Abstract: Described is a method of controlling the absorption of light in a cavity, a system in which absorption is so controlled, and an interferometer embodying the underlying physical concept. Materials can be made to completely absorb incident light when the light is imposed in a specific pattern of illumination. Coherent perfect absorption, as the process is referred to, is achieved when a cavity is illuminated coherently and monochromatically by the time-reverse of the output of a lasing mode. Varying the parameters of the incident light and/or of the cavity allows the absorption of the incident light by the cavity to be controlled; enhanced or even reduced.

Abstract: An all-photonic method to cause a WGM resonator to self-tune to a given wavelength is described. Such all photonic approaches include simply superimposing intense light of a wavelength in a range different from that of a signal wave. The wavelength of the pass band for the signal wavelength can be tuned by adjusting the wavelength (and/or the intensity) of the intense light.

Abstract: A system, e.g. an optical modulator, includes an optical waveguide and a plurality of optical resonators. The optical waveguide is located along a surface of a planar substrate. The plurality of optical resonators is also located along the surface and coupled to the optical waveguide. Each of said optical resonators is configured to resonantly couple to the optical waveguide at a different optical frequency.

Abstract: Some embodiments provided herein relate to filters for electromagnetic radiation. Some embodiments provided herein relate to phototunable compounds for which at least one optical characteristic can be changed. Some embodiments herein relate to methods of manipulating a wavelength of electromagnetic radiation.

Abstract: Variable transmittance optical filters capable of transitioning from a light state to a dark state on exposure to UV radiation and from a dark state to a light state with application of an electric voltage are provided. The optical filters comprise a switching material that comprises one or more chromophores that have electrochromic and photochromic properties.

Abstract: A spatial light modulator may include a refraction layer including first and second regions with refractive indices different from each other; and/or a metal thin film on a lower face of the refraction layer configured to generate surface plasmons due to light incident on the metal thin film via the refraction layer. When first light is incident on the refraction layer, a phase difference between light reflected by the first and second regions may occur. A spatial light modulator may include a metal thin film and a refraction layer on the metal thin film. The refraction layer may include a first region with a first refractive index and a second region with a second refractive index different from the first refractive index. When first light is incident on the refraction layer, there may be a phase difference between light reflected from the first and second regions.

Abstract: A holographic display device comprises an OLED array writing onto an OASLM, the OLED array and OASLM forming adjacent layers. The OASLM encodes a hologram and a holographic reconstruction is then generated by the device when an array of read beams illuminates the OASLM. The OASLM is suitably controlled by the OLED array. An advantage of the device is that it lends itself to compactness.

Abstract: A printed dynamic optical illusion printed on a printing device using a plurality of colorants, wherein one or more of the colorants are appearance mutable colorants having spectral characteristics that can be controllably switched between a first colorant state and a second colorant state by application of an appropriate external stimulus, and wherein one or more mutable portions of the optical illusion image are printed using at least one appearance mutable colorant. The mutable portions are controllable such that when they are in a first appearance state the printed optical illusion image has a first illusion state, and when they are in a second appearance state the printed optical illusion image has a second illusion state, thereby changing the optical illusion image from the first illusion state to the second illusion state so as to affect the perception of an optical illusion by a human observer.

Abstract: A system for controlling a printed dynamic optical illusion image, comprising: an item including a printed optical illusion image having one or more mutable portions that can be controllably switched between first and second appearance states by application of an appropriate external stimulus; a stimulus source for providing the external stimulus; and a controller for controlling the stimulus source. The printed optical illusion image is printed on a printing device using a plurality of colorants, one or more of the colorants being appearance mutable colorants having spectral characteristics that can be controllably switched between a first colorant state and a second colorant state by applying the appropriate external stimulus, the one or more mutable portions of the optical illusion image being printed using at least one appearance mutable colorant.

Abstract: A non-linear optical device comprising a non-linear element made of a plasmonic material with a periodic structure having a period smaller than the wavelength of a non-linear process intrinsic to the plasmonic material. The plasmonic material is implemented as a gold film which is structured with a periodic array of asymmetric split ring slits. The metamaterial framework of the plasmonic material itself is used as the source of a strong and fast non-linearity. The cubic non-linear response is resonantly enhanced through the effect of the metamaterial structuring by more than two orders of magnitude and its sign and magnitude can be controlled by varying the metamaterial pattern.

