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5 Nov 2012

Volume 101, Issue 19, Articles (19xxxx)

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Appl. Phys. Lett. 101, 193101 (2012); http://dx.doi.org/10.1063/1.4764508 (4 pages)

Ryan T. Tucker, Allan L. Beaudry, Joshua M. LaForge, Michael T. Taschuk, and Michael J. Brett
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Bound and anti-bound biexciton in site-controlled pyramidal GaInAs/GaAs quantum dots

C. Jarlov, P. Gallo, M. Calic, B. Dwir, A. Rudra, and E. Kapon

Appl. Phys. Lett. 101, 191101 (2012); http://dx.doi.org/10.1063/1.4765646 (4 pages)

Online Publication Date: 5 November 2012

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We present a detailed study of biexciton complexes formed in single, site-controlled pyramidal GaInAs/GaAs quantum dots (QDs). By using power dependent measurements and photon correlation spectroscopy, we identify the excitonic transitions of a large number of pyramidal QDs, exhibiting both positive and negative biexciton binding energies. Separation of charges within the QD, caused by piezoelectric fields, is believed to be responsible for the positive to negative crossover of the biexciton binding energy with increasing QD size. In particular, QDs exhibiting vanishing biexciton binding energies are evidenced, with potential applications in quantum information processing.
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71.35.-y Excitons and related phenomena
77.65.-j Piezoelectricity and electromechanical effects
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
81.05.Ea III-V semiconductors
81.07.Ta Quantum dots

Can interference patterns in the reflectance spectra of GaN epilayers give important information of carrier concentration?

C. C. Zheng, S. J. Xu, F. Zhang, J. Q. Ning, D. G. Zhao, H. Yang, and C. M. Che

Appl. Phys. Lett. 101, 191102 (2012); http://dx.doi.org/10.1063/1.4766188 (3 pages)

Online Publication Date: 6 November 2012

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Low-temperature reflectance spectra of a series of Si-doped GaN epilayers with different doping concentrations grown on sapphire by metal-organic chemical vapour deposition were measured. In addition to the excitonic polariton resonance structures at the band edge, interference oscillating patterns were observed in the energy region well below the band gap. The amplitudes of these oscillation patterns show a distinct dependence on the doping concentrations of the samples. From the thin-film optical interference principle, an approach connecting the amplitude of the interference oscillations and the impurity scattering was established. Good agreement between experiment and theory is achieved.
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78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
71.35.-y Excitons and related phenomena
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Differential reflectance modulation sensing with diffractive microstructures

N. Kumawat and M. M. Varma

Appl. Phys. Lett. 101, 191103 (2012); http://dx.doi.org/10.1063/1.4766190 (4 pages)

Online Publication Date: 6 November 2012

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We present a method for differential ratiometric measurement of reflectance change due to molecular adsorption using a diffractive microstructure fabricated on a reflectance contrast enhancing substrate for bulk refractometry and surface molecular binding detection applications. The differential method suppresses signal fluctuations due to thermal or concentration gradients in the sample flow cell by more than 40× and enables the real-time measurement of molecular interactions on the surface with a noise floor of about 70 pm.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.60.Hv Refractometers and reflectometers

Relevance of intra- and inter-subband scattering on the absorption in heterostructures

C. Ndebeka-Bandou, F. Carosella, R. Ferreira, A. Wacker, and G. Bastard

Appl. Phys. Lett. 101, 191104 (2012); http://dx.doi.org/10.1063/1.4766192 (4 pages) | Cited 1 time

Online Publication Date: 6 November 2012

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We analyze the absorption lineshape for inter-subband transitions in disordered quasi two-dimensional heterostructures by an exact calculation. The intra-subband scatterings control the central peak, while the tails of the absorption line are dominated by the inter-subband scattering terms. Our numerical study quantitatively assesses the magnitude of the free carrier absorption. The accuracy of different models currently used for gain/absorption is discussed.
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78.40.-q Absorption and reflection spectra: visible and ultraviolet
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

High single-spatial-mode pulsed power from 980 nm emitting diode lasers

Martin Hempel, Jens W. Tomm, Thomas Elsaesser, and Mauro Bettiati

Appl. Phys. Lett. 101, 191105 (2012); http://dx.doi.org/10.1063/1.4766267 (5 pages)

Online Publication Date: 7 November 2012

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Single-spatial-mode pulsed powers as high as 13 W and 20 W in 150 and 50 ns pulses, respectively, are reported for 980 nm emitting lasers. In terms of energy, single-spatial-mode values of up to 2 μJ within 150 ns pulses are shown. In this high-power pulsed operation, the devices shield themselves from facet degradation, being the main degradation source in continuous wave (cw) operation. Our results pave the way towards additional applications while employing available standard devices, which have originally been designed as very reliable cw fiber pumps.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Ultrafast nonlinear optical responses of bismuth doped silicon-rich silica films

Kenji Imakita, Yuya Tsuchihashi, Ryo Naruiwa, Minoru Fujii, Hong-Tao Sun, Jianrong Qiu, and Shinji Hayashi

Appl. Phys. Lett. 101, 191106 (2012); http://dx.doi.org/10.1063/1.4766269 (4 pages)

