Project Summary

1UNCLASSIFIED

UNCLASSIFIED

Photonic-Crystals In Military Systems

Energy Harvesting, Thermal Camouflage, & Directed Energy

Leo DiDomenico3

Hwang Lee1

Marian Florescu1

Irina Puscasu2

Jonathan Dowling1

1 Department of Physics & Astronomy,Louisiana State University

2 Ion Optics Inc.3 Xtreme Energetics Inc.

Points of Contact: Dr. Leo D. DiDomenico Leoddd@XEsolar.com & Prof. Jonathan P. Dowling jdowling@lsu.edu

Project Summary

2

Contents

Introduction to Applications of Photonic Band Gap (PBG) Material

What is a Photonic Band Gap Material?

Generating Electricity from Spectral & Directional Control of IR Radiation

Controlling Thermal Radiation for IR Camouflage

Pumping Laser Weapons with Thermal Radiation from PBG Materials

Initial Experimental Studies On PBG Thermal radiation control

Project Summary

3

Power Generation Systems:Low-Temperature

ThermophotovoltaicsProblem

Solution

Applications

Performance Expectations

max max( )

( )

out

in s

P V J V

P d b!

" " "= =

# h

S. Lin et al. Sandia Labs

PBG

Optimize the input radiation band andpropagation direction to a PV

& don’t worry too much about the PV itself!

TPV using PBG is relatively Low Temperature.

Conventional TPV Systems Too Hot

Project Summary

4

Thermal Radiation Control Designs

Other Applications

Solution

Engineer the radiative thermal responseusing photonic crystals to control:

Spectral Directional Tunability

for adaptive thermal emissivity response.

Omnidirectional IR reflectors Broadband systems Multi Band Operation PBG coatings with surface effects Smart Skin Technology for Tanks

Tunable IRCamouflage Systems

Improved Thermal Imagers Thermal Camouflage Radar Signature Reduction Low Observability and Stealth Solar and Thermal Covers

ProblemThermal signatures have become too easy to

detect

Project Summary

5

High-PowerPhotonic Crystal Lasers for Power Beaming

ProblemDefense against kinetic energy weapons requiresrepeated fast interception. Chemical lasers fail to

deliver the punch over an extended fight.

Solution

Applications•High power thermally pumped PBG lasers

•Replace chemical laser

•Deep ammunition magazine

•Other -- Point-to-point laser comm.

Gas Dynamic lasers require energeticchemical reactions which limit

practical embodiments

Convert heatgradients intoA flow of incoherentnarrow band pumplight for laser usingPBG energy funnel.

Cold

Project Summary

6

Contents

Introduction to Applications of Photonic Band Gap (PBG) Material

What is a Photonic Band Gap Material?

Generating Electricity from Spectral & Directional Control of IR Radiation

Controlling Thermal Radiation for IR Camouflage

Pumping Laser Weapons with Thermal Radiation from PBG Materials

Initial Experimental Studies On PBG Thermal radiation control

Project Summary

7

Photonic Crystal Structures

•Periodic dielectric

•Scale of periodicity is ~λ/2.

•Exhibits large dielectric contrast.

•Light velocity is a function of direction.

•Temperature varies slowly relative to ~λ/2.

•Thermal radiation is selectively suppressed.

• “Semiconductor” material for Light

Project Summary

8

Simple Photonic Crystals

Joannopoulos, Meade, Winn, Photonic Crystals (1995)

Alternating materials of higher & lower refractive indices

Periodicity: on the order of wavelength of light

Functionality: semiconductors for light

Project Summary

9

3-Dimensional Photonic Crystals

The math can be very complexbut the basic idea is VERY SIMPLE...

Scattered waves can add destructivelyfor some frequencies and from somedirections…

Therefore, certain very special PBG structureshave all directions of propagation forbidden over aband of frequencies.

3D Crystal Structurewith scattering plans

shown

Each scattering sitecontributes to the total

Wave response.

Project Summary

10

•TDOS measures the number of states {kx, ky, kz, n} that radiate.•TDOS is the number of states for a given dω about the frequency ω.•Opto-Thermal applications require extending the idea of TDOS.•The TDOS must be extended to account for the overlap of

The periodic dielectricThe Radiation field.Atoms with atomic transitions.Temperature distribution.

1D 2D

New Design Tools are Needed for Opto-ThermalEngineering with Photonic Crystals

The fields do not always overlap the dielectric whereatoms can absorb or emit energy & heat the material.

An extension of basic radiation theory, which now includes photon-phononinteractions inside a PBG material with a non-uniform temperature distribution, is being developed by the authors and with the intent of develop engineering software tools for opto-thermal PBG materials.

