Abstract

We have developed a new single-laser/rf sideband technique to provide accurate frequency guiding of a tunable cw dye laser. A high efficiency, broadband electrooptic modulator produces rf sidebands on a portion of the laser output. One filtered sideband is presented and locked to the resonance of a stable optical reference cavity using the output error signal to servo control the laser frequency. Thus computer-programmed changes of the rf source frequency are directly transferred onto the laser’s carrier frequency. Drifts in the cavity are measured (and corrected) when scanning the laser over an atomic resonance by periodically relocating the center of the atomic line relative to the cavity. Computer-feedforward tuning of the laser and on/off switching of the servo locks allow frequency jumping to another resonance, perhaps many reference cavity orders away. (The FSR itself can be measured very accurately with rf sideband techniques.) We measured isotope shifts and hyperfine splittings in the Hg (6³P₂–7³S₁) transition at 546.2 nm. These frequency intervals (from 850 MHz to 32 GHz) were measured with 2 × 10⁻³ linewidth accuracy, e.g., ~50 kHz for adjacent isotopes.

© 1985 Optical Society of America