Theory behind and Experimentation on the Spectral Control of a Laser Diode with a Michelson External Cavity

Abstract

We present the theory behind and discuss experimentation on the spectral control of a laser diode with a Michelson external cavity. This structure is advantageous in terms of variable resonance mode spacing and the wavelength tuning range achieved by adjusting the path-length difference of the external cavity. This laser diode is easy to construct and uses mainly inexpensive components. In theory, we replace the end facet of the laser medium and the mirrors of the external cavity with an equivalent mirror, and therefore, resonance conditions of the laser diode with the external cavity can be analyzed. Through experiment, we investigated dependences of the bandwidth and wavelength tuning range of the laser diode on the path-length difference of the external cavity and the injection current. We achieved a 0.75 nm extension of the wavelength tuning range and a 1/6 reduction in the bandwidth.