APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

29 Oct 2007

Volume 91, Issue 18, Articles (18xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 183501 (2007); http://dx.doi.org/10.1063/1.2801554 (3 pages)

Aurelien Du Pasquier, Daniel D. T. Mastrogiovanni, Lauren A. Klein, Tong Wang, and Eric Garfunkel
Enlarge Image | Read More
Page 1 of 5 Pages Next Page | Jump to Page
back to top
RSS Feeds

Observations of interior whispering gallery modes in asymmetric optical resonators with rational caustics

Jie Gao, Pascal Heider, Charlton J. Chen, Xiaodong Yang, Chad A. Husko, and Chee Wei Wong

Appl. Phys. Lett. 91, 181101 (2007); http://dx.doi.org/10.1063/1.2800308 (3 pages) | Cited 7 times

Online Publication Date: 29 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We propose asymmetric resonant cavities with rational caustics and experimentally demonstrate interior whispering gallery modes in monolithic silicon mesoscopic microcavities. These microcavities demonstrate unique robustness of cavity quality factor against roughness Rayleigh scattering. Distinct resonant families and directional radiation from interior whispering gallery modes are observed experimentally using angle-resolved tapered fiber measurements and near-field images, which can be used for microcavity laser and cavity quantum electrodynamics applications.
Show PACS
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Sa Microcavity and microdisk lasers

Optical tomographic reconstruction of ion beam induced refractive index changes in silica

X. M. Goh, N. M. Dragomir, D. N. Jamieson, A. Roberts, and D. X. Belton

Appl. Phys. Lett. 91, 181102 (2007); http://dx.doi.org/10.1063/1.2794785 (3 pages) | Cited 1 time

Online Publication Date: 29 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Refractive index changes induced by ion beam implantation can be used to produce photonic devices such as waveguides. Here, we relate the measured three-dimensional changes in refractive index produced by ion beam implantation to modeling of the implantation process. We use a quantitative phase microscopic method in conjunction with a tomographic reconstruction process to determine the change in the refractive index distribution within a silica optical fiber that has been selectively implanted with 2.4 MeV H+ ions. The index profile is compared with numerical simulations of the ion vacancy and ionization using the stopping range of ions in matter program.
Show PACS
42.81.Cn Fiber testing and measurement of fiber parameters
61.80.Jh Ion radiation effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.30.Wb Image reconstruction; tomography

Defect related issues in the “current roll-off” in InGaN based light emitting diodes

B. Monemar and B. E. Sernelius

Appl. Phys. Lett. 91, 181103 (2007); http://dx.doi.org/10.1063/1.2801704 (3 pages) | Cited 77 times

Online Publication Date: 30 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Defect related contributions to the reduction of the internal quantum efficiency of InGaN-based multiple quantum well light emitting diodes under high forward bias conditions are discussed. Screening of localization potentials for electrons is an important process to reduce the localization at high injection. The possible role of threading dislocations in inducing a parasitic tunneling current in the device is discussed. Phonon-assisted transport of holes via tunneling at defect sites along dislocations is suggested to be involved, leading to a nonradiative parasitic process enhanced by a local temperature rise at high injection.
Show PACS
61.72.Lk Linear defects: dislocations, disclinations
73.40.Gk Tunneling
85.60.Jb Light-emitting devices

Electrically controllable and polarization-independent Fresnel zone plate in a circularly symmetric hybrid-aligned liquid crystal film with a photoconductive polymer layer

K.-C. Lo, J.-D. Wang, C.-R. Lee, and T.-S. Mo

Appl. Phys. Lett. 91, 181104 (2007); http://dx.doi.org/10.1063/1.2802568 (3 pages) | Cited 9 times

Online Publication Date: 30 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This work reports a Fresnel zone plate in a circularly symmetric hybrid-aligned liquid crystal (LC) film with a photoconductive polymer layer. An ultraviolet-induced electrodelike pattern of polymer layer under a zone plate photomask results in alternating major and minor portions of external voltage dropping on LC layer in conductive and nonconductive regions, respectively. These effects cause the discrepancy in LC reorientation between adjacent zones, generating a Fresnel zone plate. The focusing of the zone plate is electrically controllable and polarization independent. Additionally, the zone plate has advantages of a zero focusing in the voltage-off state and a very small operating dc field range from 0 to 0.3 V/μm.
Show PACS
42.79.Ci Filters, zone plates, and polarizers
42.70.Df Liquid crystals
42.70.Jk Polymers and organics

