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8 Nov 2010

Volume 97, Issue 19, Articles (19xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 97, 193101 (2010); http://dx.doi.org/10.1063/1.3504664 (3 pages)

Qingzhen Hao, Yong Zeng, Xiande Wang, Yanhui Zhao, Bei Wang, I-Kao Chiang, Douglas H. Werner, Vincent Crespi, and Tony Jun Huang
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Terahertz intersubband absorption in GaN/AlGaN step quantum wells

H. Machhadani, Y. Kotsar, S. Sakr, M. Tchernycheva, R. Colombelli, J. Mangeney, E. Bellet-Amalric, E. Sarigiannidou, E. Monroy, and F. H. Julien

Appl. Phys. Lett. 97, 191101 (2010); http://dx.doi.org/10.1063/1.3515423 (3 pages) | Cited 10 times

Online Publication Date: 8 November 2010

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We demonstrate terahertz intersubband absorptions at frequencies of 2.1 THz (λ ≈ 143 μm) and 4.2 THz (λ ≈ 70 μm) in nitride-based semiconductor quantum wells. The structures consist of a 3 nm thick GaN well, an Al0.05Ga0.95N step barrier, and a 3 nm thick Al0.1Ga0.9N barrier. The absorption is detected at 4.7 K. The structure design has been optimized to approach a flat-band potential in the wells to allow for an intersubband absorption in the terahertz frequency range and to maximize the optical dipole moments.
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73.21.Fg Quantum wells
78.70.Gq Microwave and radio-frequency interactions
78.67.De Quantum wells

Enhancement of spontaneous emission rate and reduction in amplified spontaneous emission threshold in electrodeposited three-dimensional ZnO photonic crystal

Yongchun Zhong, Zhounan Yue, George K. L. Wong, Yan Yan Xi, Yuk Fan Hsu, Aleksandra B. Djurišić, Jian-Wen Dong, Wen-Jie Chen, and Kam Sing Wong

Appl. Phys. Lett. 97, 191102 (2010); http://dx.doi.org/10.1063/1.3499274 (3 pages)

Online Publication Date: 8 November 2010

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ZnO photonic crystal (PC) with face-center-cube type structure is fabricated by electrodeposition using holographic lithographically made organic (SU-8) template. Photonic band gap effect (reflection peak and transmission dip in infrared spectral region) is clearly seen. Observation of strong enhancement and blueshift of the emission peak (from 383.8 to 378.8 nm), shortening of the exciton photoluminescence lifetime (from 88 to 34 ps), and reduction in amplified spontaneous emission threshold of ZnO PC compared to that of the reference nonstructured electrodeposited ZnO showed clear evidence of PC structure affecting the ZnO exciton emission.
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81.05.Dz II-VI semiconductors
81.15.Pq Electrodeposition, electroplating
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.55.Et II-VI semiconductors
78.45.+h Stimulated emission
42.70.Qs Photonic bandgap materials

AlGaN solar-blind avalanche photodiodes with high multiplication gain

Lu Sun, Jilin Chen, Jianfei Li, and Hao Jiang

Appl. Phys. Lett. 97, 191103 (2010); http://dx.doi.org/10.1063/1.3515903 (3 pages) | Cited 3 times

Online Publication Date: 8 November 2010

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We report the fabrication and characterization of the solar-blind AlGaN avalanche photodiodes grown by metal-organic chemical vapor deposition on c-plane sapphire substrate. The fabricated devices with 100 μm diameter active area exhibit a peak responsivity of 79.8 mA/W at 270 nm and zero bias, corresponding to an external quantum efficiency of 37%. Multiplication gains as high as more than 2500 were obtained in these devices.
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85.30.Kk Junction diodes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Enhancement of random lasing through fluorescence resonance energy transfer and light scattering mediated by nanoparticles

C. S. Wang, Y. L. Chen, H. Y. Lin, Y. T. Chen, and Y. F. Chen

Appl. Phys. Lett. 97, 191104 (2010); http://dx.doi.org/10.1063/1.3515913 (3 pages) | Cited 3 times

