OUTLINE:

• THz Frequencies

• Metamaterials

• 2-Dimensional Materials

• Experiment

TERAHERTZ (THZ)

Terahertz- is electromagnetic radiation in the frequency range from 0.1 THz to 10 THz.

Fig. 1

ADVANTAGES OF THZ:• Non-invasive

• Non-destructive

• Intrinsically safe

• Spectroscopy and material characterization

Fig.2

INTRODUCTION TO METAMATERIALS:

Metamaterials are periodic sub-wavelength structures whoseelectromagnetic material properties are derived from its geometryrather than inheriting them directly from its material composition.

Fig. 3a Fig. 3b

WHY ARE WE INTERESTED IN THZMETAMATERIALS?

•Metamaterial devices offer the design and flexibility and the potential to fill part ofthe existing gap in terahertz technology.

•Efficient means for manipulating THz wave propagation

• Thermal, optical, electrical and mechanical actuation mechanism

•Low optical loss and ease of fabrication

Fig. 4b. Invisible woman: “... she achieves these feats by bending all wavelengths of light in the vicinity around herself ... without causing any visible distortion.” – The Fantastic Four (1961)

Fig. 4a. Microwave tunable

antennae:

same antenna can be used for

multiple frequency bands

SPLIT RING RESONATORS •The Split ring resonator (SRR) is such a nanostructure that forms the basic unit of a metamaterial.o They posses the key characteristics of being much smaller than the wavelength.

o In order to exploit the exotic properties that they offer as well as extend the functionality ofmetamaterials, it is important that we have active or dynamic control over their resonance.

•Changing the geometry of SRR changes THz responses

Fig. 5 Schematic of a double-turn split-ring and

single-turn split-ring resonator with their RLC tank

circuit

Imani Jackson

Virginia Union University

June 19, 2017

REU Summer Intern, Department of Physics & Astronomy, Howard University

Study of THz Metamaterials with 2-Dimensional

Structures

THZ WIRELESS COMMUNICATIONSFeatured in the March 2017 issue of OPN

A Netflix-streaming, snapchatting, facetiming, downloading society will soon surpass the bandwidth limits of Google Fiber (>1 GBit/s)

THz VS. GHz

THz wireless communications are predicted to be ~100s of Gbit/s to TBit/s

Haymen Shams and Alwyn Seeds, "Photonics, Fiber and THz Wireless Communication," Optics &

Photonics News 28(3), 24-31 (2017)

2-DIMENSIONAL MATERIALS:

Single layer material composed of a single layer of atoms.

GRAPHENE

Fig.8

GRAPHENE THZ MODULATORSHybrid graphene metasurface based devices showed better Q factor, extinction-ratio, and tunability than devices using graphene as metasurface

Tuned frequency modulation by adding additional graphene layers (i.e. changing the conductivity)

S. Arezoomandan, et al. , Graphene-based reconfigurable terahertz

plasmonics and metamaterials, Carbon 112, 177 (2017)

GRAPHENE-BASED MULTIMODE THZ MODULATORS

0.2 0.3 0.4 0.5 0.6 0.7 0.8

Frequency (THz)

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

Tra

nsm

issio

n

(S/m) graphene

w/o graphene

0.1

0.25

0.5

1

5

0.3 0.4 0.5 0.6 0.7 0.8

Frequency (THz)

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

Tra

nsm

issio

n

=0°

=45°

symmetric SRRs non-symmetric SRRs

(c) (d)

T. A. Searles et al., “Graphene-based Metasurfaces for Multimode Tunable Terahertz Modulators”,

accepted in OSA Technical Digest

a.

b.

THZ BIOSENSORS

S. Wang et al., "Terahertz Biosensing Based on a Polarization-Insensitive Metamaterial," in IEEE Photonics

Technology Letters, vol. 28, no. 9, pp. 986-989, May1, 1 2016.

3/2/17

Sensitivity, 𝑆 =∆𝑓

∆𝐶

where Δf = f0 - fi is the frequency shift from 0 concentration

and ΔC is the change in concentration in mmol/L

f0 = 596.5 GHz

TOROIDAL DIPOLE/QUADROPOLE RESONANCES

Chen & Fan, Optics Letters, (2017).

TOROIDAL DIPOLE/QUADROPOLE RESONANCES

Chen & Fan, Optics Letters, (2017).

AutoCAD representation of Planar

Terahertz Metamaterial

Fig. 6a Fig. 6b

FABRICATION PROCESS:

Fig. 9

Photolithography

1. Photoresist 2. Expose 3. Develop 4. Bake

Photoresist. Expose & Develop. Deposit Metal.

UPCOMING TASK:

CITATIONS:Chaojun Tang, et Qiugu wang, jing chen, zhendong yan, fanxin liu, naibo chen & chenghua sui “Toroidal Dipolar Excitation in Metamaterials Consisting of Metal nanodisks and a DielectrcSpacer on Metal Substrate” app. Physics, vol IV. pp. (1760-1768), (2017)

Cai, Wenshan et AU - Chettiar, Uday K. Kildishev, Alexander V.Shalaev, Vladimir M “Optical Cloaking with Metamaterials” App. Phy, Vol. 1 pp l

Zhenyu, Zhao Suppression of terahertz dipole oscillation in split-ring resonators deformed from square to triangle app. Physics, vol. 1 pp. (1-9)(2017)

Sara Arezoomandan et Hugo O. Condori Quispe a , Nicholas Ramey b , Cesar A. Nieves c , Berardi Sensale-Rodriguez “Graphene-based reconfigurable terahertz plasmonics and metamaterials” app. Physics vol. I pp. (177-184)(2017)

Papasimakis, N “Electromagnetic toroidal excitations in matter and free space” Nature Materials, Vol 15 pp 29-36 (2016)

Longqing Cong et Ranjan Singh “The monolayer graphene sensing enabled by the strong Fano-resonant metasurface”app Physics vol .1 pp. 1-7 (2016)

TeraView http://www.teraview.com/about/what-is-terahertz-thz.html

ACKNOWLEDGMENTS:

oDepartment of Physics and Astronomy at Howard University

Gradauate Students

SIrakMekonen

oPheona Williams

oProfessor Searles

oNational Science Foundation For Financial Support

THANKS FOR LISTENING

Any questions/comments?

INFORMATION:

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