Focusing integrated mirrors realized by silver ion-exchange: application to laser Doppler velocimeter with ultrahigh spatial resolution
Résumé
Integrated reflecting mirrors based on total internal reflection are first proposed in this paper. They are design to be fabricated by ion-exchange process on a glass substrate. Theoretical modelling of parabolic and elliptic mirrors is presented. Surface and buried elliptic mirrors are fabricated at the same time as the rest of the guiding structure by a silver ion-exchange followed by a field assisted potassium exchange in the second case. Light coming out of a singlemode waveguide is focused outside the integrated component at distances of 500 μm. Light beam width of 13 μm at 1/e2 of the maximum intensity were measured. Second, those mirrors are used to design an integrated laser Doppler velocimeter with ultra-high spatial resolution. Interference pattern of 22 x 33 x 10 μm3 with fringe spacing of 0.8 μm was produced at the focal point of the integrated mirrors in air. The fringe visibility measured in the center of the measuring volume is 1.