Online Publication Date: 7 November 2012

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Nonlinear optical responses of bismuth (Bi) doped silicon-rich silicon dioxide (Si-rich SiO2) films were studied by a z-scan and an optical Kerr gate method under femtosecond excitation around 800 nm. It was found that the Bi-doping enhances the nonlinear optical response of Si-rich SiO2 films by several orders of magnitudes. The nonlinear refractive index was of the order of 10−11 cm2/W and the response time was shorter than our time resolution of 100 fs. The nonlinear refractive index was independent of the wavelength in the range from 750 to 835 nm, suggesting that virtual transitions are involved in the nonlinear optical processes.
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78.66.Nk Insulators
78.47.jh Coherent nonlinear optical spectroscopy
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Silicon-based three-dimensional photonic crystal nanocavity laser with InAs quantum-dot gain

Daoshe Cao, Aniwat Tandaechanurat, Shigeru Nakayama, Satomi Ishida, Satoshi Iwamoto, and Yasuhiko Arakawa

Appl. Phys. Lett. 101, 191107 (2012); http://dx.doi.org/10.1063/1.4766288 (4 pages)

Online Publication Date: 7 November 2012

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We report on the demonstration of lasing oscillation in a silicon-based three-dimensional photonic crystal nanocavity using InAs quantum dots as gain material by pulsed optical pumping at 11 K. An active layer embedding InAs quantum dots was inserted in the cavity using micromanipulation technique. The highest quality factor for silicon-based three-dimensional photonic crystal cavities (∼22 000) was achieved. We also evaluated the spontaneous emission coupling factor of the laser to be ∼0.78 by fitting the experimental light-in light-out curve with coupled rate equations. This result would pave the way to the realization of CMOS-compatible high-density three-dimensional photonic integrated circuits.
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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
42.70.Qs Photonic bandgap materials
42.82.-m Integrated optics
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Blue 6-ps short-pulse generation in gain-switched InGaN vertical-cavity surface-emitting lasers via impulsive optical pumping

Shaoqiang Chen, Makoto Okano, Baoping Zhang, Masahiro Yoshita, Hidefumi Akiyama, and Yoshihiko Kanemitsu

Appl. Phys. Lett. 101, 191108 (2012); http://dx.doi.org/10.1063/1.4766290 (3 pages) | Cited 1 time

Online Publication Date: 7 November 2012

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We report the demonstration of the picosecond-pulse lasing in blue region from an optically pumped gain-switched InGaN vertical-cavity-surface-emitting laser (VCSEL). Through 150-fs optical pulse excitations at room temperature, multimode pulse lasing with a main mode at 436.5 nm from the InGaN VCSEL was observed. The output pulse widths were measured to be as short as 9.8 ps for the total lasing spectra and 6.0 ps for the main mode. Since the obtained short pulses were still not limited by its photon lifetime of 0.7 ps or band-width of 0.8 nm, possible ways to generate even shorter pulses have been examined.
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42.55.Px Semiconductor lasers; laser diodes
42.60.-v Laser optical systems: design and operation
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

A bi-functional quantum cascade device for same-frequency lasing and detection

Benedikt Schwarz, Peter Reininger, Hermann Detz, Tobias Zederbauer, Aaron Maxwell Andrews, Stefan Kalchmair, Werner Schrenk, Oskar Baumgartner, Hans Kosina, and Gottfried Strasser

Appl. Phys. Lett. 101, 191109 (2012); http://dx.doi.org/10.1063/1.4767128 (4 pages)

Online Publication Date: 8 November 2012

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We demonstrate a bi-functional quantum cascade device that detects at the same wavelength as it coherently emits. Our fabricated device operates at room-temperature with a pulsed peak power emission of 45 mW and a detector responsivity of 3.6 mA/W. We show how to compensate the intrinsic wavelength mismatch between the laser and the detector, based on a bound-to-continuum design. An overlap between the laser and the detector spectra was observed from 6.4 μm to 6.8 μm. The electro-luminescence spectrum almost perfectly matches the detector spectrum, overlapping from 6.2 μm to 7.1 μm.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.60.Gz Photodetectors (including infrared and CCD detectors)

Efficient spectral broadening of supercontinuum in photonic crystal fiber with self-phase modulation induced by femtosecond laser pulse

Masayuki Suzuki, Motoyoshi Baba, Shin Yoneya, and Hiroto Kuroda

Appl. Phys. Lett. 101, 191110 (2012); http://dx.doi.org/10.1063/1.4767143 (3 pages)

Online Publication Date: 8 November 2012

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The authors experimentally demonstrated the generation of a supercontinuum (SC) in a photonic crystal fiber (PCF) using laser power of 0.8 W with 100 fs pulse duration at 1028 nm wavelength. The SC spectrum extended from 420 nm to 1650 nm using a 10 cm long PCF, for a wavelength difference of 275 nm between the pump laser and the zero dispersion wavelength (ZDW). This extension of the SC originates from the self-phase modulation induced broadening in the PCF of the femtosecond laser pulse. This study shows the effectiveness of this technique to extend the SC spectrum.
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42.81.Wg Other fiber-optical devices
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.Qs Photonic bandgap materials
42.81.Dp Propagation, scattering, and losses; solitons

