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11 Nov 2002

Volume 81, Issue 20, pp. 3705-3896

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Dynamic charge-carrier-mobility-mediated holography in thin layers of photoconducting polymers

S. Bartkiewicz, A. Miniewicz, B. Sahraoui, and F. Kajzar

Appl. Phys. Lett. 81, 3705 (2002); http://dx.doi.org/10.1063/1.1512824 (3 pages) | Cited 9 times

Online Publication Date: 4 November 2002

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The dynamic holography technique is proposed for the measurement of the charge-carrier-mobility in thin layers of a photoconducting polymer, used in optically addressed liquid-crystal spatial light modulators. The photorefractive properties of these modulators are studied under short-pulse (20 ps, 532 nm) laser illumination conditions and the charge mobility in the photoconducting polymer (μh = 10−7 cm2/V s) is obtained from the temporal evolution of intensity of the first-order diffracted beam. A mechanism responsible for the grating formation is proposed and discussed. © 2002 American Institute of Physics.
Show PACS
42.70.Gi Light-sensitive materials
42.70.Jk Polymers and organics
73.61.Ph Polymers; organic compounds
42.40.My Applications
73.50.Pz Photoconduction and photovoltaic effects
42.70.Ln Holographic recording materials; optical storage media
42.40.Eq Holographic optical elements; holographic gratings
42.79.Kr Display devices, liquid-crystal devices
42.79.Hp Optical processors, correlators, and modulators
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Development of channel waveguide lasers in Nd3+-doped chalcogenide (Ga:La:S) glass through photoinduced material modification

Arshad K. Mairaj, Christos Riziotis, Alain M. Chardon, Peter G. R. Smith, David P. Shepherd, and Daniel W. Hewak

Appl. Phys. Lett. 81, 3708 (2002); http://dx.doi.org/10.1063/1.1520698 (3 pages) | Cited 16 times

Online Publication Date: 4 November 2002

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We report the development of a waveguide laser source in a neodymium-doped chalcogenide (Ga:La:S) glass. Channel waveguide structures were directly written via above band gap (λ=244 nm) illumination provided by a focused UV-laser beam with fluencies 1.5–150 J/cm2. Effects of photoinduced material modification in the form of surface compaction and photodensification were evident. Characterization revealed a low threshold waveguide laser with emission at 1075 nm and slope efficiency of 17%. The active device was spatially single mode and exhibited laser operation with 8.6 mW peak power and attenuation <0.5 dB cm−1. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
81.05.Kf Glasses (including metallic glasses)
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.72.-g Optical sources and standards
42.62.-b Laser applications

Red electrophosphorescence from polymer doped with iridium complex

Xiong Gong, Jacek C. Ostrowski, Guillermo C. Bazan, Daniel Moses, and Alan J. Heeger

Appl. Phys. Lett. 81, 3711 (2002); http://dx.doi.org/10.1063/1.1511283 (3 pages) | Cited 79 times

Online Publication Date: 4 November 2002

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We demonstrate efficient, bright red electrophosphorescent light emitting diodes (LEDs) employing tris (2,5-bis-2′-(9′,9′-dihexylfluorene) pyridine) iridium (III), [Ir(HFP)3], doped into a blend of poly(vinylcarbazole) (PVK) with 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazol (PBD). At a current density of 2.35 mA/cm2 (brightness of 169 cd/m2), the external quantum efficiency (QEext) and luminous efficiency (LE) were 5% ph/el and 7.2 cd/A, respectively. Even at 50 mA/cm2, QEext = 3.4% ph/el and LE = 5.2cd/A. The electroluminescent emission is characteristic of Ir(HFP)3, with maximum at 600 nm. The devices exhibited no emission from either PVK or PBD, even at the lowest concentration of Ir(HFP)3 (0.05 wt %). The results demonstrate that electrophosphorescence with high brightness and efficiency can be achieved from polymer-based LEDs fabricated by processing the active materials from solution. © 2002 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
78.55.Hx Other solid inorganic materials
82.35.Jk Copolymers, phase transitions, structure

Enhancement of third-harmonic generation in absorbing media

G. Veres, S. Matsumoto, Y. Nabekawa, and K. Midorikawa

Appl. Phys. Lett. 81, 3714 (2002); http://dx.doi.org/10.1063/1.1521248 (3 pages) | Cited 9 times

Online Publication Date: 4 November 2002

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The efficiency of third-harmonic generation on glass–air interfaces near the focal point of a tightly focused laser beam is investigated for different material samples. It is found that highly absorbing materials give higher harmonic yield. Moreover, due to the systematic change of the third-harmonic yield with the absorption length, an estimation of the third-order susceptibility χ(3) of absorbing samples can be given from absorption coefficient measurements. © 2002 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.An Optical susceptibility, hyperpolarizability