Project Summary

11

Photonic Crystal Fiber

Opal

Inverted Opal

Woodpile

Butterfly Wing

Silicon Pillars

Photonic Crystals:Examples

Project Summary

12

A Dizzying Array ofPotential Applications

Band Gap: Semiconductors for Light

Band-Gap Shift: Optical Switching & Routing

Local Field Enhancement:Strong Nonlinear Optical Effects

Anomalous Group Velocity Dispersion:Negative index metamaterials for stealth applications and super-prism dispersion, true time delay lines

Micro-cavity Effects: Photodetectors, LED

Low-Threshold Lasers

Project Summary

13

Contents

Introduction to Applications of Photonic Band Gap (PBG) Material

What is a Photonic Band Gap Material?

Generating Electricity from Spectral & Directional Control of IR Radiation

Controlling Thermal Radiation for IR Camouflage

Pumping Laser Weapons with Thermal Radiation from PBG Materials

Initial Experimental Studies On PBG Thermal radiation control

Project Summary

14

PV Cells Need a Matched SpectrumPV Cells Need a Matched Spectrum

Heat Generated!

Out of band energy from PV cell,creates waste heat but no electricity !

TPV Cell

There are 2 potentialsolutions UsingPhotonic Crystals …

Project Summary

15Method 1: Thermal Gradients AllowRethermalization

Cold

Hot

Band GapLight Cone

RethermalizeOut of Band Energy

PhotonicCrystal

HeatSource

To TPV

Project Summary

16

Thermal Radiation in PBG Material

RECALL:

•Spectral Intensity: position, direction, & frequency

•Absorptivity: T(r), direction, # of levels, & frequency

•Energy velocity depends on PCS

•Total density of atom-connected photon states

Photon-PhononInteraction in

Non-PBG

Now extend principles to a PBG material

Project Summary

17

TPV Energy Conversion:PBG Spectral Control

SpectralFunnel

(Not a Filter)

TPV Cell Device

Broad BandHeat Source

Project Summary

18

TPV Energy ConversionState-of-the-art

• Intermediate Absorber/Emitter• Filter: Only the photons with right energy• Keep operating temperatures lower

• Recycle: Heat the absorber with theunused photons

Improve conversion efficiency: Recycling the unused photons to heat the Emitter/absorber

Incorporate PBG into a Classic TPV Design

Project Summary

19

!!"

#$$%

&'!!

"

#$$%

&

(

('=

As

A

S

A

TPV

T

T

T

T0

4

4

11)

absorber cell

A!

S!

AT

ST

0T

Solid angle for absorber

Solid angle for the sun

Temp of the thermal source

Temp of absorberTemp of the cell

1000 2000 3000 4000 5000 6000

0.2

0.4

0.6

0.8

85%

Full concentration !="S

TA = 2500 K

Method 2: TPV Energy Conversion:Using PBG Directional Control

Instead of increasing ΩS (concentration), decreasethe solid angle of the intermediate absorber, ΩA.

T Kelvin

Project Summary

20

Novel PBGAngle-Selective Absorber

Novel Design of an efficient angle-selective PBG absorber

• a wave-guide channel in 2D PBG embedded in a 3D PBG structure• single-mode (uni-directional) operation for a wide range of frequency• alternative structures can be designed to achieve a prescribed efficiency• LSU patent application

3D PBG

3D PBG

2D PBG1D Channel

Project Summary

21Funneling of theThermal Radiation

(,)WT!(,)WT!

!

Photonic crystal radiationPhotonic crystal radiation

Blackbody input radiationBlackbody input radiation

Filter output radiationFilter output radiation

Filter output radiationFilter output radiation

Blackbody input radiationBlackbody input radiation

!

• For a given blackbody input power, T= 400 K (area under the red curve)– Filter

• only eliminates lower and higher spectral components, selecting incident radiation in anarrow range

• Appreciable amount of energy is wasted– Photonic crystal

• funnels the incident energy into a narrow spectral range• runs at a higher effective temperature (defined by the blackbody with the samemaximum peak power)

ProposedCurrent

20 % Transfer efficiency5 % Transfer efficiency

Project Summary

22

Contents

Introduction to Applications of Photonic Band Gap (PBG) Material

What is a Photonic Band Gap Material?

Generating Electricity from Spectral & Directional Control of IR Radiation

Controlling Thermal Radiation for IR Camouflage

Pumping Laser Weapons with Thermal Radiation from PBG Materials

Initial Experimental Studies On PBG Thermal radiation control

Project Summary

23

Hiding Thermal Signatures

Project Summary

24

Doubly-Periodic Photonic Crystals:Dual-Band Optical Properties (I)

“On demand” optical transmission and reflection spectra three characteristic length scales: radius of the cylinders, distance between the cylinders and width of the rectangular veins (optimum values: r/a=0.078, L/a=0.194 and w/a=0.38) full photonic band gap (both polarizations) of Δω/ωc=18.25% centered on ωc/ω0=0.83 presents spectral regions with high reflection concomitant with a large number of modes at lower frequencies (high transmission)

