Hybrid metal-graphene terahertz optoelectronic system with tunable plasmonic resonance and method of fabrication

Patent metadata

Field	Value
Publication number	US-2018315880-A1
Application number	US-201615735662-A
Country	US
Kind code	A1
Filing date	Jun 14, 2016
Priority date	Jun 15, 2015
Publication date	Nov 1, 2018
Grant date	—

Abstract

A new approach to graphene-enabled plasmonic resonant structures in the THz is demonstrated in a hybrid graphene-metal design in which the graphene acts as a gate-tunable inductor, and metal acts as a capacitive reservoir for charge accumulation. A large resonant absorption in graphene can be achieved using the metal-graphene plasmonic scheme, and the peak can approach 100% in an optimized device, ideal for graphene-based THz detectors. Using high mobility graphene (μ>50000 cm 2 V −1 s −1 ) will allow anomalously high resonant THz transmission (near 100%) through ultra-subwavelength graphene-filled metallic apertures at a resonance frequency that is gate tunable. This metal-graphene plasmonic scheme enables near perfect tunable THz filter or modulator.

First claim

What is claimed is:

1 . A plasmon-enhanced terahertz graphene-based optoelectronic structure, comprising:
a substrate, a conductive layer formed above said substrate, at least one plasmonic graphene channel embedded in said conductive layer, and a source of an electromagnetic wave of a predetermined wavelength, wherein said electromagnetic wave is incident on said at least one plasmonic graphene channel and is polarized substantially perpendicular thereto, wherein said at least one plasmonic graphene channel has a width smaller than said predetermined wavelength of the electromagnetic wave and is tunable to produce a controllable plasmon-enhanced resonance signal.

2 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 1 , further including:
a first periodic array of conductive stripes formed in said conductive layer above said substrate, said conductive stripes extending in a spaced apart relationship each with respect to the other with a gap defined between adjacent conductive stripes, and a layer of graphene sandwiched between said substrate and said first periodic array of said conductive stripes, said layer of graphene comprising a second periodic array of said at least one plasmonic graphene channels, each confined in a respective gap between said adjacent conductive stripes, wherein a width of each of said conductive stripes exceeds the width of said at least one plasmonic graphene channel.

3 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 2 , further including an electrolyte layer positioned atop and enveloping said first periodic array of conductive stripes and said second periodic array of said plasmonic graphene channels.

4 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 3 , further including a gate terminal coupled to said electrolyte layer, and
a source of a gate voltage V g applied between said gate terminal and said graphene layer.

5 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 4 , wherein upon application of said gate voltage of a predetermined value V g , said polarized electromagnetic wave excites transverse plasmon resonance in said at least one plasmonic graphene channel, thereby producing a plasmon-enhanced resonance at a plasmon resonance frequency.

6 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 5 , wherein plasmon resonance frequency and strength of the resonance absorption is controlled by controlling said gate voltage V g to tune carriers density in said at least one plasmonic graphene layer.

7 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 5 , wherein said plasmon resonance frequency and strength of the resonance absorption is controlled by adjusting the width of said conductive stripes.

8 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 5 , wherein said plasmon resonance frequency and strength of the resonance absorption is controlled by adjusting the width of said at least one plasmonic graphene channel.

9 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 2 , wherein the width of said at least one plasmonic graphene channel is in a sub-micron range.

10 . The plasmon-enhanced terahertz graphene based optoelectronic structure of claim 2 , wherein the width of said at least one graphene channel ranges from 100 nm to few micrometers.

11 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 1 , wherein said substrate is fabricated from SiC (0001) material.

12 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 2 , wherein said plasmonic graphene channels in said second periodic array thereof extend substantially in parallel each to the other.

13 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 2 , wherein a ratio Λ/w between the width w of said at least one plasmonic graphene channel and a period Λ of said first array of conductive stripes exceeds 10.

14 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 13 , wherein said ratio is within the approximate range of 20 to 23.

15 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 13 , wherein said period Λ of said first array of conductive stripes ranges between 1 μm to 9 μm.

16 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 6 , wherein a ratio Λ/w of a period Λ of said first array of conductive stripes to the width w of said at least one plasmonic graphene channel is approximately 20:1, wherein the mobility μ of carriers in said at least one plasmonic graphene channel is approximately 1,000 cm 2 /V·s, and the carrier density n in said at least one plasmonic graphene layer is approximately 1.5×10 13 cm −2 .

17 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 6 , wherein said mobility μ of carriers in said at least one plasmonic graphene layer is approximately 50,000 cm 2 /V·s or higher.

18 . The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 2 , wherein said conductive stripes are made from at least one metal.

19 . A method of fabrication of a plasmon-enhanced terahertz graphene-based optoelectronic structure comprising:
(a) epitaxially forming a single layer of graphene on a SiC substrate, and (b) forming, on said single layer of graphene, a first periodic array of metallic stripes extending substantially in paralleled relationship one with respect to another with respective gaps defined between neighboring metallic stripes, wherein a second periodic array of graphene channels is sandwiched between said substrate and said first periodic array of metallic stripes, said second periodic array including a plurality of graphene channels defined by areas of said single layer of graphene confined in respective gaps between neighboring metallic stripes, (c) applying a layer of electrolyte atop of said first periodic array of metallic stripes to envelope and being in contact with said first array of metallic stripes and said second array of graphene channels, (d) connecting a gate terminal to said electrolyte layer, and (e) coupling a source of gate voltage between said gate terminal and said graphene layer, wherein a ratio of a period Λ of said first periodic array to a width w of each said graphene channel exceeds 10, wherein the width w of said each graphene channel is in sub-micron range, and wherein the mobility μ of carriers in said graphene layer ranges from 1000 to 100,000 cm 2 /V·s.

20 . The method of claim 19 , further comprising:
exposing said optoelectronic structure to an incident light polarized in a direction perpendicular to elements selected from a group consisting of said graphene channels and said metallic stripes, to excite transverse plasmon resonance in graphene, and controlling said gate voltage to tune carrier density of said graphene layer, to obtaining a plasmon resonance response.

Assignees

• Univ Maryland
• Us Gov Sec Navy
• Univ Monash

Inventors

• Jadidi Mohammad M
• Sushkov Andrei B
• Gaskill David Kurt
• Fuhrer Michael
• Drew Howard Dennis
• Murphy Thomas E

Classifications

• H01L31/09 Primary

  Electricity · mapped topic

• G01N2021/258

  Surface plasmon spectroscopy, e.g. micro- or nanoparticles in suspension · CPC title

• G01N21/3581

  using far infrared light; using Terahertz radiation · CPC title

• H01G9/2045 Primary

  comprising a semiconductor electrode comprising elements of the fourth group of the Periodic Table with or without impurities, e.g. doping materials · CPC title

• H10F30/10 Primary

  the devices being sensitive to infrared radiation, visible or ultraviolet radiation, and having no potential barriers, e.g. photoresistors · CPC title