InGaAs quantum wire infrared photodetector

C. L. Tsai, K. Y. Cheng, S. T. Chou, and S. Y. Lin

Appl. Phys. Lett. 91, 181105 (2007); http://dx.doi.org/10.1063/1.2805224 (3 pages) | Cited 3 times

Online Publication Date: 30 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report a 20-layer InxGa1−xAs/In0.52Al0.24Ga0.24As quantum wire infrared photodetector grown on (001)-axis InP substrate by molecular beam epitaxy. High density InGaAs quantum wires were formed, utilizing the strained-induced lateral-layer ordering process by growing a strain-balanced (GaAs)1.80/(InAs)2.35 short-period superlattice. This device shows a unique polarized photoresponse which favors the normal-incident infrared radiation polarizing perpendicular to the wire orientation. The photoresponse at 6.3 μm exhibited a peak detectivity of 3.13×109 cm Hz1/2/W at 10 K.
Show PACS
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Gz Photodetectors (including infrared and CCD detectors)

Fingerprint detection using full-field swept-source optical coherence tomography

Satish Kumar Dubey, Tulsi Anna, Chandra Shakher, and Dalip Singh Mehta

Appl. Phys. Lett. 91, 181106 (2007); http://dx.doi.org/10.1063/1.2800823 (3 pages) | Cited 14 times

Online Publication Date: 30 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the application of full-field swept-source optical coherence tomography for fingerprint detection. This system consists of a superluminescent diode as broadband light source and an acousto-optic tunable filter as wavelength-tuning device. The conventional optical coherence tomographic system was modified by coating aluminum oxide on one side of the beam splitter which is used as reference mirror and fingerprints on the glass slide as object. Low-coherence interferometry, nonmechanical scanning, and compactness are the main advantages of the proposed system over conventional fingerprint detection techniques. The present technique is noninvasive in nature and does not require any physical or chemical processing.
Show PACS
42.30.Wb Image reconstruction; tomography
85.60.Jb Light-emitting devices
42.79.Ci Filters, zone plates, and polarizers
42.79.Jq Acousto-optical devices

Fourfold increase of the ultraviolet (314 nm) electroluminescence from SiO2:Gd layers by fluorine coimplantation and flash lamp annealing

S. Prucnal, J. M. Sun, L. Rebohle, and W. Skorupa

Appl. Phys. Lett. 91, 181107 (2007); http://dx.doi.org/10.1063/1.2803855 (3 pages) | Cited 2 times

Online Publication Date: 30 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Efficient ultraviolet electroluminescence (UVEL) is obtained from metal-oxide-silicon (MOS) structures with the SiO2:Gd/F active layers prepared by flash lamp annealing and Gd and F coimplantation. We observed a doubling of both the UVEL intensity and the defect related luminescence by increasing the fluorine concentration. This is due to suppression of the hot electron scattering on the donor-type level of the E′ center, the number of which is reduced by fluorine, and to increase of the optical active Gd3+ centers by Gd–F3 molecule formation. Also, fluorine coimplantation has no influence on the operating time of the MOS diode. Additionally, the flash lamp annealing doubled the ultraviolet electroluminescence from SiO2 layers implanted by gadolinium alone or in combination with fluorine. This is related to the suppression of cluster formation of rare earth atoms occurring during conventional annealing methods.
Show PACS
78.60.Fi Electroluminescence
78.55.Hx Other solid inorganic materials
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
85.30.Kk Junction diodes
78.66.Nk Insulators

An ultrathin ( ∼ 100 μm thick) flexible light plate fabricated using self-alignment and lift-off techniques

Cheng-Chung Chiang, Dong-Sing Wuu, and Ray-Hua Horng

Appl. Phys. Lett. 91, 181108 (2007); http://dx.doi.org/10.1063/1.2804001 (3 pages) | Cited 3 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An ultrathin ( ∼ 100 μm thick) flexible light plate was designed and fabricated on a parylene template using a combination of self-alignment and lift-off techniques. The solid-state InGaN light-emitting diodes (LEDs) (λp = 465 nm) was used as the light source to overcome the problem of conventional organic light-emitting devices which require perfect encapsulation against the permeation of water and oxygen. After the sidewalls of LEDs were passivated by the photodefinable polymer, the LED chip array can be further sandwiched by the indium-tin oxide (ITO) and Al electrodes to form a thin-film package with all the processing temperatures below 250 °C. The ITO-coated transparent parylene template can be peeled off from the glass carrier after forming the ultrathin LED light plate. The flexible light plates present no damage even after they were flexed 1000 times around a 3-cm-diameter cylinder. The present self-alignment or mask-less process is a very promising approach to flexible backlight applications.
Show PACS
81.05.Ea III-V semiconductors
85.60.Jb Light-emitting devices

