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

Patent metadata

Field	Value
Publication number	US-10672933-B2
Application number	US-201615735662-A
Country	US
Kind code	B2
Filing date	Jun 14, 2016
Priority date	Jun 15, 2015
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

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 cm2V−1s−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, and
hybrid metal-graphene plasmonic elements supporting plasmon resonance fully tunable in a range of terahertz frequencies, said hybrid metal-graphene plasmonic elements being configured by:
a graphene layer formed on said substrate,
a patterned conductive layer formed on said graphene layer, said patterned conductive layer forming a first periodic array of a plurality of conductive stripes separated by respective gaps,
a second periodic array of a plurality of plasmonic graphene channels defined in said graphene layer and embedded in said patterned conductive layer, said plasmonic graphene channels being confined within said respective gaps between said conductive stripes,
an electrolyte layer positioned atop said patterned conductive layer to envelop and contact said first periodic array of the conductive stripes and said second periodic array of the plasmonic graphene channels,
a source of an electromagnetic wave of a predetermined wavelength, wherein said electromagnetic wave is incident on said hybrid metal-graphene plasmonic elements, said incident electromagnetic wave being polarized substantially perpendicular to said plasmonic graphene channels,
wherein each of said plasmonic graphene channels has a width smaller than said predetermined wavelength of the electromagnetic wave, and wherein said hybrid metal-graphene plasmonic elements support the controllable plasmon-enhanced resonance fully tunable in a range of terahertz frequencies.

2. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 1 , wherein
said plurality of conductive stripes of said first periodic array are formed in said conductive layer, said conductive stripes extending in a spaced apart relationship each with respect to the other with one of said respective gaps defined between adjacent conductive stripes, and
each of said plasmonic graphene channels of said second periodic array is confined in said one of said respective gaps between said adjacent conductive stripes, wherein said second periodic array of said plasmonic graphene channels is sandwiched between said substrate and said electrolyte layer, wherein a width of each of said conductive stripes exceeds the width of each said plasmonic graphene channel.

3. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 2 , wherein the width of said each of plasmonic graphene channels is in a sub-micron range.

4. The plasmon-enhanced terahertz graphene based optoelectronic structure of claim 2 , wherein the width of each of said plasmonic graphene channels ranges from 100 nm to few micrometers.

5. 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.

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

7. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 6 , wherein said ratio is within the approximate range of 20 to 23.

8. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 6 , wherein said period Λ of said first array of conductive stripes ranges between 1 μm to 9 μm.

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

10. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 1 , wherein said conductive stripes are sandwiched between said graphene layer and said electrolyte layer.

11. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 1 , 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, wherein the controllable plasmon enhanced resonance signal is controlled via a tuning mechanism selected from a group including: an application of the gate voltage V g between said graphene layer and said electrolyte layer forming a direct contact with the conductive stripes and said plasmonic graphene channels, adjustment of a width of said conductive stripes, adjustment of a width of said plasmonic graphene channels, and combination thereof.

12. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 11 , wherein, upon application of said gate voltage of the predetermined value V g , said polarized electromagnetic wave excites transverse plasmon at a plasmon resonance resonance in said plasmonic graphene channels, thereby producing a plasmon-enhanced resonance frequency.

13. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 12 , 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 plasmonic graphene channels.

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

15. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 13 , wherein said mobility μ of carriers in said plasmonic graphene layer is approximately 50,000 cm 2 /V·s or higher.

16. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 12 , wherein said plasmon resonance frequency and strength of the resonance absorption is controlled by adjusting the width of said conductive stripes.

17. The plasmon-enhanced terahertz graphene-based optoelectronic structure of claim 12 , wherein said plasmon resonance frequency and strength of the resonance absorption is controlled by adjusting the width of said plasmonic graphene channels.

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

19. A method of fabrication of a plasmon-enhanced terahertz graphene-based optoelectronic structure comprising:
forming hybrid metal-graphene plasmonic elements capable of supporting plasmon resonance fully tunable in a range of terahertz frequencies, said hybrid metal-graphene plasmonic elements being formed by:
(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 a direct contact wit

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

• Y02E10/542

  Dye sensitized solar cells · CPC title

• 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

• H01L31/09 Primary

  Electricity · mapped topic