An Auto-Locked Diode Laser System for Precision Metrology

We describe a diode laser system for precision metrology that relies on adaptations of a well-known design based on optical feedback from an interference filter. The laser head operates with an interchangeable base-plate, which allows for single-mode performance at distinct wavelengths of 633 nm and 780 nm. Frequency drifts are effectively suppressed by using a vacuum-sealed laser head, thereby allowing the laser frequency to be stabilized on time-scales of several hours. Using a digital auto-lock controller, we show that the laser frequency can be stabilized with respect to selected iodine and rubidium spectral lines. The controller can be programmed to use a pattern-matching algorithm or generate first- and third-derivative error signals for peak locking. Beat note characterization has demonstrated a short-term linewidth of similar to 2 MHz and an Allan deviation of 3.5 x 10(-9) for a measurement time tau = 500 s. The laser characteristics have also enabled high-precision gravity measurements with accuracies of a few parts-per-billion (ppb).