@article { ISI:000270670200013, title = {3 W continuous-wave room temperature single-facet emission from quantum cascade lasers based on nonresonant extraction design approach}, journal = {APPLIED PHYSICS LETTERS}, volume = {95}, number = {14}, year = {2009}, month = {OCT 5}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {A strain-balanced, InP-based quantum cascade laser structure, designed for light emission at 4.6 mu m using a new nonresonant extraction design approach, was grown by molecular beam epitaxy. Removal of the restrictive two-phonon resonant condition, currently used in most structure designs, allows simultaneous optimization of several design parameters influencing laser performance. Following the growth, the structure was processed in buried heterostructure. Maximum single-ended continuous-wave optical power of 3 W was obtained at 293 K for devices with stripe dimensions of 5 mm x 11.6 mu m. Corresponding maximum wallplug efficiency and threshold current density were measured to be 12.7\% and 0.86 kA/cm(2). (C) 2009 American Institute of Physics. [doi: 10.1063/1.3238263]}, issn = {0003-6951}, doi = {10.1063/1.3238263}, author = {Lyakh, A. and Maulini, R. and Tsekoun, A. and Go, R. and Pfluegl, C. and Diehl, L. and Wang, Q. J. and Federico Capasso and Patel, C. Kumar N.} } @article { ISI:000263652900007, title = {Aligned carbon nanotubes as polarization-sensitive, molecular near-field detectors}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, volume = {106}, number = {8}, year = {2009}, month = {FEB 24}, pages = {2495-2499}, publisher = {NATL ACAD SCIENCES}, type = {Article}, address = {2101 CONSTITUTION AVE NW, WASHINGTON, DC 20418 USA}, abstract = {Near-field scanning optical microscopes are widely used in imaging of subwavelength features in various material systems and nanostructures. For a variety of applications, polarization-sensitive near-field probes can provide valuable information on the nature and symmetry of the imaged nanoparticles and emitters. Conventional near-field optical microscopy lacks in-plane polarization sensitivity. Here, we use aligned single-wall carbon nanotubes as polarization-sensitive molecular scale probes to image the transverse near-field components of an optical Hertzian dipole antenna. Because of the Raman {\textquoteleft}{\textquoteleft}antenna effect{\textquoteright}{\textquoteright} in carbon nanotubes, only the near-field components along the nanotube axis are detected. These findings demonstrate that aligned carbon nanotubes can be used as polarization-sensitive near-field detectors.}, keywords = {optical antenna, plasmonics}, issn = {0027-8424}, doi = {10.1073/pnas.0812217106}, author = {Cubukcu, Ertugrul and Degirmenci, Fatih and Kocabas, Coskun and Zimmler, Mariano A. and Rogers, John A. and Federico Capasso} } @article { ISI:000266906400087, title = {Angular emission characteristics of quantum cascade spiral microlasers}, journal = {OPTICS EXPRESS}, volume = {17}, number = {12}, year = {2009}, month = {JUN 8}, pages = {10335-10343}, publisher = {OPTICAL SOC AMER}, type = {Article}, address = {2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA}, abstract = {We perform ray and wave simulations of passive and active spiral-shaped optical microcavities, comparing our results to experimental data obtained with mid-infrared quantum cascade spiral microlasers. Focusing on the angular emission characteristics, we find that both ray and wave simulations are consistent with the experimental data, showing richly-featured, multidirectional far-field emission patterns in the case of uniform pumping and TM-polarized light. Active cavity simulations using the Schrodinger-Bloch model indicate that selective pumping of the quantum cascade spiral microlasers near the resonator boundary will yield unidirectional laser emission. (c) 2009 Optical Society of America}, issn = {1094-4087}, doi = {10.1364/OE.17.010335}, author = {Hentschel, Martina and Kwon, Tae-Yoon and Belkin, Mikhail A. and Audet, Ross and Federico Capasso} } @article { ISI:000269781700085, title = {Beam combining of quantum cascade laser arrays}, journal = {OPTICS EXPRESS}, volume = {17}, number = {18}, year = {2009}, month = {AUG 31}, pages = {16216-16224}, publisher = {OPTICAL SOC AMER}, type = {Article}, address = {2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA}, abstract = {Wavelength beam combining was used to co-propagate beams from 28 elements in an array of distributed-feedback quantum cascade lasers (DFB-QCLs). The beam-quality product of the