Linewidth measurement of a NIR VCSEL by self-mixing interferometry using voltage detection scheme

Self-mixing based on Vertical Cavity Surface Emitting Lasers (VCSEL), offers a compact and low-cost coherent detection scheme for interferometric accessible measurements. The direct detection of the junction voltage change simplifies the setup further by adding detector-less capability. The linewidth of a NIR VCSEL was estimated by using a method based on the statistical analysis of the Laser Self-Mixing fringe period in the moderate feedback regime. We compared the traditional optical power modulation measurements with the detector-less voltage self-mixing signal. A high SNR was obtained for both signals and the measured linewidths are in good agreement within the experimental errors.