Diffractive optical elements (DOE) show great promise for imaging optics that are thinner and more lightweight than conventional refractive lenses while preserving their light efficiency. Unfortunately, severe spectral dispersion currently limits the use of DOEs in consumer-level lens design. In this article, we jointly design lightweight diffractive-refractive optics and post-processing algorithms to enable imaging under white light illumination. Using the Fresnel lens as a general platform, we show three phase-plate designs, including a super-thin stacked plate design, a diffractive-refractive-hybrid lens, and a phase coded-aperture lens. Combined with cross-channel deconvolution algorithm, both spherical and chromatic aberrations are corrected. Experimental results indicate that using our computational imaging approach, diffractive-refractive optics is an alternative candidate to build light efficient and thin optics for white light imaging.
International audienceThis paper describes the possibility to achieve a TE-TM mode conversion in a magneto-optical hybrid waveguide operating at k¼1550 nm. This hybrid device is made by coating a SiO2/ZrO2 layer doped with magnetic nanoparticles on an ion-exchanged glass waveguide. Soft annealing (90 C) and UV treatment, both compatible with the ion exchange process, have been implemented to finalize the magneto-optical film. Optical characterizations that have been carried out demonstrated the efficiency of these hybrid structures in terms of lateral confinement and mode conversion. Indeed, TE to TM mode conversion has been observed when a longitudinal magnetic field is applied to the device. The amount of this conversion is discussed taking into account the distribution of light between the layer and the guide, and the modal birefringence of the structure
Ground-based high contrast imaging (HCI) and extreme adaptive optics (AO) technologies have advanced to the point of enabling direct detections of gas-giant exoplanets orbiting beyond the snow lines around nearby young star systems. However, leftover wavefront errors using current HCI and AO technologies, realized as "speckles" in the coronagraphic science image, still limit HCI instrument sensitivities to detecting and characterizing lowermass, closer-in, and/or older/colder exoplanetary systems. Improving the performance of AO wavefront sensors (WFSs) and control techniques is critical to improving such HCI instrument sensitivity. Here we present three different ongoing wavefront sensing and control project developments on the Santa cruz Extreme AO Laboratory (SEAL) testbed: (1) "multi-WFS single congugate AO (SCAO)" using the Fast Atmospheric Self-coherent camera (SCC) Technique (FAST) and a Shack Hartmann WFS, (2) pupil chopping for focal plane wavefront sensing, first with an external amplitude modulator and then with the DM as a phase-only modulator, and (3) a laboratory demonstration of enhanced linearity with the non-modulated bright Pyramid WFS (PWFS) compared to the regular PWFS. All three topics share a common theme of multi-WFS SCAO and/or second stage AO, presenting opportunities and applications to further investigate these techniques in the future.
Reactive-ion etching (RIE) based lithography has been the prevailing technology for the fabrication of diffractive optical elements (DOEs). However, the inherent physical effects, such as RIE lag and aspect ratio dependent etching, make it challenging to produce spatially-varying features with uniform depths in large areas. In this work, we propose an additive lithographic fabrication process for a reflective Tilt-Gaussian-Vortex (TGV) mask for focal plane wavefront sensing. The unique design of the TGV mask requires simultaneous presence of feature sizes ranging from micrometers to millimeters with low surface roughness. The proposed additive fabrication eliminates the error-prone RIE step after lithography, but instead, a sputter deposition and bi-layer liftoff step is fine-tuned to form the microstructures. Compared to removing materials from the substrate in RIE, our method grows materials up onto the substrate. The combination of sputter deposition and liftoff is uniform across the whole wafer area, resulting in high surface quality and depth accuracy. We demonstrate the effectiveness of the fabrication method by a reflective TGV mask with aluminum deposition on a fused silica substrate. The central Gaussian pattern has a diameter of 130 µm with minimum spacing of 2 µm, and the background vortex pattern is 3 mm × 3 mm, with the largest flat region spanning 1.5 mm. A preliminary 4-level prototype has been tested in the Gemini Planet Imaging calibration unit upgrading project, and an improved 16-level sample has been measured. The results show uniform depth and surface roughness control for both the Gaussian and Vortex patterns.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.