Enhanced light extraction from GaN-based green light-emitting diode with photonic crystal

Ja-Yeon Kim, Min-Ki Kwon, Ki-Sung Lee, Seong-Ju Park, Sang Hoon Kim, and Ki-Dong Lee

Appl. Phys. Lett. 91, 181109 (2007); http://dx.doi.org/10.1063/1.2804005 (3 pages) | Cited 22 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This letter reports the properties of GaN-based green light-emitting diodes (LEDs) having a p-GaN photonic crystal layer with a photonic bandgap (PCWG) and without a photonic bandgap (PCOG). With decreasing the photoluminescence (PL) detection angle from 140° to 60°, the enhancement of PL intensity of LED with PCWG was largely increased from 9 to 25 times, compared to that of LEDs without a patterned structure, while the PL intensity of LED with PCOG was increased from 4.6 to 5.6 times. The electroluminescence output power of green LEDs with a PCWG was enhanced about two times compared to LEDs with a PCOG. These results suggest that the light extraction of green LEDs can be greatly increased by using PCWG instead of PCOG.
Show PACS
85.60.Jb Light-emitting devices
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
85.30.De Semiconductor-device characterization, design, and modeling
42.70.Qs Photonic bandgap materials

Electrically tunable extraordinary optical transmission gratings

E. A. Shaner, J. G. Cederberg, and D. Wasserman

Appl. Phys. Lett. 91, 181110 (2007); http://dx.doi.org/10.1063/1.2804572 (3 pages) | Cited 15 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report a semiconductor based mechanism for electrically controlling the frequency of light transmitted through extraordinary optical transmission gratings. In doing so, we demonstrate active control over the surface plasmon (SP) resonance at the metal/dielectric interface. The gratings, designed to operate in the midinfrared spectral range, are fabricated upon a doped GaAs epilayer. Tuning of over 25 cm−1 is achieved, and the devices are modeled to investigate the physical origin of the tuning mechanism. Though our structures are designed for the midinfrared, the tuning mechanism demonstrated could be applied to other wavelength ranges, especially the visible and near infrared.
Show PACS
42.79.Dj Gratings
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors

Built-in electric field enhancement/retardation on intermixing

C. D. Xu, T. Mei, M. K. Chin, J. R. Dong, and S. J. Chua

Appl. Phys. Lett. 91, 181111 (2007); http://dx.doi.org/10.1063/1.2805018 (3 pages) | Cited 2 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The built-in electric field may impose a drift on charged point defects and may thus enhance or retard the intermixing during annealing. Electric field is built-in near the surface due to the pinning of surface Fermi level after argon plasma treatment on InP surfaces of InP/InGaAs quantum well samples. Subsequent annealing leads to different intermixing results due to the different field directions on InP cap layers in different doping types. Experiments also showed different influences of the built-in field on the two sublattices largely due to different charge numbers of point defects on the respective sublattices.
Show PACS
61.72.J- Point defects and defect clusters
68.65.Fg Quantum wells
73.21.Fg Quantum wells
61.72.Cc Kinetics of defect formation and annealing

Ordered, uniform-sized ZnO nanolaser arrays

Huijuan Zhou, Markus Wissinger, Johannes Fallert, Robert Hauschild, Felix Stelzl, Claus Klingshirn, and Heinz Kalt

Appl. Phys. Lett. 91, 181112 (2007); http://dx.doi.org/10.1063/1.2805073 (3 pages) | Cited 44 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ordered ZnO nanorod arrays with almost uniform rod size have been grown perpendicularly on GaN/Al2O3 substrates by a controlled vapor phase transport growth method. The ZnO nanorods are [0001] oriented single crystals with diameter of 200 nm and length of 4.7 μm, with a rod-to-rod spacing of 500 nm. Photoluminescence spectra of the rod arrays indicate that the rods are of high crystal quality: very strong, well-separated bound and free exciton emission in the ultraviolet (UV) region are resolved at low temperature. Time resolved microphotoluminescence measurements are performed on single nanorods standing on the substrate which demonstrates lasing behavior with multiple UV lasing modes. Under quasistationary excitation lasing is observed up to room temperature. The lasing emission peaks are sharp, with a linewidth about 0.1 nm, and have a fast decay time of ∼ 8 ps. These high crystal quality nanorod arrays may be promising candidates for UV nanolaser devices.
Show PACS
81.16.Be Chemical synthesis methods
81.10.Bk Growth from vapor
61.46.-w Structure of nanoscale materials
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena

