Department of Electrical Engineering and Materials Research Institute Pennsylvania State University University Park, PA 16802 dhw@psu.edu

Douglas H. Werner, Director Computational Electromagnetics and Antennas Research Lab

Metamaterial-Enabled and Bio-Inspired

Electromagnetic/Optical Devices

Overview

What are Metamaterials?

Electromagnetic/Optical Metamaterials and Metasurfaces

Tunable and Reconfigurable Metamaterials

Invisibility Cloaks and Illusion Devices

Body Area Networks and Wearable Antennas

Bio-inspired Electromagnetics/Optics

Electromagnetic Metamaterials (Greek prefix "meta" – "beyond")

Artificial materials that can be engineered to exhibit extraordinary electromagnetic properties that do not occur, or may not be readily found, in nature.

Metamaterial-enabled devices have a wide range of applications in the RF, THz, IR, and visible spectrum.

Conventional vs. Metamaterials

Properties derived from

constituent atoms.

Properties derived from

constituent units (artificial atoms),

which can be engineered.

Negative Refraction

Empty glass Positive refraction Negative refraction!

Beam Bender Invisibility Cloaks

Perfect Lens

Carpet Cloak

The metamaterial technology and transformation optics approach enables unprecedented design flexibility and novel device applications.

Optical Black Hole

Negative Index Materials

Chiral Metamaterial

Active Metamaterial

GA

PSO

WDO

Nature-inspired Optimization Algorithms

Numerical EM Solvers

Novel Antennas and Metamaterials

+ Robust & Global Optimization + Large Number of Parameters + Real- and Discrete-valued Search Spaces

+ Improve Existing Antennas + Develop New Antennas + Design and Verify by Modeling, Fabrication and Characterization

+ Custom In-house EM Solvers + Industry Standard Software + Proven Computationally Efficient Techniques

CMA-ES

CLONALG

Design and Optimization of Antennas

Groundbreaking Meta-Antennas Octave Bandwidth Negligible Loss Metahorn Antenna

Lightweight*,

low cost

alternative to

machined, heavy

corrugated horns

* Critical for Space

Applications

A wire-grid metamaterial gives low E-plane

sidelobes from 3.4 GHz to 7.0 GHz.

Metahorn

Conventional

Horn

Simulation Measurement

Broadband Square Metahorn with Polarization-

Independent Radiation Patterns 12 GHz 18 GHz

14 GHz 16 GHz

0 dB

-40 dB

Broadband Monopole Enabled by

Ultra-Thin Metamaterial Coating

the bandwidth to over an octave while preserving the

radiation pattern of a simple monopole.

Measurements

confirmed that the

metamaterial increased

Press Coverage:

Metamaterial Lenses for Multi-Beam Radiation - 3D Radiation Pattern Comparison

monopole

Radiation

Pattern

1

3

4

2

monopole

x

y

z

Radiation Pattern

A redistribution of the radiated energy in desired directions!

4.25 GHz 4.85 GHz 5.10 GHz

The simulated and measured E-plane realized gain patterns with and without the lens confirm the wave bending effect in the elevation plane.

Simulation without the lens (dashed blue lines), simulation with the lens (solid blue lines), measurement without the lens (dashed black lines), measurement with the lens (solid black lines).

Z. H. Jiang, M. D. Gregory, and D.

H. Werner, "Experimental

Demonstration of a Broadband

Transformation Optics Lens for

Highly Directive Multibeam

Emission," Phys. Rev. B, vol. 84,

pp. 165111/1-6, October 2011.

DIGITALLY-CONTROLLED ELECTRICALLY-STEERABLE METAMATERIAL LENS ANTENNA

Tuning Demonstration Prototype Lens and Display Board

The physics of effective zero-index metamaterials (infinite phase velocity) allow for a completely steerable lens to be constructed with only two metamaterial states: on and off.

Hexagonal Unit Cell Design

Ideal Implementation Scanning Behavior Conceptual Design

Digitally-controlled switches within each resonator turn the

metamaterial on and off.

TUNABLE CROSSED ELD WITH METAMATERIAL SUBSTRATE FOR CIRCULAR POLARIZATION

(Simulated) Simulated Reflection Phase from the Metamaterial Surface

• The development of WBAN technology started around 1995 based on the idea of using wireless personal area network (WPAN) technologies to implement communications on, near, and around the human body.

