We propose a snapshot spectral imaging method for the visible spectral range using two digital cameras placed side-by-side: a regular red-green-blue (RGB) camera and a monochromatic camera equipped with a dispersive diffractive diffuser placed at the pupil of the imaging lens. While spectral imaging was shown to be feasible using a single monochromatic camera with a pupil diffuser [Appl. Opt.55, 432 (2016)APOPAI0003-693510.1364/AO.55.000432], adding an RGB camera provides more spatial and spectral information for stable reconstruction of the spectral cube of a scene. Results of optical experiments confirm that the combined data from the two cameras relax the complexity of the underdetermined reconstruction problem and improve the reconstructed image quality obtained using compressed sensing-based algorithms.

We propose designs of pupil-domain optical diffusers for a snapshot spectral imaging system using binary-phase encoding. The suggested designs enable the creation of point-spread functions with defined optical response, having profiles that are dependent on incident wavefront wavelength. This efficient combination of dispersive and diffusive optical responses enables us to perform snapshot spectral imaging using compressed sensing algorithms while keeping a high optical throughput alongside a simple fabrication process. Experimental results are reported.

Colour RGB imaging with high throughput was achieved by a monochromatic digital camera with a dispersive diffuser at its pupil. An acquired snapshot monochromatic image was converted to colour coordinates through spectra, by resorting to digital processing with a compressed sensing-based algorithm of spectral imaging. Results of optical evaluation and calibration of an optical system and colour imaging experiments are reported.

Design of Fourier holograms of 3D objects with analytical equations on general polygonal mesh enabled to consider shading effects. Optical experiments proved feasibility for 3D aerial reconstruction from computer-generated Fourier holograms in RGB colors.

We report here on design and computer simulation of computer-generated holograms for three dimensional (3D) imaging and display. Angular spectrum of general polygon patches was calculated in closed analytical form that includes angular dependence of the intensity and linear gradient of phase at each polygon. Special attention was paid to reduction of the dynamic range in the amplitude transmittance of the hologram by proper random choices of slopes and initial phases of each polygon. Numerical computer simulation results proved that our polygon-patched design demonstrates halftones of object shades and shows expected sharp focusing of different parts of the reconstructed 3D images in their different cross-sections.

High-efficiency resonance-domain diffractive microlens arrays with high numerical apertures and 100% fill factor were designed, fabricated, and characterized. Fabricated arrays of eight off-axis microlenses with pitch 127 μm and numerical aperture 0.2 demonstrated diffraction-limited collimation of fiber light at 632.8 nm wavelength. Optical measurements revealed diffraction efficiency exceeding 93%, in match to numerical calculations with rigorous conical diffraction. The resonance-domain diffractive microlens arrays are highly suitable for applications in fiber optics, multispot optical tweezers, optical sensors, and spectrometry.

A set of diffractive optical elements for multiple-stripe structured illumination was designed, fabricated and characterized. Each of these elements with a single layer of binary surface relief combines functions of a diffractive lens, Gaussian-to-tophat beam shaper, and Dammann beam splitter. The optical investigations of laser light patterns at 20° fanout angle reveal up to 88% diffraction efficiency, high contrast, and nearly diffraction limited resolution. The developed technology has the potential for reducing complexity, number of optical components, power consumption and costs of structured light projectors in mobile and stationary 3D sensors.

Resonance domain diffractive optical elements for combining RGB laser beams into a single collimated beam were designed, fabricated, and experimentally investigated. The input RGB beams were angular separated up to tens of degrees and set in a nearly Bragg arrangement for high diffraction efficiency. A single resonance domain diffractive lens delivered beam combining and collimation functions with reasonable residue divergence. The resonance domain diffraction grating delivered diffraction-limited residue divergence in combining the collimated RGB beams. Optical experiments with fiber-coupled RGB lasers and e-beam-fabricated beam combiners proved low residue beam divergence, a high polarization extinction ratio, and total measured diffraction efficiency of about 80%.

Color RGB imaging with high throughput was achieved by a monochromatic digital camera with a dispersive diffuser at its pupil. An acquired snapshot monochromatic image was converted to color coordinates through spectra, by resorting to digital processing with a compressed sensing-based algorithm of spectral imaging. Results of optical evaluation and calibration of an optical system and color imaging experiments are reported.

We report here on applications of computer-generated holograms in fiber optical communication with mode-division multiplexing. It is shown that a pair of multichannel spatial filters matched to spatial modes provides a viable solution for transmission of several temporal signals of the same wavelength in a sole multimode fiber. Spatial filters for combining and decomposition of modes were designed, analyzed, fabricated with diffractive optics technology, and optically evaluated.

