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7 Jan 2013

Volume 102, Issue 1, Articles (01xxxx)

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Appl. Phys. Lett. 102, 011102 (2013); http://dx.doi.org/10.1063/1.4755756 (4 pages)

Qingzhen Hao, Seth M. Morton, Bei Wang, Yanhui Zhao, Lasse Jensen, and Tony Jun Huang
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Role of collisional broadening in Monte Carlo simulations of terahertz quantum cascade lasers

Alpar Matyas, Paolo Lugli, and Christian Jirauschek

Appl. Phys. Lett. 102, 011101 (2013); http://dx.doi.org/10.1063/1.4773516 (4 pages)

Online Publication Date: 2 January 2013

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Using a generalized version of Fermi's golden rule, collisional broadening is self-consistently implemented into ensemble Monte Carlo carrier transport simulations, and its effect on the transport and optical properties of terahertz quantum cascade lasers is investigated. The inclusion of broadening yields improved agreement with the experiment, without a significant increase of the numerical load. Specifically, this effect is crucial for a correct modeling at low biases. In the lasing regime, broadening can lead to significantly reduced optical gain and output power, affecting the obtained current-voltage characteristics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
02.50.Ng Distribution theory and Monte Carlo studies
41.60.Cr Free-electron lasers
FREE

Tuning surface-enhanced Raman scattering from graphene substrates using the electric field effect and chemical doping

Qingzhen Hao, Seth M. Morton, Bei Wang, Yanhui Zhao, Lasse Jensen, and Tony Jun Huang

Appl. Phys. Lett. 102, 011102 (2013); http://dx.doi.org/10.1063/1.4755756 (4 pages)

Online Publication Date: 2 January 2013

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Graphene recently has been demonstrated to support surface-enhanced Raman scattering. Here, we show that the enhancement of the Raman signal of methylene blue on graphene can be tuned by using either the electric field effect or chemical doping. Both doping experiments show that hole-doped graphene yields a larger enhancement than one which is electron-doped; however, chemical doping leads to a significantly larger modulation of the enhancements. The observed enhancement correlates with the changes in the Fermi level of graphene, indicating that the enhancement is chemical in nature, as electromagnetic enhancement is ruled out by hybrid electrodynamical and quantum mechanical simulations.
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78.68.+m Optical properties of surfaces
78.30.Na Fullerenes and related materials
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Spatial and temporal frequency domain laser-ultrasound applied in the direct measurement of dispersion relations of surface acoustic waves

Clemens Grünsteidl, István A. Veres, Jürgen Roither, Peter Burgholzer, Todd W. Murray, and Thomas Berer

Appl. Phys. Lett. 102, 011103 (2013); http://dx.doi.org/10.1063/1.4773234 (4 pages)

Online Publication Date: 3 January 2013

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We present a laser-ultrasound measurement technique which combines adjustable spatial and temporal modulation of the excitation laser beam. Our method spreads the intensity of an amplitude modulated continuous wave laser over a micro-scale pattern on the sample surface to excite surface acoustic waves. The excitation pattern consists of parallel, equidistant lines and the waves generated from the individual lines interfere on the sample surface. Measurement is done in the spatial-temporal frequency domain allowing the direct determination of dispersion relations. The technique performs with high signal-to-noise-ratios and low peak power densities on the sample.
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68.35.Iv Acoustical properties
02.10.-v Logic, set theory, and algebra

Polariton multistability and fast linear-to-circular polarization conversion in planar microcavities with lowered symmetry

S. S. Gavrilov, A. V. Sekretenko, S. I. Novikov, C. Schneider, S. Höfling, M. Kamp, A. Forchel, and V. D. Kulakovskii

Appl. Phys. Lett. 102, 011104 (2013); http://dx.doi.org/10.1063/1.4773523 (4 pages)

Online Publication Date: 3 January 2013

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The multistability of cavity-polariton systems with lowered symmetry (e.g., in laterally strained microcavities) allows implementing a few picoseconds long switching from linear to almost circular polarization of the cavity transmission under a resonant linearly polarized optical pump with slowly changing intensity. This effect has been observed in a high-Q GaAs microcavity using spectrally narrow 70 ps long pump pulses.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Enhanced performance of GaN based light-emitting diodes with a low temperature p-GaN hole injection layer

Hongjian Li, Junjie Kang, Panpan Li, Jun Ma, Hui Wang, Meng Liang, Zhicong Li, Jing Li, Xiaoyan Yi, and Guohong Wang

