Publications by Year: 2009

2009
Jiming Bao, David C. Bell, Federico Capasso, Natasha Erdman, Dongguang Wei, Linus Froberg, Thomas Martensson, and Lars Samuelson. 2009. “Nanowire-induced Wurtzite InAs Thin Film on Zinc-Blende InAs Substrate.” ADVANCED MATERIALS, 21, 36, Pp. 3654+.Abstract
InAs pyramids and platelets on a zinc-blende InAs substrate are found to exhibit a wurtzite crystal structure. induced by wurtzite InAs nanowires, wurtzite InAs thin film and its associated zinc-blende/wurtzite heterocrystalline heterostructures may open up new opportunities in band-gap engineering and related device applications.
2009_bao_et_al_advancedmaterials.pdf
Elizabeth J. Smythe, Michael D. Dickey, Jiming Bao, George M. Whitesides, and Federico Capasso. 2009. “Optical Antenna Arrays on a Fiber Facet for in Situ Surface-Enhanced Raman Scattering Detection.” NANO LETTERS, 9, 3, Pp. 1132-1138.Abstract
This paper reports a bidirectional fiber optic probe for the detection of surface-enhanced Raman scattering (SERS). One facet of the probe features an array of gold optical antennas designed to enhance Raman signals, while the other facet of the fiber is used for the input and collection of light. Simultaneous detection of benzenethiol and 2-[(E)-2-pyridin-4-ylethenyl]pyridine is demonstrated through a 35 cm long fiber. The array of nanoscale optical antennas was first defined by electron-beam lithography on a silicon wafer. The array was subsequently stripped from the wafer and then transferred to the facet of a fiber. Lithographic definition of the antennas provides a method for producing two-dimensional arrays with well-defined geometry, which allows (i) the optical response of the probe to be tuned and (I!) the density of ``hot spots'' generating the enhanced Raman signal to be controlled. It is difficult to determine the Raman signal enhancement factor (EF) of most fiber optic Raman sensors featuring hot spots because the geometry of the Raman enhancing nanostructures is poorly defined. The ability to control the size and spacing of the antennas enables the EF of the transferred array to be estimated. EF values estimated after focusing a laser directly onto the transferred array ranged from 2.6 x 10(5) to 5.1 x 10(5).
2009_smythe_et_al_nanoletters.pdf
Ertugrul Cubukcu and Federico Capasso. 2009. “Optical nanorod antennas as dispersive one-dimensional Fabry-Peacuterot resonators for surface plasmons.” APPLIED PHYSICS LETTERS, 95, 20.Abstract
Resonant optical nanoantennas exhibit a different length scaling due to the surface plasmons compared to their radio frequency counterparts. In this letter, we address this difference by calculating the wavelength-dependent effective mode index n(eff) for a cylindrical one-dimensional gold nanowire waveguide. Our results show that nanorod optical antennas act as dispersive and lossy Fabry-Peacuterot resonators for surface plasmons.
2009_cubukcu_et_al_apl.pdf
Nanfang Yu, Qijie Wang, Christian Pflugl, Laurent Diehl, Federico Capasso, Tadataka Edamura, Shinichi Furuta, Masamichi Yamanishi, and Hirofumi Kan. 2009. “Semiconductor lasers with integrated plasmonic polarizers.” APPLIED PHYSICS LETTERS, 94, 15.Abstract
The authors reported the plasmonic control of semiconductor laser polarization by means of metallic gratings and subwavelength apertures patterned on the laser emission facet. An integrated plasmonic polarizer can project the polarization of a semiconductor laser onto other directions. By designing a facet with two orthogonal grating-aperture structures, a polarization state consisting of a superposition of a linearly and right-circularly polarized light was demonstrated in a quantum cascade laser; a first step toward a circularly polarized laser.
