# US 10,481,433 B1 · Dynamic optical and RF devices based on structured plasmonics and liquid crystal hybrids

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- Number: US 10,481,433 B1
- Document ID: US10481433B1
- Status: Granted
- Kind: B1
- Application number: 16/117,488
- Filed: 2018-08-30
- Granted: 2019-11-19
- Earliest claimed: 2018-08-30
- Assignees: The United States of America as represented by the Secretary of the Air Force
- Applicants: Government of the United States as Represented by the Secretary of the Air Force
- Inventors: Victor Yu Reshetnyak; Dean R. Evans
- Web page: https://patentgrep.com/patent/US10481433B1

## CPC

- G02F 1/13362: {providing polarized light, e.g. by converting a polarisation component into another one}
- G02B 5/003: {Light absorbing elements}
- G02B 5/008: {Surface plasmon devices (diffractive gratings with a pitch less than or comparable to the wavelength G02B5/1809; surface plasmons in integrated optics G02B6/1226; optical analysis of materials by means of surface plasmons G01N21/553)}
- G02F 1/0063: {Optical properties, e.g. absorption, reflection or birefringence (materials for non-linear optics G02F1/355)}
- G02F 1/0136: {for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation (G02F1/0353 takes precedence)}
- G02F 1/1313: {specially adapted for a particular application}
- G02F 1/133509: {Filters, e.g. light shielding masks}
- G02F 2203/10: plasmon
- G02F 2203/11: involving infrared radiation
- G02F 2203/12: spatial light modulator
- G02F 2203/13: involving THZ radiation
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical/RF apparatus comprising a liquid crystal (LC) layer placed above or below a plasmon layer (e.g., a periodic array of graphene ribbons) to enable the tuning of the surface plasmons by varying the voltage applied to the LC to realize thereby devices such as tunable mid-IR, far-IR or THz modulators and filters.

## Claims

### Claim 1

An apparatus, comprising:
a substrate having permittivity and absorption characteristics supporting plasmon excitation within a spectral region of interest;
a plasmonic layer, disposed upon the substrate and including plasmonic material configured to exhibit surface plasmon polaritons (SPP) when exposed to an incident light beam of a first polarization; and
a liquid crystal (LC) layer, disposed upon at least a portion of the plasmonic layer and configured to change a polarization of a light beam passing therethrough;
said LC layer, in response to a first electric field applied thereto, changes said polarization of said light beam passing therethrough to said first polarization;
said LC layer, in response to a second electric field applied thereto, changes said polarization of said light beam passing therethrough to a second polarization, said second polarization being substantially orthogonal to said first polarization, wherein the plasmonic material comprises at least one layer of graphene ribbons having a geometry and spacing selected to provide sensitivity to the spectral region of interest, wherein said first polarization is perpendicular to a long axis of said graphene ribbons.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein said plasmonic material is configured to not exhibit SPP when exposed to an incident light beam of said second polarization.

### Claim 3 (depends on 1)

The apparatus of claim 1, wherein the plasmonic material is formed within said plasmonic layer as one or more of a ribbon form, a monolayer form, a particle/colloid form and a nanoparticle/nanocolloid form.

### Claim 4 (depends on 3)

The apparatus of claim 3, wherein each monolayer of plasmonic material comprises at least one of graphene, gold, silver, copper, VO2, and VxOy.

### Claim 5 (depends on 3)

The apparatus of claim 3, wherein said plasmonic layer comprises an elastomeric plasmonic layer configured to expand or contract in response to an applied stimuli to change a geometry of plasmonic material formed therein.

### Claim 6 (depends on 3)

The apparatus of claim 3, wherein said plasmonic layer comprises a deformable plasmonic layer and said LC layer comprises an elastomeric LC elastomer layer mechanically cooperating with said deformable plasmonic layer and configured to expand or contract in response to an applied stimuli to thereby change a geometry of plasmonic material within said deformable plasmonic layer.

### Claim 7 (depends on 3)

The apparatus of claim 3, wherein the plasmonic layer comprises a stack of plasmonic material ribbon layers separated by at least one of tunable dielectric layers, metallic layers and phase change layers.

### Claim 8 (depends on 1)

The apparatus of claim 1, wherein:
said plasmonic material further comprises anisometric shaped plasmonic material; and
said LC layer, in response to each of at least one additional electric field applied thereto, changes said polarization of said light beam passing therethrough to, respectively, at least one additional polarization.

### Claim 9 (depends on 1)

The apparatus of claim 1, wherein said apparatus further comprises a controllable electric potential source configured to impart each of a plurality of electric fields to said LC layer to provide thereby a tuning function of said apparatus.

### Claim 10 (depends on 1)

The apparatus of claim 1, wherein the substrate comprises at least one of silicon, SiO2, Al2O3, VO2, VxOy, CdTe, and ITO.

### Claim 11 (depends on 1)

The apparatus of claim 1, wherein the liquid crystal layer comprises at least one of cholesteric liquid crystals (CLC), nematic liquid crystals), twisted nematic liquid crystals, smectic liquid crystal, and swinging nematic liquid crystals (SLC).

### Claim 12 (depends on 1)

The apparatus of claim 1, wherein said incident light comprises one of an optical wavelength light and a millimeter wavelength light.

### Claim 13 (depends on 1)

The apparatus of claim 1, wherein said plasmonic layer comprises a deformable plasmonic layer configured to expand or contract in response to an applied stimuli such that a distance between said graphene ribbons changes in response to said expanding or contracting.

### Claim 14 (depends on 1)

The apparatus of claim 1, wherein the plasmonic material comprises a metallic layer having disposed thereon a distributed Bragg mirror configured to excite Tamm plasmons therebetween when exposed to an incident light beam.

### Claim 15 (depends on 14)

The apparatus of claim 14, wherein the distributed Bragg mirror comprises a stack of dielectric layers wherein the thicknesses of each layer multiplied by the refractive index of the respective layer is equal to one fourth of the wavelength of the incident light beam.

### Claim 16 (depends on 15)

The apparatus of claim 15, wherein the distributed Bragg mirror further comprises a metallic layer disposed within the stack of dielectric layers.

### Claim 17

A method, comprising:
disposing, upon a substrate having permittivity and absorption characteristics supporting plasmon excitation within spectral region of interest, a plasmonic layer including plasmonic material configured to exhibit surface plasmon polaritons (SPP) when exposed to an incident light beam of a first polarization; and
disposing, upon at least a portion of the plasmonic layer, a liquid crystal (LC) layer configured to change a polarization of a light beam passing therethrough;
the LC layer, in response to a first electric field applied thereto, changes the polarization of the light beam passing therethrough to the first polarization;
the LC layer, in response to a second electric field applied thereto, changes the polarization of the light beam passing therethrough to a second polarization, the second polarization being substantially orthogonal to the first polarization, wherein the plasmonic material comprises at least one layer of graphene ribbons having a geometry and spacing selected to provide sensitivity to the spectral region of interest wherein said first polarization is perpendicular to a long axis of said graphene ribbons.