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22 May 2006

Volume 88, Issue 21, Articles (21xxxx)

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Appl. Phys. Lett. 88, 211101 (2006); http://dx.doi.org/10.1063/1.2206087 (3 pages)

Kengo Nozaki and Toshihiko Baba
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Laser characteristics with ultimate-small modal volume in photonic crystal slab point-shift nanolasers

Kengo Nozaki and Toshihiko Baba

Appl. Phys. Lett. 88, 211101 (2006); http://dx.doi.org/10.1063/1.2206087 (3 pages) | Cited 35 times

Online Publication Date: 22 May 2006

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We recently reported the laser operation of a nanocavity consisting only of a shift in two of the lattice points in a GaInAsP photonic crystal slab. In this study, we investigated the laser characteristics in detail. For lithographic tuning, three different modes were observed, and good agreement between the experimental results and theoretical calculations performed using the finite-difference time-domain method was obtained. These results suggest that the fundamental mode has a modal volume of 0.02 μm3 ∼ 2.1(λ/2n)3, which is the smallest in any kind of laser. Such an ultrasmall modal volume will ensure efficient electron-photon coupling.
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42.55.Tv Photonic crystal lasers and coherent effects
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.55.Sa Microcavity and microdisk lasers
42.60.Fc Modulation, tuning, and mode locking

Fractional quasi-phase-matching by Fresnel birefringence

Riad Haidar

Appl. Phys. Lett. 88, 211102 (2006); http://dx.doi.org/10.1063/1.2207217 (3 pages) | Cited 4 times

Online Publication Date: 22 May 2006

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In order to reach the optical parametric oscillation in an isotropic semiconductor, it is of prime importance to enhance the nonlinear conversion efficiency per crystal length unity. In this letter, we describe the concept of fractional quasi-phase-matching which is theoretically shown to provide very high conversion yield, close to those of perfectly phase matched scenarios. The conceptual design in the case of second-harmonic generation is presented, along with predicted performances.
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42.65.Yj Optical parametric oscillators and amplifiers
42.70.Mp Nonlinear optical crystals
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Experimental demonstration of a long-period grating based on the sampling theorem

Min-Suk Kwon, Young-Bo Cho, and Sang-Yung Shin

Appl. Phys. Lett. 88, 211103 (2006); http://dx.doi.org/10.1063/1.2206093 (3 pages) | Cited 3 times

Online Publication Date: 22 May 2006

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We demonstrate experimentally the feasibility of a long-period grating whose index change pattern is in the form of sampling a raised-cosine function. We call such a grating a long-period grating based on the sampling theorem (LPGST). The LPGST is thermo-optically induced by an array of electrodes with individual widths. The array period is equal to the sampling period of 100 μm, and the period of the sampled function is 395 μm. A fabricated polymer long-period waveguide grating using the LPGST has a desired resonance band in its transmission spectrum, which is generated by the periodicity of the sampled function.
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42.79.Dj Gratings
42.70.Jk Polymers and organics
02.50.-r Probability theory, stochastic processes, and statistics

Definitive number of atoms on demand: Controlling the number of atoms in a few-atom magneto-optical trap

Seokchan Yoon, Youngwoon Choi, Sangbum Park, Jaisoon Kim, Jai-Hyung Lee, and Kyungwon An

Appl. Phys. Lett. 88, 211104 (2006); http://dx.doi.org/10.1063/1.2206118 (3 pages) | Cited 11 times

Online Publication Date: 22 May 2006

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A few math atoms were trapped in a micron-size magneto-optical trap with a high quadrupole magnetic-field gradient and the number of atoms was precisely controlled by suppressing stochastic loading and loss events via real-time feedback on the magnetic-field gradient. The measured occupation probability of a single atom was as high as 99%. Atoms up to five were also trapped with high occupation probabilities. The present technique could be used to make a deterministic atom source.
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37.10.De Atom cooling methods
37.10.Gh Atom traps and guides
32.60.+i Zeeman and Stark effects
37.20.+j Atomic and molecular beam sources and techniques
02.50.Ey Stochastic processes

Broadening and tuning of spontaneous Raman emission in porous silicon at 1.5 μm

L. Sirleto, M. A. Ferrara, I. Rendina, and B. Jalali

Appl. Phys. Lett. 88, 211105 (2006); http://dx.doi.org/10.1063/1.2206123 (3 pages) | Cited 7 times