Appl. Phys. Lett. 102, 011105 (2013); http://dx.doi.org/10.1063/1.4773558 (4 pages)

Online Publication Date: 4 January 2013

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A hole injection layer (HIL) is designed in GaN-based light emitting diodes (LEDs) between multiple quantum wells and p-AlGaN electron blocking layer (EBL). Based on numerical simulation by apsys, the band diagram is adjusted by HIL, leading to the improved hole-injection efficiency. The designed HIL is a p-GaN buffer layer grown at low temperature (LT_pGaN) on last quantum barrier before p-AlGaN EBL. The output power of the fabricated GaN-based LED device with LT_pGaN HIL is enhanced by 128% at 100 A/cm2, while the efficiency droop is reduced by 33% compared to the conventional LED.
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85.60.Jb Light-emitting devices

Near milliwatt power AlGaN-based ultraviolet light emitting diodes based on lateral epitaxial overgrowth of AlN on Si(111)

Yinjun Zhang, Simon Gautier, Chu-Young Cho, Erdem Cicek, Zahra Vashaei, Ryan McClintock, Can Bayram, Yanbo Bai, and M. Razeghi

Appl. Phys. Lett. 102, 011106 (2013); http://dx.doi.org/10.1063/1.4773565 (5 pages)

Online Publication Date: 4 January 2013

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We report on the growth, fabrication, and device characterization of AlGaN-based thin-film ultraviolet (UV) (λ ∼ 359 nm) light emitting diodes (LEDs). First, AlN/Si(111) template is patterned. Then, a fully coalesced 7-μm-thick lateral epitaxial overgrowth (LEO) of AlN layer is realized on patterned AlN/Si(111) template followed by UV LED epi-regrowth. Metalorganic chemical vapor deposition is employed to optimize LEO AlN and UV LED epitaxy. Back-emission UV LEDs are fabricated and flip-chip bonded to AlN heat sinks followed by Si(111) substrate removal. A peak pulsed power and slope efficiency of ∼0.6 mW and ∼1.3 μW/mA are demonstrated from these thin-film UV LEDs, respectively. For comparison, top-emission UV LEDs are fabricated and back-emission LEDs are shown to extract 50% more light than top-emission ones.
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85.60.Jb Light-emitting devices

Photonic crystal coupled cavities with increased beaming and free space coupling efficiency

S. Haddadi, A. M. Yacomotti, I. Sagnes, F. Raineri, G. Beaudoin, L. Le Gratiet, and J. A. Levenson

Appl. Phys. Lett. 102, 011107 (2013); http://dx.doi.org/10.1063/1.4772955 (5 pages)

Online Publication Date: 4 January 2013

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We implement the band-folding approach in coupled photonic crystal L3 (three missing holes) nanocavities and demonstrate a dramatic beaming improvement compatible with high-Q operation. Directional laser effect is achieved. In addition, resonant free-space coupling to the symmetric and anti-symmetric hybrid modes of the photonic molecule is shown. We measure the coupling to each mode as a function of the spatial position of the laser spot, which can be used as a technique to probe the symmetry of coupled cavity modes.
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61.82.-d Radiation effects on specific materials
42.82.-m Integrated optics

Demonstration of high performance bias-selectable dual-band short-/mid-wavelength infrared photodetectors based on type-II InAs/GaSb/AlSb superlattices

A. M. Hoang, G. Chen, A. Haddadi, and M. Razeghi

Appl. Phys. Lett. 102, 011108 (2013); http://dx.doi.org/10.1063/1.4773593 (4 pages)

Online Publication Date: 4 January 2013

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High performance bias-selectable dual-band short-/mid-wavelength infrared photodetector based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 μm and 4 μm was demonstrated. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0 × 10−9 A/cm2 at −50 mV bias voltage, providing an associated shot noise detectivity of 3.0 × 1013 Jones. The mid-wavelength channel exhibited a quantum efficiency of 33% and a dark current density of 2.6 × 10−5 A/cm2 at 300 mV bias voltage, resulting in a detectivity of 4.0 × 1011 Jones. The spectral cross-talk between the two channels was also discussed for further optimization.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Terahertz time-domain measurement of non-Drude conductivity in silver nanowire thin films for transparent electrode applications

Jaeseok Kim, Inhee Maeng, Jongwook Jung, Hyunjoon Song, Joo-Hiuk Son, Kilsuk Kim, Jaeik Lee, Chul-Hong Kim, Geesung Chae, Myungchul Jun, YongKee Hwang, Su Jeong Lee, Jae-Min Myoung, and Hyunyong Choi