Online Publication Date: 8 November 2010

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A simple approach for the enhancement of random lasing based on fluorescence resonance energy transfer and light scattering mediated by nanoparticles is reported. To illustrate our working principle, ZnO nanorods decorated with TiO2 nanoparticles were chosen as an example. It is shown that the random laser action of ZnO nanorods can be significantly improved by the assistance of TiO2 nanoparticles. Moreover, due to the inherent nature of higher refractive index of TiO2 than ZnO, the TiO2 nanoparticles can serve efficiently as better nanoscatterers, which can promote the formation of closed-loop paths. Our strategy provided here is very useful for the future development of high efficiency optoelectronic devices.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Electroluminescence from AlN nanowires grown on p-SiC substrate

H. Y. Yang, S. F. Yu, Y. Y. Hui, and S. P. Lau

Appl. Phys. Lett. 97, 191105 (2010); http://dx.doi.org/10.1063/1.3513308 (3 pages) | Cited 1 time

Online Publication Date: 8 November 2010

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Aluminum nitride (AlN) nanowires were prepared by the carbothermal reduction method. A heterojunction light-emitting diode (LED) was fabricated by depositing randomly aligned AlN nanowires onto p-type 4H–SiC substrate. When a forward bias voltage greater than 8 V was applied to the LED, a broad band emission peaked at 417 nm could be observed. The peak deconvolution revealed four emission peaks at ∼ 400, 420, 468, and 525 nm. These emission peaks may be attributed to the radiative recombination between electrons from trap-level states and holes from the valence band of the AlN nanowires.
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85.60.Jb Light-emitting devices
81.07.Gf Nanowires
78.67.Lt Quantum wires
81.05.Ea III-V semiconductors
78.60.Fi Electroluminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Crystal defect topography of Stranski–Krastanow quantum dots by atomic force microscopy

K. Gradkowski, T. C. Sadler, L. O. Mereni, V. Dimastrodonato, P. J. Parbrook, G. Huyet, and E. Pelucchi

Appl. Phys. Lett. 97, 191106 (2010); http://dx.doi.org/10.1063/1.3514237 (3 pages) | Cited 1 time

Online Publication Date: 8 November 2010

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We demonstrate a technique to monitor the defect density in capped quantum dot (QD) structures by performing an atomic force microscopy (AFM) of the final surface. Using this method we are able to correlate their density with the optical properties of the dot structures grown at different temperatures. Parallel transmission electron microscopy analysis shows that the AFM features are directly correlated with the density of stacking faults that originate from abnormally large dots. The technique is rapid and noninvasive making it an ideal diagnostic tool for optimizing the parameters of practical QD-based devices.
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68.37.Ps Atomic force microscopy (AFM)
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
61.72.Nn Stacking faults and other planar or extended defects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Strong light-matter coupling at terahertz frequencies at room temperature in electronic LC resonators

Markus Geiser, Christoph Walther, Giacomo Scalari, Mattias Beck, Milan Fischer, Laurent Nevou, and Jérôme Faist

Appl. Phys. Lett. 97, 191107 (2010); http://dx.doi.org/10.1063/1.3511446 (3 pages) | Cited 3 times

Online Publication Date: 9 November 2010

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Strong light-matter coupling at room temperature in the terahertz (THz) range is demonstrated. The studied system consists of electronic intersubband transitions in AlxGa1−xAs parabolic quantum wells coupled to an electronic LC microcavity resonator allowing strong subwavelength confinement of the cavity mode. The measured Rabi frequency is 0.48 THz, corresponding to 14% of the center frequency, independent of the temperature of the system in the range 10–300 K.
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78.67.De Quantum wells
81.05.Ea III-V semiconductors
73.21.Fg Quantum wells

Zero-cell photonic crystal nanocavity laser with quantum dot gain

Masahiro Nomura, Yasutomo Ota, Naoto Kumagai, Satoshi Iwamoto, and Yasuhiko Arakawa

Appl. Phys. Lett. 97, 191108 (2010); http://dx.doi.org/10.1063/1.3514556 (3 pages) | Cited 3 times

