Characterization of planar microlenses made of high contrast gratings

摘要

We report on the focusing performance of reflective 2D high contrast grating lenses based on silicon. The combination of their subwavelength nature and their high refractive index contrast make it possible to create highly tolerant and planar microlenses. We used a rigorous mathematical code to design the lenses and verified their performance with finite element simulations. We also investigated the effects of grating thickness, angle and wavelength of incidence in these simulations. Experimentally, we show the evolution of the beam profile along the optical axis for a lens with a high (0.37) numerical aperture. We have explored a wide range of numerical apertures (0.1 - 0.93) and focal lengths (5 μm -140 μm) and show that the lenses behave as expected across the full range. Our analyses demonstrate the large design flexibility with which these lenses can be made along with ease of fabrication and potential for a number of applications in micro-optics.