Appl. Phys. Lett. 102, 011109 (2013); http://dx.doi.org/10.1063/1.4773179 (4 pages)

Online Publication Date: 4 January 2013

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We have investigated the complex conductivity of silver nanowire thin films using terahertz time-domain spectroscopy. Maxwell-Garnett effective medium theory, which accounts for the effective complex conductivity of silver nanowires, is presented in detail theoretically and experimentally. The conductivity of nanowires exhibits a characteristic non-Drude response in which the applied terahertz field is polarized in the longitudinal nanowire direction. The non-Drude responses of the silver nanowires are explained by the Gans approximation and the Drude-Smith model, and both agree well with the experimental data. Our results provide a basis for further explorations of charge carrier dynamics in nanowire-based transparent electrode applications.
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73.61.At Metal and metallic alloys
78.70.Gq Microwave and radio-frequency interactions

Accurate alignment of a photonic crystal nanocavity with an embedded quantum dot based on optical microscopic photoluminescence imaging

T. Kojima, K. Kojima, T. Asano, and S. Noda

Appl. Phys. Lett. 102, 011110 (2013); http://dx.doi.org/10.1063/1.4773882 (3 pages)

Online Publication Date: 7 January 2013

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We have developed a technique to align a two-dimensional photonic-crystal nanocavity (PCNC) with an indium arsenide/gallium arsenide self-assembled quantum dot (QD), using microscopic photoluminescence (μ-PL) spectroscopy to image a wafer with a low-density of QDs and pre-formed positioning marks. Individual QD emission wavelengths were evaluated from μ-PL spectra, and positions relative to the marks were determined. The wavelength detuning between the QD-emission peak and the PCNC resonant frequency was < 4 nm, and the alignment standard deviation was < 50 nm. The emission peaks of a single QD and a PCNC aligned by this technique showed anti-crossing, implying high accuracy.
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42.70.Qs Photonic bandgap materials

Mid-infrared Raman sources using spontaneous Raman scattering in germanium core optical fibers

Pengfei Wang, Christy Charlton O'Mahony, Timothy Lee, Rand Ismaeel, Thomas Hawkins, Yuliya Semenova, Lin Bo, Qiang Wu, Colette McDonagh, Gerald Farrell, John Ballato, and Gilberto Brambilla

Appl. Phys. Lett. 102, 011111 (2013); http://dx.doi.org/10.1063/1.4773884 (4 pages)

Online Publication Date: 7 January 2013

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Mid-infrared Raman sources based on spontaneous Raman scattering have been demonstrated in a 15-μm diameter glass-clad crystalline germanium optical fiber and in a germanium-wire. A quantum cascade laser was used as pump at a wavelength of 5.62 μm. Because of their ultra-high optical nonlinearities and extremely broad transparency window, germanium core fibers offer the possibility of fabricating compact and efficient mid-infrared sources.
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42.81.-i Fiber optics
42.65.-k Nonlinear optics
42.70.Ce Glasses, quartz

Tunable Fano resonances based on two-beam interference in microring resonator

Ting Hu, Ping Yu, Chen Qiu, Huiye Qiu, Fan Wang, Mei Yang, Xiaoqing Jiang, Hui Yu, and Jianyi Yang

Appl. Phys. Lett. 102, 011112 (2013); http://dx.doi.org/10.1063/1.4773917 (4 pages)

Online Publication Date: 7 January 2013

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In this paper, a resonant system is demonstrated on silicon-on-insulator wafer to achieve tunable Fano resonances. In this system, the Fano resonance originates from the interference of two beams resonant in the microring resonator. The shapes of the Fano resonances are tunable through controlling the phase difference of the two beams. Both large slope and high extinction ratio (ER) are obtained when the phase difference is 0.5π or 1.5π. Experimental results show that Fano resonances with steep slope and ER over 20 dB are achieved in the whole free spectral range by controlling the microheaters to meet the phase condition.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

Low voltage and high contrast blue phase liquid crystal with red-shifted Bragg reflection

Jin Yan, Zhenyue Luo, Shin-Tson Wu, Jyh-Wen Shiu, Yu-Cheng Lai, Kung-Lung Cheng, Shih-Hsien Liu, Pao-Ju Hsieh, and Yuan-Chun Tsai

Appl. Phys. Lett. 102, 011113 (2013); http://dx.doi.org/10.1063/1.4773985 (5 pages) | Cited 3 times