• The FCC has approved a 40 MHz spectrum allocation for medical BAN low-power, wide-area radio links at the 2360-2400 MHz band. This will allow off-loading MBAN communication from the already saturated standard Wi-Fi spectrum to a standard band*

Applications: • Health monitoring, patient tracking, telemedicine, wearable

computing, battlefield survival, personal multimedia, etc.

Type of communication: • On-body, Off-body, and In-body.

Existing frequency bands for BAN systems: • Very/Ultra high frequency (VHF/UHF): ~ 10 MHz • Medical Implant Communication Services (MICS): 402 – 405 MHz • Wireless Medical Telemetry Services (WMTS): 608 – 614 MHz,

1395 – 1400 MHz, and 1427 – 1429.5 MHz • BodyLAN: ~ 900 MHz • Bluetooth: 2400 – 2480 MHz • ZigBee: ~ 2400 MHz, 915 MHz, and 868 MHz • Wireless Local Area Network (WLAN): 2400 & 5200 MHz • Ultra-wide band (UWB): 3.1 – 10.76 GHz

Body Area Network (BAN) Technology

ASSIST sensor node * Low-Rate Wireless Personal Area Networks (LR-WPANs) Amendment 4, IEEE Standard 802.15.4j, 2013.

Integrated Antenna Being Bent Integrated Antenna Conformed to Body

Reflection at Input Port of the Antenna

Measurement

Measurement

Robust to environment change!

Robust to structural deformation!

Measurements show that the antenna input impedance is very robust to bending and human body loading.

Metasurface-enabled Wearable Antenna --- 2.4 GHz MBAN band antenna measurement

0.1V/m

0.48W/kg

0.001W/kg

SAR E-field

Observing field distribution on human body – majority of the field is propagating on the back, right leg, head, and chest.

Metasurface-enabled Wearable Antennas --- MBAN band CP Wearable Antenna

x-y plane

RHCP

LHCP

x-z plane

RHCP LHCP

2.38 GHz

10V/m

y x

z

Stripline feed

Coupling aperture

Antenna

*J.B. Pendry et al., Science 312, 1780 (2006).

Invisibility and Cloaking: Science Fiction on the Verge of Becoming Reality…

Uniform-Thickness Cloak Uncloaked PEC

Cloaked PEC

D.-H. Kwon and D. H. Werner, “Two-dimensional Electromagnetic Cloak Having a Uniform Thickness for Elliptic Cylindrical

Regions,” Appl. Phys. Lett. 92, pp. 113502/1-3, 2008.

*Schurig et al., Science 314,

977 (2006). *Liu et al., Science 323, 366

(2009).

16

Lai et al., PRL 102, 253902 (2009)

Electromagnetic Illusion Created by Metasurfaces Using a single layer metasurface to achieve illusion.

PEC cylinder

Dielectric cylinder 1 (εr = 2) Dielectric cylinder 2 (εr = 20)

PEC cylinder with metasurface coating to mimic free space

Dielectric cylinder 1 with metasurface coating to mimic dielectric cylinder 2

Metasurfaces made of periodic metallic patterns

Super-Resolution / TO Lenses

Extreme-Angle Broadband Metamaterial Flat

Lens by Transformation Optics

The lens works by an

index of refraction tapering

from 1 at the edges to 4 in

the focal plane.

Transformation Optics Gradient Index Flat Lens

Biconvex Lens Layered TO

Flat Lens Many TO designs

require impractical

material

properties, but this

uses a quasi-

conformal

mapping to create

a design with

broadband, low-

loss, gradient-

index materials.

Isotropic µ = -1 Metamaterial for MRI Enhancement at 8.5MHz for Prostate Cancer Detection

Low-frequency performance is made possible by ring

resonators loaded with capacitors and inductors.

With the lens (green),

the lens resolves two

magnetic sources that

cannot be distinguished

without the lens (blue).

The lens also

increases the received

magnetic field by a

factor of 20 or more.

