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2 May 2011

Volume 98, Issue 18, Articles (18xxxx)

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Appl. Phys. Lett. 98, 183101 (2011); http://dx.doi.org/10.1063/1.3584006 (3 pages)

Tuba Oznuluer, Ercag Pince, Emre O. Polat, Osman Balci, Omer Salihoglu, and Coskun Kocabas
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Ultimate photovoltage in perovskite oxide heterostructures with critical film thickness

Cong Wang, Kui-juan Jin, Rui-qiang Zhao, Hui-bin Lu, Hai-zhong Guo, Chen Ge, Meng He, Can Wang, and Guo-zhen Yang

Appl. Phys. Lett. 98, 181101 (2011); http://dx.doi.org/10.1063/1.3586250 (3 pages) | Cited 2 times

Online Publication Date: 2 May 2011

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One order larger photovoltage is obtained with critical thicknesses of La0.9Sr0.1MnO3 films in both kinds of heterostructures of La0.9Sr0.1MnO3/SrTiO3 (0.8 wt % Nb-doped) and La0.9Sr0.1MnO3/Si fabricated at various oxygen pressures. Our self-consistent calculation reveals that the critical thickness of the La0.9Sr0.1MnO3 film with the ultimate value of photovoltage is just the thickness of the depletion layer of La0.9Sr0.1MnO3 in both heterojunctions, respectively.
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73.50.Pz Photoconduction and photovoltaic effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors

Room temperature quantum cascade lasers with 27% wall plug efficiency

Y. Bai, N. Bandyopadhyay, S. Tsao, S. Slivken, and M. Razeghi

Appl. Phys. Lett. 98, 181102 (2011); http://dx.doi.org/10.1063/1.3586773 (3 pages) | Cited 32 times

Online Publication Date: 2 May 2011

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Using the recently proposed shallow-well design, we demonstrate InP based quantum cascade lasers (QCLs) emitting around 4.9 μm with 27% and 21% wall plug efficiencies in room temperature (298 K) pulsed and continuous wave (cw) operations, respectively. The laser core consists of 40 QCL-stages. The highest cw efficiency is obtained from a buried-ridge device with a ridge width of 8 μm and a cavity length of 5 mm. The front and back facets are antireflection and high-reflection coated, respectively. The maximum single facet cw power at room temperature amounts to 5.1 W.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.15.Eq Optical system design
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Wc Optical coatings

Self-frequency-doubling of ultrafast laser inscribed neodymium doped yttrium aluminum borate waveguides

Ningning Dong, J. Martínez de Mendivil, E. Cantelar, G. Lifante, J. Vázquez de Aldana, G. A. Torchia, Feng Chen, and Daniel Jaque

Appl. Phys. Lett. 98, 181103 (2011); http://dx.doi.org/10.1063/1.3584852 (3 pages) | Cited 5 times

Online Publication Date: 3 May 2011

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Buried channel optical waveguides, supporting orthogonal polarizations, have been fabricated in a neodymium doped yttrium aluminum borate nonlinear laser crystal by ultrafast laser inscription following the so-called “double line” approach. Confocal fluorescence and second harmonic imaging experiments have revealed that the original fluorescence and nonlinear properties have been not deteriorated by the waveguide inscription procedure. Preliminary laser experiments have shown the ability of the fabricated structures for green laser light generation under 808 nm optical pumping by self-frequency-doubling of the 1.06 μm laser line of neodymium ions.
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42.79.Gn Optical waveguides and couplers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.62.-b Laser applications

Green GaInN photonic-crystal light-emitting diodes with small surface recombination effect

Hitoshi Kitagawa, Masayuki Fujita, Toshihide Suto, Takashi Asano, and Susumu Noda

Appl. Phys. Lett. 98, 181104 (2011); http://dx.doi.org/10.1063/1.3576927 (3 pages) | Cited 5 times