Photonic crystal structure Photonic band structure

Project Summary

25

Doubly-Periodic Photonic Crystals:Dual-Band Optical Properties (II)

“On demand” field distribution depending on the frequency the field can be localized in different regions of the high-index of refraction dielectric or in the air fraction spatial field distribution can be used to optimize the coupling to absorbers placed into the structure in order to enhance thermal emission

Electromagnetic field distribution for TM modes for the first three bands at the M-point

Project Summary

26

Dynamical Tuningof Spectral Emissivity

Normalized emission from photonic crystal test structure at 325 C under different gasconditions: different concentration values for CO2 and N2. (right side-zoom in)

Possibility of tuning the emissivity of the structure by gas choice and by controlling its gasconcentration

3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7

0.00

0.05

0.10

0.15

0.20

0.25

% n

orm

aliz

ed e

mis

sio

n

wavelength (microns)

Baselinenog C-10C-12.5 C-15 C-2.5 C-20 C-5 N2-a N2-b N2-c N2-d N2-e N2purge

Project Summary

27

Contents

Introduction to Applications of Photonic Band Gap (PBG) Material

What is a Photonic Band Gap Material?

Generating Electricity from Spectral & Directional Control of IR Radiation

Controlling Thermal Radiation for IR Camouflage

Pumping Laser Weapons with Thermal Radiation from PBG Materials

Initial Experimental Studies On PBG Thermal radiation control

Project Summary

28

Energy Separation - IEnergy Separation - I

Schematic of energy flow: 1. Temperature gradient moves phonons left to right & Rethermalizes.2. Photonic Band Gap restricts photons to move downward.

Hot ColdNarrow BandPhotons Laser Gain

Medium

Phonons

Light Spectral Distribution vs Position

Three types of insulators are possible: electrical, thermal, & light. We are using the lightinsulating properties of Photonic Crystals to force the desired narrow-band photons intothe Lasing gain medium & rethermalizing the remaining out-of-band photons into thedesired band for further extraction.

Project Summary

29

Energy Separation - IIEnergy Separation - II

Cold

Hot

PhotonicCrystal

LasingMedium

Designing thespectral and directionalProperties of PCS is a

hard synthesis problem.

Project Summary

30

Contents

Introduction to Applications of Photonic Band Gap (PBG) Material

What is a Photonic Band Gap Material?

Generating Electricity from Spectral & Directional Control of IR Radiation

Controlling Thermal Radiation for IR Camouflage

Pumping Laser Weapons with PBG & Thermal Radiation

Initial Experimental Studies On PBG Thermal radiation control

Project Summary

31

Photonic Crystals:Thermal Radiation Control in IR

Three-dimensional photonic crystal emitterfor thermophotovoltaic power generation,Lin et al.,(2003) Sandia Labs

Photonic-crystal enhanced narrow-bandinfrared emitters, Pralle et al. (2002) Ion Optics

Enhancement and suppression of thermal emission by a three-dimensional photonic crystal, Lin et al. (2000) Sandia Labs

Direct calculation of thermal emission for three-dimensionallyperiodic photonic crystal slabs, Chan et al.(2006) MIT

Thermal emission and absorption of radiation in finite inverted-opalphotonic crystals, Florescu et al.,(2005) JPL&LSU

New, $4.6M, world-class, JEOLJBX-9300FS e-beam lithographysystem (third of its kind) MDL JPL

512 node, dual-processor IA32 Linuxcluster with 3.06 GHz Intel Pentium IVXeon processors and 2 GB RAM Super- Mike LSU

Spectral and angular optical FTIRcharacterization facilities

Ion Optics Inc.

Project Summary

32

BB, Pin = 315 mW, T2 = 420.1 oC

BB, Pin = 130 mW, T1 = 273.4 oC

PC, Pin = 130 mW, T2 = 420.1 oC

– Funneling of thermal radiation of largerwavelength (orange area) to thermalradiation of shorter wavelength (greyarea).

BB (273.4oC) and PC (273.4oC)plots have the same input powerwhile the photonic crystalproduces lower wavelengthphotons

BB (420.1oC) and PC (273.4oC)plots have the same peak powerwavelength

Funneling of the Thermal RadiationExperimental Results

JPL (micro-fab), Ion Optics (testing), LSU (analysis)

Project Summary

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Conclusions

TPV cell efficiencies can be dramatically improved by employing thespectral and angular control provided by photonic crystals

Dual-band spectral radiation management systems using doubly-periodic photonic crystals are now being designed using a restrictedset of “practical” structures

Experimental results confirm the photonic crystal ability to controlthe thermal radiation properties

New vistas exist for using photonic crystals in lasers, IR thermalsignature suppression, and high-power ( non-chemical ) lasers forcommunications and weapons.