The technology provides two or more spectrometers having uniform focal lengths that facilitate comparing spectral results obtained therefrom. The spectrometers include a collimating lens that receives light rays therethrough, a grating that is optically coupled to the collimating lens, and a focus lens that is optically coupled to the grating. The focus lens includes an outer body having a first lens set, an inner body having a second lens set, and an air gap defined between the first lens set and the second lens set. The inner body is moveable relative to the outer body to adjust a size of the air gap in order to modify a focal length of the focus lens. The inner body moves relative to the outer body to change an image size in the x-dimension. A fastener is provided to fixedly secure the inner body and the outer body.

A volume Bragg grating (VBG) containing one or more controlled phase profiles holographically embedded therein that is operable over a broad wavelength range, methods for making such controlled phase profile-embedded VBGs, and applications thereof.

A method of operating a display device comprising a drive circuit is disclosed. The drive circuit comprises a plurality of single grey-level channels, each comprising an input (412, 422), an output (418, 428) and a signal processor connected between the input and output. Each signal processor comprises a digital-to-analog converter (414, 424) and an operational amplifier (416, 426) having a voltage offset. The method comprises: converting a digital signal received at the input (412, 422) into an analog voltage (410, 420) at the output (418, 428) using each respective signal processor; switching between the analog voltage (410, 420) of each single grey-level channel using a switching circuit (430); receiving and analysing the analog voltages (410, 420) in a calibration subsystem (440), and individually compensating for the voltage offset of each op-amp (416, 426) based on the received analog voltage (410, 420) for that grey-level channel using the calibration subsystem (440).

A dielectric based metasurface hologram device includes: a substrate layer provided at a lowermost portion of the dielectric based metasurface hologram device; and a dielectric layer forming a geometric metasurface on the substrate layer. The substrate layer includes a plurality of unit cells which are continuous, and the dielectric layer includes a plurality of nano-structures which are disposed with a predetermined distance therebetween. The single nano-structure is disposed on the unit cell, and a hologram image is formed when an incident light from a light source is reflected by the nano-structure so that a phase of the light is controlled.

An optical device includes one or more volume phase holographic gratings each of which includes a photosensitive layer whose optical properties are spatially modulated. The spatial modulation of optical properties are recorded in the photosensitive layer by generating an optical interference pattern using a beam of light and one or more liquid crystal master gratings. The volume phase holograms may be configured to redirect light of visible or infrared wavelengths propagating in free space or through a waveguide. Advantageously, fabricating the volume phase holographic gratings using liquid crystal master grating allows independent control of the optical function and the selectivity of the volume phase holographic grating during the fabrication process.

A method for recording a diffractive nanostructure is provided. The method includes: providing a holographic recording mixture including a monomer, an inert material, and a photoinitiator; depositing a layer of the mixture onto a substrate; exposing the mixture to a holographic recording beam to form a nanostructure of polymer regions and inert material regions within the mixture layer; and depositing a surface-conditioning optical layer on top of the nanostructure after curing of the expose mixture.

A device for producing a subwavelength hologram. The device comprises a metasurface layer attached to a substrate. The metasurface layer includes an array of plasmonic antennas that simultaneously encode both wavelength and phase information of light directed through the array to produce a hologram. The wavelength is determined by the size of the antennas, and the phase is determined by the orientation of the antennas.

A device for producing a subwavelength hologram. The device comprises a metasurface layer attached to a substrate. The metasurface layer includes an array of plasmonic antennas that simultaneously encode both wavelength and phase information of light directed through the array to produce a hologram. The wavelength is determined by the size of the antennas, and the phase is determined by the orientation of the antennas.

A light modulation element reproduces a light image in a specific color other than iridescence where white light is incident, without a layer that selectively transmits or reflects a specific wavelength band, and clearly reproduces a desired light image by reducing an influence of 0th-order diffracted light, and an information recording medium including the same. The light modulation element includes a factor element that reproduces a light image by modulating a phase of incident reproduction light, and has an uneven surface. A maximum diffraction efficiency Dmax in a wavelength band of between 380 nm and 780 nm in wavelength distribution of first-order diffracted light and of negative first-order diffracted light with respect to diffraction efficiency for the factor element has a local maximum value with a full width at half maximum FWHM of 200 nm or less in wavelength distribution with respect to diffraction efficiency having the maximum diffraction efficiency.

A metasurface structure including an array of sub-wavelength structures including a phase change material (PCM), encoded with different holographic images based on different phases of the PCM, the different phases including a first phase and a second phase. Phase transition between the first phase and the second phase occurs when the metasurface structure is thermally tuned. Each sub-wavelength structure in the array has a distinctive phase difference between the first phase and the second phase of the PCM.