Oxford University Innovation Ltd

International Business Machines Corporation

E Ink Corporation

Bodle Technologies Limited

Karlsruher Institut Fur Technologie

University of Exeter

University of Muenster

Harish Bhaskaran

Peiman L Hosseini

Ben Broughton

Michel Despont

Abu Sebastian

Wolfram Pernice

Urs T Duerig

Bernd W Gotsmann

Armin W Knoll

Rachel Cannara

Nathan Youngblood

Xuan Li

Manuel Le Gallo-Bourdeau

Ute Drechsler

Christopher David Wright

Carlos Rios

Johannes Feldmann

Carlos A Rios Ocampo

Carlos Andres Rios-Ocampo

Zengguang Cheng

Matthias Stegmaier

Wen Zhou

Peiman Hosseini

Richard Holliday

James Tan You Sian

A photonic content addressable memory (CAM) () is provided. The photonic CAM () comprises: N search lines () and a plurality of match lines (), each match line comprising N photonic CAM cells (). Each search line () is configured to receive a search optical signal and each search optical signal comprises a different wavelength encoding one of N parallel search symbols. Each match line () is configured to receive: a wavelength division multiplexed content optical signal comprising a plurality of wavelengths, each wavelength encoding one of N parallel content symbols; and the N search optical signals from the N search lines (). Each photonic CAM cell is configured to compare a respective search symbol with a respective content symbol and provide an output optical signal that is responsive to the comparison. Each match line () also comprises a content optical demultiplexer (), configured to demultiplex the wavelength division multiplexed content optical signal and provide each CAM cell () with the respective content symbol.

Photonic content addressable memory

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 nπ/2 radians, where n is an integer.

Display apparatus

An optical waveguide () is disclosed, for guiding light in a photonic circuit comprising a layer of phase change material () for modulating the phase of the guided light. The phase change material () is switchable between at least a stable crystalline state and a stable amorphous state each with different refractive indexes. The phase change material (101) exhibits an extinction coefficient of less than 0.1 in both states for wavelengths greater than 1000 nm.

Optical waveguide and devices

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.

The invention is notably directed to a transflective display device. The device comprises a set of pixels, wherein each of the pixels comprises a portion of bi-stable, phase change material, hereafter a PCM portion, having at least two reversibly switchable states, in which it has two different values of refractive index and/or optical absorption. The device further comprises one or more spacers, optically transmissive, and extending under PCM portions of the set of pixels. One or more reflectors extend under the one or more spacers. An energization structure is in thermal or electrical communication with the PCM portions, via the one or more spacers. Moreover, a display controller is configured to selectively energize, via the energization structure, PCM portions of the pixels, so as to reversibly switch a state of a PCM portion of any of the pixels from one of its reversibly switchable states to the other. A backlight unit is furthermore configured, in the device, to allow illumination of the PCM portions through the one or more spacers. The backlight unit is controlled by a backlight unit controller, which is configured for modulating one or more physical properties of light emitted from the backlight unit. The invention is further directed to related devices and methods of operation.

Transflective, PCM-based display device

A method of performing a multiplication operation in the optical domain using a device () comprising: an optical waveguide (), and a modulating element () that is optically coupled to the optical waveguide (), the modulating element () modifying a transmission, reflection or absorption characteristic of the waveguide () dependant on its state, wherein the state of the modulating element () is adjustable by a write signal (). The method comprises: encoding a first value to the write signal (), using the write signal () to map the first value to a state of the modulating element (); encoding a second value to a read signal (); producing an output signal intensity as the transmitted or reflected read signal, wherein the product of the first value and the second value is encoded in the output signal intensity.

Optical methods and devices

An optical device comprising a stack of the following layers: a capping layer; a layer of light absorber material; and a reflective layer, wherein the refractive index of the capping layer is at least 1.6.

