# US 2021/0240016 A1 · All-Optical Spatial Light Modulator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0240016 A1 - Document ID: US20210240016A1 - Status: Published application - Kind: A1 - Application number: 17/216,272 - Filed: 2021-03-29 - Published: 2021-08-05 - Earliest claimed: 2019-07-12 - Assignees: Massachusetts Institute of Technology - Applicants: Massachusetts Institute of Technology - Inventors: Christopher Louis Panuski; Dirk Robert ENGLUND - Web page: https://patentgrep.com/patent/US20210240016A1 ## CPC - G02F 1/025: in an optical waveguide structure (G02F1/017, {G02F1/2257} take precedence) - G02F 1/0126: {Opto-optical modulation, i.e. control of one light beam by another light beam, not otherwise provided for in this subclass} - G02F 1/015: based on semiconductor elements having potential barriers, e.g. having a PN or PIN junction (G02F1/03 takes precedence) - H04N 9/3138: {using arrays of modulated light sources (electroluminescent display devices G09G3/30)} - G02F 2202/32: Photonic crystals - G02F 2203/12: spatial light modulator - G02F 2203/15: involving resonance effects, e.g. resonantly enhanced interaction - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A spatial light modulator (SLM) comprised of a 2D array of optically-controlled semiconductor nanocavities can have a fast modulation rate, small pixel pitch, low pixel tuning energy, and millions of pixels. Incoherent pump light from a control projector tunes each PhC cavity via the free-carrier dispersion effect, thereby modulating the coherent probe field emitted from the cavity array. The use of high-Q/V semiconductor cavities enables energy-efficient all-optical control and eliminates the need for individual tuning elements, which degrade the performance and limit the size of the optical surface. Using this technique, an SLM with 106 pixels, micron-order pixel pitch, and GHz-order refresh rates could be realized with less than 1 W of pump power. ## Claims ### Claim 1 A spatial light modulator, comprising: a layer patterned with a two-dimensional array of semiconductor cavities, the layer scattering signal light at a resonant wavelength; and at least one incoherent light source, in optical communication with the two-dimensional array of semiconductor cavities, to tune the resonant wavelength of at least one semiconductor cavity in the two-dimensional array of semiconductor cavities via optical free carrier injection. ### Claim 2 (depends on 1) The spatial light modulator of claim 1, wherein each semiconductor cavity in the two-dimensional array of semiconductor cavities has a quality factor Q of at least 1000. ### Claim 3 (depends on 1) The spatial light modulator of claim 1, wherein the two-dimensional array of semiconductor cavities is comprised of: H1 photonic crystal cavities; L4/3 photonic crystal cavities; or micropillar cavities. ### Claim 4 (depends on 1) The spatial light modulator of claim 1, wherein the two-dimensional array of semiconductor cavities has a pitch of about half the resonant wavelength to about the resonant wavelength. ### Claim 5 (depends on 1) The spatial light modulator of claim 1, wherein the at least one incoherent light source comprises a two-dimensional array of light-emitting diodes (LEDs). ### Claim 6 (depends on 1) The spatial light modulator of claim 1, wherein optical free carriers emitted by the at least one incoherent light source are at a wavelength of less than 500 nm and the signal light is at a wavelength of more than 500 nm. ### Claim 7 (depends on 1) The spatial light modulator of claim 1, wherein a free carrier lifetime of the layer is about 100 ps or less. ### Claim 8 (depends on 1) The spatial light modulator of claim 1, wherein a free carrier lifetime of the layer is about 1 ns or more. ### Claim 9 (depends on 1) The spatial light modulator of claim 1, further comprising: a signal light source, in optical communication with the layer, to illuminate the layer with the signal light. ### Claim 10 (depends on 9) The spatial light modulator of claim 9, wherein the spatial light modulator does not include a waveguide between the signal light source and the layer. ### Claim 11 (depends on 9) The spatial light modulator of claim 9, further comprising: a control layer, operably coupled to the at least one incoherent light source, to modulate the at least one incoherent light source at a rate of at least 1 GHz. ### Claim 12 (depends on 9) The spatial light modulator of claim 9, wherein the signal light source is positioned for normal incidence of the signal light on the surface of the layer. ### Claim 13 (depends on 12) The spatial light modulator of claim 12, further comprising: a polarizing beam splitter, in optical communication with the layer, to receive the signal light reflected by the layer and to separate the signal light into directly reflected light and cavity reflected light. ### Claim 14 (depends on 9) The spatial light modulator of claim 9, wherein the signal light source is positioned for off-normal incidence of the signal light on the surface of the layer. ### Claim 15 (depends on 14) The spatial light modulator of claim 14, wherein the signal light includes directly reflected light and cavity reflected light. ### Claim 16 (depends on 9) The spatial light modulator of claim 9, further comprising: a sensing device to detect the reflected signal light. ### Claim 17 A spatial light modulator, comprising: a resonant surface to reflect incident signal light at a resonant wavelength; and at least one incoherent light source, in optical communication with the resonant surface, to tune the resonant wavelength of at least one oscillator of the resonant surface via optical free carrier injection. ### Claim 18 (depends on 17) The spatial light modulator of claim 17, further comprising: a signal light source, in optical communication with the resonant surface, to reflect the signal light off the resonant surface to generate reflected signal light. ### Claim 19 (depends on 18) The spatial light modulator of claim 18, further comprising: a sensing device to detect the reflected signal light. ### Claim 20 (depends on 17) The spatial light modulator of claim 17, wherein the resonant surface is defined by a photonic crystal slab guided mode resonator. ### Claim 21 (depends on 17) The spatial light modulator of claim 17, wherein the resonant surface includes a wavelength-scale patterned semiconductor slab. ### Claim 22 (depends on 21) The spatial light modulator of claim 21, wherein the resonant surface supports a spatially distributed resonant mode.