Ultrafast dynamics of interfacial electric fields in semiconductor heterostructures monitored by pump-probe second-harmonic generation

Yu. D. Glinka, T. V. Shahbazyan, I. E. Perakis, N. H. Tolk, X. Liu, Y. Sasaki, and J. K. Furdyna

Appl. Phys. Lett. 81, 3717 (2002); http://dx.doi.org/10.1063/1.1521573 (3 pages) | Cited 7 times

Online Publication Date: 4 November 2002

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We report measurements of the ultrafast dynamics of interfacial electric fields in semiconductor multilayers using pump-probe second-harmonic generation (SHG). A pump beam was tuned to excite carriers in all the layers in GaAs/GaSb and GaAs/GaSb/InAs heterostructures. The resulting carrier dynamics manifests itself via electric fields created by charge separation due to carrier redistribution at the interfaces. The evolution of interfacial fields is monitored by a probe beam through an eletric-field-induced SHG signal. We distinguish between several stages of dynamics originating from redistribution of carriers between the layers. We also find a strong enhancement of the induced electric field caused by hybridization of the conduction and valence bands at the GaSb/InAs interface. © 2002 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.20.Jq Electro-optical effects
73.21.Ac Multilayers
78.47.-p Spectroscopy of solid state dynamics
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Coefficient determination related to optical gain in erbium-doped silicon-rich silicon oxide waveguide amplifier

Hak-Seung Han, Se-Young Seo, Jung H. Shin, and Namkyoo Park

Appl. Phys. Lett. 81, 3720 (2002); http://dx.doi.org/10.1063/1.1520710 (3 pages) | Cited 3 times

Online Publication Date: 4 November 2002

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Gain-determining coefficients in Er-doped, nanocrystal-Si (nc-Si) sensitized silica waveguide amplifiers are investigated. Single-mode, Er-doped silica waveguides with nc-Si embedded in them were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition of Er-doped a-Si:Ox (x<2) followed by a high-temperature anneal to precipitate nc-Si. Exciting the Er ions via nc-Si by pumping the waveguide from the top with the 477 nm line of an Ar laser resulted in an enhancement of the transmitted 1535 nm signal of up to 14 dB/cm, indicating a possible net gain of up to 7 dB/cm. From the dependence of the signal enhancement upon the pump power, an emission cross section of 2×10−19 cm2 at 1535 nm and an effective excitation cross section of ≥ 10−17 cm2 at 477 nm is obtained. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.55.Rz Doped-insulator lasers and other solid state lasers
42.79.Gn Optical waveguides and couplers

1212 nm pumping of 2 μm Tm–Ho-codoped silica fiber laser

Atsushi Taniguchi, Tetsuro Kuwayama, Akira Shirakawa, Mitsuru Musha, Ken-ichi Ueda, and Mahendra Prabhu

Appl. Phys. Lett. 81, 3723 (2002); http://dx.doi.org/10.1063/1.1521242 (3 pages) | Cited 13 times

Online Publication Date: 4 November 2002

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A Tm–Ho-codoped silica fiber laser pumped by a third-stokes Raman Fiber Laser at 1212 nm is demonstrated. For the 30-cm-long Tm–Ho-codoped fiber, a 400 mW output power is obtained at a wavelength of 1790 nm due to the laser emission from the Tm3+ ions. For the 270-cm-long Tm–Ho-codoped fiber, a 450 mW output power is obtained at 1970 nm due to the laser emission from Ho3+ ions. © 2002 American Institute of Physics.
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42.55.Wd Fiber lasers

Generation of bright low-divergence high-order harmonics in a long gas jet

D. G. Lee, H. T. Kim, K. H. Hong, C. H. Nam, I. W. Choi, A. Bartnik, and H. Fiedorowicz

Appl. Phys. Lett. 81, 3726 (2002); http://dx.doi.org/10.1063/1.1521241 (3 pages) | Cited 10 times

Online Publication Date: 4 November 2002

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Guided propagation of intense 28 fs laser pulses through a long gas jet made it feasible to produce a bright 27th harmonic from argon with a divergence of 0.5 mrad. This harmonic saturated an x-ray charge-coupled device of an extreme ultraviolet spectrometer in a single laser shot of 5 mJ. The low-divergence harmonic generation resulted from a well-guided pumping laser pulse, achieved by balancing diffraction and plasma defocusing with nonlinear self-focusing, and a large harmonic-generation cross section. © 2002 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
52.38.-r Laser-plasma interactions
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Analysis of coupling between two-dimensional photonic crystal waveguide and external waveguide

Eiji Miyai, Makoto Okano, Masamitsu Mochizuki, and Susumu Noda

Appl. Phys. Lett. 81, 3729 (2002); http://dx.doi.org/10.1063/1.1521586 (3 pages) | Cited 24 times

