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Metamaterial-Enabled and Bio-Inspired Electromagnetic/Optical Devices Douglas H. Werner, Director Computational Electromagnetics and Antennas Research Lab

Department of and Materials Research Institute Pennsylvania State University University Park, PA 16802 [email protected]

Overview

 What are ?  Electromagnetic/Optical Metamaterials and Metasurfaces  Tunable and Reconfigurable Metamaterials  Cloaks and Illusion Devices  Body Area Networks and Wearable Antennas  Bio-inspired Electromagnetics/

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

Conventional vs. Metamaterials

Properties derived from Properties derived from constituent . constituent units (artificial atoms), which can be engineered.

Empty glass Positive refraction Negative refraction! Negative Index Materials Beam Bender Invisibility Cloaks

Perfect

Chiral Metamaterial

Optical Black Hole Active Metamaterial Carpet Cloak

The metamaterial technology and approach enables unprecedented design flexibility and novel device applications. Design and Optimization of Antennas Nature-inspired Numerical Novel Antennas and Optimization Algorithms EM Solvers Metamaterials PSO

GA

WDO

CLONALG

CMA-ES

+ Robust & Global Optimization + Custom In-house EM Solvers + Improve Existing Antennas + Large Number of Parameters + Industry Standard Software + Develop New Antennas + Real- and Discrete-valued + Proven Computationally + Design and Verify by Modeling, Search Spaces Efficient Techniques Fabrication and Characterization Groundbreaking Meta-Antennas

Octave Bandwidth Negligible Loss Metahorn A wire-grid metamaterial gives low E-plane sidelobes from 3.4 GHz to 7.0 GHz.

Conventional Horn

Press Coverage:

Metahorn

Simulation Measurement Broadband Square Metahorn with - Broadband Monopole Enabled by Independent Radiation Patterns Ultra-Thin Metamaterial Coating 12 GHz 18 GHz

Lightweight*, 0 dB low cost Measurements alternative to confirmed that the machined, heavy metamaterial increased corrugated horns the bandwidth to over an octave while preserving the * Critical for Space radiation pattern of a simple monopole. 14 GHz 16 GHz -40 dB Applications Metamaterial for Multi-Beam Radiation - 3D Radiation Pattern Comparison monopole monopole

3 2

4 1

z y Radiation Pattern

x A redistribution of the radiated energy in desired directions! 4.25 GHz 4.85 GHz 5.10 GHz

Radiation Pattern

Z. H. Jiang, M. D. Gregory, and D. H. Werner, "Experimental Demonstration of a Broadband Transformation Optics Lens for Highly Directive Multibeam Simulation without the lens (dashed blue lines), simulation with the lens ( blue lines), measurement without the lens Emission," Phys. Rev. B, vol. 84, (dashed black lines), measurement with the lens (solid black lines). pp. 165111/1-6, October 2011. The simulated and measured E-plane realized gain patterns with and without the lens confirm the wave effect in the elevation plane. DIGITALLY-CONTROLLED ELECTRICALLY-STEERABLE METAMATERIAL The physics of effective zero-index metamaterials (infinite ) allow for a completely steerable lens to be constructed with only two metamaterial states: on and off. Conceptual Design Scanning Behavior Ideal Implementation

Hexagonal Unit Cell Design Tuning Demonstration Prototype Lens and Display Board

Digitally-controlled switches within each turn the metamaterial on and off. TUNABLE CROSSED ELD WITH METAMATERIAL SUBSTRATE FOR CIRCULAR POLARIZATION

Simulated Reflection Phase from the Metamaterial Surface (Simulated) Body Area Network (BAN) Technology • 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

* Low-Rate Wireless Personal Area Networks (LR-WPANs) Amendment 4, IEEE Standard 802.15.4j, 2013. ASSIST sensor node Metasurface-enabled Wearable Antenna --- 2.4 GHz MBAN band antenna measurement

Integrated Antenna Being Bent Integrated Antenna Conformed to Body Reflection at Input Port of the Antenna

Robust to structural Robust to ! environment change!

Measurement Measurement

Measurements show that the antenna input impedance is very robust to bending and human body loading. Metasurface-enabled Wearable Antennas --- MBAN band CP Wearable Antenna Observing field distribution on human body – majority of the field is propagating on the back, right leg, head, and chest.

RHCP

Antenna LHCP

x-y plane z Coupling aperture

y Stripline feed x LHCP RHCP 0.48W/kg 10V/m

SAR E-field x-z plane

0.001W/kg 0.1V/m 2.38 GHz Invisibility and Cloaking: Science Fiction on the Verge of Becoming Reality…

*J.B. Pendry et al., Science 312, 1780 (2006). Uniform-Thickness Cloak

Uncloaked PEC

*Schurig et al., Science 314, *Liu et al., Science 323, 366 977 (2006). (2009).

