EFFECTS OF EXTERNAL REFLECTOR ALIGNMENT IN SENSING APPLICATIONS OF OPTICAL FEEDBACK IN LASER-DIODES

The alignment of the components in sensor systems based on external op tical feedback is a critical factor due to the small size of laser ape rture into which the returned light must be coupled. This paper presen ts experimental results and a theoretical explanation which show that the fringe frequency of a self-mixing interferometric sensor system ca n be doubled due to misalignment of the external reflector. The double frequency fringes are less sensitive to the alignment of the reflecto r than the normal fringes and offer a potential increase in the resolu tion of a sensing system of a factor of two.