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In this Letter, we present a new approach to processing data from a standard spectral domain optical coherence tomography (OCT) system using depth filtered digital holography (DFDH). Intensity-based OCT processing has an axial resolution of the order of a few micrometers. When the phase information is used to obtain optical path length differences, subwavelength accuracy can be achieved, but this limits the resolvable step heights to half of the wavelength of the system. Thus there is a metrology gap between phase- and intensity-based methods. Our concept addresses this metrology gap by combining DFHD with multiwavelength phase unwrapping. Additionally, the measurements are corrected for aberrations. Here, we present proof of concept measurements of a structured semiconductor sample.
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http://dx.doi.org/10.1364/OL.39.004160 | DOI Listing |
Nature
August 2025
Electrical and Computer Engineering Department, University of California Los Angeles, Los Angeles, CA, USA.
Generative models cover various application areas, including image and video synthesis, natural language processing and molecular design, among many others. As digital generative models become larger, scalable inference in a fast and energy-efficient manner becomes a challenge. Here we present optical generative models inspired by diffusion models, where a shallow and fast digital encoder first maps random noise into phase patterns that serve as optical generative seeds for a desired data distribution; a jointly trained free-space-based reconfigurable decoder all-optically processes these generative seeds to create images never seen before following the target data distribution.
View Article and Find Full Text PDFAugmented reality head-mounted displays (AR-HMDs) utilizing diffractive waveguides have attracted considerable research attention. However, addressing color non-uniformity remains a key challenge in full-color waveguide displays employing volume holographic gratings (VHGs). This paper proposes an AR full-color waveguide display system addressing color non-uniformity.
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February 2025
The liquid crystal optical phased array (LCOPA), as a key beam steering device, has gained increasing significance in the field of space laser communication. With the rapid advancement of space laser communication technology, the demand for precise synchronous control of multi-wavelength beams has significantly increased, particularly in ensuring reliable communication links through synchronized control of signal and beacon beams. The signal beam is primarily utilized for data transmission, while the beacon beam is responsible for path calibration and real-time tracking.
View Article and Find Full Text PDFWe propose and experimentally demonstrate a 16-wavelength high-power DFB laser array (HPLA) with phase compensators and 200 GHz spacing for optical I/O technologies. The grating of the proposed HPLA is fabricated using the reconstruction equivalent chirp (REC) technique to simplify the grating fabrication and enhance the precise control of the wavelength. The AR and HR films were coated on the front and rear facets of the laser to increase output power.
View Article and Find Full Text PDFThis study presents a deep learning framework for the forward and inverse design of metasurface unit structures, integrating a residual network (ResNet)-based forward predictor, a conditional variational autoencoder (CVAE)-based inverse generator, and a hierarchical hyperparameter optimization strategy. The forward model, enhanced with residual connections and dual-convolution modules, achieves over 96% prediction accuracy. The inverse model, using a CVAE architecture with a dual-convolution decoder, generates high-dimensional structural encodings from target spectra.
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