ILPB Metamaterial Research SUNY at Buffalo Department of
ILPB Metamaterial Research SUNY at Buffalo Department of Chemistry “Lighting the Way to Technology through Innovation” www. photonics. buffalo. edu
Overview Ø Basic Metamaterial Concepts Ø ILPB Capabilities Ø ILPB NIM Group Ø ILPB Metamaterial Research • Approaches to NIM fabrication • Experimental and Experimental Results ØPublications and Presentations
Electromagnetic Material Properties The electromagnetic response of a material is defined by its electromagnetic properties: permittivity and permeability Plasmas Conventional Materials no transmission Negative Index Materials Split Rings no transmission
Metamaterials: artificially engineered materials possessing electro-magnetic properties that do not exist in naturally occurring materials. n>0 Normal water = 1. 7, = 1 NIM water* = -1. 3, = -1. 3 Light deflection *Gunnar Dolling, et. al. , Opt. Exp. 14, 1842 (2006) n<0 Light focusing Perfect Lens (Pendry, 2000)
ILPB Metamaterial Research/Development Capabilities Modeling - Design - Fabrication - Characterization PLASMONICS Nanoparticles Nanostructure Media NANOPHOTONICS Materials - Devices Systems Metamaterials NIM Applications Novel Photonic Devices
Characterization Facilities Macroscopic Scale • CD spectroscopy • Interferometry • Reflectometry
ILPB NIM Group • Prof. Paras N. Prasad – Nanophotonics, Photonic Devices and Materials • Prof. Edward Furlani – Multiphysics and Photonics Modeling, Device Physics • Dr. Alexander Baev – Multiscale Modeling, Material and Device Physics • Dr. Heong Oh - Polymer Chemistry/Chiral Media • Researcher Rui Hu – Materials Synthesis and Characterization • Researcher Won Jin Kim – Polymer Chemistry, Material Synthesis • Researcher Shobha Shukla - Lithography for Nanostructured Media
ILPB Metamaterials Research ILPB is pursuing a bottom-up approach to NIM fabrication Bottom-up approach: Chiral NIM Media Top-down approach Resonant Metallic Nanostructures (Chemical Synthesis/Assembly) (Lithography) Chiral molecules doped with plasmonic nanoinclusions Achieves < 0, < 0 from EM coupling between paired plasmonic elements
Chiral Media Development Selected model structures: Helical polyacetylenes Theoretical modeling: Preliminary quantum chemical and EM modeling predicts enhanced chirality and lowered permittivity Plasmonic nanoparticles attached to chiral components lower dielectric permittivity Proposed synthetic route to chiral components
Basic Chiral Media Relations Current Status of Chiral Media Properties Dnplasmonic = 0. 5 composite = 10 -2 Target Properties for next year Dnplasmonic ~ 1 composite ~ 5 x 10 -1
Materials Development Objectives: 1. Development/characterization of composite material with lowered refractive index. 2. Development/characterization of composite material with enhanced chirality. Strategy: 1. In-situ generation of gold/silver nanoparticles to obtain a high load in the host material. 2. Synthesis of molecular units with high chirality and its polymeric helical form. 3. Characterization. 4. Multiscale modeling and feedback. Realization: The use of photochemical decomposition of noble metal precursors to generate plasmonic particles loaded composites.
PVP host doped with silver nanoparticles. Suppression of the refractive index on the high energy side of plasmonic resonance. Dn = 0. 5 Dn l = 337 nm
Approaches planned for enhancing the load Higher load of NPs may be possible with: 1. Using direct mixing in the organic phase. Example: PMMA host doped with gold nanoparticles prepared in chlorobenzene. 2. Using templates with high density of binding sites. 3. In-situ generation by two-photon lithography. 4. Using nanoparticles of different morphology i. Nanorods. ii. Multipods. iii. Core-shell structures.
TEM image of gold nanoshell TEM image of gold nanorods Plasmonic band tuning: Ormosil/gold NPs Gold nanorods Aspect ratio dependence
Materials Development Objectives: 1. Development/characterization of composite material with lowered refractive index. 2. Development/characterization of composite material with enhanced chirality. Strategy: 1. In-situ generation of gold/silver nanoparticles to obtain a high loading in the host material. 2. Synthesis of molecular units with high chirality and its polymeric helical form. 3. Characterization. 4. Multiscale modeling and feedback. Realization: Synthesis of new chiral molecule, M-chitosan, and mixing it with water soluble gold nanoparticles.
