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24 Sep 2001

Volume 79, Issue 13, pp. 1933-2115

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Transport and trapping of photocharges in liquid crystals placed between photoconductive polymer layers

Junho Mun, Choon Sup Yoon, Hyun-Wuk Kim, Su-An Choi, and Jong-Duk Kim

Appl. Phys. Lett. 79, 1933 (2001); http://dx.doi.org/10.1063/1.1400087 (3 pages) | Cited 11 times

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The transport and trapping of photocharges in liquid crystals placed between photoconductive polymer layers was investigated systematically. The transport of the photocharges is explained in terms of current paths that are formed along the bright sites of an interference pattern. Our study shows clearly that charge trapping occurs predominantly in the photoconductive poly(N-vinylcarbazole) layers and not in the insulating poly(vinyl alcohol) layers, contrary to a previous report. © 2001 American Institute of Physics.
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42.70.Df Liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
78.20.Jq Electro-optical effects
73.50.Pz Photoconduction and photovoltaic effects
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
73.61.Ph Polymers; organic compounds
42.79.Dj Gratings
42.70.Gi Light-sensitive materials
42.70.Jk Polymers and organics

Efficiency of GaN/InGaN light-emitting diodes with interdigitated mesa geometry

X. Guo, Y.-L. Li, and E. F. Schubert

Appl. Phys. Lett. 79, 1936 (2001); http://dx.doi.org/10.1063/1.1405145 (3 pages) | Cited 32 times

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GaN/InGaN light-emitting diodes (LEDs) with different mesa structures are studied. The optical emission power as well as current–voltage characteristics of different mesa patterns are measured. The results show that the optical emission of the device with interdigitated patterns is higher than devices with traditional square-shaped patterns. The leakage current is found to increase as the mesa sidewall perimeter increases. Based on the analysis, it is concluded that a surface leakage current flows across the mesa sidewall and the leakage current is directly proportional to the mesa perimeter. The implications of the results for large-area scalable LED structures are discussed. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors

Nonlinear optical properties of chalcogenide glasses: Observation of multiphoton absorption

K. S. Bindra, H. T. Bookey, A. K. Kar, B. S. Wherrett, X. Liu, and A. Jha

Appl. Phys. Lett. 79, 1939 (2001); http://dx.doi.org/10.1063/1.1402158 (3 pages) | Cited 24 times

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We report observation of four- and five-photon absorption in the chalcogenide glasses at the telecommunication wavelengths. The nonlinear refractive index is sufficiently large that the optical switching criterion is satisfied. © 2001 American Institute of Physics.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Infrared and visible emission from organic electroluminescent devices based on praseodymium complex

Ziruo Hong, Chunjun Liang, Ruigang Li, Faxin Zang, Di Fan, Wenlian Li, L. S. Hung, and S. T. Lee

Appl. Phys. Lett. 79, 1942 (2001); http://dx.doi.org/10.1063/1.1391239 (3 pages) | Cited 37 times

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Praseodymium(dibenzoylmethanato)3(bathophenanthroline) [Pr(DBM)3bath] was employed as an emitting and electron transport layer, and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1, 1′-biphenyl-4,4′-diamine (TPD) as a hole transport layer in organic electroluminescent (EL) devices. Bilayer device TPD/Pr(DBM)3bath and trilayer devices TPD/TPD:Pr(DBM)3bath/Pr(DBM)3bath with a different ratio of TPD to the Pr-complex were fabricated. Emission bands at 608 nm (1D2→3H6), 890 nm (1D2→3F2), 1015 nm (1D2→3F3), 1065 nm (1D2→3F4) and 1550 nm (1D2→1G4) originating from the internal f–f transitions of a Pr3+ ion were observed from EL devices using both bilayer and trilayer structures. Decreasing the ratio of TPD to the Pr-complex, the emission of the 1D2→3H6 transition was promoted and that from the exciplex suppressed, which was explained in terms of energy transfer from the ligand to the central ion. © 2001 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

Pumping picosecond optical parametric oscillators by a pulsed Nd:YAG laser mode locked using a nonlinear mirror

A. A. Mani, L. Dreesen, Ph. Hollander, C. Humbert, Y. Caudano, P. A. Thiry, and A. Peremans

Appl. Phys. Lett. 79, 1945 (2001); http://dx.doi.org/10.1063/1.1405433 (3 pages) | Cited 27 times