2009_yu_et_al_apl_01.pdf
Elizabeth J. Smythe, Michael D. Dickey, George M. Whitesides, and Federico Capasso. 2009. “A Technique to Transfer Metallic Nanoscale Patterns to Small and Non-Planar Surfaces.” ACS NANO, 3, 1, Pp. 59-65.Abstract
Conventional lithographic methods (e.g., electron-beam lithography, photolithography) are capable of producing high-resolution structures over large areas but are generally limited to large (> 1 cm(2)) planar substrates. Incorporation of these features on unconventional substrates (i.e., small (< 1 mm(2)) and/or non-planar substrates) would open possibilities for many applications, including remote fiber-based sensing, nanoscale optical lithography, three-dimensional fabrication, and integration of compact optical elements on fiber and semiconductor lasers. Here we introduce a simple method in which a thin thiol-ene film strips arbitrary nanoscale metallic features from one substrate and is then transferred, along with the attached features, to a substrate that would be difficult or impossible to pattern with conventional lithographic techniques. An oxygen plasma removes the sacrificial film, leaving behind the metallic features. The transfer of dense and sparse patterns of isolated and connected gold features ranging from 30 nm to 1 mu m, to both an optical fiber facet and a silica microsphere, demonstrates the versatility of the method. A distinguishing feature of this technique is the us? of a thin, sacrificial film to strip and transfer metallic nanopatterns and its ability to directly transfer metallic structures produced by conventional lithography.
2009_smytheet_al_acs_nano.pdf
Daniel Recht, Federico Capasso, and Michael J. Aziz. 2009. “On the temperature dependence of point-defect-mediated luminescence in silicon.” APPLIED PHYSICS LETTERS, 94, 25.Abstract
We present a model of the temperature dependence of point-defect-mediated luminescence in silicon derived from basic kinetics and semiconductor physics and based on the kinetics of bound exciton formation. The model provides a good fit to data for W line electroluminescence and G line photoluminescence in silicon. Strategies are discussed for extending luminescence to room temperature.
2009_recht_et_al_apl.pdf
Hyunyong Choi, Laurent Diehl, Zong-Kwei Wu, Marcella Giovannini, Jerome Faist, Federico Capasso, and Theodore B. Norris. 2009. “Time-Resolved Investigations of Electronic Transport Dynamics in Quantum Cascade Lasers Based on Diagonal Lasing Transition.” IEEE JOURNAL OF QUANTUM ELECTRONICS, 45, 4, Pp. 307-321.Abstract
In this study, the nature of electronic transport in quantum cascade lasers (QCLs) has been extensively investigated using an ultrafast time-resolved, degenerate, pump-probe optical technique. Our investigations enable a comprehensive understanding of the gain recovery dynamics in terms of a coupling of the electronic transport to the oscillating intracavity laser intensity. In QCLs that have a lasing transition diagonal in real space, studies of the near-threshold reveal that the transport of electrons changes bias region from phonon-limited relaxation (tens of picoseconds) below threshold to photon-driven transport via stimulated emission (a few picoseconds) above threshold. The gain recovery dynamics in the photon-driven regime is compared with conventional four-level lasers such as atomic, molecular, and semiconductor interband lasers. The depopulation dynamics out of the lower lasing state is explained using a tight-binding tunneling model and phonon-limited relaxation. For the superlattice relaxation, it is possible to explain the characteristic picosecond transport via dielectric relaxation; Monte Carlo simulations with a simple resistor model are developed, and the Esaki-Tsu model is applied. Subpicosecond dynamics due to carrier heating in the upper subband are isolated and appear to be at most about 10% of the gain compression compared with the contribution of stimulated emission. Finally, the polarization anisotropy in the active waveguide is experimentally shown to be negligible on our pump-probe data, supporting our interpretation of data in terms of gain recovery and transport.
2009_choi_et_al_ieee_jqe.pdf
R. Maulini, I. Dunayevskiy, A. Lyakh, A. Tsekoun, C. K. N. Patel, L. Diehl, C. Pfluegl, and F. Capasso. 2009. “Widely tunable high-power external cavity quantum cascade laser operating in continuous-wave at room temperature.” ELECTRONICS LETTERS, 45, 2, Pp. 107-U30.Abstract
A grating-coupled external cavity quantum cascade laser operating in continuous-wave at room temperature is reported. Single-frequency operation tunable over more than 160 cm(-1) around the centre wave-length of 4.6 mu m has been observed at a chip temperature of 300 K. The maximum optical power at the gain peak was 300 mW, corresponding to a wall-plug efficiency of 6%. Observed power output at the gain bandwidth edges was in excess of 125 mW.
2009_maulini_et_al_electronics_letters.pdf

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