# US 2010/0166364 A1 · Integrated silicon-based nonlinear photodetector

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- Number: US 2010/0166364 A1
- Document ID: US20100166364A1
- Status: Published application
- Kind: A1
- Application number: 12/611,287
- Filed: 2009-11-03
- Published: 2010-07-01
- Earliest claimed: 2008-11-04
- Assignees: Massachusetts Institute of Technology
- Inventors: Jorge Bravo Abad; Erich P. Ippen; Marin Soljacic
- Web page: https://patentgrep.com/patent/US20100166364A1

## CPC

- G02B 6/12004: {Combinations of two or more optical elements}
- B82Y 20/00: Nanooptics, e.g. quantum optics or photonic crystals
- G02B 6/1225: {comprising photonic band-gap structures or photonic lattices}
- H10F 30/21: the devices being sensitive to infrared, visible or ultraviolet radiation
- H10F 77/14: Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

Disclosed is a system including an integrated silicon-based structure including a microcavity configured to receive optical energy from an input beam carrying an optical signal and absorb the optical energy by a nonlinear multi-photon absorption process. For example, the multi-photon absorption process can be two-photon absorption (TPA). The integrated silicon-based structure further includes electrodes responsive to the nonlinear multi-photon absorption process in the microcavity for producing an electronic signal indicative of the optical signal. A related method is also disclosed.

## Claims

### Claim 1

A system comprising:
an integrated silicon-based structure comprising an optical waveguide for receiving an input beam carrying an optical signal and a microcavity optically coupled to the waveguide and configured to receive optical energy from the input beam and absorb the optical energy by a nonlinear multi-photon absorption process,
the integrated silicon-based structure further comprising electrodes responsive to the nonlinear multi-photon absorption process in the microcavity for producing an electronic signal indicative of the optical signal.

### Claim 2 (depends on 1)

The system of claim 1, wherein the microcavity comprises silicon and wherein the nonlinear multi-photon absorption process is in the silicon.

### Claim 3 (depends on 1)

The system of claim 1, wherein the microcavity has a resonant frequency ωn, a quality factor Q, and a modal volume VMODE, and wherein the input beam carrying the optical signal has a wavelength in air equal to λAIR, with 1.2 μm<λAIR<2.4 μm.

### Claim 4 (depends on 1)

The system of claim 1, wherein the microcavity has a resonant frequency μn, a quality factor Q, and a modal volume VMODE, and wherein the system further comprises a source for the input beam, and wherein the input beam carrying the optical signal has a wavelength in air equal to λAIR.

### Claim 5 (depends on 3)

The system of claim 3, wherein Q>100 and VMODE<1000 λAIR3.

### Claim 6 (depends on 5)

The system of claim 5, wherein Q>1000 and VMODE<100 λAIR3.

### Claim 7 (depends on 6)

The system of claim 6, wherein VMODE<10 λAIR3.

### Claim 8 (depends on 5)

The system of claim 5, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, and wherein |ω−ω0|/ω0<10/Q.

### Claim 9 (depends on 8)

The system of claim 8, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, and wherein |ω−ω0|/ω0<5/Q.

### Claim 10 (depends on 9)

The system of claim 9, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, and wherein |ω−ω0|/ω0<1/Q.

### Claim 11 (depends on 1)

The system of claim 1, wherein the microcavity is configured to achieve a conversion efficiency for the multi-photon absorption of the optical energy in the input beam of greater than 15% for an input beam power smaller than 0.2 mW.

### Claim 12 (depends on 1)

The system of claim 1, wherein the microcavity is a photonic crystal structure.

### Claim 13 (depends on 1)

The system of claim 1, wherein the waveguide is a photonic crystal structure.

### Claim 14 (depends on 1)

The system of claim 1, wherein the integrated silicon-based structure is implemented in a Complementary metal-oxide-semiconductor (CMOS) platform.

### Claim 15 (depends on 1)

The system of claim 1, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, wherein N photons, with N>1, are absorbed simultaneously by a material in the microcavity during the multi-photon absorption process, and wherein the multi-photon absorption material has an indirect electronic bandgap Eg larger than the energy corresponding to a single photon of frequency ω and smaller than the energy of the N photons absorbed simultaneously by the material.

### Claim 16

A method comprising:
directing an input beam carrying an optical signal into an optical waveguide of an integrated silicon-based structure, the integrated silicon-based structure further comprising a microcavity optically coupled to the waveguide;
receiving optical energy in the microcavity from the input beam and absorbing the optical energy in the microcavity by a nonlinear multi-photon absorption process; and
producing an electronic signal in response to the nonlinear multi-photon absorption process in the microcavity, the electrical signal indicative of the optical signal.

### Claim 17 (depends on 16)

The method of claim 16, wherein the integrated silicon-based structure further comprises electrodes responsive to the nonlinear multi-photon absorption process in the microcavity for producing the electronic signal indicative of the optical signal.

### Claim 18 (depends on 16)

The method of claim 16, wherein the microcavity comprises silicon and wherein the nonlinear multi-photon absorption process is in the silicon.

### Claim 19 (depends on 16)

The method of claim 16, wherein the microcavity has a resonant frequency ω0, a quality factor Q, and a modal volume VMODE, wherein the input beam carrying the optical signal has a wavelength in air equal to λAIR, and wherein Q>100 and VMODE<1000 λAIR3.

### Claim 20 (depends on 19)

The method of claim 19, wherein Q>1000 and VMODE<100 λAIR3.