array, defined as the product of near-field spot size and far-field divergence for the entire array, was improved by a factor of 21 by using wavelength beam combining. To demonstrate the applicability of wavelength beam combined DFB-QCL arrays for remote sensing, we obtained the absorption spectrum of isopropanol at a distance of 6 m from the laser array. (C) 2009 Optical Society of America}, issn = {1094-4087}, doi = {10.1364/OE.17.016216}, author = {Lee, Benjamin G. and Kansky, Jan and Goyal, Anish K. and Pfluegl, Christian and Diehl, Laurent and Belkin, Mikhail A. and Sanchez, Antonio and Federico Capasso} } @article { ISI:000268019300007, title = {Broadband Distributed-Feedback Quantum Cascade Laser Array Operating From 8.0 to 9.8 mu m}, journal = {IEEE PHOTONICS TECHNOLOGY LETTERS}, volume = {21}, number = {13}, year = {2009}, month = {JUL 1}, pages = {914-916}, publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC}, type = {Article}, address = {445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA}, abstract = {An ultra-broadband distributed-feedback quantum cascade laser array was fabricated, using a heterogeneous cascade based on two bound-to-continuum designs centered at 8.4 and 9.6 mu m. This array emitted in a range over 220 cm(-1) near a 9-mu m wavelength, operated in pulsed mode at room temperature. The output power of the array varied between 100- and 1100-mW peak intensity.}, keywords = {Distributed-feedback (DFB) lasers, Infrared Spectroscopy, mid-infrared, Quantum cascade lasers (QCLs), semiconductor lasers}, issn = {1041-1135}, doi = {10.1109/LPT.2009.2020440}, author = {Lee, Benjamin G. and Zhang, Haifei A. and Pfluegl, Christian and Diehl, Laurent and Belkin, Mikhail A. and Fischer, Milan and Wittmann, Andreas and Faist, Jerome and Federico Capasso} } @article { ISI:000262355000023, title = {Coherent Coupling of Multiple Transverse Modes in Quantum Cascade Lasers}, journal = {PHYSICAL REVIEW LETTERS}, volume = {102}, number = {1}, year = {2009}, month = {JAN 9}, publisher = {AMER PHYSICAL SOC}, type = {Article}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {Quantum cascade lasers are a unique laboratory for studying nonlinear laser dynamics because of their high intracavity intensity, strong intersubband optical nonlinearity, and an unusual combination of relaxation time scales. Here we investigate the nonlinear coupling between the transverse modes of quantum cascade lasers. We present evidence for stable phase coherence of multiple transverse modes over a large range of injection currents. We explain the phase coherence by a four-wave mixing interaction originating from the strong optical nonlinearity of the gain transition. The phase-locking conditions predicted by theory are supported by spectral data and both near- and far-field mode measurements.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.102.013901}, author = {Nanfang Yu and Diehl, Laurent and Cubukcu, Ertugrul and Bour, David and Corzine, Scott and Hoefler, Gloria and Wojcik, Aleksander K. and Kenneth B. Crozier and Belyanin, Alexey and Federico Capasso} } @article { ISI:000262933300001, title = {Controlled modification of erbium lifetime by near-field coupling to metallic films}, journal = {NEW JOURNAL OF PHYSICS}, volume = {11}, year = {2009}, month = {JAN 30}, publisher = {IOP PUBLISHING LTD}, type = {Article}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {Systematic measurements of the photoluminescence lifetime of the 1.54 mu m transition of erbium implanted at different energies in SiO2 films with different metallic overlayers are reported. The lifetime shows a strong reduction up to a factor of 20 with decreasing distance between the erbium and the metal overlayer. The reduction of lifetime is mainly due to a near-field interaction between the erbium ions and the metal overlayers through generation of surface plasmon polaritons at the metal/SiO2 interface and direct generation of heat in the metal. These experiments combined with rigorous theoretical modeling demonstrate that a high degree of control over the radiative properties of erbium can be achieved in erbium-implanted materials in a wide range of implantation energies. The experiments also allow us to determine the radiative efficiency of erbium in bulk SiO2.