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24 May 2004

Volume 84, Issue 21, pp. 4141-4340

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Appl. Phys. Lett. 84, 4316 (2004); http://dx.doi.org/10.1063/1.1756684 (3 pages)

Seok Pil Jang and Stephen U. S. Choi
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Visible quantum cutting through downconversion in Eu3+-doped KGd3F10 and KGd2F7 crystals

Nobuhiro Kodama and Yamato Watanabe

Appl. Phys. Lett. 84, 4141 (2004); http://dx.doi.org/10.1063/1.1713038 (3 pages) | Cited 39 times

Online Publication Date: 6 May 2004

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Visible quantum cutting (visible two-photon luminescence) through downconversion is observed for the Gd3+–Eu3+ couple in Eu3+-doped KGd3F10 (KG3F) and KGd2F7 (KG2F). The dependence of the efficiency of cross-relaxation required for visible quantum cutting on the Eu3+-doping concentration and crystal structure is discussed in terms of the probability of energy transfer as a function of the rare-earth interatomic distance. Eu3+-doped KG3F exhibits a higher efficiency in the cross-relaxation step than Eu3+-doped KG2F. The highest efficiency of the cross-relaxation step, 0.65, is obtained for the KG3F crystal doped with 2 at. % Eu3+. It is also suggested from dependence of the lifetime of 5D0 emission of Eu3+ in KG3F on Eu3+ concentration that interactions between rare-earth ions are strong at greater than 2 at. % Eu3+. © 2004 American Institute of Physics.
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78.40.Ha Other nonmetallic inorganics
61.72.S- Impurities in crystals
61.66.Fn Inorganic compounds
78.55.Hx Other solid inorganic materials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Lasing mode pattern of a quantum cascade photonic crystal surface-emitting microcavity laser

Kartik Srinivasan, Oskar Painter, Raffaele Colombelli, Claire Gmachl, Donald M. Tennant, A. Michael Sergent, Deborah L. Sivco, Alfred Y. Cho, Mariano Troccoli, and Federico Capasso

Appl. Phys. Lett. 84, 4164 (2004); http://dx.doi.org/10.1063/1.1755423 (3 pages) | Cited 8 times

Online Publication Date: 6 May 2004

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The identification of the lasing mode within a quantum cascade photonic crystal microcavity laser emitting at λ∼8 μm is presented. The symmetry of the lasing mode is determined by the position of nodal lines within micro-bolometer camera measurements of its polarized spatial distribution. Full three-dimensional finite-difference time-domain simulations are also performed, and the resulting vertically emitted radiation field pattern is seen to follow the experimental results closely. © 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.55.Tv Photonic crystal lasers and coherent effects
42.55.Sa Microcavity and microdisk lasers
85.30.De Semiconductor-device characterization, design, and modeling

Fluidic adaptive lens of transformable lens type

De-Ying Zhang, Nicole Justis, and Yu-Hwa Lo

Appl. Phys. Lett. 84, 4194 (2004); http://dx.doi.org/10.1063/1.1756679 (3 pages) | Cited 25 times

Online Publication Date: 6 May 2004

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Fluidic adaptive lenses with a transformable lens type were demonstrated. By adjusting the fluidic pressure, not only can the lens properties, such as the focal distance and numerical aperture, be tuned dynamically but also different lens types, such as planoconvex, planoconcave, biconvex, biconcave, positive meniscus, and negative meniscus lenses, can be formed. The shortest focal length for a 20 mm aperture adaptive lens is 14.3 mm when the device is transformed into a positive lens, and −6.3 mm when transformed into a negative lens. The maximum resolution of the fluidic lens is better than 40 line pairs/mm. © 2004 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors

All-optical polymeric interferometeric wavelength converter comprising an excited state intramolecular proton transfer dye

Jae-Wook Kang, Sehoon Kim, Soo Young Park, and Jang-Joo Kim

Appl. Phys. Lett. 84, 4221 (2004); http://dx.doi.org/10.1063/1.1755839 (3 pages) | Cited 1 time

