A python-based software for wavelength stabilization of external cavity diode lasers*

The Middlebury College ion trapping group is building a lab to trap atomic ytterbium ions for quantum information and spectroscopy experiments. We report on the development of a software program to wavelength stabilize our lab's multiple external cavity diode lasers (ECDLs) using feedback from a commercial wavemeter. By connecting to a Fizeau wavelength meter and multiplexed fiberoptic switch (Bristol Instruments), the python-based and open-source software can monitor the wavelength of multiple lasers simultaneously relative to their respective lock points. A proportional-integral-derivative (PID) algorithm calculates a correction voltage, generates it through connection to a DAC device (LabJack), and sends it to the ECDL piezo for feedback at rates of up to 30 Hz. The software includes robust features, including independent control of up to four lasers through a graphical user interface, the ability to rapidly toggle each laser between two different lock points, and wavelength monitoring via trend plots. The software has been demonstrated on both commercial and home built ECDLs, effectively eliminating their long-term wavelength drift. This long-term stability may be accompanied by an increase in the short-term noise by to 33% compared to when the lock is off, although additional testing relative to other frequency references is still needed to verify these results.