Optical device

A co-processor for performing a matrix multiplication of an input matrix with a data matrix in one step may be provided. The co-processor receives input signals for the input matrix as optical signals. A plurality of photonic memory elements is arranged at crossing points of an optical waveguide crossbar array. The plurality of memory elements is configured to store values of the data matrix. Input signals are connected to input lines of the optical waveguide crossbar array. Output lines of the optical waveguide crossbar array represent a dot-product between a respective column of the optical waveguide crossbar array and the received input signals, and values of elements of the input matrix to be multiplied with the data matrix correspond to light intensities received at input lines of the respective photonic memory elements. Additionally, different wavelengths are used for each column of the input matrix optical signals.

Photonic in-memory co-processor for convolutional operations

The present invention is notably directed to an optical device () comprising a layer structure () with: a thermally conducting, optical reflector (); a thermally conducting spacer (), which is transmissive to light and arranged above the reflector (); and a phase change material (), or PCM, arranged above the spacer () and having at least two reversibly switchable states, in which the PCM exhibits two different values of refractive index. The reflector (), the spacer () and the PCM () are successively stacked along a stacking direction (z) of the layer structure. The optical device further comprises: a heating element (), opposite to the PCM () with respect to the reflector (), the layer structure () being configured so as to electrically insulate the PCM () from the heating element (), while the heating element () is in thermal communication with the PCM () via the reflector () and the spacer (); and a controller () configured to energize the heating element (), so as to heat the PCM () and thereby reversibly change a refractive index and/or an absorption of said PCM (). The invention is further directed to related optical devices (notably devices comprising one or more pixels formed, each, by a set of layer structures such as described above) and actuation methods.

Optical device with thermally switching phase change material

A photonic device () comprising: an optical waveguide (), and a modulating element () that is evanescently coupled to the waveguide (); wherein the modulating element () modifies a transmission, reflection or absorption characteristic of the waveguide () dependant on its state, and the state of the modulating element () is switchable by an optical switching signal () carried by the waveguide (), or by an electrical signal that heats the modulating element ().

Photonic device

The present invention is notably directed to display device (), comprising a set of pixels, each having a layer structure () that includes: a bi-stable, phase change material (), or bi-stable PCM, having at least two reversibly switchable states, in which the PCM exhibits two different values of refractive index and/or optical absorption; and a heating element (), electrically insulated from the PCM () and in thermal communication with the PCM () in the layer structure (). The display device further comprises a set of nonlinear, monostable resistive switching elements (), each in electrical communication with the heating element () of one of the pixels. The resistive switching elements are designed so as to exhibit, each: a low resistance, unstable state, which allows the heating element () to be energized via the resistive switching element (), so as to heat the PCM () and reversibly change a refractive index and/or an optical absorption thereof, in operation; and a high-resistance, stable state, which allows leakage currents to be mitigated, so as to prevent inadvertent switching of the PCM () from one of its states to the other, in operation. The device further comprises a controller () configured to energize any of the pixels via a respective one of the resistive switching elements (), so as to switch the latter from its high-resistance state to its low resistance state, in order to energize a respective heating element () and, in turn, reversibly change a refractive index and/or an optical absorption of a respective PCM (). The present invention is further directed to related devices or apparatuses, such as passive matrix addressing displays, and methods of operations.

Phase change material-based display device with resistive switching elements

A display apparatus includes an optically opaque layer and one or more stacks of additional layers provided on the optically opaque layer. Each stack has an optically switchable layer. A plurality of switching elements are located on a side of the optically opaque layer opposite to the one or more stacks. Each switching element is operable to apply a signal, for example an electrical signal or a thermal signal, through the optically opaque layer 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 surface area of the optically opaque layer on the viewing side is at least 10% larger than the total surface area of the switchable portions on the viewing side.

An optical device comprising a stack of the following layers: a capping layer () having a high refractive index for guiding incident light; a layer of light absorber material (), preferably a phase-changing material; and a reflective layer (), wherein the refractive index of the capping layer is at least 1.6.

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Oxford, United Kingdom

Harish Bhaskaran