Online Publication Date: 7 January 2013

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We demonstrated a low voltage and high contrast polymer-stabilized blue phase liquid crystal (BPLC) by shifting the Bragg reflection to a red wavelength. To retain high contrast ratio, a left-handed BPLC is sandwiched between a right-handed circular polarizer and a left-handed circular analyzer. The driving voltage is reduced by 35% as compared to that of a transparent BPLC, while keeping submillisecond response time. The proposed approach would accelerate the emergence of BPLC for next-generation display and photonic applications.
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42.79.Kr Display devices, liquid-crystal devices

Experimental approach to the microscopic phase-sensitive surface plasmon resonance biosensor

Chonglei Zhang, Rong Wang, Changjun Min, Siwei Zhu, and X.-C. Yuan

Appl. Phys. Lett. 102, 011114 (2013); http://dx.doi.org/10.1063/1.4773997 (5 pages) | Cited 1 time

Online Publication Date: 7 January 2013

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We designed and proposed a microscopic configuration of wide-dynamic-range phase-sensitive surface plasmon resonance biosensor based on differential interferometry between focused radially polarized and azimuthally polarized cylindrical vector beams recently (R. Wang et al., Opt. Lett. 37, 2091 (2012)). In this Letter, we follow the simulation results up with experimental verifications with a sensitivity of 7.385 × 10−7refractive index unit (RIU)/0.1°. It is also verified that the dynamic range of this system could be as large as 0.35 RIU in principle, which is only confined by numerical aperture of the microscopic objective lens.
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87.80.Ek Mechanical and micromechanical techniques
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems
07.60.Ly Interferometers
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Influence of dislocation density on carrier injection in InGaN/GaN light-emitting diodes operated with alternating current

Dong-Yul Lee, Sang-Heon Han, Dong Ju Lee, Jeong Wook Lee, Dong-Joon Kim, Young Sun Kim, Sung-Tae Kim, and Jae-Young Leem

Appl. Phys. Lett. 102, 011115 (2013); http://dx.doi.org/10.1063/1.4773588 (4 pages)

Online Publication Date: 8 January 2013

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The frequency dependence of current spreading and light output power (LOP) was investigated for InGaN/GaN light-emitting diodes (LEDs) grown on n-GaN templates with different threading dislocation densities (TDDs) that were operated using alternating-current (AC). By comparison with LEDs with low TDDs, the LEDs with high TDDs showed a strong frequency dependence for both current spreading and LOP during high-frequency AC operation. The results were attributed to a weak carrier injection into InGaN quantum wells (QWs) during high frequency AC operation, which resulted from the suppression of carrier transport induced by the carrier scattering around negatively charged dislocation cores.
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85.60.Jb Light-emitting devices

Material-based three-dimensional imaging with nanostructured surfaces

Yousef Nazirizadeh, Julia Reverey, Ulf Geyer, Uli Lemmer, Christine Selhuber-Unkel, and Martina Gerken

Appl. Phys. Lett. 102, 011116 (2013); http://dx.doi.org/10.1063/1.4773875 (4 pages)

Online Publication Date: 8 January 2013

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Visualizing three-dimensional (3D) structures at the micrometer and nanometer scale is essential not only for characterizing materials and corrosion but also biological samples. Here, we present a material-based nano-optical method using the near-field properties of periodically nanostructured surfaces (photonic crystal slabs) to obtain 3D images. The wavelength and the quality factor of resonances in the transmission spectrum provide optical thickness information of objects on the surface, which we use for rapid topography determination of cells.
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07.60.Pb Conventional optical microscopes
42.30.Va Image forming and processing
42.70.Qs Photonic bandgap materials

Mode recombination and alternation of surface plasmons in anisotropic mediums

Rui Luo, Ying Gu, Xiankuo Li, Luojia Wang, Iam-Choon Khoo, and Qihuang Gong

Appl. Phys. Lett. 102, 011117 (2013); http://dx.doi.org/10.1063/1.4773877 (4 pages) | Cited 1 time

Online Publication Date: 8 January 2013

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Dispersion relations of surface plasmon polaritons with transverse-magnetic- and transverse-electric-polarized waves coexisting in insulator-metal-anisotropic planar waveguides are analytically derived. Aligned nematic liquid crystal, as an anisotropic medium, is employed to manipulate the mode properties. By varying its optical axis, two kinds of mode transformation are found: one is mode recombination, accompanied by dramatically extended propagation lengths at the cutoff angles, and the other is mode alternation, associated with an obvious shift of the electromagnetic energy flux from one insulator to the other. The results may have applications in actively modulated plasmon-based nanodevices and tunable surface plasmon sources.
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73.20.At Surface states, band structure, electron density of states
77.22.Ch Permittivity (dielectric function)
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.68.+m Optical properties of surfaces
42.70.Df Liquid crystals
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Strong coupling at room temperature in ultracompact flexible metallic microcavities