Material Development
Experimental activity: Mixing of gold NPs with chiral template (M-chitosan, N = 10 -4 M) New bands due to gold conjugation 1. 34 mg/ml Increasing concentration Au NPs 1. 16 mg/ml 0. 97 mg/ml 0. 76 mg/ml 0. 53 mg/ml 0. 28 mg/ml Modified Chitosan, 1 mg/ml First observation of nanoparticle induced chirality TEM image of the mixture Partial aggregation is evident
Possible mechanisms of gold conjugation Smaller particles: Induced conformational effect helical arrangement due to chiral template. Larger particles: Coating-like arrangement. Plasmon mediated coupling results in new band. Check-up: Change particle morphology (nanorods), composition and size
Characterization 1. Using CD measurements to obtain chirality parameter. 2. Using Kramers-Kronig transform of reflectance spectra to obtain refractive index. CD spectrum Measured reflectance KK transform Chirality parameter obtained from CD spectrum Lowered n Complex RI
Modeling Multiscale Chiral Media Quantum chemical molecular analysis and design used to predict and optimize chiral parameter . A. Baev et al. , Optics Express 15, 5730 (2007) Characterized Material Chirality parameter from CD spectrum Computed chirality parameter Monomeric Ni Complex (chiral organometallic complex)
Modeling NIM assisted optical power limiting (OPL) TPA enhancement factor for a “sandwiched” structure containing 12. 5 mm of TPA material. Baev, E. Furlani, M. Samoc, and P. N. Prasad, Negative refractivity assisted optical power limiting, J. Appl. Phys. 102, 043101, 2007. Conclusion: TPA-based OPL can be enhanced and optimized using focusing by NIM slabs. Optical limiting curves
Modeling NIM assisted OPL Measure Iout PML 40 mm Measure Iinp Two-photon absorbing slab s = 1000 GM, d = 200 mm PML 40 mm Concave lense, n = 1. 2, to compensate for aperture-induced focusing TPA + NIM slab s = 1000 GM, n = -1. 4, d = 200 mm
OPL performance
Modeling plasmonic nanoscale trapping TM analysis Polarization Dependent Trapping TE Analysis FScat TM Trap TE Trap k -|E|2 Plot of Fx and Fy Use of gradient force potential Vtrap -|E|2 to verify 3 D trapping
Modeling Scattering Optical Elements (SOE) Example: Demultiplexer A. Hakansson et al, Appl. Phys. Lett. 87, 193506 (2005) 1600 nm 1560 nm Possible realization: Dynamical patterning liquid crystal with optical tweezers
ILPB Metamaterial Publications and Presentations • E. P. Furlani and A. Baev, “Electromagnetic Analysis of Cloaking Metamaterial Structures, ” Proc. COMSOL Conf. October 2008. • E. P. Furlani and A. Baev, “Full-Wave Analysis of Nanoscale Optical Trapping, ” Proc. COMSOL Conf. October 2008. • E. P. Furlani and A. Baev, “Free-space Excitation of Resonant Cavities Formed from Cloaking Metamaterial, ” submitted to Metamaterials, Sept 2008. • E. P. Furlani, A. Baev and P. N. Prasad, “Optical Nanotrapping Using Illuminated Metallic Nanostructures: Analysis and Applications, ” Proc. Nanotech Conf. 2008. • E. P. Furlani and A. Baev, “Optical Nanotrapping using Cloaking Metamaterial, first revision under review, ” Metamaterials, 2008. • A. Baev, E. P. Furlani, P. N. Prasad, A. N. Grigorenko, and N. W. Roberts, “Laser Nnanotrapping and Manipulation of Nanoscale Objects using Subwavelength Apertured Plasmonic Media, ” J. Appl. Phys. 103, 084316, 2008. • A. Baev, M. Samoc, P. N. Prasad, M. Krykunov, and J. Autschbach, “A Quantum Chemical Approach to the Design of Chiral Negative Index Materials, ” Opt. Exp. 15, 9, 5730 -5741, 2007. • A. Baev, E. P. Furlani, M. Samoc, and P. N. Prasad, “Negative Refractivity assisted Optical Power Limiting, ” J. Appl. Phys. 102, 043101, 2007.
- Slides: 26