Abstract: A device (100) is described for actively or passively modulating incident radiation, the device comprising at least one diffraction means (10) adapted for evanescent wave excitation upon irradiation with the incident radiation, and an absorption layer (40) adjacent the at least one diffraction means (10) so that the evanescent waves can interact with the absorption layer (40). The absorption layer (40) has alterable absorption properties so as to alter the absorption of the evanescent waves resulting in modulating of the incident radiation. The device (100) may be for actively modulating incident radiation thus being e.g. a modulator for laser radiation. Alternatively, the device may be for passively modulating incident radiation, thus acting as a sensing device for sensing environmental parameters.

Abstract: Described herein are optical devices comprising a photorefractive layer and at least two inert layers, such that the photorefractive layer is sandwiched between the two inert layers. The photorefractive layer may include a photorefractive composition that is photorefractive upon irradiation by a laser beam. In some embodiments, the photorefractive composition is formulated such that a grating that is irradiated into the photorefractive composition can be read out of the photorefractive composition without applying an external bias voltage. Furthermore, a grating that is written into the composition may be controlled using thermal treatment.

Abstract: A control system and apparatus for use with an ultra-fast laser is provided. In another aspect of the present invention, the apparatus includes a laser, pulse shaper, detection device and control system. A multiphoton intrapulse interference method is used to characterize the spectral phase of laser pulses and to compensate any distortions in an additional aspect of the present invention. In another aspect of the present invention, a system employs multiphoton intrapulse interference phase scan. Furthermore, another aspect of the present invention locates a pulse shaper and/or MIIPS unit between a laser oscillator and an output of a laser amplifier.

Abstract: A method of generating a photoluminescence map for an indium gallium nitride (InGaN) well can include presenting data on a pixel by pixel basis. The data can be generated as a function of emission wavelength, line width of emission, polarization of emission, and intensity of emission. The data can also be generated as a function of excitation polarization and polarization angle orientation with respect to film crystalline axes of the InGaN well. The data can also be generated as a function of multiple wavelengths of light to generate the photoluminescence map. The photoluminescence maps can be correlated to device internal quantum efficiency as measured in test devices. The resulting correlation maps can serve as line monitors of indium rich InGaN wafers used for green LEDs.

Abstract: A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and a spectrometer. Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal. In yet another aspect of the present invention, a multiphoton intrapulse interference phase scan system and method characterize the spectral phase of femtosecond laser pulses. Fiber optic communication systems, photodynamic therapy and pulse characterization tests use the laser system with additional aspects of the present invention.

Abstract: An optical deflection apparatus includes a signal light source configured to emit signal light having one or more wavelengths, a control light source configured to emit control light having a wavelength different from the wavelength of the signal light, a thermal lens forming optical element including a light absorption layer configured to transmit the signal light and selectively absorb the control light, and a beam-condensing unit configured to cause beam-condensation of the control light and the signal light at different convergence points in the light absorption layer.

Abstract: Window tinting systems provides a vehicle window tint control within the interior of a vehicle permitting a driver and/or passenger to adjust the level of tint of the vehicle window. The system may generally comprise an integrally wired photochromic component, a wiring assembly, a driver's control panel, and at least one passenger's controller. A specialty film may be coupled to the vehicle window and may serve to control the amount of sun light penetrating the vehicle window. The driver's control panel and passenger's control panel may adjustably control the tint level of the vehicle window.

Abstract: Disclosed are an optical image modulator, an optical apparatus including the same, and methods of manufacturing and operating the optical image modulator. The optical image modulator includes a light amount increasing unit increasing the amount of forward light emission of an electric-optical unit. The light amount increasing unit includes a first reflector reflecting light, which travels from the inside of the electric-optical unit toward the optical-electric unit, to the electric-optical unit. The light amount increasing unit may further include a second light reflector reflecting light, which passes through the optical-electric unit without optical-electric conversion, to the optical-electric unit.

Abstract: Described is a method of controlling the absorption of light in a cavity, a system in which absorption is so controlled, and an interferometer embodying the underlying physical concept. Materials can be made to completely absorb incident light when the light is imposed in a specific pattern of illumination. Coherent perfect absorption, as the process is referred to, is achieved when a cavity is illuminated coherently and monochromatically by the time-reverse of the output of a lasing mode. Varying the parameters of the incident light and/or of the cavity allows the absorption of the incident light by the cavity to be controlled; enhanced or even reduced.

