of the stabilized diode laser. Optical feedback can cause amplitude variations and harmonic distortion of the frequency modulation of the diode laser and, subsequently, cause a significant shift of the locking point of the laser. The optical feedback is shown to have undesired effects even at very small (7×10^-10) levels