Efficiency droop behaviors of InGaN/GaN multiple-quantum-well light-emitting diodes with varying quantum well thickness

Y.-L. Li, Y.-R. Huang, and Y.-H. Lai

Appl. Phys. Lett. 91, 181113 (2007); http://dx.doi.org/10.1063/1.2805197 (3 pages) | Cited 50 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
InGaN/GaN multiple-quantum-well (MQW) light-emitting diodes with varied InGaN quantum well thicknesses are fabricated and characterized. The investigation of luminous efficiency versus current density reveals a variety of efficiency droop behaviors. It is found that the efficiency droop can be drastically reduced by increasing the quantum well thickness of the MQW structures. On the other hand, relative internal quantum efficiency (IQE) measurements indicate that a thinner well results to higher IQEs owing to the greater spatial overlap of electron and hole distribution functions.
Show PACS
85.60.Jb Light-emitting devices

External cavity laser using a long-range surface plasmon grating as a distributed Bragg reflector

Stéphanie Jetté-Charbonneau and Pierre Berini

Appl. Phys. Lett. 91, 181114 (2007); http://dx.doi.org/10.1063/1.2805228 (3 pages) | Cited 14 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The use of metal stripe step-in-width Bragg gratings operating in the long-range surface plasmon-polariton mode as distributed Bragg reflectors in external cavity lasers is explored. Lasing using a gain element coupled via an optical fiber to such a grating is demonstrated at λ0 ∼ 1544 nm, and a high output polarization extinction ratio of about 35 dB is measured. Single mode lasing is feasible using direct end-fire coupled gain and grating chips, and wavelength tuning over a broad range is possible using thermally tuned Au gratings embedded in polymer.
Show PACS
42.55.Wd Fiber lasers
42.60.Fc Modulation, tuning, and mode locking
42.60.By Design of specific laser systems
42.81.-i Fiber optics
42.79.Dj Gratings
42.70.Jk Polymers and organics

Efficiency enhancement using electron energy detuning in a laser seeded free electron laser amplifier

X. J. Wang, T. Watanabe, Y. Shen, R. K. Li, J. B. Murphy, T. Tsang, and H. P. Freund

Appl. Phys. Lett. 91, 181115 (2007); http://dx.doi.org/10.1063/1.2803772 (3 pages) | Cited 11 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the experimental characterization of efficiency enhancement in a single-pass seeded free-electron laser (FEL) where the electron energy is detuned from resonance. Experiments show a doubling of the efficiency for beam energies above the resonant energy. Measurements of the FEL spectra versus energy detuning shows that the wavelength is governed by the seed laser. The variation in the gain length with beam energy was also observed. Good agreement is found between the experiment and numerical simulations using the MEDUSA simulation code.
Show PACS
41.60.Cr Free-electron lasers

Substrate-emitting, distributed feedback quantum cascade lasers

A. Lyakh, P. Zory, M. D’Souza, D. Botez, and D. Bour

Appl. Phys. Lett. 91, 181116 (2007); http://dx.doi.org/10.1063/1.2803851 (3 pages) | Cited 6 times

Online Publication Date: 31 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
By using a semiconductor/metal grating formed on the episide of a quantum-cascade structure, distributed feedback lasing has been achieved with beam emission through the substrate. Using short-pulse excitation (100 ns, 16 kHz), single-longitudinal-mode operation near 5.1 μm is demonstrated over wide ranges in heatsink temperature and drive current. The beam divergence in the longitudinal direction at a distance 40 cm away from the 2.5 mm wide aperture is ∼ 0.5°.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Dj Gratings

A method to identify shallow dopants in semiconductor nanowires

H. B. Huo, C. Liu, L. Dai, L. P. You, W. Q. Yang, R. M. Ma, Y. F. Zhang, and G. G. Qin

Appl. Phys. Lett. 91, 181117 (2007); http://dx.doi.org/10.1063/1.2805019 (3 pages)