Online Publication Date: 4 November 2002

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Coupling between conventional wire waveguide and two-dimensional photonic crystal waveguide was analyzed by means of a three-dimensional finite difference time domain method. We evaluated the transmittance corresponding to the coupling efficiency between two waveguides. By using SiO2 clad below the wire and setting the width of the wire to be an appropriate value, we obtained single mode guiding and a coupling efficiency over 80% for the wave length around 1.55 μm. © 2002 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers

Sum frequency generation of synchronously-seeded, high-power Yb and Er fiber amplifiers in periodically poled KTP

P. A. Champert, S. V. Popov, A. V. Avdokhin, and J. R. Taylor

Appl. Phys. Lett. 81, 3732 (2002); http://dx.doi.org/10.1063/1.1521582 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2002

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Synchronous temporal seeding of single-mode, high-peak, and average-power Yb and Er fiber amplifiers allowed efficient, single-pass, sum frequency generation in periodically poled KTP. 3.5 W average power in the red, at 630 nm, is generated with Gaussian spatial beam quality. © 2002 American Institute of Physics.
Show PACS
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.55.Wd Fiber lasers

Ultralow threshold powers for optical pumping of homoepitaxial InGaN/GaN/AlGaN lasers

V. Yu. Ivanov, M. Godlewski, H. Teisseyre, P. Perlin, R. Czernecki, P. Prystawko, M. Leszczynski, I. Grzegory, T. Suski, and S. Porowski

Appl. Phys. Lett. 81, 3735 (2002); http://dx.doi.org/10.1063/1.1521243 (3 pages) | Cited 5 times

Online Publication Date: 4 November 2002

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We report ultralow threshold powers for optically pumped laser emission from InGaN/GaN/AlGaN laser structures grown on bulk GaN substrates. The threshold powers at room temperature (for excitation with 355 nm third harmonic of Nd:YAG laser) are between 2.4 and 5.8 kW/cm2, depending on a cavity length. We believe that this is the consequence of a significant reduction of concentration of nonradiative centers in the active layer of homoepitaxial structures. We report also that spacing of the longitudinal laser modes exceeds by a factor of 6–7 the values predicted from the standard calculations. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Electro-optic modulation at 1.5 GHz using single-crystal film of an organic molecular salt

M. Thakur, A. Mishra, J. Titus, and A. C. Ahyi

Appl. Phys. Lett. 81, 3738 (2002); http://dx.doi.org/10.1063/1.1520713 (3 pages) | Cited 4 times

Online Publication Date: 4 November 2002

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Electro-optic modulation using single-crystal film of an organic molecular salt with light propagating perpendicular to the film (transverse configuration) has been recently reported. In this letter, we report results of measurements at high speed (up to 1.5 GHz) using such films in the same configuration. Excellent signal-to-noise ratio has been observed even at a low applied voltage (1 V across 15 μm gap) for a 3 μm thick film. The magnitudes of the electro-optic coefficients are: r11 = 445 pm/V and r21 = 148 pm/V at 750 nm. A wide range of applications of these films are predicted. © 2002 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
78.47.-p Spectroscopy of solid state dynamics
78.66.Qn Polymers; organic compounds
78.20.Jq Electro-optical effects

Flexible mirrorless laser based on a free-standing film of photopolymerized cholesteric liquid crystal

Tatsunosuke Matsui, Ryotaro Ozaki, Kazuhiro Funamoto, Masanori Ozaki, and Katsumi Yoshino

Appl. Phys. Lett. 81, 3741 (2002); http://dx.doi.org/10.1063/1.1522498 (3 pages) | Cited 73 times

Online Publication Date: 4 November 2002

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Optically pumped mirrorless laser action has been observed in a dye-doped flexible free-standing film of photopolymerized cholesteric liquid crystal (PCLC). In the PCLC film, self-organized helical structure acts as one-dimensional (1D) photonic crystal. At high excitation intensity above the threshold, a laser action is observed at an edge of the 1D photonic band of the PCLC helical structure. This PCLC film laser possesses an excellent mechanical flexibility, and the laser action is also observed in a bent film of PCLC. This implies that the one-dimensional periodic structure for the laser action is maintained even in the deformed film. Using such flexibility of the PCLC film, a focusing effect of laser emission is demonstrated in a circularly deformed film. Moreover, the helical pitch of the PCLC has no temperature dependence in contrast to that of unpolymerized cholesteric liquid crystal. This means that the operation wavelength of laser action is thermally stable, which is the great advantage for the device application. © 2002 American Institute of Physics.
Show PACS
42.55.Mv Dye lasers
42.70.Qs Photonic bandgap materials
42.70.Df Liquid crystals
42.70.Hj Laser materials
82.35.-x Polymers: properties; reactions; polymerization
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