Abstract: In the production of optical devices or the like utilizing an intersubband transition of a coupled quantum well, a quantum well structure having strong coupling is provided. In addition, a coupled well structure of excellent productivity capable of avoiding thinning of coupling barrier layer for strengthening the coupling is provided. In the semiconductor coupled well structure of the present invention, a coupled quantum well structure disposed on the semiconductor single crystal substrate includes a coupling barrier layer 1a disposed between two or more quantum well layers 2a and 2b, wherein the coupling barrier layer 1a has an energy barrier that is smaller than an excitation level (E4 and E3) and is larger than a ground level (E2 and E1).

Abstract: Plasmons on a waveguide may deliver energy to photocatalyze a reaction. The waveguide or other energy carrier may be configured to carry electromagnetic energy and generate plasmon energy at one or more locations proximate to the waveguide, where the plasmon energy may react chemically with a medium or interaction material.

Abstract: A holographic display device comprises a first OLED array writing onto a first OASLM, the first OLED array and the first OASLM forming adjacent layers, and a second OLED array writing onto a second OASLM, the second OLED array and the second OASLM forming adjacent layers. The first and the second OASLMs encode a hologram and a holographic reconstruction is generated by the device when an array of read beams illuminates the first and second OASLMs and the first and second OASLMs are suitably controlled by the first and second OLED arrays. Advantages include that this device permits independent control of phase and amplitude, and the device lends itself to compactness.

Abstract: A MEMS-based display device is described, wherein an array of interferometric modulators are configured to reflect light through a transparent substrate. The transparent substrate is sealed to a backplate and the backplate may contain electronic circuitry fabricated on the backplane. The electronic circuitry is placed in electrical communication with the array of interferometric modulators and is configured to control the state of the array of interferometric modulators.

Abstract: The present invention contemplates a variety of methods and techniques for fabricating a carbon nanotube (CNT) signal modulator for reducing, eliminating, or enhancing the resonance interaction between photonic elements, and a photonic transmission device that may incorporate the signal modulator. The CNT signal modulator comprises a gate CNT on a substrate in a position for receiving an input photonic signal and an input modulation signal; and transmitting an output photonic signal that is reduced, eliminated, or enhanced through the selection of the input modulation signal; and an input modulation signal sender for sending the input modulation signal to the gate CNT and creating the modulated output photonic signal from the gate CNT. The photonic transmission device can contain a plurality of CNTs, each having functional antenna forms that are capable of a resonance interaction of photons between adjacent CNTs when formed as an array on a substrate.

Abstract: Provided is a wavelength converter having a simple and low-cost structure. The wavelength converter generates converted light having a wavelength different from that of input light. The wavelength converter includes (1) a pump light source that outputs pump light, (2) an optical multiplexer that combines and outputs input light and the pump light, (3) a first optical fiber that receives and guides the input light and the pump light that have been combined and output by the optical multiplexer and generates converted light using a nonlinear optical phenomenon that occurs while the first optical fiber guides the input light and the pump light, the first optical fiber being coiled, and (4) zero-dispersion wavelength adjusting means that adjusts a zero-dispersion wavelength of the first optical fiber.

Abstract: An optically addressed, photoconductive spatial light modulator (SLM) operates in a transmissive mode and is capable of modulating a wide spectrum of visible light. There is no pixel structure or native pixel resolution in the SLM. The SLM has no photodiodes and does not rectify. A light projection system (100) in which one or more SLMs (128, 130, 132) are placed includes a write (image definition) UV light path (102) and a read (illumination) visible light path (104) to form a color image projection display. The write UV light propagates from an image display pattern source (120) and either sequentially or continuously writes image patterns on the photoconductive SLMs. The read visible light propagates through the SLM and is modulated by an electro-optical material, the optical properties of which change in response to the image structure carried by the write light. The result is a high efficiency display system that delivers high resolution color images through a projection lens (190) onto a display screen.

Abstract: An optical device which can operate as a single photon emitter 1, comprising a three dimensional optical cavity 7 which spatially confines a photon to the order of the photon wavelength in all three dimensions. The cavity 7 is configured to define preferred emission direction for photons entering the cavity. A photon can be supplied to the cavity using a quantum dot 5. Strong coupling can occur between the cavity 7 and the quantum dot 5 which causes the formation of two hybridised modes. Switching on an off the coupling by irradiating the device with radiation having an energy equal to that of one of the hybridised modes allows the device to act as an optical switch.

