Embedded high resolution sensor based on optical feedback in a Vertical Cavity Surface Emitting Laser

This paper describes the fabrication of a novel type of pressure sensor based on optical feedback in a Vertical Cavity Surface Emitting Laser (VCSEL). The detection mechanism of the sensor is based on a displacement measurement through self-mixing interferometry in the laser cavity. Using this technique a sensing resolution of half the laser wavelength can be achieved. The use of unpackaged VCSELs allows the integration of the sensor in a flexible polymer material, which enables thin and ultimately bendable optical sensing foils. Moreover, the use of unpackaged dies limits the sensor dimensions and minimizes the distance between two sensing points. Consequently, dense matrices of highly accurate sensing points can be fabricated. A proof of principle set-up for this new sensing mechanism has been developed and a first demonstrator has been fabricated and characterized