}, issn = {1367-2630}, doi = {10.1088/1367-2630/11/1/015003}, author = {Nanfang Yu and Belyanin, Alexey and Bao, Jiming and Federico Capasso} } @article { ISI:000273085900007, title = {Deformed microcavity quantum cascade lasers with directional emission}, journal = {NEW JOURNAL OF PHYSICS}, volume = {11}, year = {2009}, month = {DEC 17}, publisher = {IOP PUBLISHING LTD}, type = {Article}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {We report the experimental realization of deformed microcavity quantum cascade lasers (QCLs) with a Lima on-shaped chaotic resonator. Directional light emission with a beam divergence of theta(parallel to) approximate to 33 degrees from QCLs emitting at lambda approximate to 10 mu m was obtained in the plane of the cavity for deformations in the range 0.37 \< epsilon \< 0.43. An excellent agreement between measured and calculated far-field profiles was found. Both simulations and experiments show that the Lima on-shaped microcavity preserves whispering gallery-like modes with high Q-factors for low deformations (epsilon \< 0.50). In addition, while the measured spectra show a transition from whispering gallery-like modes to a more complex mode structure at higher pumping currents, we observed {\textquoteleft}universal far-field behavior{\textquoteright} for different intracavity mode distributions in the Lima on}, issn = {1367-2630}, doi = {10.1088/1367-2630/11/12/125018}, author = {Wang, Qijie and Yan, Changling and Diehl, Laurent and Hentschel, Martina and Wiersig, Jan and Nanfang Yu and Pfluegl, Christian and Belkin, Mikhail A. and Edamura, Tadataka and Yamanishi, Masamichi and Kan, Hirofumi and Federico Capasso} } @article { ISI:000266454300016, title = {DFB Quantum Cascade Laser Arrays}, journal = {IEEE JOURNAL OF QUANTUM ELECTRONICS}, volume = {45}, number = {5-6}, year = {2009}, month = {MAY-JUN}, pages = {554-565}, publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC}, type = {Article}, address = {445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA}, abstract = {DFB quantum cascade laser (DFB-QCL) arrays operating between 8.7 and 9.4 mu m are investigated for their performance characteristics-single-mode selection of the DFB grating, and variability in threshold, slope efficiency, and output power of different lasers in the array. Single-mode selection refers to the ability to choose a desired mode/frequency of laser emission with a DFB grating. We apply a theoretical framework developed for general DFB gratings to analyze DFB-QCL arrays. We calculate how the performance characteristics of DFB-QCLs are affected by the coupling strength kappa L of the grating, and the relative position of the mirror facets at the ends of the laser cavity with respect to the grating. We discuss how single-mode selection can be improved by design. Several DFB-QCL arrays are fabricated and their performance examined. We achieve desired improvements in single-mode selection, and we observe the predicted variability in the threshold, slope efficiency, and output power of the DFB-QCLs. As a demonstration of potential applications, the DFB-QCL arrays are used to perform infrared absorption spectroscopy with fluids.}, keywords = {DFB lasers, Infrared Spectroscopy, mid-infrared, Quantum cascade lasers (QCLs), semiconductor lasers}, issn = {0018-9197}, doi = {10.1109/JQE.2009.2013175}, author = {Lee, Benjamin G. and Belkin, Mikhail A. and Pfluegl, Christian and Diehl, Laurent and Zhang, Haifei A. and Audet, Ross M. and MacArthur, Jim and Bour, David P. and Corzine, Scott W. and Hoefler, Gloria E. and Federico Capasso} } @article { ISI:000267431700001, title = {Directional emission and universal far-field behavior from semiconductor lasers with limaccedilon-shaped microcavity}, journal = {APPLIED PHYSICS LETTERS}, volume = {94}, number = {25}, year = {2009}, month = {JUN 22}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {We report experimental demonstration of directional light emission from limaccedilon-shaped microcavity semiconductor lasers. Quantum cascade lasers (QCLs) emitting at lambda approximate to 10 mu m are used as a model system. Both ray optics and wave simulations show that for deformations in the range 0.37}, keywords = {current density, laser cavity resonators, microcavities, optical chaos, optical pumping, Q-factor, Quantum cascade lasers, whispering gallery modes}, issn = {0003-6951}, doi = {10.1063/1.3153276}, author = {Yan, Changling and Wang, Qijie and Diehl, Laurent and Hentschel, Martina and Wiersig, Jan and Nanfang Yu and Pfluegl, Christian and Federico Capasso and Belkin, Mikhail A. and Edamura, Tadataka and Yamanishi, Masamichi and Kan, Hirofumi} } @article { ISI:000266262400007, title = {Epitaxial Catalyst-Free Growth of InN Nanorods on c-Plane Sapphire}, journal = {NANOSCALE RESEARCH