Online Publication Date: 1 November 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, an electrical measurement method to identify shallow dopants in lowly doped semiconductor nanowires was suggested. Room temperature electrical measurement indicates that electron concentrations of the n-GaN nanowires are about 5.4×1017 cm−3. Temperature-dependent measurement of conductivities of single nanowires in low temperature region gives activation energy of 13.3 meV, which is consistent with the reported activation energy of 14 meV for Si donor in n-GaN films with donor concentration of 7.4×1017 cm−3. Our results confirm that the shallow donors in the as-synthesized GaN nanowires are silicon. We consider such a method may be applicable to other semiconductor nanowires.
Show PACS
61.72.uj III-V and II-VI semiconductors
61.46.-w Structure of nanoscale materials
73.61.Ey III-V semiconductors
73.63.Nm Quantum wires
71.55.Cn Elemental semiconductors
81.05.Ea III-V semiconductors
81.07.Vb Quantum wires
78.67.Lt Quantum wires

Enlarging the bandwidth of nanoscale propagating plasmonic modes in deep-subwavelength cylindrical holes

Peter B. Catrysse and Shanhui Fan

Appl. Phys. Lett. 91, 181118 (2007); http://dx.doi.org/10.1063/1.2803849 (3 pages) | Cited 1 time

Online Publication Date: 1 November 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Subwavelength cylindrical holes in optically thick metallic films always support a propagating HE11 mode near the surface plasmon frequency, regardless of how small the holes are. For holes filled with a uniform dielectric material, the bandwidth of the HE11 mode asymptotically approaches zero as the hole size is reduced to deep-subwavelength scales. We show that it is possible to create nanoscale propagating plasmonic modes with a very large bandwidth in holes that are concentrically filled with two different dielectric materials, even when the hole radius goes to zero.
Show PACS
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations

Strong optical confinement and multimode emission of organic photonic dots

M. Langner, R. Gehlhaar, C. Schriever, H. Fröb, V. G. Lyssenko, and K. Leo

Appl. Phys. Lett. 91, 181119 (2007); http://dx.doi.org/10.1063/1.2804565 (3 pages) | Cited 10 times

Online Publication Date: 2 November 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report on the optical mode structure of laterally confined organic microcavities. For preparation, an organic semiconductor is evaporated through a mask with square sized holes, resulting in photonic dots with approximately 5 μm diameter. Using a microscope setup, we observe a complex mode structure in transmission and photoluminescence. From the mode mapping, we conclude a strong three-dimensional optical confinement. The near and far field spectra are modeled by transfer matrix calculations and a Fourier transform of the internal electric field distribution, respectively.
Show PACS
42.70.Qs Photonic bandgap materials
78.55.-m Photoluminescence, properties and materials

Study of nonpolar m-plane InGaN/GaN multiquantum well light emitting diodes grown by homoepitaxial metal-organic chemical vapor deposition

Kwang-Choong Kim, Mathew C. Schmidt, Hitoshi Sato, Feng Wu, Natalie Fellows, Zhongyuan Jia, Makoto Saito, Shuji Nakamura, Steven P. DenBaars, James S. Speck, and Kenji Fujito

Appl. Phys. Lett. 91, 181120 (2007); http://dx.doi.org/10.1063/1.2805029 (3 pages) | Cited 29 times

Online Publication Date: 2 November 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nonpolar m-plane (1math00) InGaN-based light emitting diodes (LEDs) grown on low-extended defect density bulk m-plane GaN substrates offer great potential for high performance devices due to the absence of polarization-related internal electric fields. To optimize the quantum well (QW) structure, systematic sets of near blue-ultraviolet LEDs using different well widths, barrier widths, and QW periods were packaged and tested. With increasing current, high power LEDs were realized with fairly flat external quantum efficiency and blueshift-free peak wavelength for QWs with thicknesses from 8 to 20 nm, barrier widths from 10 to 22 nm, and QW numbers from 4 to 10.
Show PACS
85.60.Jb Light-emitting devices
85.40.Sz Deposition technology

On spectral and thermal behaviors of AlGaInP light-emitting diodes under pulse-width modulation

Pasi Manninen and Pasi Orreveteläinen

Appl. Phys. Lett. 91, 181121 (2007); http://dx.doi.org/10.1063/1.2805198 (3 pages) | Cited 13 times