Online Publication Date: 3 May 2011

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We have fabricated green GaInN light-emitting diodes (LEDs) containing two-dimensional photonic crystals (PCs). The PC structure is comprised of air holes that penetrate through the active layer. The observed emission intensity at room temperature was enhanced by a factor of ∼ 3 when a PC was introduced, which is close to the theoretical enhancement calculated without taking into account surface recombination at the air-hole edges. The carrier lifetime changes little when a PC is incorporated due to the low surface recombination. In contrast, the carrier lifetime in blue-emitting LEDs decreased by a factor of 4 when a PC was introduced. The surface-recombination velocity in green-emitting devices is estimated to be 3×102 cm/s, an order of magnitude smaller than in blue-emitting devices. This is due to the strong carrier localization effect in green-emitting GaInN.
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85.60.Jb Light-emitting devices
85.30.Kk Junction diodes

Lead silicate glass microsphere resonators with absorption-limited Q

Pengfei Wang, Ganapathy Senthil Murugan, Timothy Lee, Xian Feng, Yuliya Semenova, Qiang Wu, Wei Loh, Gilberto Brambilla, James S. Wilkinson, and Gerald Farrell

Appl. Phys. Lett. 98, 181105 (2011); http://dx.doi.org/10.1063/1.3586771 (3 pages) | Cited 2 times

Online Publication Date: 3 May 2011

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We report the fabrication and characterization of a lead-silicate glass microsphere resonator. We show that at the wavelengths near 1555 nm high Q modes can be efficiently excited from a 109 μm diameter lead-silicate glass microsphere via evanescent coupling using a tapered silica fiber with a waist diameter of 2 μm. Resonances with Q-factors as high as 0.9×107 were observed. This is very close to the theoretical material-limited Q-factor and is the highest Q-factor reported so far from a nonlinear glass microsphere.
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42.65.-k Nonlinear optics
42.81.Qb Fiber waveguides, couplers, and arrays
42.70.Ce Glasses, quartz
42.86.+b Optical workshop techniques

2.4 W room temperature continuous wave operation of distributed feedback quantum cascade lasers

Q. Y. Lu, Y. Bai, N. Bandyopadhyay, S. Slivken, and M. Razeghi

Appl. Phys. Lett. 98, 181106 (2011); http://dx.doi.org/10.1063/1.3588412 (3 pages) | Cited 19 times

Online Publication Date: 4 May 2011

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We demonstrate high power continuous-wave room-temperature operation surface-grating distributed feedback quantum cascade lasers at 4.8 μm. High power single mode operation benefits from a combination of high-reflection and antireflection coatings. Maximum single-facet continuous-wave output power of 2.4 W and peak wall plug efficiency of 10% from one facet is obtained at 298 K. Single mode operation with a side mode suppression ratio of 30 dB and single-lobed far field without beam steering is observed.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Terahertz emission from InAs/GaAs quantum dot based photoconductive devices

N. S. Daghestani, M. A. Cataluna, G. Berry, G. Ross, and M. J. Rose

Appl. Phys. Lett. 98, 181107 (2011); http://dx.doi.org/10.1063/1.3586774 (3 pages)

Online Publication Date: 4 May 2011

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We report terahertz (THz) generation from InAs/GaAs quantum-dot based photoconductive antennae with femtosecond optical excitation at 800 nm, with an estimated infrared-to-THz conversion efficiency of ∼ 0.9×10−5. The quantum dots act as recombination centers for carriers generated in the GaAs layers within the structure. Photoreflective pump-probe measurements reveal a decrease in the carrier lifetime when a lateral voltage is applied. These antennae displayed resilience to Joule heating when operated at a field strength of 46 MV/m. The breakdown field of the devices was 48 MV/m, which is comparable to the breakdown field of bulk GaAs.
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85.60.Bt Optoelectronic device characterization, design, and modeling
84.40.Ba Antennas: theory, components and accessories
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Anisotropic structural and optical properties of a-plane (11math0) AlInN nearly-lattice-matched to GaN

Masihhur R. Laskar, Tapas Ganguli, A. A. Rahman, Ashish Arora, Nirupam Hatui, M. R. Gokhale, Sandip Ghosh, and Arnab Bhattacharya

Appl. Phys. Lett. 98, 181108 (2011); http://dx.doi.org/10.1063/1.3583457 (3 pages) | Cited 3 times