LETTERS}, volume = {4}, number = {6}, year = {2009}, month = {JUN}, pages = {532-537}, publisher = {SPRINGEROPEN}, type = {Article}, address = {CAMPUS, 4 CRINAN ST, LONDON, N1 9XW, ENGLAND}, abstract = {We report observation of catalyst-free hydride vapor phase epitaxy growth of InN nanorods. Characterization of the nanorods with transmission electron microscopy, and X-ray diffraction show that the nanorods are stoichiometric 2H-InN single crystals growing in the [0001] orientation. The InN rods are uniform, showing very little variation in both diameter and length. Surprisingly, the rods show clear epitaxial relations with the c-plane sapphire substrate, despite about 29\% of lattice mismatch. Comparing catalyst-free with Ni-catalyzed growth, the only difference observed is in the density of nucleation sites, suggesting that Ni does not work like the typical vapor-liquid-solid catalyst, but rather functions as a nucleation promoter by catalyzing the decomposition of ammonia. No conclusive photoluminescence was observed from single nanorods, while integrating over a large area showed weak wide emissions centered at 0.78 and at 1.9 eV.}, keywords = {Catalyst-free, Epitaxial growth, InN, Nanorods, nanowires, Ni, Sapphire}, issn = {1931-7573}, doi = {10.1007/s11671-009-9276-z}, author = {Shalish, I. and Seryogin, G. and Yi, W. and Bao, J. M. and Zimmler, M. A. and Likovich, E. and D.C. Bell and F. Capasso and V. Narayanamurti} } @article { ISI:000267166600020, title = {Exciton-related electroluminescence from ZnO nanowire light-emitting diodes}, journal = {APPLIED PHYSICS LETTERS}, volume = {94}, number = {24}, year = {2009}, month = {JUN 15}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {The authors study the microscopic origin of the electroluminescence from zinc oxide (ZnO) nanowire light-emitting diodes (LEDs) fabricated on a heavily doped p-type silicon (p-Si) substrate. By comparing the low-temperature photoluminescence and electroluminescence of a single nanowire LED, bound- and free-exciton related recombination processes, together with their longitudinal-optical phonon replicas, can be identified as the origin of both electroluminescence and photoluminescence.}, keywords = {electroluminescence, electron-hole recombination, excitons, II-VI semiconductors, light emitting diodes, nanowires, Phonons, photoluminescence, Zinc Compounds}, issn = {0003-6951}, doi = {10.1063/1.3157274}, author = {Zimmler, Mariano A. and Voss, Tobias and Ronning, Carsten and Federico Capasso} } @article { ISI:000273085900001, title = {Focus on advanced semiconductor heterostructures for optoelectronics}, journal = {NEW JOURNAL OF PHYSICS}, volume = {11}, year = {2009}, month = {DEC 17}, publisher = {IOP PUBLISHING LTD}, type = {Article}, address = {DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND}, abstract = {Semiconductor heterostructures are the basic materials underlying optoelectronic devices, particularly lasers and light-emitting diodes (LEDs). Made from various III-V-, II-VI-, SiGe- and other compound semiconductors, modern semiconductor devices are available for the generation, detection and modulation of light covering the entire ultra-violet to far-infrared spectral region. Recent approaches that introduced multilayer heterostructures tailored on the lower nanometre scale made possible artificial semiconductors with new properties, such as extended wavelength coverage, that enabled new applications. Together with ongoing progress on wide-gap semiconductors, the optical wavelengths accessible by semiconductor devices are steadily expanding towards the short-wavelength ultra-violet regime, as well as further into the far-infrared and terahertz spectral regions. It is the aim of this focus issue to present cutting-edge research topics on the most recent optoelectronic material and device developments in this field using advanced semiconductor heterostructures.