Online Publication Date: 7 May 2004

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We designed and demonstrated an all-optical wavelength converter using a polymeric Mach–Zehnder interferometer (MZI) comprised of an excited state intramolecular proton transfer (ESIPT) dye, 2,2′-{oxybis[4-(4-methoxyphenyl)quinoline-6,2-diyl]}bis(5-methoxyphenol) (MQ). This MZI wavelength converter is composed of the MQ dye-doped polymeric waveguide and a thick light blocking metal film. A feature of this device is that one arm of the MZI can be irradiated by 355 nm pulses (signal beam), while the other arm was not, thus allowing a differential phase shift in the submicrosecond time scale. Because of the refractive index change of the ESIPT dye in one arm of interferometer upon irradiation with the signal beam, phase modulation of the continuous-wave probe light propagating in the irradiated arm of the MZI takes place, leading to the intensity modulation at the output defined by the signal beam, resulting in an all-optical wavelength converter, that is, the conversion of the signal modulation to output signal modulation of the probe light of the MZI. The characteristics of the wavelength converter are well described by a simple kinetic model. © 2004 American Institute of Physics.
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42.79.Nv Optical frequency converters
42.70.Jk Polymers and organics

Laser trapping and manipulation under focused evanescent wave illumination

Min Gu, Jean-Baptiste Haumonte, Yoan Micheau, James W. M. Chon, and Xiaosong Gan

Appl. Phys. Lett. 84, 4236 (2004); http://dx.doi.org/10.1063/1.1756200 (3 pages) | Cited 47 times

Online Publication Date: 7 May 2004

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Laser trapping is based on the radiation pressure on a small particle in the focal region of a high numerical-aperture objective. Currently, the focal spot of a trapping beam is elongated along the longitudinal direction and thus the axial size of the trapping volume is approximately three times larger than that in the transverse direction. We report on a laser trapping technique under focused evanescent wave illumination. Therefore laser trapping of micro/nano-objects can be achieved in the near-field region with an axial trapping size of approximately 60 nm, which is reduced by approximately one order of magnitude. Hence, this technique is of significant importance in nanometry including single molecule detection and manipulation. © 2004 American Institute of Physics.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
81.16.Ta Atom manipulation

Photoinduced birefringence in tellurite glasses

V. K. Tikhomirov, K. E. Asatryan, T. V. Galstian, R. Vallee, and A. B. Seddon

Appl. Phys. Lett. 84, 4263 (2004); http://dx.doi.org/10.1063/1.1758307 (2 pages) | Cited 3 times

Online Publication Date: 7 May 2004

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We report on photoinduced birefringence in TeO2-based glasses on exposure to linearly polarized subbandgap light. It is shown that the influence of glass-network modifiers, such as ZnO, Na2O, BaO, and of dopant Er2O3, on the photoinduced birefringence is not substantial indicating a dominating role of the TeO2 component. Photoinduced birefringence is optically reversible and its mechanism is proposed to be due to laser-induced alignment of intrinsic anisotropic defects of tellurite glass, such as distorted TeO4 bipyramids. © 2004 American Institute of Physics.
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78.20.Fm Birefringence
61.82.Rx Nanocrystalline materials
61.43.Fs Glasses

Frequency locking and wavelength tuning of nanosecond pulsed broad-area semiconductor lasers

Y. Liu, V. Kireev, and Y. Braiman

Appl. Phys. Lett. 84, 4265 (2004); http://dx.doi.org/10.1063/1.1758782 (3 pages) | Cited 1 time

Online Publication Date: 7 May 2004

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We discuss experimental results of frequency locking and wavelength tuning of a nanosecond pulsed broad-area semiconductor laser. Nanosecond optical pulses with peak power of 25 W and repetition rates of 4–240 kHz are generated from a broad-area laser. An external cavity with a diffractive grating is used to reduce the linewidth of the laser from over 5 nm to less than 0.1 nm. The wavelength of the pulsed laser is tunable over more than 10 nm. The dependence of the laser linewidth on pulse parameters has been investigated. © 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Fc Modulation, tuning, and mode locking

Tilt angle dependent three-dimensional-position detection of a trapped cylindrical particle in a focused laser beam