Online Publication Date: 2 November 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Behavior of the emission spectrum, junction temperature, and charge carrier temperature of low-power AlGaInP light-emitting diodes (LEDs) with different colors under pulse-width-modulation (PWM) dimming is investigated. The blueshift of the peak wavelength and the bandwidth narrowing in the emission spectra of the studied LEDs with shortening pulse are found. A linear relation of the junction temperature and carrier temperature of the studied LEDs to their duty cycle is detected. Perceivable changes in color of AlGaInP LEDs under the PWM scheme are observed.
Show PACS
85.60.Jb Light-emitting devices

Tapered quantum cascade lasers

Lars Nähle, Julia Semmel, Wolfgang Kaiser, Sven Höfling, and Alfred Forchel

Appl. Phys. Lett. 91, 181122 (2007); http://dx.doi.org/10.1063/1.2805628 (3 pages) | Cited 14 times

Online Publication Date: 2 November 2007

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
The authors report on the fabrication of quantum cascade lasers with tapered gain sections. In order to obtain optimal results, index guided devices were realized with tapered angles varying between 0.9° and 2.6°. Compared to a common ridge waveguide laser (divergence of 48.7°), a very small horizontal beam divergence of 6.6° in the single lobe far field is achieved. The tapered quantum cascade lasers show good performance with peak output powers of more than 200 mW at room temperature at an emission wavelength of ∼ 8.9 μm.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Dispersion control in two-dimensional superlattice photonic crystal slab waveguides by atomic layer deposition

D. P. Gaillot, E. Graugnard, J. Blair, and C. J. Summers

Appl. Phys. Lett. 91, 181123 (2007); http://dx.doi.org/10.1063/1.2793188 (3 pages) | Cited 8 times

Online Publication Date: 2 November 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The frequency and dispersion of photonic bands in two-dimensional triangular-based superlattice photonic crystal Si slab waveguides were manipulated using atomic layer deposition. The samples were conformally coated with increasing thicknesses of TiO2 and characterized by polarized angular-dependent reflectance measurements, which revealed shifts in the photonic band frequencies of 16% as well as continuous changes in band dispersion. The ability to tune toward zero group velocity by tuning band repulsion between same-polarization bands is demonstrated. Finite-difference time-domain calculations, combined with a dielectric weighting model, were used to assess the observed band and dispersion tuning.
Show PACS
42.82.Et Waveguides, couplers, and arrays
42.70.Qs Photonic bandgap materials

Characterization of low temperature GaAs antenna array terahertz emitters

M. Awad, M. Nagel, H. Kurz, J. Herfort, and K. Ploog

Appl. Phys. Lett. 91, 181124 (2007); http://dx.doi.org/10.1063/1.2800885 (3 pages) | Cited 18 times

Online Publication Date: 2 November 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a fabrication concept for photoconductive terahertz antenna arrays based on substrate-transferred thin films of low-temperature-grown GaAs semiconductor material. Adjacent array elements are physically decoupled by removing completely the photoconductive material in between. In contrast to former array devices based on intrinsic bulk GaAs substrates, this method allows the use of arbitrary carrier substrates with enhanced transmission properties. The emission characteristics of the device are investigated in terms of bandwidth, directivity, and saturation caused by charge-carrier induced field-screening effects. Screening-free operation is experimentally observed for an average optical power density below 2.2×10−4 mW/μm2.
Show PACS
84.40.Ba Antennas: theory, components and accessories
back to top
RSS Feeds

On the role of oxygen in dielectric barrier discharge actuation of aerodynamic flows

W. Kim, H. Do, M. G. Mungal, and M. A. Cappelli

Appl. Phys. Lett. 91, 181501 (2007); http://dx.doi.org/10.1063/1.2803755 (3 pages) | Cited 18 times

Online Publication Date: 29 October 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Phase-locked particle image velocimetry is used to study the mechanism of induced flow in the near field of a rf dielectric barrier discharge actuator mounted in the separated flow region of a bluff body. Flow actuation is found to be asymmetric, with suction toward the buried downstream electrode when it is biased positively relative to the upstream exposed electrode. Lesser flow is seen on the reverse voltage swing, where the buried electrode should attract positive ions. This phenomenon is enhanced when oxygen is added to the flow, suggesting that oxygen negative ions, possibly O2−, play a dominant role in plasma actuation.
Show PACS
52.30.-q Plasma dynamics and flow
47.85.Gj Aerodynamics
47.80.-v Instrumentation and measurement methods in fluid dynamics
47.65.-d Magnetohydrodynamics and electrohydrodynamics
Page 1 of 5 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close