}, issn = {1367-2630}, doi = {10.1088/1367-2630/11/12/125012}, author = {Amann, Markus C. and Federico Capasso and Larsson, Anders and Pessa, Markus} } @article { ISI:000271629200072, title = {The forces from coupled surface plasmon polaritons in planar waveguides}, journal = {OPTICS EXPRESS}, volume = {17}, number = {22}, year = {2009}, month = {OCT 26}, pages = {19996-20011}, publisher = {OPTICAL SOC AMER}, type = {Article}, address = {2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA}, abstract = {We analytically investigate the forces due to Surface Plasmon Polariton (SPP) modes between finite and infinitely thick metal slabs separated by an air gap. Using the Drude model and experimentally determined values of the dielectric functions of gold and silver, we study how frequency dispersion and loss in the metals affects the behavior of the SPP modes and the forces generated by them. We calculate the force using the Maxwell Stress Tensor for both the attractive and repulsive modes. (C) 2009 Optical Society of America}, issn = {1094-4087}, doi = {10.1364/OE.17.019996}, author = {Woolf, David and Loncar, Marko and Federico Capasso} } @article { ISI:000262357800003, title = {High performance quantum cascade lasers based on three-phonon-resonance design}, journal = {APPLIED PHYSICS LETTERS}, volume = {94}, number = {1}, year = {2009}, month = {JAN 5}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {A quantum cascade laser structure based on three-phonon-resonance design is proposed and demonstrated. Devices, emitting at a wavelength of 9 mu m, processed into buried ridge waveguide structures with a 3 mm long, 16 mu m wide cavity and a high-reflection (HR) coating have shown peak output powers of 1.2 W, slope efficiencies of 1 W/A, threshold current densities of 1.1 kA/cm(2), and high wall-plug efficiency of 6\% at 300 K. A 3 mm long, 12 mu m wide buried-heterostructure device without a HR coating exhibited continuous wave output power of as high as 65 mW from a single facet at 300 K.}, keywords = {Phonons, Quantum cascade lasers, waveguide lasers}, issn = {0003-6951}, doi = {10.1063/1.3062981}, author = {Wang, Qijie and Pflugl, Christian and Diehl, Laurent and Federico Capasso and Edamura, Tadataka and Furuta, Shinichi and Yamanishi, Masamichi and Kan, Hirofumi} } @article { ISI:000270915700012, title = {High power thermoelectrically cooled and uncooled quantum cascade lasers with optimized reflectivity facet coatings}, journal = {APPLIED PHYSICS LETTERS}, volume = {95}, number = {15}, year = {2009}, month = {OCT 12}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {We present a method of preserving the device wall-plug efficiency by adjusting mirror losses with facet coatings for longer cavity quantum cascade lasers. An experimental study of output power and wall-plug efficiency as functions of mirror losses was performed by varying the front facet coating reflectivity with a high-reflectivity-coated rear facet. The use of optimized reflectivity coatings on 7-mm-long chips resulted in continuous-wave output power of 2.9 W at 293 K for thermoelectrically cooled devices mounted on AlN submounts and average and continuous-wave output power in excess of 1 W for uncooled devices emitting at 4.6 mu m. (C) 2009 American Institute of Physics. [doi:10.1063/1.3246799]}, issn = {0003-6951}, doi = {10.1063/1.3246799}, author = {Maulini, Richard and Lyakh, Arkadiy and Tsekoun, Alexei and Go, Rowel and Pfluegl, Christian and Diehl, Laurent and Federico Capasso and Patel, C. Kumar N.} } @article { ISI:000266928700058, title = {High-Temperature Operation of Terahertz Quantum Cascade Laser Sources}, journal = {IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS}, volume = {15}, number = {3}, year = {2009}, month = {MAY-JUN}, pages = {952-967}, publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC}, type = {Article}, address = {445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA}, abstract = {Terahertz (THz) quantum cascade lasers (QCLs) are currently the most advanced electrically pumped semiconductor lasers in the spectral range 1-5 THz. However, their operation at room temperature is still an unresolved challenge. In this paper, we discuss our efforts to improve the temperature performance of these devices. In particular, we present THz QCLs that approach thermoelectric cooled operation and discuss factors that limit their high-temperature performance. We also discuss a different type of THz QCL source that produces coherent THz radiation without population inversion across the THz transition. These devices are based on intracavity difference-frequency generation in dual-wavelength mid-IR QCLs, and can now provide microwatt levels of coherent THz radiation up to room temperature. We discuss how the output power of these devices can be further improved to produce milliwatts of THz radiation at room temperature.