“Lighting the Way to Technology through Innovation” SUNY at Buffalo Department of Chemistry ILPB Metamaterial Research

Overview  Basic Metamaterial Concepts  ILPB Capabilities  ILPB NIM Group  ILPB Metamaterial Research Approaches to NIM fabrication Approaches to NIM fabrication Experimental and Experimental Results Experimental and Experimental Results  Publications and Presentations

Electromagnetic Material Properties ConventionalMaterials Plasmas Negative Index Materials Split Rings no transmission The electromagnetic response of a material is defined by its electromagnetic properties: permittivity  and permeability 

Metamaterials Normal water  = 1.7,  = 1 NIM water*  = -1.3,  = -1.3 *Gunnar Dolling, et. al., Opt. Exp.14, 1842 (2006) Perfect Lens (Pendry, 2000) Light deflection n > 0 n < 0 Light focusing Metamaterials: artificially engineered materials possessing electro-magnetic properties that do not exist in naturally occurring materials.

Modeling - Design - Fabrication - Characterization PLASMONICS Nanoparticles Nanostructure Media NANOPHOTONICS Materials - Devices Systems Metamaterials NIM Applications Novel Photonic Devices ILPB Metamaterial Research/Development Capabilities

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 Bottom-up approach: Chiral NIM Media (Chemical Synthesis/Assembly) Top-down approach Resonant Metallic Nanostructures (Lithography) Chiral molecules doped with plasmonic nanoinclusions Achieves  < 0,  < 0 from EM coupling between paired plasmonic elements ILPB is pursuing a bottom-up approach to NIM fabrication

Chiral Media Development Selected model structures: Helical polyacetylenes Theoretical modeling: Preliminary quantum chemical and EM modeling predicts enhanced chirality and lowered permittivity Proposed synthetic route to chiral components Plasmonic nanoparticles attached to chiral components lower dielectric permittivity

Current Status of Chiral Media Properties  n plasmonic = 0.5  composite = Target Properties for next year  n plasmonic ~ 1  composite ~ 5 x Basic Chiral Media Relations

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. nnnn = 337 nm  n = 0.5

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. Approaches planned for enhancing the load

TEM image of gold nanoshell Plasmonic band tuning: Ormosil/gold NPs Gold nanorods TEM image of 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 = M) Modified Chitosan, 1mg/ml Increasing concentration Au NPs 0.28mg/ml 0.53mg/ml 0.76mg/ml 0.97mg/ml 1.16mg/ml 1.34mg/ml New bands due to gold conjugation TEM image of the mixture Partial aggregation is evident First observation of nanoparticle induced chirality

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. Complex RI Lowered n CD spectrum Measured reflectance Chirality parameter  obtained from CD spectrum KK transform

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) Monomeric Ni Complex (chiral organometallic complex) Characterized Material Computed chirality parameter  Chirality parameter  from CD spectrum

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, , Optical limiting curves Conclusion: TPA-based OPL can be enhanced and optimized using focusing by NIM slabs.

Modeling NIM assisted OPL TPA + NIM slab  = 1000 GM, n = -1.4, d = 200  m PML Concave lense, n = 1.2, to compensate for aperture-induced focusing 40  m Measure I inp Measure I out Two-photon absorbing slab  = 1000 GM, d = 200  m PML

OPL performance

Modeling plasmonic nanoscale trapping F Sca t Polarization Dependent Trapping k TE Trap TM Trap TM analysis TE Analysis Use of gradient force potential V trap  -|E| 2 to verify 3D trapping -|E| 2 Plot of F x and F y

Modeling Scattering Optical Elements (SOE) Example: Demultiplexer A. Hakansson et al, Appl. Phys. Lett. 87, (2005) 1560 nm 1600 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 E. P. Furlani and A. Baev, “Full-Wave Analysis of Nanoscale Optical Trapping,” Proc. COMSOL Conf. October E. P. Furlani and A. Baev, “Free-space Excitation of Resonant Cavities Formed from Cloaking Metamaterial,” submitted to Metamaterials, Sept E. P. Furlani, A. Baev and P. N. Prasad, “Optical Nanotrapping Using Illuminated Metallic Nanostructures: Analysis and Applications,” Proc. Nanotech Conf E. P. Furlani and A. Baev, “Optical Nanotrapping using Cloaking Metamaterial, first revision under review,” Metamaterials, 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, , 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, , A. Baev, E. P. Furlani, M. Samoc, and P. N. Prasad, “Negative Refractivity assisted Optical Power Limiting,” J. Appl. Phys. 102, , 2007.