1. Photonic-Crystals In Military Systems
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 & Prof. Jonathan P. Dowling
UNCLASSIFIED

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

3. Power Generation Systems: TPV using PBG is relatively Low Temperature.
Thermophotovoltaics
Problem
Applications
PBG
Conventional TPV Systems Too Hot
Solution
Performance Expectations
Optimize the input radiation band and propagation direction to a PV & don’t worry too much about the PV itself!
TPV using PBG is relatively Low Temperature.
S. Lin et al. Sandia Labs

4. Thermal signatures have become too easy to detect
Tunable IR
Camouflage Systems
Other Applications
Problem
Thermal signatures have become too easy to detect
Improved Thermal Imagers
Thermal Camouflage
Radar Signature Reduction
Low Observability and Stealth
Solar and Thermal Covers
Solution
Thermal Radiation Control Designs
Engineer the radiative thermal response using 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

5. High-Power Photonic Crystal Lasers for Power Beaming
Problem
Applications
Defense against kinetic energy weapons requires
repeated fast interception. Chemical lasers fail to
deliver the punch over an extended fight.
High power thermally pumped PBG lasers
Replace chemical laser
Deep ammunition magazine
Other -- Point-to-point laser comm.
Solution
Gas Dynamic lasers require energetic chemical reactions which limit practical embodiments
Convert heat gradients into
A flow of incoherent narrow band pump light for laser using PBG energy funnel.
Cold

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

7. Photonic Crystal Structures
Periodic dielectric
Scale of periodicity is ~l/2.
Exhibits large dielectric contrast.
Light velocity is a function of direction.
Temperature varies slowly relative to ~l/2.
Thermal radiation is selectively suppressed.
“Semiconductor” material for Light

8. Simple Photonic Crystals
Alternating materials of higher & lower refractive indices
Periodicity: on the order of wavelength of light
Functionality: semiconductors for light
Joannopoulos, Meade, Winn, Photonic Crystals (1995)

9. 3-Dimensional Photonic Crystals
Each scattering site contributes to the total
Wave response.
The math can be very complex but the basic idea is VERY SIMPLE...
Scattered waves can add destructively for some frequencies and from some directions…
Therefore, certain very special PBG structures have all directions of propagation forbidden over a band of frequencies.
3D Crystal Structure with scattering plans shown

10. New Design Tools are Needed for Opto-Thermal Engineering with Photonic Crystals
TDOS measures the number of states {kx, ky, kz, n} that radiate.
TDOS is the number of states for a given dw about the frequency w.
Opto-Thermal applications require extending the idea of TDOS.
The TDOS must be extended to account for the overlap of
The periodic dielectric
The Radiation field.
Atoms with atomic transitions.
Temperature distribution.
The fields do not always
overlap the dielectric where atoms can absorb or emit energy & heat the material.
An extension of basic radiation theory, which now includes photon-phonon
interactions 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.

11. Photonic Crystals: Examples
Butterfly Wing
Opal
Inverted Opal
Silicon Pillars
Photonic Crystal
Fiber
Woodpile

12. A Dizzying Array of Potential 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

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

14. PV Cells Need a Matched Spectrum
TPV Cell
There are 2 potential solutions Using Photonic Crystals …
Heat Generated!
Out of band energy from PV cell,creates waste heat but no electricity !

15. Method 1: Thermal Gradients Allow Rethermalization
Heat
Source
Photonic
Crystal
Hot
Cold
Band Gap Light Cone
To TPV
Rethermalize Out of Band Energy

16. Thermal Radiation in PBG Material
Photon-Phonon Interaction in
Non-PBG
RECALL:
Now extend principles to a PBG material
Spectral Intensity: position, direction, & frequency
Absorptivity: T(r), direction, # of levels, & frequency
Energy velocity depends on PCS
Total density of atom-connected photon states

17. TPV Energy Conversion: PBG Spectral Control
TPV Cell Device
Spectral
Funnel (Not a Filter)
Broad Band Heat Source

18. Incorporate PBG into a Classic TPV Design
TPV Energy Conversion
State-of-the-art
Improve conversion efficiency:
Recycling the unused photons to heat the Emitter/absorber
Intermediate Absorber/Emitter
Filter: Only the photons with right energy
Keep operating temperatures lower
Recycle: Heat the absorber with the unused photons
Incorporate PBG into a Classic TPV Design