C. Grossmann, G. Christmann, J. J. Baumberg, I. Farrer, H. Beere, and D. A. Ritchie

Appl. Phys. Lett. 102, 011118 (2013); http://dx.doi.org/10.1063/1.4773881 (4 pages)

Online Publication Date: 8 January 2013

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Strong coupling between metallic microcavity modes and inorganic quantum well (QW) excitons at room temperature is observed in an ultracompact flexible sample design less than 100 nm thick. Four GaAs QWs embedded in a 65 nm AlGaAs/GaAs cavity are sandwiched between gold mirrors. The strong electromagnetic confinement and metallic phase shifts provide substantial local field enhancement and angular-resolved reflectivity spectra clearly show the anti-crossing in the dispersion relation resolving a Rabi splitting of 21 meV at room temperature, in good agreement with calculations. Flex-tuning metal thin foil microcavities demonstrate new possibilities for tunable optoelectronics and the study of polaritonic micromechanical effects.
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73.21.Fg Quantum wells
73.22.Lp Collective excitations
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.De Quantum wells
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Thermal annealing effect on material characterizations of β-Ga2O3 epilayer grown by metal organic chemical vapor deposition

Chiung-Yi Huang, Ray-Hua Horng, Dong-Sing Wuu, Li-Wei Tu, and Hsiang-Shun Kao

Appl. Phys. Lett. 102, 011119 (2013); http://dx.doi.org/10.1063/1.4773247 (3 pages)

Online Publication Date: 8 January 2013

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In this work, a single-crystalline β-Ga2O3 epilayer was grown on (0001) sapphire at low temperature by low-pressure metal organic chemical vapor deposition. The optimized parameters for the chamber pressure, oxygen flow, and growth temperature were 15 Torr, 200 sccm, and 500 °C, respectively. The β-Ga2O3 epilayer was fabricated as a metal-semiconductor-metal solar-blind deep ultraviolet photodetector. Due to the gallium oxide grown at low temperature, the as-grown β-Ga2O3 epilayer was annealed at 800 °C in atmosphere or in a nitrogen environment. The effects of defects of the β-Ga2O3 epilayer before and after N2 annealing were studied using x-ray diffraction system, cathodoluminescence at differential temperature, and Hall measurement. The β-Ga2O3 epilayer that was N2 annealed for 15 min presented better photodetector performance than the as-grown β-Ga2O3 epilayer. The annealed epilayer exhibited a dark current of 1.6 × 10−13 A under 5 V bias.
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68.55.ag Semiconductors
61.72.Cc Kinetics of defect formation and annealing
73.61.Le Other inorganic semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Nk Insulators
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Resonantly overcoming metal opacity

J. D. Edmunds, M. J. Lockyear, A. P. Hibbins, J. R. Sambles, and I. J. Youngs

Appl. Phys. Lett. 102, 011120 (2013); http://dx.doi.org/10.1063/1.4773477 (3 pages) | Cited 1 time

Online Publication Date: 8 January 2013

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The near-perfect response of electrons in metals to low-frequency electromagnetic fields makes even a sub-skin-depth film almost completely opaque to microwave radiation. Here, it is experimentally demonstrated that by surrounding a ∼60 nm aluminium film with an array of thin resonant cavities, over 35% of the microwave radiation incident can be transmitted over a discrete set of narrow bands. This represents an enhancement of ∼1000 times over an isolated film and allows for a frequency selective screen with a thickness less than 1/70th of the operating wavelength that may be tuned through choice of resonant geometry.
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68.55.-a Thin film structure and morphology
78.20.-e Optical properties of bulk materials and thin films

Two-channel interferometric detection for the compensation of phase fluctuation noise in nonlinear infrared microscopy

E. S. Lee, S. W. Lee, J. H. Park, and J. Y. Lee

Appl. Phys. Lett. 102, 011121 (2013); http://dx.doi.org/10.1063/1.4773999 (4 pages)