Abstract: A MEMS-based display device is described, wherein an array of interferometric modulators are configured to reflect light through a transparent substrate. The transparent substrate is sealed to a backplate and the backplate may contain electronic circuitry fabricated on the backplane. The electronic circuitry is placed in electrical communication with the array of interferometric modulators and is configured to control the state of the array of interferometric modulators.

Abstract: An optical signal low energy method for coupling electrical signals on-chip between component circuits of for example a CMOS circuit array. The described coupling method employs infrared signals communicated along a nano-scale resonant semiconductor waveguide between for example PIN diode signal transducers. The coupling may employ an electrically pumped laser, an electro absorption modulator and a photodetector all for typically the 1.5 to 2.0 micrometer spectral region with each formed using for example PIN heterodiode semiconductor devices. Each of these three devices includes active semiconductor crystal material situated in a resonator within a strip waveguide. The resonator is defined by two fabricated mirrors having a tapered location one dimensional photonic crystal lattice of oxide hole or slot apertures.

Abstract: An optical logic device has a first mirror confronting a second mirror, and a saturable absorber located between the mirrors. Radiation that is output from the device is output via the first mirror. The reflectivity of the first mirror is such that, in use, for incident radiation which has an intensity that is above a given value, the intensity of exiting radiation is below a threshold. For incident radiation that is below the given value, the intensity of exiting radiation is above the threshold.

Abstract: The invention relates to an integrated film which includes a plasmonic layer including a pattern configured to support plasmon waves. The plasmonic layer is configured to receive as input light energy of an incident light including at least one photon having a first wavelength and an at least one photon of light received from one or more layers in optical communication with the plasmonic layer and to re-emit as output a guided light to the one or more layers in optical communication with the plasmonic layer. The integrated film also includes a wavelength conversion layer optically coupled to the plasmonic layer. The wavelength conversion layer is configured to receive as input the at least one photon having a first wavelength and to provide as output at least one photon having a second wavelength different than the first wave length.

Abstract: A dynamically variable lens is made from actively tunable electromagnetic metamaterial cells. The lens operates on electromagnetic radiation including: radio frequency waves, microwaves, teraherz waves, near infrared waves, infrared waves and visible waves. The focal length of the lens is changed at a selected frequency. In the alternative, the frequency of radiation operated on is changed as a function of time. A third alternative provides precise control of the index of refraction of the lens. The index of refraction is varied progressively across the lens from one edge to the opposite edge causing the radiation to be directed at an angle.

Abstract: An electron beam apparatus such as a sheet beam based testing apparatus has an electron-optical system for irradiating an object under testing with a primary electron beam from an electron beam source, and projecting an image of a secondary electron beam emitted by the irradiation of the primary electron beam, and a detector for detecting the secondary electron beam image projected by the electron-optical system; specifically, the electron beam apparatus comprises beam generating means 2004 for irradiating an electron beam having a particular width, a primary electron-optical system 2001 for leading the beam to reach the surface of a substrate 2006 under testing, a secondary electron-optical system 2002 for trapping secondary electrons generated from the substrate 2006 and introducing them into an image processing system 2015, a stage 2003 for transportably holding the substrate 2006 with a continuous degree of freedom equal to at least one, a testing chamber for the substrate 2006, a substrate transport mech

Abstract: An optical deflection apparatus includes a signal light source configured to emit signal light having one or more wavelengths, a control light source configured to emit control light having a wavelength different from the wavelength of the signal light, a thermal lens forming optical element including a light absorption layer configured to transmit the signal light and selectively absorb the control light, and a beam-condensing unit configured to cause beam-condensation of the control light and the signal light at different convergence points in the light absorption layer.

Abstract: The invention provides an electrowetting display and a method for fabricating the same. The electrowetting display comprises a first electrode formed on a first substrate. A dielectric layer is formed on the first electrode. A plurality of ribs are formed on the dielectric layer. A hydrophobic layer is formed on the dielectric layer and between the ribs. A second substrate is disposed oppositely to the first substrate. A second electrode is formed on the second substrate. A plurality of supporting members are formed on the second electrode and aligned to the ribs to form an enclosed space. A polar solution and a non-polar solution are disposed in the enclosed space.