Holger Kress, Ernst H. K. Stelzer, and Alexander Rohrbach

Appl. Phys. Lett. 84, 4271 (2004); http://dx.doi.org/10.1063/1.1737056 (3 pages) | Cited 6 times

Online Publication Date: 7 May 2004

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We investigated theoretically the applicability of an optically trapped cylindrical particle as a local probe in photonic force microscopy. To do this we calculated the far-field scattering from a subwavelength-sized dielectric cylinder in a highly focused laser field. From this we obtained interferometric three-dimensional-position detection signals and compared these to signals calculated for a spherical particle. We have calculated the accuracy to which the position of an optically trapped cylinder can be determined, as a function of the cylinder’s orientational fluctuations. The position accuracy is better than a few nanometers for tilt angle fluctuations up to several degrees. Our study is relevant for trapping experiments, where the influence of angle fluctuations needs to be estimated. © 2004 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Mechanisms of optical angular momentum transfer to nematic liquid crystalline droplets

Tiffany A. Wood, Helen F. Gleeson, Mark R. Dickinson, and Amanda J. Wright

Appl. Phys. Lett. 84, 4292 (2004); http://dx.doi.org/10.1063/1.1753067 (3 pages) | Cited 14 times

Online Publication Date: 7 May 2004

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A detailed study is presented that evaluates the relative importance of wave plate behavior, scattering processes and absorption phenomena in transferring optical torque from circularly polarized light to optically trapped nematic droplets. A wide range of parameters is considered: droplet diameters between 1 and 15 μm, birefringence values from 0.15 to 0.26 and trapping beam powers from 50 mW to 400 mW. Wave plate behavior is verified through the dependence of torque on droplet diameter and material birefringence. The dependence of the magnitude of the torque on material birefringence confirms the additional importance of the scattering mechanism. Absorption processes are found to be negligible. © 2004 American Institute of Physics.
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61.30.Pq Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems
42.70.Df Liquid crystals
78.20.Fm Birefringence

1.5-μm-wavelength light guiding in waveguides in square-lattice-of-rod photonic crystal slab

Masatoshi Tokushima, Hirohito Yamada, and Yasuhiko Arakawa

Appl. Phys. Lett. 84, 4298 (2004); http://dx.doi.org/10.1063/1.1755838 (3 pages) | Cited 42 times

Online Publication Date: 7 May 2004

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We have experimentally demonstrated the guiding of light at a 1.5 μm wavelength in straight and 90°-bent line-defect waveguides in two-dimensional square-lattice-of-rods photonic crystal slabs. The light was guided by being confined in a row of the rods that were thinner than the surrounding ones. A new structural design to greatly facilitate their fabrication process without degrading the guiding property was used. The propagation loss measured for a 1.8-mm-straight waveguide was 4.8 dB/mm, which is small enough to allow us to proceed to integrated optical circuit application. © 2004 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.82.Et Waveguides, couplers, and arrays

Blue and near-ultraviolet light-emitting diodes on free-standing GaN substrates

X. A. Cao, S. F. LeBoeuf, M. P. D’Evelyn, S. D. Arthur, J. Kretchmer, C. H. Yan, and Z. H. Yang

Appl. Phys. Lett. 84, 4313 (2004); http://dx.doi.org/10.1063/1.1756683 (3 pages) | Cited 44 times

Online Publication Date: 7 May 2004

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Blue and near-ultraviolet (UV) InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission at 465 nm and 405 nm, respectively, were grown on GaN and sapphire substrates. The densities of surface and bulk defects in the homoepitaxially grown LEDs were substantially reduced, leading to a decrease in reverse currents by more than six orders of magnitude. At a typical operating current of 20 mA, the internal quantum efficiency of the UV LED on GaN was twice as high compared to the UV LED on sapphire, whereas the performance of the blue LEDs was found to be comparable. This suggests that the high-density dislocations are of greater influence on the light emission of the UV LEDs due to less In-related localization effects. At high injection currents, both the blue and UV LEDs on GaN exhibited much higher output power than the LEDs on sapphire as a result of improved heat dissipation and current spreading. © 2004 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices
85.30.De Semiconductor-device characterization, design, and modeling
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