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15 May 2000

Volume 76, Issue 20, pp. 2815-2963

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Optical measurement of interaction potentials between a single microparticle and an evanescent field

Ken-ichiro Wada, Keiji Sasaki, and Hiroshi Masuhara

Appl. Phys. Lett. 76, 2815 (2000); http://dx.doi.org/10.1063/1.126482 (3 pages) | Cited 7 times

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Radiation pressure exerted on a single microparticle within an evanescent field has been analyzed by a three-dimensional potential measurement system. Temporal fluctuation of the particle position due to the thermal Brownian motion was sequentially measured, and the potential energy was estimated by a thermodynamical analysis. A potential profile corresponding to the evanescent-field-induced radiation pressure could be obtained as an energy difference between two potentials measured with and without illumination of the evanescent field. The exponential dependence on the longitudinal position was clearly observed. The lateral radiation force on a 4.5 μm polystyrene latex particle in water was determined to be 90 fN at the laser intensity of 1.0 kW cm−2. © 2000 American Institute of Physics.
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37.10.Vz Mechanical effects of light on atoms, molecules, and ions
61.82.Pv Polymers, organic compounds
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

High reflectivity and broad bandwidth AlN/GaN distributed Bragg reflectors grown by molecular-beam epitaxy

H. M. Ng, T. D. Moustakas, and S. N. G. Chu

Appl. Phys. Lett. 76, 2818 (2000); http://dx.doi.org/10.1063/1.126483 (3 pages) | Cited 75 times

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A number of distributed Bragg reflectors (DBRs) based on AlN/GaN quarterwave layers have been grown on (0001) sapphire by electron cyclotron resonance plasma-assisted molecular-beam epitaxy. The number of periods for the DBRs ranges from 20.5 to 25.5 and the thickness of the quarterwave layers were chosen such that the peak reflectance occurs from the near ultraviolet to green wavelength regions. Peak reflectance values between 97% and 99% were obtained for these DBRs. The best sample has a peak reflectance up to 99% centered at 467 nm with a bandwidth of 45 nm. The experimental reflectance data for this sample were compared with simulations using the transmission matrix method and show excellent agreement with respect to peak reflectance, bandwidth of high reflectance, and the locations of the sidelobes. The thickness of the quarterwave layers and uniform periodicity of the bilayers were confirmed by cross-section transmission electron microscopy. A network of cracks was observed in some of the samples and this is attributed to tensile stress in the AlN layers. We have grown asymmetric DBRs with thicker AlN layers and thinner GaN layers to reduce the tensile strength in the AlN layers. Such an approach resulted in samples that have significantly less cracks or even crack-free. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
62.20.M- Structural failure of materials
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

An optically controllable terahertz filter

I. H. Libon, S. Baumgärtner, M. Hempel, N. E. Hecker, J. Feldmann, M. Koch, and P. Dawson

Appl. Phys. Lett. 76, 2821 (2000); http://dx.doi.org/10.1063/1.126484 (3 pages) | Cited 37 times

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Using a mixed type-I/type-II GaAs/AlAs multiple-quantum-well sample, we have demonstrated an optically controllable and tunable terahertz (THz) filter. Long-lived electron–hole pairs in the quantum wells allow for efficient THz attenuation over a large THz spot size (2 mm) for extremely low optical cw power. This sample can also be used as an optically tunable THz phase shifter. The optically induced change of the GaAs quantum wells from a dielectric to a conducting material leads to the observed attenuation and the shifting of the THz wave forms. © 2000 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
84.30.Vn Filters
84.40.Dc Microwave circuits

GaNAs avalanche photodiode operating at 0.94 μm

G. S. Kinsey, D. W. Gotthold, A. L. Holmes, B. G. Streetman, and J. C. Campbell

Appl. Phys. Lett. 76, 2824 (2000); http://dx.doi.org/10.1063/1.126485 (2 pages) | Cited 7 times

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A p-i-n avalanche photodiode (APD) using GaNAs grown on GaAs has been demonstrated. Characterization of the excess noise in the material was used to determine that the ratio of ionization coefficients (k = β/α) is k = 0.4. The quantum efficiency was above 25% at 0.94 μm for 0.75% nitrogen incorporation. The APDs exhibited low dark currents (<60 nA/mm2 at 90% of breakdown) and a gain-bandwidth product of 42 GHz. GaNAs therefore shows promise for extending the operation of GaAs-based APDs to longer wavelengths. © 2000 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
81.05.Ea III-V semiconductors

Frequency-selective incoherent detection of terahertz radiation by high-Tc Josephson junctions

Y. Y. Divin, U. Poppe, O. Y. Volkov, and V. V. Pavlovskii

Appl. Phys. Lett. 76, 2826 (2000); http://dx.doi.org/10.1063/1.126486 (3 pages) | Cited 14 times

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The detector response of YBa2Cu3O7−x Josephson grain-boundary junctions to monochromatic radiation with the frequency f in the range from 60 GHz to 4 THz has been studied. Frequency-selective odd-symmetric resonances in the responses ΔI(V) of these junctions to radiation with different frequencies f have been observed near the voltages V = hf/2e in almost a decade of spectral range for any operating temperature in the range from 30 to 85 K. The spectral range of the selective detection has scaled with the IcRn product of the Josephson junction, reaching the range of 0.16–3.1 THz for a IcRn product of 1.5 mV. A resolving power δf/f of around 10−3 has been demonstrated in the selective detection by Josephson junctions. The high-frequency falldown of the amplitude of the selective response has been found to be proportional to exp[−P/P0], where P = (hf/2e)2/Rn is the power dissipated in the junction at the resonance and P0 is a characteristic power level. The values of P0 for our junctions were around 20 μW at 34 K and 2 μW at 78 K. © 2000 American Institute of Physics.
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85.25.Cp Josephson devices
74.72.-h Cuprate superconductors
74.81.-g Inhomogeneous superconductors and superconducting systems, including electronic inhomogeneities
74.50.+r Tunneling phenomena; Josephson effects

