Design, Fabrication, and Characterization of Metamaterials for Transformation Optics and Focusing Applications.

摘要

The research covered four primary areas: manufacture of on-chip transformation optics (metamaterials), metamaterials as superabsorbers, thermal characterization of metamaterials and nanophotonic devices, and use of metamaterials for plasmonic focusing and splitting. MANUFACTURE: The team designed, fabricated, and experimentally demonstrated an on-chip device for 2d plasmonic transformation optics on a chip. This was done by generating subwavelength dielectric features on a flat metallic surface; by adjusting the spacing of gratings, the team modified the index of refraction in the region of the lens , successfully focusing surface plasmon polaritons (SPP). SUPERABSORBERS: The team used the Rigorous Coupled Wave Analysis (RCWA) method to study the interaction of incident plane waves with periodic metamaterials with alternating doublepositive and double-negative materials, showing very strong effects on light propagation even if the structure s thickness is much smaller than the incident wavelength. This demonstrated the feasibility of absorbing light by very thin films of metamaterials with zero average refractive index. THERMAL CHARACTERIZATION: Since metamaterials can concentrate electromagnetic energy, nanoscale-level self-heating issues can be significant problems with nanoscale device development. The team used Scatting Thermal Microscopy to demonstrate a direct measurement of the temperature distribution of a silicon photonic chip using a thermocouple probe. By constructing a device (a doped Micro Ring Resonator (MRR)) and shining light tuned to MRR resonances, self-heating was induced, noting that when the laser is tuned to the MRR resonance there is a substantial rise in the thermal signal within the ring, but out of resonance the rise in thermal signal is marginal. Repeating the experiment with an undoped device, which showed no significant self-heating. PLASMONIC FOCUSING: The team constructed a device capable of splitting and focusing surface plasmon polaritons into different locations depending on the polarization of the excitation source, showing its possible use as a plasmonic quadrant detector or possible beam splitter, showing that the device split orthogonally polarized light into orthogonal directions.