Online Publication Date: 5 May 2011

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We report epitaxial growth of a-plane (11math0) AlInN layers nearly-lattice-matched to GaN. Unlike for c-plane oriented epilayers, a-plane Al1−xInxN cannot be simultaneously lattice-matched to GaN in both in-plane directions. We study the influence of temperature on indium incorporation and obtain nearly-lattice-matched Al0.81In0.19N at a growth temperature of 760 °C. We outline a procedure to check in-plane lattice mismatch using high-resolution x-ray diffraction, and evaluate the strain and critical thickness. Polarization-resolved optical transmission measurements of the Al0.81In0.19N epilayer reveal a difference in band gap of ∼ 140 meV between (electric field) E∥c [0001]-axis and E⊥c conditions with room-temperature photoluminescence peaked at 3.38eV strongly polarized with E∥c, in good agreement with strain-dependent band-structure calculations.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.ag Semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors

Far field subwavelength focusing using optical eigenmodes

Jörg Baumgartl, Sebastian Kosmeier, Michael Mazilu, Edward T. F. Rogers, Nikolay I. Zheludev, and Kishan Dholakia

Appl. Phys. Lett. 98, 181109 (2011); http://dx.doi.org/10.1063/1.3587636 (3 pages) | Cited 6 times

Online Publication Date: 6 May 2011

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We report the focusing of light to generate a subdiffractive, subwavelength focal spot of full width half maximum 222 nm at an operating wavelength of 633 nm using an optical eigenmode approach. Crucially, the spot is created in the focal plane of a microscope objective thus yielding a practical working distance for applications. The optical eigenmode approach is implemented using an optimal superposition of Bessel beams on a spatial light modulator. The effects of partial coherence are also discussed. This far field method is a key advance toward the generation of subdiffractive optical features for imaging and lithographic purposes.
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42.79.-e Optical elements, devices, and systems
02.10.Ud Linear algebra

Fast self-heating in GaN-based laser diodes

W. G. Scheibenzuber and U. T. Schwarz

Appl. Phys. Lett. 98, 181110 (2011); http://dx.doi.org/10.1063/1.3587810 (3 pages) | Cited 3 times

Online Publication Date: 6 May 2011

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We study the time evolution of the internal temperature of GaN-based laser diodes in pulsed operation using time resolved spectroscopy. Time dependent emission spectra are compared to continuous-wave measurements at different temperatures to relate changes in the longitudinal mode spectrum to the internal temperature. From the different shift in emission center and longitudinal modes, two subsystems are identified which heat up on different time scales: the charge carrier plasma and the crystal lattice. While the lattice takes several microseconds to reach thermal equilibrium, the plasma heats up within 20 ns after the onset of the electrical pulse. This behavior is attributed to the small heat capacity of the charge carrier plasma compared to the crystal lattice.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Strain compensation in AlInN/GaN multilayers on GaN substrates: Application to the realization of defect-free Bragg reflectors

Gatien Cosendey, Jean-François Carlin, Nils A. K. Kaufmann, Raphaël Butté, and Nicolas Grandjean

Appl. Phys. Lett. 98, 181111 (2011); http://dx.doi.org/10.1063/1.3586767 (3 pages) | Cited 11 times

Online Publication Date: 6 May 2011

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We report on the growth conditions of AlInN layers grown on free-standing GaN substrates. We found that an average indium content of ∼ 20% is needed to obtain defect-free AlInN/GaN multilayers. This is larger than the commonly accepted value of 18% for lattice-matched condition. A model where tensile strain at the GaN/AlInN interface is induced by indium surface segregation occurring in AlInN layers is proposed to explain this discrepancy. A high In/Al flux ratio is shown to reduce this effect and allowed obtaining a defect-free AlInN/GaN Bragg reflector with a peak reflectivity of 99.6% suitable for vertical cavity light emitting devices.
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68.35.Gy Mechanical properties; surface strains
68.65.Ac Multilayers
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
68.35.Dv Composition, segregation; defects and impurities
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
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