19. Method 2: TPV Energy Conversion: Using PBG Directional Control
absorber
cell
Solid angle for absorber
Solid angle for the sun
85%
Temp of the thermal source
Temp of absorber
TA = 2500 K
Temp of the cell
T Kelvin
Instead of increasing WS (concentration), decrease
the solid angle of the intermediate absorber, WA.
Full concentration

20. Angle-Selective Absorber
Novel PBG
Angle-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
1D Channel
2D PBG
3D PBG

21. Funneling of the Thermal 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 a narrow 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 same maximum peak power)
Current
Proposed
Photonic crystal radiation
5 % Transfer efficiency
20 % Transfer efficiency
Blackbody input radiation
Blackbody input radiation
Filter output radiation
Filter output radiation

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

23. Hiding Thermal Signatures

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 /c=18.25% centered on c/0=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

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

26. Dynamical Tuning of Spectral Emissivity
Normalized emission from photonic crystal test structure at 325 C under different gas conditions: 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 gas concentration

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

28. Light Spectral Distribution vs Position
Energy Separation - I
Hot
Cold
Narrow Band Photons
Laser Gain Medium
Phonons
Light Spectral Distribution vs Position
Schematic of energy flow:
Temperature gradient moves phonons left to right & Rethermalizes.
Photonic Band Gap restricts photons to move downward.
Three types of insulators are possible: electrical, thermal, & light. We are using the light insulating properties of Photonic Crystals to force the desired narrow-band photons into the Lasing gain medium & rethermalizing the remaining out-of-band photons into the desired band for further extraction.

29. Energy Separation - II Photonic Crystal Cold Lasing Medium Hot
Designing the spectral and directional Properties of PCS is a hard synthesis problem.
Lasing Medium
Hot

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

31. Thermal Radiation Control in IR
Photonic Crystals:
Thermal Radiation Control in IR
Enhancement and suppression of thermal emission by a three-dimensional photonic crystal, Lin et al. (2000) Sandia Labs
New, $4.6M, world-class, JEOL JBX-9300FS e-beam lithography system (third of its kind)
MDL JPL
512 node, dual-processor IA32 Linux cluster with 3.06 GHz Intel Pentium IV Xeon processors and 2 GB RAM
Super- Mike LSU
Spectral and angular optical FTIR characterization facilities
Ion Optics Inc.
Photonic-crystal enhanced narrow-band infrared emitters, Pralle et al. (2002) Ion Optics
Three-dimensional photonic crystal emitter for thermophotovoltaic power generation, Lin et al.,(2003) Sandia Labs
Thermal emission and absorption of radiation in finite inverted-opal photonic crystals, Florescu et al.,(2005) JPL&LSU
Direct calculation of thermal emission for three-dimensionally periodic photonic crystal slabs, Chan et al.(2006) MIT

32. Funneling of the Thermal Radiation Experimental Results
BB, Pin = 315 mW, T2 = oC
BB (273.4oC) and PC (273.4oC) plots have the same input power while the photonic crystal produces lower wavelength photons
PC, Pin = 130 mW, T2 = oC
BB, Pin = 130 mW, T1 = oC
BB (420.1oC) and PC (273.4oC) plots have the same peak power wavelength
Funneling of thermal radiation of larger wavelength (orange area) to thermal radiation of shorter wavelength (grey area).
JPL (micro-fab), Ion Optics (testing), LSU (analysis)

33. Conclusions
TPV cell efficiencies can be dramatically improved by employing the spectral and angular control provided by photonic crystals
Dual-band spectral radiation management systems using doubly-periodic photonic crystals are now being designed using a restricted set of “practical” structures
Experimental results confirm the photonic crystal ability to control the thermal radiation properties
New vistas exist for using photonic crystals in lasers, IR thermal signature suppression, and high-power ( non-chemical ) lasers for communications and weapons.