Online Publication Date: 9 November 2010

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We demonstrate laser oscillation in a hexagonal-lattice photonic crystal nanocavity using an InGaAs quantum dot gain material by optical pumping at 5 K. The cavity comprises a defect created by shifting several air holes in a two-dimensional photonic crystal slab structure without removing any air holes to achieve both small mode volume and a high cavity quality factor. The measured cavity quality factors and estimated mode volume for the nanocavity are ∼ 33 000 and 0.004 μm3 [0.23(λ0/n)3]. The laser threshold is compared between the zero-cell and L3-type nanocavity lasers, and the zero-cell nanolasers are found to have lower thresholds of about one-third of the L3-type nanolasers. This result suggests that a higher Purcell factor of the zero-cell nanolaser is reflected as a lower laser threshold.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.70.Qs Photonic bandgap materials
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Lambda shifted photonic crystal cavity laser

Martin Schubert, Troels Suhr, Sara Ek, Elizaveta S. Semenova, Jørn M. Hvam, and Kresten Yvind

Appl. Phys. Lett. 97, 191109 (2010); http://dx.doi.org/10.1063/1.3501968 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2010

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We propose and demonstrate an alternative type of photonic crystal laser design that shifts all the holes in the lattice by a fixed fraction of the targeted emission wavelength. The structures are realized in InGaAsP (λ = 1.15) with InGaAsP quantum wells (λ = 1.52) as gain material. Cavities with shifts of 1/4 and 3/4 of the emission wavelength were fabricated and characterized. Measurements show threshold behavior for several modes at room temperature. Both structures are simulated using a finite difference time domain method to identify the resonances in the spectra and calculate the mode volume of the dominant mode.
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42.55.Tv Photonic crystal lasers and coherent effects
42.70.Qs Photonic bandgap materials
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems
42.70.Hj Laser materials
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Influence of the spatial pump distribution on the performance of high power vertical-external-cavity surface-emitting lasers

A. Chernikov, J. Herrmann, M. Scheller, M. Koch, B. Kunert, W. Stolz, S. Chatterjee, S. W. Koch, T. L. Wang, Y. Kaneda, J. M. Yarborough, J. Hader, and J. V. Moloney

Appl. Phys. Lett. 97, 191110 (2010); http://dx.doi.org/10.1063/1.3515911 (3 pages) | Cited 1 time

Online Publication Date: 10 November 2010

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The performance of a 1040 nm vertical-external-cavity surface-emitting laser is studied as function of the size and shape of the pumped area. The input-output characteristics of the device are monitored while simultaneously tracking the temperature in the active region. It is shown that the pump spot shape plays a crucial role in optimizing the laser output. Improvements up to a factor of 5 are found for a super-Gaussian in comparison to the standard Gaussian shape. For the large pump-spot sizes needed for high output powers, it turns out that the power-scalability breaks down due to the suppressed lateral heat flow.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.By Design of specific laser systems

The antiguiding parameter in mid-infrared optically pumped semiconductor lasers

A. P. Ongstad, G. C. Dente, M. L. Tilton, R. Kaspi, and J. R. Chavez

Appl. Phys. Lett. 97, 191111 (2010); http://dx.doi.org/10.1063/1.3509798 (3 pages)

Online Publication Date: 10 November 2010

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We describe measurements of the antiguiding parameter, α, for several optically pumped semiconductor lasers. Three laser structures were investigated; two of the lasers utilize W-quantum wells (QWs) in which 14 InAs/In0.4 GaSb/InAs QWs are imbedded in lattice-matched In0.25 GaAsSb layers. The emission wavelengths of the W lasers were ∼ 3.5 and 4.5 μm, respectively. The other laser, a double heterostructure (DH) design, contained a ∼ 1.5 μm InAsSb active region embedded in ∼ 2.5 μm thick AlAsSb clad regions. The emission wavelength of the DH was λ ∼ 3.8 μm. We employed the Hakki–Paoli method [ B. W. Hakki and T. L. Paoli, J. Appl. Phys., 44, 4113, (1973)] in conjunction with a Fourier transform infrared spectrometer to measure subthreshold gain and index variations as a function of pump intensity. To reduce errors associated with incoherent background emission a full spectral curve fit was used to determine the differential gain and index. The results reveal the antiguiding factor in the W lasers to be low with α ∼ 1.0. The antiguiding factor for the DH was markedly larger with α = 9.4±1.3. We attribute the low α for the W lasers to the higher QW gain as well as to inhomogeneous broadening induced by the 14 QWs. The differing well widths and the independent optical pumping of the wells, leads to a net gain spectrum that is symmetrical about the gain peak. This symmetry, in turn, leads to small differential index shifts at the gain peak; the result of the small differential index and large differential gain is low antiguiding
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Electrostatically tunable optomechanical “zipper” cavity laser