Two-color generation in a rare-earth-doped quasiphase-matched structure

A. V. Kir’yanov, I. V. Mel’nikov, and K. Wagner

Appl. Phys. Lett. 76, 2829 (2000); http://dx.doi.org/10.1063/1.126487 (3 pages) | Cited 1 time

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A numerical study of two-color operation of quasiphase-matched structure in the lasing regime is presented for the case when a 980 nm pump produces the output both at 1550 and 775 nm. Successful operation of the two-color device relies on the use of a novel gain medium which consists of diode-pumped high-density rare-earth ions and on the utilization of a saturable amplification and absorption in the pumped and unpumped section of the device, correspondingly. © 2000 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.55.Rz Doped-insulator lasers and other solid state lasers
42.55.Ah General laser theory
42.60.By Design of specific laser systems
71.55.-i Impurity and defect levels

The origin of optical gain in cubic InGaN grown by molecular beam epitaxy

J.-Chr. Holst, A. Hoffmann, D. Rudloff, F. Bertram, T. Riemann, J. Christen, T. Frey, D. J. As, D. Schikora, and K. Lischka

Appl. Phys. Lett. 76, 2832 (2000); http://dx.doi.org/10.1063/1.126488 (3 pages) | Cited 25 times

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The optical properties of cubic InGaN samples with varying In content are investigated to provide insight into the processes responsible for optical amplification. The samples were grown by molecular beam epitaxy on GaAs substrates. The structural and optical properties were studied by means of time-resolved and time-integrated photoluminescence spectroscopy and cathodoluminescence microscopy, as well as gain measurements at various temperatures. From these measurements, localized states are proposed to be responsible as recombination mechanism. The cathodoluminescence measurements evidence a direct correlation of the degree of In fluctuation and the efficiency of optical amplification of the samples. © 2000 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
68.55.-a Thin film structure and morphology
78.47.-p Spectroscopy of solid state dynamics
71.55.Jv Disordered structures; amorphous and glassy solids
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Performance and spectral response of Pb1−xSnxTe(In) far-infrared photodetectors

D. R. Khokhlov, I. I. Ivanchik, S. N. Raines, D. M. Watson, and J. L. Pipher

Appl. Phys. Lett. 76, 2835 (2000); http://dx.doi.org/10.1063/1.126489 (3 pages) | Cited 16 times

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We have compared directly the performance of a Pb1−xSnxTe(In) photodetector with that of two other state-of-the-art far-infrared detectors: a Si(Sb) blocked impurity band (BIB) detector and a Ge(Ga) photoconductor in an integrating cavity. The Pb1−xSnxTe(In) photodetector has current responsivity SI several orders of magnitude higher than the Si(Sb) BIB at wavelength λ=14.5 μm. Persistent photoresponse with SI ∼ 103 A/W at 40 mV bias and 1 s integration time at the wavelengths λ=90 and 116 μm has also been observed in the Pb1−xSnxTe(In) photodetector. This is larger by a factor of ∼100 than the responsivity of the Ge(Ga) photoconductor in the same conditions. © 2000 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
73.50.Pz Photoconduction and photovoltaic effects
71.55.Ht Other nonmetals

Deep levels in high-energy proton-irradiated tin-doped n-type Czochralski silicon

E. Simoen, C. Claeys, V. B. Neimash, A. Kraitchinskii, N. Krasko, O. Puzenko, A. Blondeel, and P. Clauws

Appl. Phys. Lett. 76, 2838 (2000); http://dx.doi.org/10.1063/1.126490 (3 pages) | Cited 5 times

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A deep level transient spectroscopy study of defects created by 61 MeV proton irradiation of tin-doped n-type Czochralski silicon is reported. A comparison is made with the deep levels observed in irradiated p–n junction diodes fabricated in n-type float-zone silicon, without tin doping. The main conclusions are that in Sn-doped material, at least two additional deep radiation centers are introduced at 0.29±0.01 and 0.61±0.02 eV below the conduction band. From annealing experiments, it is concluded that these electron traps dissociate below 120 °C, which is lower than observed before for Sn–V related levels. It is demonstrated that the introduction rates of the well-known radiation defects are significantly smaller in Sn-doped material. © 2000 American Institute of Physics.
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71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Reflection-type 2×2 optical waveguide switch using the Goos–Hänchen shift effect

Tomomi Sakata, Hiroyoshi Togo, and Fusao Shimokawa

Appl. Phys. Lett. 76, 2841 (2000); http://dx.doi.org/10.1063/1.126491 (3 pages) | Cited 19 times

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We have designed a structure for a 2×2 silica-based optical waveguide switch that is based on a thermocapillarity effect. This switch can use the reflection walls on both sides of the slit, because the Goos–Hänchen shift effect was taken into account when the structure of the waveguides and the slit was designed. This switch can provide a cross/bar function through a single element, and the measured reflection losses in the reflection walls on both sides of the slit were consistent. The loss was comparable to the insertion loss of a Mach–Zender-interferometer-type thermo-optic switch. © 2000 American Institute of Physics.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.65.Wi Nonlinear waveguides
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