Stabilization and calibration of an ECDL system with a Michelson interferometer

The experimental setup developed to stabilize a red diode laser using a mode-locking technique with a reference gas cell is presented. This system has an external cavity diode laser (ECDL) in a Littrow configuration and is used to calibrate gauge blocks. The electronic controller limits the bandwidth of the laser and does not allow the setup to establish the wavelength of the tuned iodine transition, which is needed to calculate the gauge block values. To solve this limitation, we have set up a laser wavemeter based on a two-beam scanning Michelson interferometer. The unknown wavelength is determined from the ratio of the number of fringes obtained by the He-Ne reference laser and our ECDL. This technique measures the laser wavelength with an accuracy of 1ppm. As the resolution of the system is influenced by the optical path length, the stability of the reference laser and the phase ratio of both lasers, an electronic Vernier counter is used to improve the accuracy of these values below 1ppm. The uncertainty evaluation is also presented.