R. Perahia, J. D. Cohen, S. Meenehan, T. P. Mayer Alegre, and O. Painter

Appl. Phys. Lett. 97, 191112 (2010); http://dx.doi.org/10.1063/1.3515296 (3 pages) | Cited 5 times

Online Publication Date: 12 November 2010

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A tunable nanoscale “zipper” laser cavity, formed from two doubly clamped photonic crystal nanobeams, is demonstrated. Pulsed, room temperature, optically pumped lasing action at λ = 1.3 μm is observed for cavities formed in a thin membrane containing InAsP/GaInAsP quantum-wells. Metal electrodes are deposited on the ends of the nanobeams to allow for microelectromechanical actuation. Electrostatic tuning over a range of Δλ = 20 nm for an applied voltage amplitude of 9 V and modulation at a frequency as high as νm = 6.7 MHz of the laser wavelength is demonstrated.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Continuous control of spatial mode rotation using second harmonic generation

Jun-Hee Park, Woo-Kyung Kim, Woo-Jin Jeong, Myung-Gun Song, Hun-Hwa Kim, Kyung-Hwan Koo, Yeung-Lak Lee, Yena Kim, Ju-Han Lee, Woo-Seok Yang, and Han-Young Lee

Appl. Phys. Lett. 97, 191113 (2010); http://dx.doi.org/10.1063/1.3507267 (3 pages)

Online Publication Date: 12 November 2010

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This paper reports a continuously rotating spatial mode contributed from the interference between two second harmonic (SH) high-order modes, TM10 and TM01, which were generated in z-cut MgO:LN ridge waveguides with a periodically poled structure. The TM10 and TM01 SH modes were generated from the mixed first harmonic (FH) modes, the phase-matching conditions of the two modes were controlled to be close and to overlap so that the two modes can interference each other. The experiment results showed the interference of the two modes created an odd mode distribution with a specific angle and the distribution was continuously rotating according to the operation temperature.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Wi Nonlinear waveguides
42.79.Nv Optical frequency converters

Birefringence controlled room-temperature picosecond spin dynamics close to the threshold of vertical-cavity surface-emitting laser devices

M. Y. Li, H. Jähme, H. Soldat, N. C. Gerhardt, M. R. Hofmann, and T. Ackemann

Appl. Phys. Lett. 97, 191114 (2010); http://dx.doi.org/10.1063/1.3515855 (3 pages) | Cited 4 times

Online Publication Date: 12 November 2010

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We analyze the spin-induced circular polarization dynamics at the threshold of vertical-cavity surface-emitting lasers at room-temperature using a hybrid excitation combining electrically pumping without spin preference and spin-polarized optical injection. After a short pulse of spin-polarized excitation, fast oscillations of the circular polarization degree (CPD) are observed within the relaxation oscillations. A theoretical investigation of this behavior on the basis of a rate equation model shows that these fast oscillations of CPD could be suppressed by means of a reduction of the birefringence of the laser cavity.
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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

Ultrasharp edge filtering in nanotethered photonic wires

A. Talneau, I. Sagnes, R. Gabet, Y. Jaouen, and H. Benisty

Appl. Phys. Lett. 97, 191115 (2010); http://dx.doi.org/10.1063/1.3513279 (3 pages) | Cited 1 time

Online Publication Date: 12 November 2010

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Within a suspended photonic wire, the periodically-spaced nanotethers sustaining the wire can behave as damped transverse resonators that interact with the partially reflecting effect of the wire-tether intersection, and thus modify the Bragg reflection mechanism. This specific resonant mechanism is explored using a transfer matrix model, and is shown to result in an ultrasharp filter edge. This sharp behavior is evidenced experimentally on 300–400-nm-wide InP suspended wires through transmission data and further consolidated by optical low coherence reflectometry time-frequency analysis.
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42.79.Ci Filters, zone plates, and polarizers
81.07.Gf Nanowires
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
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