DD-Net: spectral imaging from a monochromatic dispersed and diffused snapshot.

We propose a snapshot spectral imaging method for the visible spectral range using a single monochromatic camera equipped with a two-dimensional (2D) binary-encoded phase diffuser placed at the pupil of the imaging lens and by resorting to deep learning (DL) algorithms for signal reconstruction. While spectral imaging was shown to be feasible using two cameras equipped with a single, one-dimensional (1D) binary diffuser and compressed sensing (CS) algorithms [Appl. Opt.59, 7853 (2020).APOPAI0003-693510.1364/AO.395541], the suggested diffuser design expands the optical response and creates optical spatial and spectral encoding along both dimensions of the image sensor. To recover the spatial and spectral information from the dispersed and diffused (DD) monochromatic snapshot, we developed novel DL algorithms, dubbed DD-Nets, which are tailored to the unique response of the optical system, which includes either a 1D or a 2D diffuser. High-quality reconstructions of the spectral cube in simulation and lab experiments are presented for system configurations consisting of a single monochromatic camera with either a 1D or a 2D diffuser. We demonstrate that the suggested system configuration with the 2D diffuser outperforms system configurations with a 1D diffuser that utilize either DL-based or CS-based algorithms for the reconstruction of the spectral cube.

Design of binary-phase diffusers for a compressed sensing snapshot spectral imaging system with two cameras.

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.

Dual-camera snapshot spectral imaging with a pupil-domain optical diffuser and compressed sensing algorithms.

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.

Mapping of spectral signatures with snapshot spectral imaging.

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.

Compressed sensing snapshot spectral imaging by a regular digital camera with an added optical diffuser.

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.

Design and experimental investigation of highly efficient resonance-domain diffraction gratings in the visible spectral region.

Surface-relief resonance-domain diffraction gratings with deep and dense grooves provide considerable changes in light propagation direction, wavefront curvature, and nearly 100% Bragg diffraction efficiency usually attributed only to volume optical holograms. In this paper, we present design, computer simulation, fabrication, and experimental results of binary resonance-domain diffraction gratings in the visible spectral region. Performance of imperfectly fabricated diffraction groove profiles was optimized by controlling the DC and the depth of the grooves. Indeed, more than 97% absolute Bragg diffraction efficiency was measured at the 635 nm wavelength with binary gratings having periods of 520 nm and groove depths of about 1000 nm, fabricated by direct electron-beam lithography and reactive ion etching.

Microbattery technologies for miniaturized implantable medical devices.

Implanted medical devices (IMDs), in particular neuro-stimulators, drug delivery chips and cochlear implants are undergoing miniaturization. Some of these miniaturized IMDs are "active" in the sense that they require a power source for operation. In most cases, the ideal power source needs to be an implanted battery of dimensions similar to that of the device. The state-of-the-art of battery miniaturization is reviewed with emphasis on novel Li and Li-ion two- and three-dimensional thin-film microbatteries. It is shown that three-dimensional thin-film batteries may provide a solution to the power requirements of miniaturized IMDs.

Spectral multiplexing method for digital snapshot spectral imaging.

We propose a spectral imaging method for piecewise "macropixel" objects, which allows a regular digital camera to be converted into a digital snapshot spectral imager by equipping the camera with only a disperser and a demultiplexing algorithm. The method exploits a "multiplexed spectrum" intensity pattern, i.e., the superposition of spectra from adjacent different image points, formed on the image sensor of the digital camera. The spatial image resolution is restricted to a macropixel level in order to acquire both spectral and spatial data (i.e., an entire spectral cube) in a single snapshot. Results of laboratory experiments with a special macropixel object image, composed of small, spatially uniform squares, provide to our knowledge a first verification of the proposed spectral imaging method.

All-optical nano modulator on a silicon chip.

We present an all-optical modulator realized on a silicon chip. The proposed modulator has nano scale dimensions and a high extinction ratio. Its operation principle is based on a spatially non-uniform variation of the absorption of a miniaturized, silicon waveguide - based Mach-Zehnder interferometer (MZI). The absorption variation is obtained by illuminating the MZI with visible light. Our modulator may be used as an interfacing link between microelectronic processing circuits and optical information transmission links. We provide details on the fabrication and the experimental characterization of the suggested device. Since the operation principle is not based on a high Finesse resonator, the modulator is less sensitive to wavelength changes and its operation rate is not connected to the time required for the optical response to reach steady state but rather to material related effects.

Nano photonic and ultra fast all-optical processing modules.

In this paper we present an all-optical approach allowing the realization of logic gates and other building blocks of a processing unit. The modules have dimensions of only few microns, operation rate of tens of Tera Hertz, low power consumption and high energetic efficiency. The operation principle is based upon construction of unconventional wave guiding nano-photonic structures which do not include non-linear materials or interactions. The devices developed and presented in this paper include logic diffractive phase detector, generalized diffractive phase detector, logic gates as AND, OR and NOT, amplitude modulator and analog adder/subtractor.