Abstract: In the production of optical devices or the like utilizing an intersubband transition of a coupled quantum well, a quantum well structure having strong coupling is provided. In addition, a coupled well structure of excellent productivity capable of avoiding thinning of coupling barrier layer for strengthening the coupling is provided. In the semiconductor coupled well structure of the present invention, a coupled quantum well structure disposed on the semiconductor single crystal substrate includes a coupling barrier layer 1a disposed between two or more quantum well layers 2a and 2b, wherein the coupling barrier layer 1a has an energy barrier that is smaller than an excitation level (E4 and E3) and is larger than a ground level (E2 and E1).

Abstract: Data to be sent are, in a data communication unit, first divided into electric signal packets by a data transmission/receipt control unit, whereby an electric signal sequence tag is added to each electric signal packet, then converted into optical packets by an optical signal transmitting unit, and transmitted through an optical signal path. At optical switch, the optical paths of the packets are switched to optical signal paths by the actions of optical destination tags that are respectively synchronized with optical packets and irradiated by an optical signal transmitting unit. At optical signal receiving units, the received optical packets are converted to electric signal packets, and reassembled to be original data according to the identification information on the reassembly sequence recorded in the sequence tag in an electric signal packet by data transmission/receipt control units, and distributed to client devices as electric signals.

Abstract: Provided is a composition comprising a nonmicellar twisted nematic liquid crystal having cholesteric near infrared-reflecting properties and at least one near infrared absorptive material. This composition reduces the transmission of near infrared radiation. The composition can be used as a layer, optionally in conjunction with polymeric films, polymeric sheets, rigid sheets, and the like, to form multilayer laminates. In some embodiments these multilayer laminates are useful as solar control windows or window films to reduce energy consumption necessary to cool the interior of a structure such as an automobile or building.

Abstract: The present invention contemplates a variety of methods and techniques for fabricating a carbon nanotube (CNT) signal modulator for reducing, eliminating, or enhancing the resonance interaction between photonic elements, and a photonic transmission device that may incorporate the signal modulator. The CNT signal modulator comprises a gate CNT on a substrate in a position for receiving an input photonic signal and an input modulation signal; and transmitting an output photonic signal that is reduced, eliminated, or enhanced through the selection of the input modulation signal; and an input modulation signal sender for sending the input modulation signal to the gate CNT and creating the modulated output photonic signal from the gate CNT. The photonic transmission device can contain a plurality of CNTs, each having functional antenna forms that are capable of a resonance interaction of photons between adjacent CNTs when formed as an array on a substrate.

Abstract: A simulated eye includes a semi-spherical eyeball with a light-transmitting area, a light source, a light transmitting board, and a photochromic layer. The light transmitting board disposed between the eyeball and the light source faces the light-transmitting area. The light transmitting board includes a first portion and a second portion surrounding the first position. The first portion is in a first color. The second portion is in a second color other than the first color. The photochromic layer is formed by photochromic materials coated on a side of the second portion facing the light source. When the light source is turned on, the emitted light irradiates the photochromic layer, whereby an area of the second portion covered by the photochromic layer changes from the second color to a third color similar to or the same as the first color.

Abstract: An apparatus for controlling propagation of incident electromagnetic radiation is described, comprising a composite material having electromagnetically reactive cells of small dimension relative to a wavelength of the incident electromagnetic radiation. At least one of a capacitive and inductive property of at least one of the electromagnetically reactive cells is temporally controllable to allow temporal control of an associated effective refractive index encountered by the incident electromagnetic radiation while propagating through the composite material.

Abstract: In the three-terminal optical signal amplifying device 10, a portion of the neighboring light LS at other wavelength than that of the first wavelength ?1 that is selected from the output light from the element 14 by the optical add drop filter 16, and the control light Lc at the second wavelength ?2 input from the external are together input to the second semiconductor optical amplifying element 18. The output light including the output signal light LOUT at the second wavelength ?2 and the neighboring light at the neighboring wavelength to the second wavelength ?2 that is modulated and controlled by the control light LC in the cross gain modulation is output from the second semiconductor optical amplifying element 18. And the output signal light LOUT at the second wavelength ?2 passes through the wavelength selecting filter 20.

Abstract: A method for using an optical sensor array to control a labeling device includes scanning a surface texture of an imageable media with the optical sensor array, collecting surface data corresponding to the surface texture of the imageable media, and controlling the labeling device in response to the surface data.

