Publications

Results 51–75 of 87

Search results

Jump to search filters

A Summary of the Theory and Design Team Efforts for the Sandia Metamaterials Science and Technology Grand Challenge LDRD

Basilio, Lorena I.; Brener, Igal; Burckel, David B.; Shaner, Eric A.; Wendt, Joel R.; Luk, Ting S.; Ellis, A.R.; Bender, Daniel A.; Clem, Paul; Rasberry, Roger D.; Langston, William L.; Ihlefeld, Jon F.; Dirk, Shawn M.; Warne, Larry K.; Peters, David; El-Kady, Ihab F.; Reinke, Charles M.; Loui, Hung; Williams, Jeffery T.; Sinclair, Michael B.; Mccormick, Frederick B.

Abstract not provided.

More Details
TYPE Presentation YEAR 2012
OSTI

Nanoantenna-enabled midwave infrared focal plane arrays

Proceedings of SPIE - The International Society for Optical Engineering

Peters, David; Reinke, Charles M.; Davids, Paul; Klem, John F.; Leonhardt, Darin; Wendt, Joel R.; Kim, Jin K.; Samora, Sally

We demonstrate the effects of integrating a nanoantenna to a midwave infrared (MWIR) focal plane array (FPA). We model an antenna-coupled photodetector with a nanoantenna fabricated in close proximity to the active material of a photodetector. This proximity allows us to take advantage of the concentrated plasmonic fields of the nanoantenna. The role of the nanoantenna is to convert free-space plane waves into surface plasmons bound to a patterned metal surface. These plasmonic fields are concentrated in a small volume near the metal surface. Field concentration allows for a thinner layer of absorbing material to be used in the photodetector design and promises improvements in cutoff wavelength and dark current (higher operating temperature). While the nanoantenna concept may be applied to any active photodetector material, we chose to integrate the nanoantenna with an InAsSb photodiode. The geometry of the nanoantenna-coupled detector is optimized to give maximal carrier generation in the active region of the photodiode, and fabrication processes must be altered to accommodate the nanoantenna structure. The intensity profiles and the carrier generation rates in the photodetector active layers are determined by finite element method simulations, and iteration between optical nanoantenna simulation and detector modeling is used to optimize the device structure. © 2012 SPIE.

More Details
TYPE Conference YEAR 2012
OSTIScopus

Phonon manipulation with phononic crystals

Olsson, Roy H.; Kim, Bongsang K.; Reinke, Charles M.

In this work, we demonstrated engineered modification of propagation of thermal phonons, i.e. at THz frequencies, using phononic crystals. This work combined theoretical work at Sandia National Laboratories, the University of New Mexico, the University of Colorado Boulder, and Carnegie Mellon University; the MESA fabrication facilities at Sandia; and the microfabrication facilities at UNM to produce world-leading control of phonon propagation in silicon at frequencies up to 3 THz. These efforts culminated in a dramatic reduction in the thermal conductivity of silicon using phononic crystals by a factor of almost 30 as compared with the bulk value, and about 6 as compared with an unpatterned slab of the same thickness.

More Details
TYPE SAND Report YEAR 2011
DOIOSTI

Thermal conductivity manipulation in lithographically patterned single crystal silicon phononic crystal structures

IEEE International Ultrasonics Symposium, IUS

Kim, Bongsang; Nguyen, Janet; Reinke, Charles M.; Shaner, Eric A.; Harris, Charles T.; El-Kady, Ihab F.; Olsson, Roy H.

The thermal conductivity of single crystal silicon was engineered using lithographically formed phononic crystals. Specifically, sub-micron periodic through-holes were patterned in 500nm-thick silicon membranes to construct phononic crystals, and through phonon scattering enhancement, heat transfer was significantly reduced. The thermal conductivity of silicon phononic crystals was measured as low as 32.6W/mK, which is a ∼75% reduction compared to bulk silicon thermal conductivity [1]. This corresponds to a 37% reduction even after taking into account the contributions of the thin-film and volume reduction effects, while the electrical conductivity was reduced only by as much as the volume reduction effect. The demonstrated method uses conventional lithography-based technologies that are directly applicable to diverse micro/nano-scale devices, leading toward huge performance improvements where heat management is important. © 2011 IEEE.

More Details
TYPE Conference YEAR 2011
ScopusOSTI

Manipulation of thermal phonons: A phononic crystal route to High-ZT thermoelectrics

Proceedings of SPIE - The International Society for Optical Engineering

El-Kady, Ihab F.; Su, Mehmet F.; Reinke, Charles M.; Hopkins, Patrick E.; Goettler, Drew; Leseman, Zayd C.; Shaner, Eric A.; Olsson, Roy H.

Phononic crystals (PnCs) are acoustic devices composed of a periodic arrangement of scattering centers embedded in a homogeneous background matrix with a lattice spacing on the order of the acoustic wavelength. When properly designed, a superposition of Bragg and Mie resonant scattering in the crystal results in the opening of a frequency gap over which there can be no propagation of elastic waves in the crystal, regardless of direction. In a fashion reminiscent of photonic lattices, PnC patterning results in a controllable redistribution of the phononic density of states. This property makes PnCs a particularly attractive platform for manipulating phonon propagation. In this communication, we discuss the profound physical implications this has on the creation of novel thermal phenomena, including the alteration of the heat capacity and thermal conductivity of materials, resulting in high-ZT materials and highly-efficient thermoelectric cooling and energy harvesting. © 2011 SPIE.

More Details
TYPE Conference YEAR 2011
ScopusOSTI
Results 51–75 of 87
Results 51–75 of 87