Normal Incidence 45 degree

Bulk TO

Flat Lens

C. Scarborough, et al., Appl. Phys. Lett., 101, 014101 (2012).

Fractal Geometry in Electromagnetics

Fractals in Nature

Sea Urchin

Leaf Growth

Lightning

Broccoli

Fractals in Electromagnetics

Sierpinski Monopole

Multiband Antenna

10 µm

Fractal Cross-Dipole

Frequency Selective Surface

Multiband Filter for the Mid-IR*

* J.A. Bossard, et al., IEEE Trans. Antennas Propagat., 54, pp. 1265-1276 (2006).

Bio-Inspired Electromagnetics:

Broadband Reflectors Found in Nature

* A.R. Parker, J. R. Soc. Interface, 2, pp. 1-17 (2005).

‘Chirped’ Gold

Beetle Shell

“Random”

Stack

“Chirped”

Stack

“Quarter-Wave”

Stacks

Butterfly

Chrysalis

‘Chaotic/Random’ Silvery Fish

εr1 εr2 εr1 > εr2

Dielectric Multilayers/Superlattices

Fractal Random Multilayers

Sta

ge

0

Sta

ge

1

Sta

ge

2

Sta

ge

3

Generator 1 Generator 2 Generator 3

Fractal random Cantor bar can

produce dielectric multilayer stacks

that appear ‘chaotic’

Sta

ge

0

Sta

ge

1

Sta

ge

2

Sta

ge

3

Sta

ge

4

Optimized fractal random dielectric

multilayer with broadband reflectivity in

the Mid-IR

SiO2

a-Si SiO2

27.9

µm

air R

T

2.5 3 3.5 4 4.5 5 5.5 6-90

-80

-70

-60

-50

-40

-30

-20

-10

0

Wavelength (m)

Sca

tte

rin

g M

ag

nitud

es (

dB

)

|RTE

|

|TTE

|

Normal Incidence

Super-Octave Absorbers for the Infrared

* J. A. Bossard, et al., ACS Nano (2014).

Absorptivity vs. Wavelength and Angle

polyimide

Pd metal

Si substrate

A

Measured

GA Optimized Unit Cell Geometry

Simulated

A

200 nm 600 nm

>90% Absorptivity

>1 Octave Bandwidth

>±45º Angular Stability

Polarization Independent

Optical Metamaterial Filters and Mirrors

Broadband Dispersion Engineered Photonic Metamaterial Filter

Transmission band: 3 ~ 3.5 μm Mean in-band insertion loss: < 1dB Mean out-of-band transmission: ~ -10.1dB In-band group delay variation: ~ 12fs

S. Yun, et al., Appl. Phys. Lett., 96, 223101 (2010).

Angle-tolerant Mid-IR All-Dielectric FSS Filter

Q. Hao, et al., Appl. Phys. Lett., 97, 193101 (2010).

Optical Complementary Metallic Membranes

All-Dielectric ZIM Perfect Mirror

468nm patterned a-Si on 0.5mm fused silica

Solid: Measurements Dots: Simulations

2.05 μm

S. Yun, et al., Appl. Phys. Lett., 102, 171114 (2013).

Z. Jiang, et al., Scientific Reports, 3, 1571 (2013).

Photonic Integrated Circuits Based on

Transformation Optics Devices

Transformation optics devices that perform diverse, simple functions can be integrated together to build complex photonic systems for optical communications, imaging, computing, and sensing.

Coordinate Transformation

At least 50 Awards and Recognitions have been received by the students and post-docs in CEARL since 1998 which include several prestigious Best Paper Awards given by international journals/societies, Feature Articles (selected for cover art) in highly rated international journals, as well as numerous Student Research Competition Awards given by international professional societies such as the IEEE, the University, the College and the Department.

2010 IEEE APS

Conference,

Toronto, Canada

2009 IEEE APS

Conference,

Charleston, SC

2009 ACES

Conference,

Monterey, CA

2008 IEEE APS

Conference,

San Diego, CA

We have at least 550 published journal articles and conference proceedings: IEEE Trans. on Nanotechnology Nature Materials Optics Express Physics Review B JOSA B ACS Nano Journal of Applied Physics Applied Physics Letters New Journal of Physics IEEE Antennas and Propag. Mag. IEEE Trans. on Antennas and Propag. IEEE Antennas and Wireless Propagation Letters …

CEARL Group

Conference Photos

2008 Metamaterial

Conference,

Barcelona, Spain

2008 URSI

Conference,

Chicago, IL