Micro-optiques sur VCSELs par photopolymérisation auto-guidée dans le proche Infrarouge (NIR) – NIR-OPTICS

The objectives of this project consist in the design, the fabrication and the characterization of innovative integrated polymer micro-optics elements onto the surface of VCSELs devices (Vertical Cavity Surface Emitting Lasers). VCSELs (Vertical Cavity Surface-Emitting Lasers) constitute now strategic light sources for optical communications as well as for instrumentation or sensing applications. The potentialities which have already been demonstrated as well as the flexibility of these optoelectronic components have recently strongly contributed to the rise of new applications related to microsystems and in particular to biomedical instrumentation. Using VCSELs instead of standard laser diodes or gas lasers for biosensors Microsystems provides the ability to meet the requirements of most of the applications, that the sensing devices be small and have the ability of being replicated in order to obtain arrays such that multiple, simultaneous experiments can be performed in parallel and at low cost. Moroever, the optical beam emitted by a singlemode VCSEL is gaussian, symmetric and exhibits a relatively low divergence. Consequently, the use of VCSELs makes optical alignments between elements easier than with other laser diodes. However, despite a limited far-field beam divergence, these sources have more and more to be associated with micro-optical elements to enhance their optical performance, to increase the coupling efficiency to optical fibers or to meet stringent collimation requirements of many microsystem applications. To address VCSEL beam shaping problem, different processes have been developed but they all comprise a delicate alignment step. The NIR-OPTICS project is aimed at developing a new method for integrating polymer optical micro-elements (micropillars, microlenses) on VCSELs by an innovative and simple process. The idea is to use the NIR source to trigger the photopolymerization and fabricate the optical micro-element by self-guiding polymerization. Among other interests, such process is simple, fast, it gives access to a wide variety of geometries and it is compatible with post-processing. One of the main issues is to develop new NIR-photopolymers suitable for microfabrication in the NIR region. To reach this goal, the study of photophysical and photochemical properties of these resins will be carried out. Their capacities for microfabrication in a self-guiding process will be evaluated and optimized using photofabrication at the end of optical fibers. Then, the best candidates will be used to produce microlenses and micropillar on VCSELs. We will also develop tools for modelling and characterizing the optical response of the micro-optical elements. Such approach will allow reaching the optimum structural configuration for applications in focusing, collimating and spatial control of the mode. NIR-OPTICS project involves breakthrough strategies in materials and processing. It aims to break a bottleneck that hinders the VCSEL device integration potentialities in microsystems. Solving these issues will give access to controlled-beam VCSELs, reliable devices with a large flexibility for integration, novel VCSELs with tunable beams; these will meet the requirements of numerous MEMS applications, up to now held up by these limitations.