We propose a snapshot spectral imaging method that enables direct reconstruction of spatial maps for spectral signatures of given materials using a monochromatic image sensor. An image-plane array of dispersive shapers converts an aerial image of an object into a tailored mixture of spectral and spatial data that is sensed and digitally processed to reconstruct weight coefficients of the spectral signatures. The feasibility of the method is proven by computer simulations.

Spectral imaging (SI) refers to the acquisition of the three-dimensional (3D) spectral cube of spatial and spectral data of a source object at a limited number of wavelengths in a given wavelength range. Snapshot spectral imaging (SSI) refers to the instantaneous acquisition (in a single shot) of the spectral cube, a process suitable for fast changing objects. Known SSI devices exhibit large total track length (TTL), weight and production costs and relatively low optical throughput. We present a simple SSI camera based on a regular digital camera with (i) an added diffusing and dispersing phase-only static optical element at the entrance pupil (diffuser) and (ii) tailored compressed sensing (CS) methods for digital processing of the diffused and dispersed (DD) image recorded on the image sensor. The diffuser is designed to mix the spectral cube data spectrally and spatially and thus to enable convergence in its reconstruction by CS-based algorithms. In addition to performing SSI, this SSI camera is capable to perform color imaging using a monochromatic or gray-scale image sensor without color filter arrays.

Critical combination of high diffraction efficiency and large diffraction angles can be delivered by resonance-domain diffractive optics with high aspect ratio and wavelength-scale grating periods. To advance from static to electrically tunable resonance-domain diffraction grating, we resorted to its replication onto 2-5 μm thick P(VDF-TrFE-CFE) electrostrictive ter-polymer membranes. Electromechanical and optical computer simulations provided higher than 90% diffraction efficiency, a large continuous deflection range exceeding 20°, and capabilities for adiabatic spatial modulation of the grating period and slant. A prototype of the tunable resonance-domain diffraction grating was fabricated in a soft-stamp thermal nanoimprinting process, characterized, optically tested, and provided experimental feasibility proof for the tunable sub-micron-period gratings on electrostrictive polymers.

Capabilities of beam shaping with diffractive optics are substantially improved by a concept of crossed zones. We generalized the map transformation design of beam shapers by additional set of diffractive zone borders orthogonal to phase isolines. Application of nonlinear transformation to diffractive grooves profile, provided another method of building crossed-zones. Computer simulation results confirm feasibility and flexibility of the proposed approach.

Restricting trade-off between efficiency and numerical aperture of scalar diffractive optics leads to clear supremacy of resonance domain diffractive optics. We present experimental results for resonance domain diffractive lenses in imaging, beam combining and fibers.

We experimentally demonstrate a compact optical spectrometer with a resolution of up to ~0.1 nm suitable for spectral line measurements of laser diodes. This spectrometer is based on a transmission, 4-mm in diameter, and 0.14-NA off-axis binary resonance domain diffractive lens with strong lateral and longitudinal chromatic dispersion. After calibration with a mercury-argon source and a helium-neon laser, we measured the spectrum of RGB laser diodes. The results confirm the theoretical resolution and are in good match to data from optical spectrum analyzer with 0.05-nm resolution.

We propose a spectral imaging method that allows a regular digital camera to be converted into a snapshot spectral imager by equipping the camera with a dispersive diffuser and with a compressed sensing-based algorithm for digital processing. Results of optical experiments are reported.

We investigated coherent imaging with a binary off-axis resonance domain diffractive lens using three lasers in visible wavelengths. The relations between the dispersion of this lens, shape of its point spread function, and spectral properties of these lasers were analyzed theoretically and experimentally. In particular, we measured the point spread function, imaging contrast, and diffraction efficiency. Experimental results proved the feasibility of imaging with low distortion and more than 83% diffraction efficiency in laser light.

In this letter, we report on the excitation of low order Laguerre-Gaussian mode groups with a common propagation constant in a multimode gradient index optical fiber. Enabling generic space-division multiplexer was based on a key multichannel diffractive optical element. The experimental results show integrity of the excited mode groups in an OM2 multimode fiber optic patch cord.

Resonance-domain-transmission diffractive optics with grating periods comparable to those of the illumination wavelength offers large angles of light deflection and nearly 100% Bragg diffraction efficiency. Optical design preferences for nearly normal incidence can be met by proper choice for the slant of the diffraction grooves relative to the substrate. However, straightforward fabrication of the slanted submicron high-aspect-ratio grooves is challenging. In this paper, optical performance comparable to that of the slanted grooves was achieved by an alternative solution of bonding two half-height symmetrical gratings with a lateral shift and an optional small longitudinal spacing. Results of design, nanofabrication, and optical testing are presented.