Talmage Tyler

Design, theory, and measurement of a polarization-insensitive absorber for terahertz imaging

We present the theory, design, and realization of a polarization-insensitive metamaterial absorber for terahertz frequencies. Effective-medium theory is used to describe the absorptive properties of the metamaterial in terms of optical constants\char22{}a description that has been thus far lacking. From our theoretical approach, we construct a device that yields over 95% absorption in simulation. Our fabricated design consists of a planar single unit-cell layer of metamaterial and reaches an absorptivity of 77% at 1.145 THz.

Infrared metamaterial phase holograms

As a result of advances in nanotechnology and the burgeoning capabilities for fabricating materials with controlled nanoscale geometries, the traditional notion of what constitutes an optical device continues to evolve. The fusion of maturing low-cost lithographic techniques with newer optical design strategies has enabled the introduction of artificially structured metamaterials in place of conventional materials for improving optical components as well as realizing new optical functionality. Here we demonstrate multilayer, lithographically patterned, subwavelength, metal elements, whose distribution forms a computer-generated phase hologram in the infrared region (10.6 μm). Metal inclusions exhibit extremely large scattering and can be implemented in metamaterials that exhibit a wide range of effective medium response, including anomalously large or negative refractive index; optical magnetism; and controlled anisotropy. This large palette of metamaterial responses can be leveraged to achieve greater control over the propagation of light, leading to more compact, efficient and versatile optical components.

Hybrid metamaterials enable fast electrical modulation of freely propagating terahertz waves

We demonstrate fast electrical modulation of freely propagating terahertz waves at room temperature using hybrid metamaterial devices. The devices are planar metamaterials fabricated on doped semiconductor epitaxial layers, which form hybrid metamaterial—Schottky diode structures. With an applied ac voltage bias, we show modulation of terahertz radiation at inferred frequencies over 2MHz. The modulation speed is limited by the device depletion capacitance which may be reduced for even faster operation.

Dual-band planar electric metamaterial in the terahertz regime

We present the design, fabrication, and measurement of a dual-band planar metamaterial with two distinct electric resonances at 1.0 and 1.2 THz, as a step towards the development of frequency agile or broadband THz materials and devices. A method of defining the effective thickness of the metamaterial layer is introduced to simplify the material design and characterization. Good agreement between the simulated and measured transmission is obtained for the fabricated sample by treating the sample as multi-layer system, i. e. the effective metamaterial layer plus the rest of the substrate, as well as properly modeling the loss of the substrate. The methods introduced in this paper can be extended to planar metamaterial structures operating in infrared and optical frequency ranges.

A dual-resonant terahertz metamaterial based on single-particle electric-field-coupled resonators

We report the design, fabrication, and measurement of a terahertz metamaterial composed of single geometry electric field coupled resonators that has two closely spaced electric resonances near 1.0 and 1.5THz. Due to the mutual coupling between the different resonances in the particle, the lower frequency resonance of this metamaterial is stronger than that in a metamaterial composed of identically sized single-resonant particles, leading to a larger insertion loss and broader bandwidth. This feature provides more flexibility in metamaterial design and application in the terahertz regime.

Chip scale integrated microresonator sensing systems.

Medicine, environmental monitoring, and security are application areas for miniaturized, portable sensing systems. The emerging integration of sensors with other components (electronic, photonic, fluidic) is moving sensing toward higher levels of portability through the realization of self-contained chip scale sensing systems. Planar optical sensors, and in particular, microresonator sensors, are attractive components for chip scale integrated sensing systems because they are small, have high sensitivity, can be surface customized, and can be integrated singly or in arrays in a planar format with other components using conventional semiconductor fabrication technologies. This paper will focus on the progress and prospects for the integration of microresonator sensors at the chip scale with photonic input/output components and with sample preparation microfluidics, toward self-contained, portable sensing systems.

Directional coupling between dielectric and long-range plasmon waveguides

We have designed, fabricated and characterized integrated directional couplers capable of converting the mode of an optical dielectric waveguide into a long-range plasmon propagating along a thin metal stripe. We demonstrate that the coupling between the two types of waveguides is generally very weak unless specific conditions are met. This sensitivity could be potentially exploited in sensing applications or for developing novel active photonic components.

Planar, flattened Luneburg lens at infrared wavelengths

Employing artificially structured metamaterials provides a means of circumventing the limits of conventional optical materials. Here, we use transformation optics (TO) combined with nanolithography to produce a planar Luneburg lens with a flat focal surface that operates at telecommunication wavelengths. Whereas previous infrared TO devices have been transformations of free-space, here we implement a transformation of an existing optical element to create a new device with the same optical characteristics but a user-defined geometry.

Progress in Chip-Scale Photonic Sensing

Chip-scale integrated planar photonic sensing systems for portable diagnostics and monitoring are emerging, as photonic components are integrated into systems with silicon (Si), Si complementary metal-oxide semiconductor, and fluidics. This paper reviews progress in these areas. Medical and environmental applications, candidate photonic sensors, integration methodologies, integrated subsystem demonstrations, and challenges facing this emerging field are discussed in this paper.

Electronically reconfigurable metal-on-silicon metamaterial

This work was supported by Toyota Motor Engineering and Manufacturing North America and partially supported by the Air Force Office of Scientific Research (Grant No. FA9550-09-1-0562).