Biomedical subjects

Donald J Sirbuly

Publications and source records attributed to Donald J Sirbuly.

5 recordsLinked to original sources

PubMed2006

Semiconductor nanowire ring resonator laser.

Nanowires of the wide band-gap semiconductor gallium nitride (GaN) have been shown to act as room-temperature uv lasers. Recent advances in nanomanipulation have made it possible to modify the shape of these structures from a linear to a pseudoring conformation. Changes to the optical boundary conditions of the lasing cavity affect the structure's photoluminescence, photon confinement, and lasing as a function of ring diameter. For a given cavity, ring-mode redshifting is observed to increase with decreasing ring diameter. Significant shifts, up to 10 nm for peak emission values, are observed during optical pumping of a ring resonator nanolaser compared to its linear counterpart. The shifting appears to result from conformational changes of the cavity rather than effects such as band-gap renormalization, allowing the mode spacing and position to be tuned with the same nanowire gain medium.

Journal Article↗

PubMed2005

Semiconductor nanowires for subwavelength photonics integration.

This article focuses on one-dimensional (1D) semiconductor subwavelength optical elements and assesses their potential use as active and passive components in photonic devices. An updated overview of their optical properties, including spontaneous emission, ultrafast carrier dynamics, cavity resonance feedback (lasing), photodetection, and waveguiding, is provided. The ability to physically manipulate these structures on surfaces to form simple networks and assemblies is the first step toward integrating chemically synthesized nanomaterials into photonic circuitry. These high index semiconductor nanowires are capable of efficiently guiding light through liquid media, suggesting a role for such materials in microfluidics-based biosensing applications.

Journal Article↗

PubMed2005

Optical routing and sensing with nanowire assemblies.

The manipulation of photons in structures smaller than the wavelength of light is central to the development of nanoscale integrated photonic systems for computing, communications, and sensing. We assemble small groups of freestanding, chemically synthesized nanoribbons and nanowires into model structures that illustrate how light is exchanged between subwavelength cavities made of three different semiconductors. The coupling strength of the optical linkages formed when nanowires are brought into contact depends both on their volume of interaction and angle of intersection. With simple coupling schemes, lasing nanowires can launch coherent pulses of light through ribbon waveguides that are up to a millimeter in length. Also, interwire coupling losses are low enough to allow light to propagate across several right-angle bends in a grid of crossed ribbons. The fraction of the guided wave traveling outside the wire/ribbon cavities is used to link nanowires through space and to separate colors within multiribbon networks. In addition, we find that nanoribbons function efficiently as waveguides in liquid media and provide a unique means for probing molecules in solution or in proximity to the waveguide surface. Our results lay the spadework for photonic devices based on assemblies of active and passive nanowire elements and presage the use of nanowire waveguides in microfluidics and biology.

Journal Article↗

PubMed2005

ZnO nanowire transistors.

ZnO nanowire field-effect transistors (FETs) were fabricated and studied in vacuum and a variety of ambient gases from 5 to 300 K. In air, these n-type nanowire transistors have among the highest mobilities yet reported for ZnO FETs (mu(e) = 13 +/- 5 cm(2) V(-1) s(-1)), with carrier concentrations averaging 5.2 +/- 2.5 x 10(17) cm(-3) and on-off current ratios ranging from 10(5) to 10(7). Four probe measurements show that the resistivity of the Ti/Au-ZnO contacts is 0.002-0.02 Omega.cm. The performance characteristics of the nanowire transistors are intimately tied to the presence and nature of adsorbed surface species. In addition, we describe a dynamic gate effect that seems to involve mobile surface charges and causes hysteresis in the transconductance, among other effects.

Nanowires↗

PubMed2004

Nanoribbon waveguides for subwavelength photonics integration.

Although the electrical integration of chemically synthesized nanowires has been achieved with lithography, optical integration, which promises high speeds and greater device versatility, remains unexplored. We describe the properties and functions of individual crystalline oxide nanoribbons that act as subwavelength optical waveguides and assess their applicability as nanoscale photonic elements. The length, flexibility, and strength of these structures enable their manipulation on surfaces, including the optical linking of nanoribbon waveguides and other nanowire elements to form networks and device components. We demonstrate the assembly of ribbon waveguides with nanowire light sources and detectors as a first step toward building nanowire photonic circuitry.

Journal Article↗