}, keywords = {Difference-frequency generation, intersubband transitions, nonlinear optics, Quantum cascade lasers (QCLs), terahertz (THz) sources}, issn = {1077-260X}, doi = {10.1109/JSTQE.2009.2013183}, author = {Belkin, Mikhail A. and Wang, Qijie and Pfluegl, Christian and Belyanin, Alexey and Khanna, Suraj P. and Davies, Alexander Giles and Linfield, Edmund Harold and Federico Capasso} } @article { ISI:000262360200027, title = {Measured long-range repulsive Casimir-Lifshitz forces}, journal = {NATURE}, volume = {457}, number = {7226}, year = {2009}, month = {JAN 8}, pages = {170-173}, publisher = {NATURE PUBLISHING GROUP}, type = {Article}, address = {MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND}, abstract = {Quantum fluctuations create intermolecular forces that pervade macroscopic bodies(1-3). At molecular separations of a few nanometres or less, these interactions are the familiar van der Waals forces(4). However, as recognized in the theories of Casimir, Polder and Lifshitz(5-7), at larger distances and between macroscopic condensed media they reveal retardation effects associated with the finite speed of light. Although these long- range forces exist within all matter, only attractive interactions have so far been measured between material bodies(8-11). Here we show experimentally that, in accord with theoretical prediction(12), the sign of the force can be changed from attractive to repulsive by suitable choice of interacting materials immersed in a fluid. The measured repulsive interaction is found to be weaker than the attractive. However, in both cases the magnitude of the force increases with decreasing surface separation. Repulsive Casimir - Lifshitz forces could allow quantum levitation of objects in a fluid and lead to a new class of switchable nanoscale devices with ultra-low static friction(13-15).}, issn = {0028-0836}, doi = {10.1038/nature07610}, author = {Munday, J. N. and Federico Capasso and Parsegian, V. Adrian} } @article { ISI:000268399500075, title = {Mode-locked pulses from mid-infrared Quantum Cascade Lasers}, journal = {OPTICS EXPRESS}, volume = {17}, number = {15}, year = {2009}, month = {JUL 20}, pages = {12929-12943}, publisher = {OPTICAL SOC AMER}, type = {Article}, address = {2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA}, abstract = {In this study, we report the unequivocal demonstration of mid-infrared mode-locked pulses from quantum cascade lasers. The train of short pulses was generated by actively modulating the current and hence the gain of an edge-emitting quantum cascade laser (QCL). Pulses with duration of about 3 ps at full-width-at-half-maxima and energy of 0.5 pJ were characterized using a second-order interferometric autocorrelation technique based on a nonlinear quantum well infrared photodetector. The mode-locking dynamics in the QCLs was modeled based on the Maxwell-Bloch equations in an open two-level system. Our model reproduces the overall shape of the measured autocorrelation traces and predicts that the short pulses are accompanied by substantial wings as a result of strong spatial hole burning. The range of parameters where short mode-locked pulses can be formed is found. (C) 2009 Optical Society of America}, issn = {1094-4087}, doi = {10.1364/OE.17.012929}, author = {Wang, Christine Y. and Kuznetsova, Lyuba and Gkortsas, V. M. and Diehl, L. and Kaertner, F. X. and Belkin, M. A. and Belyanin, A. and Li, X. and Ham, D. and Schneider, H. and Grant, P. and Song, C. Y. and Haffouz, S. and Wasilewski, Z. R. and Liu, H. C. and Federico Capasso} } @article { ISI:000272627700122, title = {Multi-beam multi-wavelength semiconductor lasers (vol 95, 161108, 2009)}, journal = {APPLIED PHYSICS LETTERS}, volume = {95}, number = {23}, year = {2009}, month = {DEC 7}, publisher = {AMER INST PHYSICS}, type = {Correction}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, issn = {0003-6951}, doi = {10.1063/1.3270186}, author = {Nanfang Yu and Mikhail A. Kats and Pfluegl, Christian and Geiser, Markus and Wang, Qijie and Belkin, Mikhail A. and Federico Capasso and Fischer, Milan and Wittmann, Andreas and Faist, Jerome and Edamura, Tadataka and Furuta, Shinichi and Yamanishi, Masamichi and Kan, Hirofumi} } @article { ISI:000270441700005, title = {Nanowire-induced Wurtzite InAs Thin Film on Zinc-Blende InAs Substrate}, journal = {ADVANCED MATERIALS}, volume = {21}, number = {36}, year = {2009}, month = {SEP 25}, pages = {3654+}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, 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.