# US 2017/0285262 A1 · Passive Optical Diode on Semiconductor Substrate > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0285262 A1 - Document ID: US20170285262A1 - Status: Published application - Kind: A1 - Application number: 15/627,335 - Filed: 2017-06-19 - Published: 2017-10-05 - Earliest claimed: 2012-03-02 - Assignees: Purdue Research Foundation - Applicants: Purdue Research Foundation - Inventors: Minghao Qi; Li Fan; Jian Wang; Leo Tom Varghese - Web page: https://patentgrep.com/patent/US20170285262A1 ## CPC - G02B 6/122: Basic optical elements, e.g. light-guiding paths - G02B 6/12007: {forming wavelength selective elements, e.g. multiplexer, demultiplexer} - G02B 6/2746: {comprising non-reciprocal devices, e.g. isolators, FRM, circulators, quasi-isolators (magneto-optic non-reciprocal devices G02F1/093)} - G02B 6/29343: {Cascade of loop resonators} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A method of fabricating an optical device includes forming on a semiconductor substrate a first optical cavity, a second optical cavity, a first light guide and a second light guide. The first light guide has an input, and is optically coupled to the first optical cavity by a first coupling strength. In addition, the first light guide is optically coupled to the second optical cavity by a second coupling strength. The second light guide has an output, and is coupled to the second optical cavity by a third coupling strength. The first coupling strength is greater than the second coupling strength, and the third coupling strength is greater than the second coupling strength. ## Claims ### Claim 1 A method of fabricating an optical device, comprising: forming a first optical cavity formed on a semiconductor substrate, the first optical cavity configured to store light; forming a second optical cavity on the semiconductor substrate, the second optical cavity configured to store light; forming a first light guide on the semiconductor substrate, the first light guide having an input, the first light guide optically coupled to the first optical cavity by a first coupling strength, the first light guide optically coupled to the second optical cavity by a second coupling strength; and forming a second light guide on the semiconductor substrate, the second light guide having an output, the second light guide coupled to the second optical cavity by a third coupling strength; wherein the first coupling strength is greater than the second coupling strength, and the third coupling strength is greater than the second coupling strength. ### Claim 2 (depends on 1) The method of claim 1, wherein forming the first optical cavity comprises forming a first optical resonator, and wherein forming the second optical cavity comprises forming a second optical resonator. ### Claim 3 (depends on 2) The method of claim 2, wherein forming the first optical cavity further comprises forming the first optical resonator of single crystal silicon on an SiO2 substrate. ### Claim 4 (depends on 3) The method of claim 3, wherein forming the first optical resonator further comprises patterning the optical resonator using electron-beam lithography, and reactive ion-etching. ### Claim 5 (depends on 2) The method of claim 2, wherein the first optical resonator and the second optical resonator have substantially identical resonant wavelengths for a given optical power within the cavity. ### Claim 6 (depends on 2) The method of claim 2, wherein forming the first light guide comprises forming a first waveguide and wherein forming the second light guide comprises forming a second waveguide. ### Claim 7 (depends on 6) The method of claim 6, wherein forming the first light guide comprises forming the first waveguide of single crystal silicon on an SiO2 substrate ### Claim 8 (depends on 6) The method claim 6, wherein the first waveguide is separated from the second optical resonator by a first gap having a first gap width, the second waveguide is separated is separated from the second optical resonator by a second gap having a second gap width, and the first gap width is greater than the second gap width. ### Claim 9 (depends on 8) The method of claim 8, wherein the first waveguide is separated from the first resonator by a third gap having a third gap width, and the first gap width is greater than the third gap width. ### Claim 10 (depends on 6) The method of claim 6, wherein the first waveguide is separated from the second optical resonator by a first gap, the second waveguide is separated is separated from the second optical resonator by a second gap, and wherein a first refractive index of the first waveguide proximate the first gap is different from a second refractive index of the second waveguide proximate the second gap. ### Claim 11 (depends on 1) The method of claim 1, further comprising forming a micro-heater on the semiconductor substrate such that the micro-heater is closer to the first optical cavity than to the second optical cavity. ### Claim 12 (depends on 11) The method of claim 11, wherein forming the micro-heater further comprises evaporating titanium onto a buried oxide layer proximate the first optical resonator. ### Claim 13 A method of fabricating an optical device, comprising: forming an optical cavity on the semiconductor substrate, the optical cavity configured to store light; forming on the semiconductor substrate a first light guide having an input, the first light guide optically coupled to the optical cavity by a first coupling strength, the first light guide having an input coupling; and forming on the semiconductor substrate a second light guide having an output coupling, the second light guide optically coupled to the optical cavity by a second coupling strength; wherein the second coupling strength is greater than the first coupling strength, and wherein the optical cavity, the first light guide and the second light guide are formed such that a first wavelength of light propagates from the input coupling to the output coupling with a first attenuation, and the first wavelength of light propagates from the output coupling to the input coupling with a second attenuation that is greater than the first attenuation. ### Claim 14 (depends on 13) The method of claim 13, wherein the optical cavity comprises an optical trap. ### Claim 15 (depends on 13) The method of claim 13, wherein the optical resonator comprises a micro-ring resonator. ### Claim 16 A method of using an optical device, comprising: receiving an optical signal at a first light guide via a first input coupling, the first light guide coupled to an optical cavity by a first coupling strength, the optical cavity disposed on a semiconductor substrate and configured to store light; coupling the optical signal from first light guide to the optical cavity; coupled the optical signal from the optical cavity to a second light guide, the second light guide coupled to the optical cavity by a second coupling strength, the second light guide having an output coupling; wherein the second coupling strength is greater than the first coupling strength, and wherein the optical device is configured such that a first wavelength of light propagates from the input coupling to the output coupling with a first attention, and the first wavelength of light propagates from the output coupling to the input coupling with a second attenuation that is greater than the first attenuation. ### Claim 17 (depends on 16) The method of claim 16, further comprising passing the received optical signal through a notch filter formed by a part of the first light guide coupled to a further optical cavity by a third coupling strength, wherein the third coupling strength is greater than the first coupling strength. ### Claim 18 (depends on 17) The method of claim 17, wherein the optical cavity and the further optical cavity have substantially identical resonant wavelengths for a given optical power within the cavity. ### Claim 19 (depends on 17) The method of claim 17, further comprising applying current to a micro-heater, the microheater configured to heat the further optical cavity more than the optical cavity. ### Claim 20 (depends on 17) The method of claim 17, wherein the further optical cavity is disposed on the semiconductor substrate, and further comprising applying the received optical signal to the first light guide at a power level at which the further optical cavity heats the semiconductor substrate sufficiently to change a resonant wavelength of the further optical cavity.