### Claim 21 (depends on 20)

The method of claim 20, wherein VMODE<10 λAIR3.

### Claim 22 (depends on 19)

The method of claim 19, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, and wherein |ω−ω0|/ω0<10/Q.

### Claim 23 (depends on 22)

The method of claim 22, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, and wherein |ω−ω0|/ω0<5/Q.

### Claim 24 (depends on 23)

The method of claim 23, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, and wherein |ω−ω0|/ω0<1/Q.

### Claim 25 (depends on 16)

The method of claim 16, wherein the input beam carrying the optical signal has a wavelength in air equal to λAIR, and 1.2 μm<λAIR<2.4 μm.

### Claim 26 (depends on 16)

The method of claim 16, wherein the microcavity is configured to achieve a conversion efficiency for the multi-photon absorption of the optical energy in the input beam of greater than 15% for an input beam power smaller than 0.2 mW.

### Claim 27 (depends on 16)

The method of claim 16, wherein the microcavity is a photonic crystal structure.

### Claim 28 (depends on 16)

The method of claim 16, wherein the waveguide is a photonic crystal structure.

### Claim 29 (depends on 16)

The method of claim 16, wherein the integrated silicon-based structure is implemented in a Complementary metal-oxide-semiconductor (CMOS) platform.

### Claim 30 (depends on 16)

The method of claim 16, wherein the input beam carrying the optical signal has a carrier frequency equal to ω, wherein N photons, with N>1, are absorbed simultaneously by a material in the microcavity during the multi-photon absorption process, and wherein the multi-photon absorption material has an indirect electronic bandgap Eg larger than the energy corresponding to a single photon of frequency w and smaller than the energy of the N photons absorbed simultaneously by the material.

### Claim 31

Apparatus comprising:
an integrated silicon-based structure comprising an optical waveguide for receiving an input beam carrying an optical signal and a microcavity optically coupled to the waveguide and configured to receive optical energy from the input beam and absorb the optical energy by a nonlinear multi-photon absorption process,
the integrated silicon-based structure further comprising electrodes responsive to the nonlinear multi-photon absorption process in the microcavity for producing an electronic signal indicative of the optical signal,
wherein the microcavity comprises silicon and wherein the nonlinear multi-photon absorption process is in the silicon, and
wherein the microcavity has a resonant frequency ω0, a quality factor Q, and a modal volume VMODE, and wherein the input beam carrying the optical signal has a wavelength in air equal to λAIR, with 1.2 μm<λAIR<2.4 μm, and wherein Q>100 and VMODE<1000 λAIR3.

### Claim 32 (depends on 1)

The system of claim 1, wherein the integrated silicon-based structure further comprises an output optical waveguide optically coupled to the microcavity and configured to output optical energy from the microcavity that is not absorbed by the multi-photon absorption process.

### Claim 33 (depends on 16)

The method of claim 16, wherein the integrated silicon-based structure further comprises an output optical waveguide optically coupled to the microcavity, and wherein the method further comprises outputting optical energy from the microcavity that is not absorbed by the multi-photon absorption process through the output optical waveguide.

### Claim 34 (depends on 1)

The system of claim 1, wherein the multi-photon absorption process is a two-photon absorption (TPA).

### Claim 35 (depends on 16)

The method of claim 16, wherein the multi-photon absorption process is a two-photon absorption (TPA).

### Claim 36

A system comprising:
an integrated silicon-based structure comprising a microcavity configured to receive optical energy from an input beam carrying an optical signal and absorb the optical energy by a nonlinear multi-photon absorption process,
the integrated silicon-based structure further comprising electrodes responsive to the nonlinear multi-photon absorption process in the microcavity for producing an electronic signal indicative of the optical signal,
wherein the microcavity comprises silicon and wherein the nonlinear multi-photon absorption process is in the silicon.

### Claim 37 (depends on 36)

The system of claim 36, wherein the integrated silicon-based structure further comprises an optical waveguide for receiving the input beam carrying an optical signal, and wherein the microcavity is optically coupled to the waveguide to receive the optical energy from the input beam.

### Claim 38

A method comprising:
directing an input beam carrying an optical signal into an integrated silicon-based structure comprising a microcavity;
receiving optical energy in the microcavity from the input beam and absorbing the optical energy in the microcavity by a nonlinear multi-photon absorption process; and
producing an electronic signal in response to the nonlinear multi-photon absorption process in the microcavity, the electrical signal indicative of the optical signal, wherein the microcavity comprises silicon and wherein the nonlinear multi-photon absorption process is in the silicon.

### Claim 39 (depends on 38)

The method of claim 38, wherein the integrated silicon-based structure further comprises an optical waveguide for receiving the input beam carrying an optical signal, and wherein the microcavity is optically coupled to the waveguide to receive the optical energy from the input beam.

### Claim 40 (depends on 1)

The system of claim 1, wherein the integrated silicon-based structure comprises multiple microcavities each optically coupled to the waveguide and configured to receive optical energy from the input beam and absorb the optical energy by a nonlinear multi-photon absorption process.

### Claim 41 (depends on 16)

The method of claim 16, wherein the integrated silicon-based structure comprises multiple microcavities each optically coupled to the waveguide and configured to receive optical energy from the input beam and absorb the optical energy by a nonlinear multi-photon absorption process.

### Claim 42 (depends on 16)

The method comprising using the method of claim 16 to perform optical performance monitoring (OPM) of one or more channels of an optical telecommunications network.