Online Publication Date: 9 January 2013

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We demonstrate an interferometric implementation of nonlinear optical infrared microscopy in which a probe beam interrogates the refractive index change of samples that is induced by molecular vibrational absorption of an infrared pump beam. To compensate for the phase noise caused by the ambient airflow and external vibration, we configure two coupled Mach-Zehnder interferometers sharing a single microscope setup in the sample arm. Proper control over the phase between the two interference channels allows two simultaneous quadrature mode outputs. The validity of our method is proven by imaging polystyrene bead aggregates and comparing the images with the conventional single-channel results.
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78.30.-j Infrared and Raman spectra
07.60.Ly Interferometers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Ultrafast manipulation of near field coupling between bright and dark modes in terahertz metamaterial

Dibakar Roy Chowdhury, Ranjan Singh, Antoinette J. Taylor, Hou-Tong Chen, and Abul K. Azad

Appl. Phys. Lett. 102, 011122 (2013); http://dx.doi.org/10.1063/1.4774003 (5 pages)

Online Publication Date: 9 January 2013

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We demonstrate ultrafast optical control of near field coupling between bright and dark mode resonances in metamaterials. The meta-molecule design consists of two orthogonally twisted resonators tightly coupled through near fields. We place ion implanted silicon patch with ultrafast carrier lifetime inside dark resonator split gap to achieve active control of its fundamental resonance that determines the near field coupling in the meta-molecule. Upon near infrared photoexcitation, we observed ultrafast dynamical transition of near field coupling between bright and dark resonators allowing the meta-molecule to change its state from coupled to decoupled and eventually back to the coupled state.
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42.70.-a Optical materials

Hot electron bolometer heterodyne receiver with a 4.7-THz quantum cascade laser as a local oscillator

J. L. Kloosterman, D. J. Hayton, Y. Ren, T. Y. Kao, J. N. Hovenier, J. R. Gao, T. M. Klapwijk, Q. Hu, C. K. Walker, and J. L. Reno

Appl. Phys. Lett. 102, 011123 (2013); http://dx.doi.org/10.1063/1.4774085 (4 pages) | Cited 1 time

Online Publication Date: 9 January 2013

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We report on a heterodyne receiver designed to observe the astrophysically important neutral atomic oxygen [OI] line at 4.7448 THz. The local oscillator is a third-order distributed feedback quantum cascade laser operating in continuous wave mode at 4.741 THz. A quasi-optical, superconducting NbN hot electron bolometer is used as the mixer. We recorded a double sideband receiver noise temperature (TrecDSB) of 815 K, which is ∼ 7 times the quantum noise limit (math) and an Allan variance time of 15 s at an effective noise fluctuation bandwidth of 18 MHz. Heterodyne performance was confirmed by measuring a methanol line spectrum.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

InAs/AlSb widely tunable external cavity quantum cascade laser around 3.2 μm

T. Kruczek, K. A. Fedorova, G. S. Sokolovskii, R. Teissier, A. N. Baranov, and E. U. Rafailov

Appl. Phys. Lett. 102, 011124 (2013); http://dx.doi.org/10.1063/1.4774088 (3 pages)

Online Publication Date: 9 January 2013

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Room temperature, tunable, external-cavity short-wavelength InAs/AlSb quantum cascade laser (QCL) is reported. Wavelength tuning of 85 nm for the spectral range between 3190 nm and 3275 nm has been achieved by rotating the diffraction grating forming the external cavity. To suppress lasing inside the QCL cavity, its ridge was tilted by 7° at the external cavity end. The optimal tilting angle of the laser ridge was chosen by careful consideration of the return losses of the TM-polarized waveguide mode from the diffraction grating in a quasi-Littrow configuration and the Fabry-Pérot feedback from the tilted laser facet. No antireflection coating was used.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
42.79.Dj Gratings

Optically tunable long wavelength infrared quantum cascade laser operated at room temperature

S. Suchalkin, S. Jung, R. Tober, M. A. Belkin, and G. Belenky

Appl. Phys. Lett. 102, 011125 (2013); http://dx.doi.org/10.1063/1.4774267 (4 pages)

Online Publication Date: 9 January 2013

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We demonstrate rapid tuning of the emission frequency of a room-temperature mid-infrared quantum cascade laser by external optical pumping. Emission frequency tuning over 0.3 cm−1 (10 GHz) has been achieved for a λ = 9 μm device by optical generation of electron-hole pairs along the entire length of the laser stripe. Measurements indicate that this approach allows for rapid broadband frequency-modulation of mid-infrared quantum cascade lasers at above 300 MHz modulation frequencies.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
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