Abstract: A light source apparatus with modulation function has a wavelength conversion module (75) composed of a nonlinear optical material with a structure having a nonlinear constant modulated periodically. It outputs a difference frequency or sum frequency produced by multiplexing pumping light from semiconductor laser light sources (71) and (72) with different wavelengths through a WDM coupler (74) and by launching the multiplexed light into the optical waveguide. The semiconductor laser light source (72) includes a diffraction grating. The semiconductor laser light source (71) includes a section for modulating output light emitted from its semiconductor laser, and is connected to an external FBG (73) which has a reflection band narrower than a resonance wavelength spacing determined by the device length of the semiconductor laser. The FBG (73) is supplied with the modulated output.

Abstract: Materials and structures whose index of refraction can be tuned over a broad range of negative and positive values by applying above band-gap photons to a structure with a strip line element, a split ring resonator element, and a substrate, at least one of which is a photoconductive semiconductor material. Methods for switching between positive and negative values of n include applying above band-gap photons to different numbers of elements. In another embodiment, a structure includes a photoconductive semiconductor wafer, the wafer operable to receive above band-gap photons at an excitation frequency in an excitation pattern on a surface of the wafer, the excitation patterns generating an effective negative index of refraction. Methods for switching between positive and negative values of n include projecting different numbers of elements on the wafer. The resonant frequency of the structure is tuned by changing the size of the split ring resonator excitation patterns.

Abstract: A planar mid-infrared (mid-IR) integrated microphotonic platform includes at least one laser performing lasing functions. The at least one laser comprises chalcogenide glass. At least amplifier structure is coupled to the at least one laser for performing optical amplification. The at least amplifier structure comprises chalcogenide glass. At least one waveguide structure is coupled to the at least one amplifier structure for guiding an optical signal in the microphotonic platform. The at least waveguide structure comprises chalcogenide glass. At least one modulator structure is coupled to the at least one waveguide structure for modulating the optical signal. The at least modulator structure comprises chalcogenide glass. At least one photodetector is coupled to the at least one modulator structure for performing photodetecting functions of the microphotonic platform. The at least photodetector comprises chalcogenide glass.

Abstract: An exemplary optical limiter device (100) has an optically transmissive substrate (102) and a layer (104) on a first surface (106) of the substrate, the layer having a trimetallic nitride endohedral metallofullerene. The layer can be a thin film of the trimetallic nitride endohedral metallofullerene, a layer material with a cavity containing a solution with the trimetallic nitride endohedral metallofullerene, a sol-gel with a trimetallic nitride endohedral metallofullerene, and a self assembled monolayer with a trimetallic nitride endohedral metallofullerene. The layers of trimetallic nitride endohedral metallofullerenes can be vapor deposited, solution deposited and/or self assembled onto optical components. The third-order nonlinear properties of these films provide desired transmission characteristics.

Abstract: The present invention provides a display element including a layered body. The layered body includes a layered portion comprising a plurality of transparent thin films with different refractive indexes, and a plurality of electrodes which are adapted to apply an electric field to each of the plurality of transparent thin films. Each of the plurality of transparent thin films comprises a material whose thickness changes according to the electric field.

Abstract: In one general aspect, a tunable electromagnetic metamaterial as described herein includes a substrate and an array of split ring resonators formed on the substrate. At least one of the split ring resonators is a capacitively tuned split ring resonator. The capacitively tuned split ring resonator includes a structure having a gap and is formed of an electrically conductive material. The capacitively tuned split ring resonator also includes a region of photo-capacitive material formed in close proximity to the structure such that the capacitance of the metamaterial is changed when illuminated by controlling electromagnetic radiation having a selected range of wavelengths.

Abstract: A spatial light modulator imaging system comprises an electrically addressed spatial light modulator (EASLM 4, 30) whose optical image output is projected onto different areas of an optically addressed spatial light modulator (OASLM, 6, 8, 31) in a sequence. The OASLM carries electrodes which allow separate areas to be selectively addressed by application of a voltage whilst receiving light from the EASLM. The combined output from all areas of the OASLM forms a visible image to an observer (11). When illuminated by coherent light the OASLM may produce a holographic image, otherwise incoherent light is used to provide a two dimensional image. The OASLM in one example contains a layer of nematic liquid crystal material between two cell walls both treated with an alignment layer providing low tilt surface alignment that is parallel in opposite direction; the product of layer thickness d and material birefringence ?n approximately equals one quarter of the wavelength ? of read light (12, 37).