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Polarisation Control in Arrays of Microlenses and Gratings: Performance in Visible-IR Spectral Ranges.

Haoran MuDaniel SmithTomas KatkusDarius GaileviciusMangirdas MalinauskasYoshiaki NishijimaPaul R StoddartDong RuanMeguya RyuJunko MorikawaTaras VasilievValeri LozovskiDaniel MoraruSoon Hock NgSaulius Juodkazis
Published in: Micromachines (2023)
Microlens arrays (MLAs) which are increasingly popular micro-optical elements in compact integrated optical systems were fabricated using a femtosecond direct laser write (fs-DLW) technique in the low-shrinkage SZ2080 TM photoresist. High-fidelity definition of 3D surfaces on IR transparent CaF 2 substrates allowed to achieve ∼50% transmittance in the chemical fingerprinting spectral region 2-5 μm wavelengths since MLAs were only ∼10 μm high corresponding to the numerical aperture of 0.3 (the lens height is comparable with the IR wavelength). To combine diffractive and refractive capabilities in miniaturised optical setup, a graphene oxide (GO) grating acting as a linear polariser was also fabricated by fs-DLW by ablation of a 1 μm-thick GO thin film. Such an ultra-thin GO polariser can be integrated with the fabricated MLA to add dispersion control at the focal plane. Pairs of MLAs and GO polarisers were characterised throughout the visible-IR spectral window and numerical modelling was used to simulate their performance. A good match between the experimental results of MLA focusing and simulations was achieved.
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