# US 8,785,855 B2 · Interlaced terahertz transceiver using plasmonic resonance

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- Number: US 8,785,855 B2
- Document ID: US8785855B2
- Status: Granted
- Kind: B2
- Application number: 14/055,825
- Filed: 2013-10-16
- Published: 2014-04-17
- Granted: 2014-07-22
- Earliest claimed: 2012-10-16
- Assignees: UVic Industry Partnerships Inc.
- Applicants: Thomas E. Darcie; Reuven Gordon; Barmak Heshmat
- Inventors: Thomas E. Darcie; Reuven Gordon; Barmak Heshmat
- Web page: https://patentgrep.com/patent/US8785855B2

## CPC

- H10F 77/20: Electrodes
- H10F 30/10: the devices being sensitive to infrared radiation, visible or ultraviolet radiation, and having no potential barriers, e.g. photoresistors
- H10F 77/1248: {having three or more elements, e.g. GaAlAs, InGaAs or InGaAsP}
- H10H 20/831: characterised by their shape
- Y02E 10/544: Solar cells from Group III-V materials
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

Disclosed are devices and methods for enhancing the performance of photoconductive switches or photomixers used to generate or receive terahertz radiation. An interlaced electrode is used to minimize carrier transit times across an absorbing semiconductor photoconductor. This electrode is designed to support a plasmonic resonance such that coupling of the optical pump signal to the absorbing photoconductor is enhanced.

## Claims

### Claim 1

A photoconductive switch for generating or detecting electromagnetic signals using an optical pump signal, comprising:
a periodically interlaced electrode structure, wherein a gap separating two electrode contacts is substantially less than a wavelength of the optical pump signal; and
wherein the periodicity of the interlaced electrode structure supports a plasmonic resonance that enhances coupling of the optical pump signal through the electrode structure to an absorbing semiconductor substrate.

### Claim 2 (depends on 1)

The photoconductive switch of claim 1, wherein the interlaced electrode structure provides a carrier transit time that is substantially shorter than a carrier recombination time.

### Claim 3 (depends on 1)

The photoconductive switch of claim 1, wherein the periodicity of the interlaced electrode structure is selected such that the plasmonic resonance frequency corresponds to the frequency of the optical pump signal.

### Claim 4 (depends on 1)

The photoconductive switch of claim 1, wherein the interlaced electrode structure is formed by conductive fingers alternating in connection between each of the two electrode contacts.

### Claim 5 (depends on 1)

The photoconductive switch of claim 1, wherein the interlaced electrode structure is formed by at least one sub-wavelength gap that meanders back and forth between each of two electrode contacts.

### Claim 6 (depends on 1)

The photoconductive switch of claim 1, wherein the electromagnetic signals contain frequency components within a terahertz band extending from 0.1 THz to 10 THz.

### Claim 7

A method for generating and detecting electromagnetic signals, comprising:
detecting an optical pump signal on a photoconductive switch, the switch comprising a periodically interlaced electrode structure wherein the gap separating two conductors is substantially less than the wavelength of the optical pump signal; and
wherein the periodicity of the interlaced electrode structure supports a plasmonic resonance at a frequency corresponding to the frequency of the optical pump signal.

### Claim 8

A THz transmitter for generating electromagnetic signals, comprising:
a photoconductive switch, comprising:
a periodically interlaced electrode structure, wherein a gap separating two electrode contacts is substantially less than a wavelength of an optical pump signal;
wherein the periodicity of the interlaced electrode structure supports a plasmonic resonance that enhances coupling of the optical pump signal through the electrode structure to an absorbing semiconductor substrate.

### Claim 9 (depends on 8)

The THz transmitter of claim 8, further comprising an antenna coupled to the photoconductive switch, and configured to radiate THz radiation when fed by currents generated by the photoconductive switch in response to the optical pump signal.

### Claim 10 (depends on 8)

The THz transmitter of claim 8, further comprising a waveguide coupled to receive a THz signal from the photoconductive switch generated in response to the optical pump signal.

### Claim 11

A receiver for detecting THz electromagnetic signals, comprising:
a photoconductive switch that generates a detected signal in response to an optical pump signal,
the photoconductive switch comprising:
a periodically interlaced electrode structure, wherein a gap separating two electrode contacts is substantially less than a wavelength of an optical pump signal, wherein the periodicity of the interlaced electrode structure supports a plasmonic resonance that enhances coupling of the optical pump signal through the electrode structure to an absorbing semiconductor substrate.

### Claim 12 (depends on 11)

The receiver of claim 11, further comprising an antenna coupled to deliver received THz radiation to the photoconductive switch.

### Claim 13 (depends on 11)

The receiver of claim 11, further comprising a waveguide coupled to deliver received THz radiation to the photoconductive switch.