}, issn = {0935-9648}, doi = {10.1002/adma.200900617}, author = {Bao, Jiming and David C. Bell and Federico Capasso and Erdman, Natasha and Wei, Dongguang and Froberg, Linus and Martensson, Thomas and Samuelson, Lars} } @article { ISI:000264142100038, title = {Optical Antenna Arrays on a Fiber Facet for in Situ Surface-Enhanced Raman Scattering Detection}, journal = {NANO LETTERS}, volume = {9}, number = {3}, year = {2009}, month = {MAR}, pages = {1132-1138}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, 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 {\textquoteleft}{\textquoteleft}hot spots{\textquoteright}{\textquoteright} 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).}, issn = {1530-6984}, doi = {10.1021/nl803668u}, author = {Smythe, Elizabeth J. and Dickey, Michael D. and Bao, Jiming and George M. Whitesides and Federico Capasso} } @article { ISI:000272052200001, title = {Optical nanorod antennas as dispersive one-dimensional Fabry-Peacuterot resonators for surface plasmons}, journal = {APPLIED PHYSICS LETTERS}, volume = {95}, number = {20}, year = {2009}, month = {NOV 16}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, 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.}, keywords = {antennas, circular waveguides, Fabry-Perot resonators, Gold, nanophotonics, nanowires, optical dispersion, optical waveguides, surface plasmons}, issn = {0003-6951}, doi = {10.1063/1.3262947}, author = {Cubukcu, Ertugrul and Federico Capasso} } @article { ISI:000265285200001, title = {Semiconductor lasers with integrated plasmonic polarizers}, journal = {APPLIED PHYSICS LETTERS}, volume = {94}, number = {15}, year = {2009}, month = {APR 13}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, 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.}, keywords = {diffraction gratings, integrated optics, light polarisation, optical polarisers, plasmonics, Quantum cascade lasers, stimulated emission}, issn = {0003-6951}, doi = {10.1063/1.3093476}, author = {Nanfang Yu and Wang, Qijie and Pflugl, Christian and Diehl, Laurent and Federico Capasso and Edamura, Tadataka and Furuta, Shinichi and Yamanishi, Masamichi and Kan, Hirofumi} } @article { ISI:000262953200010, title = {A Technique to Transfer Metallic Nanoscale Patterns to Small and Non-Planar Surfaces}, journal = {ACS NANO}, volume = {3}, number = {1}, year = {2009}, month = {JAN}, pages = {59-65}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, 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.}, keywords = {Metal Nanoparticles, nanofabrication, nanopatterning, pattern transfer, soft lithography}, issn = {1936-0851}, doi = {10.1021/nn800720r}, author = {Smythe, Elizabeth J. and Dickey, Michael D. and George M. Whitesides and Federico Capasso} } @article { ISI:000267431700013, title = {On the temperature dependence of point-defect-mediated luminescence in silicon}, journal = {APPLIED PHYSICS LETTERS}, volume = {94}, number = {25}, year = {2009}, month = {JUN 22}, publisher = {AMER INST PHYSICS}, type = {Article}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, 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.}, keywords = {electroluminescence, elemental semiconductors, excitons, photoluminescence, point defects, Silicon}, issn = {0003-6951}, doi = {10.1063/1.3157277}, author = {Daniel Recht and Federico Capasso and Michael J. Aziz} } @article { ISI:000264410900001, title = {Time-Resolved Investigations of Electronic Transport Dynamics in Quantum Cascade Lasers Based on Diagonal Lasing Transition}, journal = {IEEE JOURNAL OF QUANTUM ELECTRONICS}, volume = {45}, number = {4}, year = {2009}, month = {APR}, pages = {307-321}, publisher = {IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC}, type = {Article}, address = {445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA}, 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.}, keywords = {Carrier dynamics, electronic transport, midinfrared (mid-IR), quantum cascade laser (QCL), time-resolved}, issn = {0018-9197}, doi = {10.1109/JQE.2009.2013091}, author = {Choi, Hyunyong and Diehl, Laurent and Wu, Zong-Kwei and Giovannini, Marcella and Faist, Jerome and Federico Capasso and Norris, Theodore B.} } @article { ISI:000262871800012, title = {Widely tunable high-power external cavity quantum cascade laser operating in continuous-wave at room temperature}, journal = {ELECTRONICS LETTERS}, volume = {45}, number = {2}, year = {2009}, month = {JAN 15}, pages = {107-U30}, publisher = {INST ENGINEERING TECHNOLOGY-IET}, type = {Article}, address = {MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND}, 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.}, issn = {0013-5194}, doi = {10.1049/el:20093057}, author = {Maulini, R. and Dunayevskiy, I. and Lyakh, A. and Tsekoun, A. and Patel, C. K. N. and Diehl, L. and Pfluegl, C. and F. Capasso} }