CMOS-based Integrated Wavefront Sensor

Abstract

This thesis addresses the design, implementation and performance of an integrated Hartmann-Shack wavefront sensor suitable for real-time operation and compatible with a standard technology. A wavefront sensor can be used for the detection of distortions in the profile of a light beam or of an optical component.With such a sensor, one can, for instance, estimate the distortions of a human-eye lens or the distortions present in a light beam after this has propagated through a turbulent atmosphere. Moreover, the wavefront sensor can be coupled to a deformable mirror such that this combination can compensatedistortions in a laser beam. This kind of adaptive system finds more and more applications in astronomy, industry andrecently in medicine. We propose the implementation of a Hartmann wavefront sensor that uses a matrix of integrated position-sensitive detectors which are compatible with standard Complementary Metal-Oxide-Semiconductor technology (CMOS). A wavefront is sampled into a number of light spots, whose displacements are proportional to local tilts of the wavefront. The idea is to have one position-sensitive detector per sampled spot, such that direct information about the spot-centroid position is available. This scheme renders faster operation than when a conventional imager is used because it circumvents the image-processing step. The developed wavefront sensor proved to meet all the initially proposed prerequisites: it is capable of real-time operation, compact, simple and compatible with a standard technology. In terms of performance, each particular application has its own requirements and the developed sensor, which should be used with light sources in the visible spectrum, shall perform well for applications involving enough light (> 0.5-mW beams) and there where lower-order wavefront aberrations are expected (< 30 Zernike terms). The sensor can be modified in a variety of ways to attend to particular applications.