A computer-based digital feedback control of frequency drift of multiple lasers

We report a method to monitor and control laser frequencies with an optical cavity and a digital feedback system. A frequency-stabilized He–Ne laser provides the reference that is transferred to several other lasers using a scanning Fabry–Pérot cavity. A personal computer-based multifunction data acquisition system generates the scan wave form, and reads the detector outputs synchronously with the cavity scan. The computer determines the positions of all of the peaks in the scan, and generates output signals to control the laser frequencies. It also provides a visual display of cavity spectra. We have successfully used the setup to achieve a long-term lock of the lasers for magneto-optical trapping of radioactive francium atoms.