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Organic light-emitting diodes using a gallium complex

Yuji Hamada, Hiroshi Kanno, Takeshi Sano, Hiroyuki Fujii, Yoshitaka Nishio, Hisakazu Takahashi, Tatsuro Usuki, and Kenichi Shibata

Appl. Phys. Lett. 72, 1939 (1998); http://dx.doi.org/10.1063/1.121448 (3 pages) | Cited 24 times

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A gallium complex (GaMq₂Cl) consisting of two 2-methyl-8-hydroxyquinolines (Mq) and a chlorine was synthesized and used for the fabrication of organic light-emitting diodes (OLEDs). The photoluminescent peak of GaMq₂Cl at 492 nm was as strong in intensity as that of tris(8-hydroxyquinolinato)aluminum (Alq₃). The OLED using GaMq₂Cl as an emitting material showed blue-green luminance of 10 490 cd/m². When it was used as an electron transport material in a rubrene doped cell, an OLED with a high luminance of 27 700 cd/m² was obtained. We found that GaMq₂Cl also was useful as a host material. © 1998 American Institute of Physics.

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85.60.Jb	Light-emitting devices
78.55.Kz	Solid organic materials
78.66.Qn	Polymers; organic compounds

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Photorefractive Bragg diffraction in high- and low-molar-mass liquid crystal mixtures

Hiroshi Ono, Isao Saito, and Nobuhiro Kawatsuki

Appl. Phys. Lett. 72, 1942 (1998); http://dx.doi.org/10.1063/1.121230 (3 pages) | Cited 29 times

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Orientational photorefractive Bragg diffraction is observed in high- and low-molar-mass liquid crystal mixtures doped with fullerene (C₆₀). These novel materials are in a nematic phase without phase separating. In the functionalized materials, we observe a high two-beam coupling gain coefficient (Γ = 75 cm⁻¹) with a low applied field of 4 V/μm, low total losses (32 cm⁻¹ including scattering, reflection, and absorption), a high diffraction efficiency (9%), and response time of 200 ms. © 1998 American Institute of Physics.

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61.30.-v	Liquid crystals
78.20.-e	Optical properties of bulk materials and thin films
78.70.Ck	X-ray scattering

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Electro-optic measurement of THz field pulses with a chirped optical beam

Zhiping Jiang and X.-C. Zhang

Appl. Phys. Lett. 72, 1945 (1998); http://dx.doi.org/10.1063/1.121231 (3 pages) | Cited 58 times

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Using a linearly chirped optical probe pulse in free-space electro-optic measurements, a temporal wave form of a co-propagating THz field is linearly encoded onto the frequency spectrum of the optical probe pulse, and then decoded by dispersing the probe beam from a grating to a detector array. We achieve acquisition of picosecond THz field pulses without using mechanical time-delay device. We also demonstrate a single-shot electro-optic measurement of the temporal wave form of a THz pulse. © 1998 American Institute of Physics.

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42.65.Re	Ultrafast processes; optical pulse generation and pulse compression
42.60.Fc	Modulation, tuning, and mode locking
07.57.-c	Infrared, submillimeter wave, microwave and radiowave instruments and equipment

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Laser purification of Ag using a time-division collection method

Hiroshi Mori

Appl. Phys. Lett. 72, 1948 (1998); http://dx.doi.org/10.1063/1.121232 (3 pages) | Cited 6 times

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In laser purification of Ag from an Ag-In alloy based on multistep photoexcitation for ionization, we demonstrated that a time-division collection method employing a high-speed rotation disk is effective in suppressing an impurity level. High purity Ag film of 0.11% In impurity concentration was obtained from a starting Ag-In alloy of 6.08% In. This impurity reduction was much higher than the case without the new method, in which only half reduction was obtained. This work also showed that the contamination is mainly due to neutral atoms that failed to be irradiated by pulsed-mode lasers. © 1998 American Institute of Physics.

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81.05.Bx	Metals, semimetals, and alloys
81.20.Ym	Purification
61.72.S-	Impurities in crystals
42.62.-b	Laser applications

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Thermally-actuated reflection mode asymmetric Fabry–Perot modulator utilizing a thin transparent elastomeric film

John A. Rogers, Olivier J. A. Schueller, and George M. Whitesides

Appl. Phys. Lett. 72, 1951 (1998); http://dx.doi.org/10.1063/1.121233 (3 pages) | Cited 4 times

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This letter describes a thermally-actuated reflection mode asymmetric Fabry–Perot modulator that consists of a thin transparent elastomeric film bounded by partially and highly reflecting metallic mirrors. The thickness of the transparent layer determines the intensity of light reflected from the modulator; changes in its thickness modulate the reflectivity. Electrical current flowing through the highly reflecting mirror provides a source of heat for controlling, by thermal expansion, the thickness of the elastomeric film. Modulators with this design show contrast ratios >15 dB and insertion losses <0.3 dB. © 1998 American Institute of Physics.