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We report on the performances of the mode locking of a flash-lamp-pumped Nd:YAG laser using a frequency-doubling nonlinear mirror combined with a two-photon absorber. Pulse lengths from 12 to 8 ps are generated. We show that the flat shape of the pulse-train envelope generated by the oscillator is adapted for the synchronous pumping of optical parametric oscillators and we demonstrate the efficient generation of an infrared beam tunable from 3800 to 1100 cm−1 with bandwidth of 2 cm−1 in one single conversion stage in LiNbO3 or AgGaS2. The “all-solid-state” laser system enables surface sum-frequency generation spectroscopy to be performed with high sensitivity and high resolution. © 2001 American Institute of Physics.
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42.65.Yj Optical parametric oscillators and amplifiers
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Rz Doped-insulator lasers and other solid state lasers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Bh Lenses, prisms and mirrors

Characteristics of InGaN laser diodes in the pure blue region

Shin-ichi Nagahama, Tomoya Yanamoto, Masahiko Sano, and Takashi Mukai

Appl. Phys. Lett. 79, 1948 (2001); http://dx.doi.org/10.1063/1.1399011 (3 pages) | Cited 22 times

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InGaN multi-quantum-well-structure laser diodes (LDs), whose emission wavelengths are in the pure blue region, were grown on epitaxially laterally overgrown GaN on a free-standing GaN substrate by the metaorganic chemical-vapor deposition method. The wavelength dependence of the InGaN LD characteristics was investigated. These results indicated that there is a strong relationship between the threshold current density and the emission wavelength of LDs. LDs with an emission wavelength of 460 nm were demonstrated. The threshold current density and voltage of these LDs were 3.3 kA/cm2 and 4.6 V, respectively. The estimated lifetime was approximately 3000 h under 50 °C continuous-wave operation at an output power of 5 mW. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Ultraviolet picosecond optical pulse generation from a mode-locked InGaN laser diode

S. Gee and J. E. Bowers

Appl. Phys. Lett. 79, 1951 (2001); http://dx.doi.org/10.1063/1.1405432 (2 pages) | Cited 11 times

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Ultraviolet optical pulses were generated by actively mode locking an external cavity InGaN laser at a wavelength of 409 nm with a temporal pulse duration of 30 ps. The average power was 2 mW and the time–bandwidth product was 1.2. Dynamic detuning plays a major role in pulse development. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Blue InGaN/GaN multiple-quantum-well optically pumped lasers with emission wavelength in the spectral range of 450–470 nm

G. P. Yablonskii, E. V. Lutsenko, V. N. Pavlovskii, I. P. Marko, A. L. Gurskii, V. Z. Zubialevich, A. V. Mudryi, O. Schön, H. Protzmann, M. Lünenbürger, B. Schineller, M. Heuken, H. Kalisch, and K. Heime

Appl. Phys. Lett. 79, 1953 (2001); http://dx.doi.org/10.1063/1.1400766 (3 pages) | Cited 9 times

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Optically pumped lasing in the wavelength range of 450–470 nm in InGaN/GaN multiple-quantum-well heterostructures grown by metalorganic vapor phase epitaxy was achieved and investigated. The energy and power per pulse of the laser were 80 nJ and 10 W correspondingly for one facet at room temperature. The far-field patterns of the laser emission consisted of three light spots near the angles of +30°, −15°, and −45°. The highest operating temperature was 450 K. The photoluminescence and photoluminescence excitation spectrum structures suggest that the quantum dots inside the quantum wells are involved in the recombination mechanism. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.55.Cr III-V semiconductors
78.67.De Quantum wells
FREE

Room-temperature continuous photopumped laser operation of coupled InP quantum dot and InGaP quantum well InP–InGaP–In(AlGa)P–InAlP heterostructures

G. Walter, N. Holonyak, J. H. Ryou, and R. D. Dupuis

Appl. Phys. Lett. 79, 1956 (2001); http://dx.doi.org/10.1063/1.1405153 (3 pages) | Cited 31 times