Online Publication Date: 22 May 2006

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In the last three years, the possibility of light generation and/or amplification in silicon, based on Raman emission, has achieved significant results. However, limitations inherent to the physics of silicon have been pointed out, too. In this letter, an approach based on Raman scattering in porous silicon is investigated. Two significant advantages with respect to silicon are proved: the broadening of spontaneous Raman emission and the tuning of the Stokes shift. Finally, we discuss about the prospect of Raman amplifier in porous silicon.
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78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators

Artificial control of optical gain polarization by stacking quantum dot layers

T. Kita, N. Tamura, O. Wada, M. Sugawara, Y. Nakata, H. Ebe, and Y. Arakawa

Appl. Phys. Lett. 88, 211106 (2006); http://dx.doi.org/10.1063/1.2206126 (3 pages) | Cited 41 times

Online Publication Date: 22 May 2006

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Polarization insensitivity of InAs/GaAs quantum dot (QD) optical amplifier has been demonstrated by controlling the dot shape. The height of the QD has been controlled by stacking closely InAs islands to form a columnar QD. Room-temperature polarized amplified spontaneous emission from the columnar QDs has been investigated by using variable stripe-length method. With increasing the aspect ratio, transverse-magnetic-mode-dominant optical gain has been achieved. We obtained almost polarization insensitive optical gain for QDs with seven stacking layers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Modified electrochromism of tungsten oxide via platinum nanophases

Kyung-Won Park, Hee-Sang Shim, Tae-Yeon Seong, and Yung-Eun Sung

Appl. Phys. Lett. 88, 211107 (2006); http://dx.doi.org/10.1063/1.2206130 (3 pages) | Cited 5 times

Online Publication Date: 22 May 2006

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We report electrochromic properties of WO3 modified by platinum nanophases. The WO3 incorporated by Pt metallic nanophases (Pt–WO3) showed exactly reverse electrochromic phenomenon compared with that of both pure WO3 and WO3 intercepted and coated by metallic Pt thin-film layer. In addition, to investigate the origin of modified electrochromic properties, electrodes consisting of WO3 and/or Pt layers were designed and observed in optical properties during electrochemical reaction. The change of electrochromic properties in the Pt–WO3 is caused by modified structural and electrochemical properties of the WO3 by Pt metallic nanophases dispersed in the oxide matrix.
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78.20.Jq Electro-optical effects
82.45.Yz Nanostructured materials in electrochemistry
82.45.Fk Electrodes
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials

Spin-injection dynamics in a magnetic double quantum well studied by pump-probe absorption spectroscopy

K. Nishibayashi, I. Souma, A. Murayama, and Y. Oka

Appl. Phys. Lett. 88, 211108 (2006); http://dx.doi.org/10.1063/1.2206873 (3 pages) | Cited 5 times

Online Publication Date: 23 May 2006

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We study spin-injection dynamics in a magnetic double quantum well by pump-probe absorption spectroscopy. Time dependences of the absorption saturation intensity show a tunneling of spin-polarized carriers from a diluted magnetic well (MW) of Cd0.92Mn0.08Te into a nonmagnetic well (NMW) of CdTe, where the individual tunneling of the electron and heavy hole is elucidated with time constants of 150 ps and 1 ns. The circular polarization degree of the absorption saturation in NMW increases from 0 to 70 ps, which is caused by the injection of electron spin polarized in MW with a time constant of 54 ps.
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73.63.Hs Quantum wells
72.25.Dc Spin polarized transport in semiconductors
78.67.De Quantum wells
75.50.Pp Magnetic semiconductors
78.40.Fy Semiconductors
73.40.Gk Tunneling

Tuning of a phase shift to reduce the polarization-dependent loss in an interferometer-type variable optical attenuator built in lithium niobate

Akira Terashima, Naomi Tamagawa, and Hiroshi Mori

Appl. Phys. Lett. 88, 211109 (2006); http://dx.doi.org/10.1063/1.2192578 (3 pages)

Online Publication Date: 24 May 2006

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A method to adjust the phase mismatch between two paths of a Mach-Zehnder interferometer built in lithium niobate is presented. The importance of phase adjustment is that, in reducing polarization-dependent loss (PDL) in an optical attenuator based on lithium niobate z-propagation geometry, the phase shifts of two polarizations must be minimized or equalized. The method employs partially covering a waveguide arm with resin droplets using a microdispenser. In interferometer-type variable optical attenuators built in lithium niobate in x-cut/z-propagation geometry, the phase mismatch contribution to the PDL of less than 0.7 dB was shown to be achievable by the present phase tuning method.
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42.82.Gw Other integrated-optical elements and systems
07.60.Ly Interferometers
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers

Control of directional emission in quasistadium microcavity laser diodes with two electrodes

Muhan Choi, Tomoko Tanaka, Takehiro Fukushima, and Takahisa Harayama

Appl. Phys. Lett. 88, 211110 (2006); http://dx.doi.org/10.1063/1.2206155 (3 pages) | Cited 5 times

Online Publication Date: 24 May 2006

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We fabricated the AlGaAs/GaAs three quantum well quasistadium laser diodes with two electrodes and succeeded in controlling directional laser emission by applying different currents to each electrode. We showed the ratio of laser emission with two different directions is proportional to the ratio of currents injected into two electrodes. These devices are applicable for beam switching and splitting.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Sa Microcavity and microdisk lasers
42.60.By Design of specific laser systems

Purely gain-coupled distributed feedback laser via a bright optical lattice

S. M. Sadeghi, X. Li, W.-P. Huang, and W. Li

Appl. Phys. Lett. 88, 211111 (2006); http://dx.doi.org/10.1063/1.2206994 (3 pages) | Cited 4 times

Online Publication Date: 24 May 2006

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We utilize degeneracy of Bragg resonance and the intersubband transitions in a quantum well bright optical lattice to propose a coherently induced purely gain-coupled distributed feedback laser. The optical lattice is generated via formation of periodic regions of resonant intersubband gain without inversion in the absence of any refractive index perturbation using a control laser field. We show that longitudinal mode intensity profile and standing wave effects of such an intrinsically single-mode intersubband laser can be coherently controlled. These features allow immunity against spatial hole burning and lasing when modal loss is higher than modal gain.
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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.)

Tunneling modes of photonic heterostructures consisting of single-negative materials

Guosheng Guan, Haitao Jiang, Hongqiang Li, Yewen Zhang, Hong Chen, and Shiyao Zhu

Appl. Phys. Lett. 88, 211112 (2006); http://dx.doi.org/10.1063/1.2207218 (3 pages) | Cited 38 times

Online Publication Date: 25 May 2006

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We show theoretically that heterostructures consisting of single-negative materials can possess tunneling modes inside forbidden gaps, owing to the resonant coupling of the evanescent-wave-based interface modes. The tunneling modes appear when the heterostructure becomes nihility. They are independent of incident angles and polarizations and have zero phase delay, which can be utilized to design zero-phase-shift omnidirectional filters.
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42.70.-a Optical materials
42.79.Ci Filters, zone plates, and polarizers

Above-room-temperature 3–12 μm Si emitting arrays

V. K. Malyutenko, S. S. Bolgov, and O. Yu. Malyutenko

Appl. Phys. Lett. 88, 211113 (2006); http://dx.doi.org/10.1063/1.2207833 (3 pages) | Cited 8 times

Online Publication Date: 26 May 2006

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The design and parameters are presented for 16-element infrared (IR, 3–12 μm) emitting arrays based on Si p+in+ structures and above-room-temperature (300 K<T<480 K) operated by the contact double injection. The device principle is in modulation of thermal emission beyond the fundamental absorption edge by controlling free charge carrier concentration in a base. Nearly 1.0 mW output power and 420 K apparent temperature of IR radiation could be achieved with ∼ 0.8% external power efficiency. This represents the longer wavelengths, higher operating temperatures, and output power from Si spontaneous emitters ever reported.
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85.60.Jb Light-emitting devices
42.72.Ai Infrared sources

Aluminum nanowire polarizing grids: Fabrication and analysis

Vincent Pelletier, Koji Asakawa, Mingshaw Wu, Douglas H. Adamson, Richard A. Register, and Paul M. Chaikin

Appl. Phys. Lett. 88, 211114 (2006); http://dx.doi.org/10.1063/1.2206100 (3 pages) | Cited 19 times

Online Publication Date: 26 May 2006

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We have produced metal wire grids with 33 nm periodicity, using a thin film of a self-assembling diblock copolymer as a template. These grids, supported on fused quartz wafers, function as transmission polarizers for visible and near-ultraviolet lights. Their polarization efficiency is measured to be near 50% in the visible. Quantitative comparison with a new theoretical analysis of such wire grids indicates that they should perform well into the far UV. This analysis also explains the reversal in polarization direction at shorter wavelengths which we observe in our specimens.
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42.79.Ci Filters, zone plates, and polarizers
42.86.+b Optical workshop techniques
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