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

16 Electromagnetic Illusion Created by Metasurfaces

Using a single layer metasurface to achieve illusion. Metasurfaces made of periodic metallic patterns

PEC cylinder PEC cylinder with metasurface coating to mimic free space

Dielectric cylinder 1 (εr = 2) cylinder 2 (εr = 20) Dielectric cylinder 1 with metasurface coating to mimic dielectric cylinder 2 Super-Resolution / TO Lenses Isotropic µ = -1 Metamaterial for MRI Enhancement at 8.5MHz for Prostate Cancer Detection

Low-frequency performance is made possible by ring loaded with and . With the lens (green), the lens resolves two magnetic sources that cannot be distinguished without the lens (blue).

The lens also increases the received by a factor of 20 or more. C. Scarborough, et al., Appl. Phys. Lett., 101, 014101 (2012).

Transformation Optics Gradient Index Extreme-Angle Broadband Metamaterial Flat Lens by Transformation Optics Bulk TO Layered TO Biconvex Lens Flat Lens Flat Lens Many TO designs The lens works by an require impractical material index of refraction tapering properties, but this from 1 at the edges to 4 in uses a quasi- the focal plane. conformal mapping to create a design with Normal Incidence 45 degree broadband, low- loss, gradient- index materials.

Fractal in Electromagnetics

Fractals in Nature Fractals in Electromagnetics

Sierpinski Monopole Multiband Antenna

Leaf Growth

Sea Urchin Fractal Cross- Frequency Selective Surface Multiband Filter for the Mid-IR* 10 µm

Broccoli

Lightning * J.A. Bossard, et al., IEEE Trans. Antennas Propagat., 54, pp. 1265-1276 (2006). Bio-Inspired Electromagnetics: Broadband Reflectors Found in Nature Dielectric Multilayers/Superlattices “Quarter-Wave” “Chirped” “Random” Stacks Stack Stack

‘Chaotic/Random’ Silvery Fish Butterfly Chrysalis

‘Chirped’

Beetle Shell εr1 εr2 εr1 > εr2

* A.R. Parker, J. R. Soc. Interface, 2, pp. 1-17 (2005). Fractal Random Multilayers Fractal random Cantor bar can Optimized fractal random dielectric produce dielectric multilayer stacks multilayer with broadband reflectivity in

that appear ‘chaotic’ the Mid-IR

Stage Stage 0 Stage 1

Stage Stage 2 Stage 3

Stage Stage 4

Stage Stage 0 Stage 1 Stage 2 Stage Stage 3 a-Si SiO2

air R

27.9µm

SiO2 T

0 -10 Normal Incidence -20

-30 -40 Generator 1 Generator 2 Generator 3 -50

-60 -70

Scattering Magnitudes (dB) Magnitudes Scattering |R | TE -80 |T | TE -90 2.5 3 3.5 4 4.5 5 5.5 6 (m) Super-Octave Absorbers for the GA Optimized Unit Cell Geometry

200 nm 600 nm

Absorptivity vs. Wavelength and Angle polyimide A A Pd metal Si substrate

>90% Absorptivity Simulated Measured >1 Octave Bandwidth >±45º Angular Stability Polarization Independent

* J. A. Bossard, et al., ACS Nano (2014). Optical Metamaterial Filters and Mirrors

Transmission band: 3 ~ 3.5 μm Broadband Mean in-band insertion loss: < 1dB Mean out-of-band transmission: ~ -10.1dB Angle-tolerant Mid-IR All-Dielectric FSS Filter Engineered Photonic In-band group delay variation: ~ 12fs Metamaterial Filter

Z. Jiang, et al., Scientific Reports, 3, 1571 (2013). S. Yun, et al., Appl. Phys. Lett., 96, 223101 (2010). All-Dielectric ZIM Perfect Mirror Optical Complementary Metallic Membranes

468nm patterned a-Si on 0.5mm fused silica

2.05 μm

Solid: Measurements Dots: Simulations S. Yun, et al., Appl. Phys. Lett., 102, 171114 (2013). Q. Hao, et al., Appl. Phys. Lett., 97, 193101 (2010). Photonic Integrated Circuits Based on Transformation Optics Devices Coordinate Transformation

Transformation optics devices that perform diverse, simple functions can be integrated together to build complex photonic systems for optical communications, imaging, computing, and sensing. At least 50 Awards and Recognitions .We have at least 550 published journal have been received by the students CEARL Group articles and conference proceedings: and post-docs in CEARL since 1998 . IEEE Trans. on which include several prestigious . Nature Materials Best Paper Awards given by . Optics Express international journals/societies, . Physics Review B . JOSA B Feature Articles (selected for cover . ACS Nano art) in highly rated international . Journal of journals, as well as numerous . Applied Physics Letters Student Research Competition . New Journal of Physics Awards given by international . IEEE Antennas and Propag. Mag. professional societies such as the . IEEE Trans. on Antennas and Propag. IEEE, the University, the College and . IEEE Antennas and Wireless the Department. Propagation Letters … Conference Photos

2008 Metamaterial 2010 IEEE APS 2009 ACES Conference, Conference, Conference, Barcelona, Spain Toronto, Canada Monterey, CA

2008 URSI 2009 IEEE APS 2008 IEEE APS Conference, Conference, Conference, Chicago, IL Charleston, SC San Diego, CA