Black-Box Identification of a Grating-Stabilized External-Cavity Diode Laser

Diode lasers have many useful properties and have found a variety of uses including CD and DVD players, barcode scanners, laser surgery, water purification, quantum-key cryptography, spectroscopic sensing, etc. Nevertheless, their intrinsic linewidth, or the precision of their emitted wavelengths, is not good enough for many cutting-edge applications such as atom interferometry or high-performance atomic clocks. Using active feedback control we can narrow the linewidth of a diode laser, not allowing the frequency of emitted light to drift away from a reference value. Nevertheless, such feedback designs are challenging because of a lack of first principles models and difficult sensor dynamics. This paper describes our diode laser system and reports our results identifying the system using black-box techniques.