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42.79.Hp	Optical processors, correlators, and modulators
42.70.Jk	Polymers and organics
78.66.Qn	Polymers; organic compounds
78.20.N-	Thermo-optic effects
78.20.nb	Photothermal effects
65.40.De	Thermal expansion; thermomechanical effects

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Electrical wavelength tunable and multiwavelength actively mode-locked fiber ring laser

Shenping Li and K. T. Chan

Appl. Phys. Lett. 72, 1954 (1998); http://dx.doi.org/10.1063/1.121263 (3 pages) | Cited 28 times

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Electrical single- and dual-wavelength tuning and three-wavelength operation of an actively mode-locked fiber ring laser generating picosecond pulses were demonstrated by using a cavity with large dispersion. A continuous tuning range up to ∼37 nm of single-wavelength picosecond pulses at ∼1 GHz was achieved by only changing the modulation frequency. Continuous wavelength tuning of dual-wavelength (18.5 nm spacing) 3 GHz picosecond pulses was also demonstrated with a tuning range up to ∼17 nm. The tuning ranges were mainly limited by the gain bandwidth of the Er-doped fiber. Simultaneous generation of three-wavelength picosecond pulses at ∼2 GHz was also demonstrated by further increasing the cavity dispersion. © 1998 American Institute of Physics.

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42.55.Wd	Fiber lasers
42.60.Da	Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc	Modulation, tuning, and mode locking

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Spontaneous emission from fluorescent molecules embedded in photonic crystals consisting of polystyrene microspheres

Takashi Yamasaki and Tetsuo Tsutsui

Appl. Phys. Lett. 72, 1957 (1998); http://dx.doi.org/10.1063/1.121234 (3 pages) | Cited 82 times

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Spontaneous emission from dye molecules embedded in periodic dielectric structures was investigated. The structures consist of close-packed arrays of dye-doped polystyrene microspheres. Periodic arrays of polystyrene spheres with a submicrometer diameter were shown to provide a nonoverlapping gap or pseudogap in the visible spectral region. The modification of the spontaneous emission from inside the pseudogap structure was observed as a deep dip in the photoluminescence spectra. The alteration in the emission spectra is explained in terms of the partial suppression of radiation modes due to the periodic dielectric structures. © 1998 American Institute of Physics.

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78.55.Kz	Solid organic materials
42.70.Qs	Photonic bandgap materials

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All-optical beam deflection and switching in strontium–barium–niobate waveguides

D. Kip, M. Wesner, E. Krätzig, V. Shandarov, and P. Moretti

Appl. Phys. Lett. 72, 1960 (1998); http://dx.doi.org/10.1063/1.121317 (3 pages) | Cited 11 times

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Self-focusing by thermal heating because of absorption of a guided light beam in a planar strontium–barium–niobate waveguide is of interest for all-optical data processing. When a guided probe beam intersects the pump beam under a small angle inside the waveguide, the self-focusing effect in conjunction with self-bending because of the photorefractive effect can be used for large angle deflection of the probe beam and for switching with time constants of fractions of milliseconds. Deflection angles of the outcoupled probe light up to 0.23 rad in air and frequencies up to 3 kHz for optical switching are reached in the experiment. © 1998 American Institute of Physics.

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42.65.Pc	Optical bistability, multistability, and switching, including local field effects
42.65.Jx	Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Wi	Nonlinear waveguides
42.79.Fm	Reflectors, beam splitters, and deflectors
42.82.Et	Waveguides, couplers, and arrays

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Frequency control in laser ultrasound with computer generated holography

M. Clark, F. Linnane, S. D. Sharples, and M. G. Somekh

Appl. Phys. Lett. 72, 1963 (1998); http://dx.doi.org/10.1063/1.121235 (3 pages) | Cited 8 times

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In laser ultrasonics a laser is used to excite ultrasonic waves. The intensity profile of the laser on the sample can be used to control the frequency of the ultrasound generated. In this letter we show how the frequency content of Rayleigh (surface acoustic) waves generated with an 82 MHz mode-locked laser can be controlled using computer generated holograms (CGHs). To demonstrate the effectiveness of the frequency control the CGHs used were defocused to generate new illumination profiles. The agreement between the actual and predicted amplitudes for these profiles is striking. Using this technique, the intensity output from the CGHs may be considered as a tunable Rayleigh wave source. © 1998 American Institute of Physics.

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43.38.Zp	Acoustooptic and photoacoustic transducers
43.35.Ud	Thermoacoustics, high temperature acoustics, photoacoustic effect
62.65.+k	Acoustical properties of solids
43.38.Rh	Surface acoustic wave transducers
43.35.Sx	Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
68.35.Gy	Mechanical properties; surface strains

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20 Apr 1998

Volume 72, Issue 16, pp. 1939-2058

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