MURI Meta Materials Team Meeting

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1 MURI Meta Materials Team Meeting Gang Chen Group Massachusetts Institute of Technology, May 10, 2002 DoD MURI on MetaMaterials

2 Current Activities Reconfigurable Micro-bubble Array Devices Switchable Photonic Crystal Devices Collaborative effort with the Itoh Group. Negative Refraction in Photonic Crystals Collaborative effort between the Joannopoulos, Smith/Schultz, and Chen groups at MIT. Activities in Pipeline Fabrication of Photonic Crystals with Holographic Lithography Thermophotovoltaic Devices.

3 2D Bubble-Array Devices Device size: 5mm Simple lattice, Lattice constant: 44 µm SiO 2 surface with holes for bubble nucleation Device Electrode Hole 50µm

4 Control of 2D Bubble Arrays Bubble size: 10µm 2 bubbles 3 bubbles 4 bubbles 50µm

Switchable Photonic Crystal Devices Microstrips were designed to test the concept of switchable photonic crystal before trying to fabricate

5 Switchable Photonic Crystal Devices Microstrips were designed to test the concept of switchable photonic crystal before trying to fabricate one at much smaller scales. The idea was to measure the frequency response of the above devices with different fluids filling the cavities.

6 Microstrip Frequency Response Frequency response of 3/16"microstrip Frequency response of 1/8" microstrip S21, 1/8" no water 0.8 S21, 3/16", no water 1 S21, 1/8" water S21, 3/16 with water 0.8 S S Frequency (GHz) Frequency (GHz) Material used is RT/Duroid 6010 Dielectric constant: 10.2±0.25 Water is highly absorptive in the frequency range of interest Dielectric constant varies from i7.52 to about 63.0+i29.9 in the range of interest.

$Negative Refraction in Photonic Crystals Luo et al., have proposed the idea of a photonic crystal which exhibits negative refraction (as opposed to negative refractive index).$

7 Negative Refraction in Photonic Crystals Luo et al., have proposed the idea of a photonic crystal which exhibits negative refraction (as opposed to negative refractive index). Currently a collaborative effort is on going between the Joannopoulos, Smith/Schultz, and Chen groups. From Joannopolous We are involved in the fabrication of the device which shall be used by the UCSD group to test the concept.

Fabrication of simple shapes is done by powder compaction under high

8 Fabrication Details Material being used is Barium Neodymium Titanate, which is available as nanocrystalline powder. Fabrication of simple shapes is done by powder compaction under high pressure (5000 to 1000psi) Samples used to determine dielectric constant and loss tangent of material

9 Activities in Pipeline Fabrication of Photonic Crystals with Holographic Lithography Thermophotovoltaic Devices.

10 Holographic Lithography and Photonic Crystals 1996, V. Berger et.al, Fabrication of a 2D photonic bandgap by a holographic method, Electronics Letters (collaboration with the Barbastathis group at MIT)

11 Thermophotovoltaic Applications Heat Photo-Voltaic Cells Emitter Filter Schematic of a general Thermophotovoltaic system Thermophotovoltaics essentially consist of an emitter, absorber and/or filter combination. Interference effects (wave nature), proximity effects (tunneling) and spectrally selective emitters have resulted in an improvement over conventional macroscopic TPV systems. We improve on this idea by placing the emitters and absorbers in a periodic 2D array, imitating a photonic crystal, in addition to interference and proximity effects.

12 Photonic TPV Structures TPV cell consists of a 2D array of emitters with absorbers meshed in. It consists of two sub-sets of PBGs, forming a large PBG. emitter absorber (pn junction) substrate Schematic of envisioned TPV cell T 1 T 2 A simpler 1D model Apart from effects mentioned earlier, will proper design of the structure ensure spectral selectivity of emitted radiation? Modeling of such systems begin with the analysis of a simpler 1D structure shown to the left.

13 Tasks to be completed for annual meeting Bubble arrays Try to make 4 by 4 bubble arrays Switchable photonic crystals Interpret results More experiments, preferably with non-absorbing substances such as those used for AANR. Collaborative effort Complete fabrication of structures needed for negative refraction experiment. Holographic Lithography and TPV Experimental set-up and initial modeling

Luminous Equivalent of Radiation

Intensity vs λ Luminous Equivalent of Radiation When the spectral power (p(λ) for GaP-ZnO diode has a peak at 0.69µm) is combined with the eye-sensitivity curve a peak response at 0.65µm is obtained with