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Data are presented demonstrating continuous 300 K photopumped InP quantum dot (QD) laser operation (656–679 nm) realized by modifying and coupling, via tunneling, an auxiliary InGaP quantum well (QW) to the QDs of an InP–In(AlGa)P–InAlP heterostructure grown by metalorganic chemical vapor deposition. The In0.49Ga0.51P QW coupled to the InP QDs by a thin (≲20 Å) In0.5Al0.3Ga0.2P barrier overcomes the limitations of carrier collection, lateral transport, and thermalization in the QDs, thus yielding a different form of QD laser. © 2001 American Institute of Physics.
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42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Px Semiconductor lasers; laser diodes

Determination of optical modes in two-dimensional finite-size photonic crystals by photonic resonance scattering

S. Nojima

Appl. Phys. Lett. 79, 1959 (2001); http://dx.doi.org/10.1063/1.1406985 (3 pages) | Cited 15 times

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The analogy of the resonance scattering of an electron by an atom is used to investigate optical modes in two-dimensional finite-size photonic-crystal resonators. This analysis enables us to determine complex resonance energies from which we can estimate optical modes and photon lifetimes in the resonators. The threshold amplitude gain of the laser exploiting this photonic-crystal resonator is inversely proportional to the photon lifetime. This linear relation is found to remain the same irrespective of the dimensionality of the photonic crystal structure, the number of unit cells, and the size of unit cell, as long as the filling factor of the gain cell is fixed. This implies that the two-dimensional finite-size photonic-crystal resonators work well despite complicated feedback mechanisms and the absence of clear-cut cavity mirrors. © 2001 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics

Room-temperature-grown rare-earth-doped GaN luminescent thin films

D. S. Lee and A. J. Steckl

Appl. Phys. Lett. 79, 1962 (2001); http://dx.doi.org/10.1063/1.1406138 (3 pages) | Cited 11 times

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Visible emission has been observed from rare-earth (RE)-doped GaN electroluminescent devices (ELDs) as-grown near room temperature on Si (50–100 °C): red from GaN:Eu, green from GaN:Er, and blue from GaN:Tm. Green emission at 537/558 nm from GaN:Er ELD had a measured brightness of ∼230 cd/m2 at 46 V bias. X-ray diffraction indicates that the low-temperature-grown GaN:Er structure was oriented with the c axis perpendicular to the substrate. Scanning electron and atomic force microscopy indicate that the films had a rough surface and a compact structure consisting of small grains. Electroluminescence intensity of GaN:RE was significantly improved with postgrowth annealing. For GaN:Er films, after 800 °C annealing, the green emission brightness efficiency increased by ∼10×. © 2001 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors
68.37.Ps Atomic force microscopy (AFM)
61.72.Cc Kinetics of defect formation and annealing

12 W continuous-wave diode lasers at 1120 nm with InGaAs quantum wells

F. Bugge, G. Erbert, J. Fricke, S. Gramlich, R. Staske, H. Wenzel, U. Zeimer, and M. Weyers

Appl. Phys. Lett. 79, 1965 (2001); http://dx.doi.org/10.1063/1.1405812 (3 pages) | Cited 30 times

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Highly strained InGaAs quantum wells were grown by metalorganic vapor-phase epitaxy. By lowering the growth temperature to 530 °C, a maximum photoluminescence wavelength of 1192 nm was achieved. High-power diode lasers with a maximum lasing wavelength of 1175 nm were fabricated. A continuous-wave output power of 12 W at a heat-sink temperature of 25 °C was obtained at a lasing wavelength of 1120 nm. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.67.De Quantum wells
42.60.Pk Continuous operation
68.65.Fg Quantum wells
81.07.St Quantum wells
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors

Another regime of operation for a 18.2 nm recombination laser using a capillary-discharged carbon plasma

K. Lee and D. Kim

Appl. Phys. Lett. 79, 1968 (2001); http://dx.doi.org/10.1063/1.1406554 (3 pages) | Cited 1 time

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Another regime of operation for the significant amplification of C VI Hα radiation in a capillary-discharged carbon plasma is proposed. This suggested regime of operation features the existence of gain at the axis of a capillary, the large gain region (several hundred micrometers in diameter), and the hollow electron density profile for the better guiding of the radiation being amplified. All these features help to overcome the previous problems and favor the high amplification of the radiation. © 2001 American Institute of Physics.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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