Electrical and optical interconnection for mechanically stacked multi-junction solar cells mediated by metal nanoparticle arrays

Hidenori Mizuno, Kikuo Makita, and Koji Matsubara

Appl. Phys. Lett. 101, 191111 (2012); http://dx.doi.org/10.1063/1.4766339 (4 pages)

Online Publication Date: 8 November 2012

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An interconnection approach for mechanical stacking of solar cells is described. In this approach, block copolymer-templated fabrication of metal nanoparticle arrays and van der Waals bonding were integrated to design interfaces which permit both high interfacial conductivities and minimal transmission losses upon interconnections of solar cells. A series of electrical and optical characterizations verified that the approach potentially provides resistances of as low as 3.7 Ω-cm2 with transmission losses of less than 2%. The demonstrative two-junction solar cell exhibited promising open-circuit voltage and fill factor, suggesting the possibility of achieving high-efficiency multi-junction solar cells based on this unique strategy.
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88.40.jp Multijunction solar cells
73.40.Ns Metal-nonmetal contacts
81.16.Dn Self-assembly

Using quantum memory techniques for optical detection of ultrasound

D. L. McAuslan, L. R. Taylor, and J. J. Longdell

Appl. Phys. Lett. 101, 191112 (2012); http://dx.doi.org/10.1063/1.4766341 (4 pages) | Cited 1 time

Online Publication Date: 8 November 2012

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Quantum memories are inherently highly efficient and display low noise, making them particularly suitable for the optical detection of ultrasound. Here, we use an atomic-frequency-comb based quantum memory to demonstrate sensitive ultrasound detection, realising a 49 dB discrimination between the sidebands and the carrier. The method remains valid in the case of optically thin samples and thus represents a significant improvement over other ultrasound detection methods based on rare-earth-ion-doped crystals. Furthermore, we show that this non-destructive non-contact approach is also compatible with highly scattering samples and suggest its particular suitability for the real-time imaging of biological tissues.
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43.35.Yb Ultrasonic instrumentation and measurement techniques
87.63.D- Ultrasonography
87.63.L- Visual imaging

Optical logic gates using coherent feedback

Zhifan Zhou, Cunjin Liu, Yami Fang, Jun Zhou, Ryan T. Glasser, Liqing Chen, Jietai Jing, and Weiping Zhang

Appl. Phys. Lett. 101, 191113 (2012); http://dx.doi.org/10.1063/1.4767133 (4 pages)

Online Publication Date: 9 November 2012

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We experimentally demonstrate optical logic “or” and “nor” gates via coherent feedback. Based on a four-wave mixing process in hot rubidium vapor, two feedback beams are capable of fulfilling an optical “nor” gate for the feedback-suppressed state and an optical “or” gate for the feedback-boosted state simultaneously. The logic gates exhibit transition times faster than previously demonstrated in rubidium vapor. Coherent photon conversion between the two logic states, due to the atomic coherence, is observed in the coherent feedback process.
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42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Buried anti resonant reflecting optical waveguide based on porous silicon material for an integrated Mach Zehnder structure

M. Hiraoui, M. Guendouz, N. Lorrain, L. Haji, and M. Oueslati

Appl. Phys. Lett. 101, 191114 (2012); http://dx.doi.org/10.1063/1.4766729 (5 pages)

Online Publication Date: 9 November 2012

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A buried anti resonant reflecting optical waveguide for an integrated Mach Zehnder structure based on porous silicon material is achieved using a classical photolithography process. Three distinct porous silicon layers are then elaborated in a single step, by varying the porosity (thus the refractive index) and the thickness while respecting the anti-resonance conditions. Simulations and experimental results clearly show the antiresonant character of the buried waveguides. Significant variation of the reflectance and light propagation with different behavior depending on the polarization and the Mach Zehnder dimensions is obtained. Finally, we confirm the feasibility of this structure for sensing applications.
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42.79.Gn Optical waveguides and couplers
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays
07.60.Ly Interferometers

Rare earth doped Si-rich ZnO for multiband near-infrared light emitting devices

Emanuele Francesco Pecora, Thomas I. Murphy, and Luca Dal Negro

Appl. Phys. Lett. 101, 191115 (2012); http://dx.doi.org/10.1063/1.4766947 (5 pages) | Cited 4 times

Online Publication Date: 9 November 2012

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We demonstrate a light emitting material platform based on rare-earth doping of Si-rich ZnO thin films by magnetron sputtering, and we investigate the near-infrared emission properties under both optical and electrical injection. Er and Nd radiative transitions were simultaneously activated due to energy transfer via the ZnO direct bandgap and its luminescent defect centers. Moreover, by incorporating Si atoms, we demonstrate Si-mediated enhancement of photoluminescence in Er-doped ZnO and electroluminescence. These results pave the way to novel Si-compatible light emitters that leverage the optically transparent and electrically conductive ZnO matrix for multiband near-IR telecom and bio-compatible applications.
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85.60.Jb Light-emitting devices
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