A display apparatus includes a reflective layer with reflective material. One or more stacks of additional layers are provided on the reflective layer. Each stack has an optically switchable layer. A plurality of switching elements are located on a side of the reflective layer opposite to the one or more stacks or form part of the reflective layer. Each switching element is operable to apply heating to a switchable portion of the optically switchable layer and thereby change an appearance of the switchable portion when viewed from a viewing side of the display apparatus. The apparatus applies the heating by driving an electrical current through the switching element to generate Joule heating in the switching element. The electrical current flows in an electrical circuit including a portion of the reflective layer.

Display apparatus includes reflective layer with reflective material with stacks of additional layers thereon. Each stack has an optically switchable layer. Switching elements are on a side of the reflective layer opposite to the stacks or form part of the reflective layer. Each switching element applies heating to a switchable portion of the optically switchable layer to change appearance of the switchable portion when viewed from the viewing side of the display apparatus. The optically switchable layer includes phase change material switchable between stable states each having a different refractive index. The phase change material switches by applying heat between the stable states. Switching the optically switchable layer causes the apparatus to provide one or both of the following effects for incident radiation within a predetermined frequency range: (i) a change in reflectivity of a factor of at least 50; or (ii) a change in phase within 5% of n/2 radians, where n is an integer.

Provided is an apparatus for controlling a laser light propagation direction, including: a substrate configured to transmit at least a wavelength range of a laser light incident on the apparatus and deflected; and a metasurface disposed on the substrate, and comprising a plurality of nano-antennas, wherein each of the plurality of nano-antennas may include: a first contact and a second contact that are disposed apart from each other, and comprise an electrically conductive material to transmit at least the wavelength range of the laser light; and a semiconductor p-i-n heterostructure that disposed between the first contact and the second contact and comprises a p-region, an i-region and an n-region, which are disposed in parallel to the substrate.

A method of designing a meta optical device is provided. The method includes: setting, via a processor, design data for arrangement and dimensions of a nanostructure of the meta optical device, according to a function to be implemented by the meta optical device; obtaining a phase change graph with respect to a change in the dimensions; setting a shape dimension region with phase defect in the phase change graph; and substituting a shape dimension with phase defect, which is included in the shape dimension region with phase defect among the dimensions included in the design data, with a substitution value that is outside the shape dimension region with phase defect. Accordingly, a meta optical device having no phase defect is implemented.

A mask array apparatus includes a monolithic structure that includes a substrate layer transmissive for at least a portion of an infrared wavelength band and an array of individually addressed pixel structures. Each pixel structure is in stacked relation above or below the substrate layer, and includes at least one micro-plate heating element layer, circuitry, and at least one phase change material (PCM) element. The heating element layer is transmissive for the wavelength band, and has switchable on and off states configured to produce temperature changes. The circuitry is configured to individually address the heating element layer, separately from heating element layers in other pixel structures, to switch the heating element layer between the on and off states. The PCM is in stacked relation above or below the heating element layer and configured to change transmissive states in the wavelength band in response to the temperature changes.

An optical device may include at least one optical fiber, and a phase change material (PCM) layer on the at least one optical fiber. The PCM layer may include Ge.sub.xSe.sub.y, where x is in a range of 20-40, and y is in a range of 60-80.

A silicon on insulator (SOI) photonic device having a waveguide is provided that includes a mode overlap portion with a topology optimized structure situated below an electrode of the capacitance structure. The device can significantly change a refractive index in a volume of mode overlap depending upon the applied potential to the capacitor and allows for a ? phase shift in a modest mode overlap volume. The topology optimized structure has a waveguide and substrate that are partitioned in three dimensions using an extruded projection design. The electrode is a transition metal di-chalcogenide monolayer sheet (2D TMD). The enhanced mode overlay from the topology optimized waveguide portion allows a large reduction in the length of the waveguide with the mode overlap to achieve the needed phase shift for a photonic device.

A fast optical (with or without a photonic crystal) switch is fabricated/constructed, utilizing a phase transition material/Mott insulator, activated by either an electrical pulse (a voltage pulse or a current pulse) and/or a light pulse and/or pulses in terahertz (THz) frequency of a suitable field strength and/or hot electrons. The applications of such a fast optical switch for an on-demand optical add-drop subsystem, integrating with (a) a light slowing/light stopping component (based on metamaterials and/or nanoplasmonic structures) and (b) with or without a wavelength converter are also described.

Methods and devices are disclosed for implementing quantum information processing based on electron spins in semiconductor and transition metal compositions. The transition metal electron orbitals split under semiconductor crystal field. The electron ground states are used as qubits. The transitions between the ground states involve electron spin flip. The semiconductor and transition metal compositions may be further included in optical cavities to facilitate quantum information processing. Quantum logic operations may be performed using single color or two color coherent resonant optical excitations via an excited electron state.

Alloys of GeSbSeTe (GSST) can be used to make actively tunable infrared transmission filters that are small, fast, and solid-state. These filters can be used for hyperspectral imaging, 3D LIDAR, portable bio/chem sensing systems, thermal emission control, and tunable filters. GSST is a low-loss phase-change material that can switch from a low-index (n=3), amorphous state to a high-index (n=4.5), hexagonal state with low loss (k<0.3) over a wavelength range of 2-10 microns or more. The GSST thickness can be selected to provide pure phase modulation, pure amplitude modulation, or coupled phase and amplitude modulation. GSST can be switched thermally in an oven, optically with visible light, or electrically via Joule heating at speeds from kilohertz to Gigahertz. It operates with reversible and polarization independent transmission switching over a wide incident angle (e.g., 0-60 degrees).