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1 Jul 2002

Volume 81, Issue 1, pp. 1-184

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Comparative study of InGaAs quantum dot lasers with different degrees of dot layer confinement

K. M. Groom, A. I. Tartakovskii, D. J. Mowbray, M. S. Skolnick, P. M. Smowton, M. Hopkinson, and G. Hill

Appl. Phys. Lett. 81, 1 (2002); http://dx.doi.org/10.1063/1.1489702 (3 pages) | Cited 27 times

Online Publication Date: 25 June 2002

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We report a comparative study of the gain and lasing characteristics of two different InGaAs quantum dot (QD) laser designs, with multiple QD layers separated by barriers of (A) GaAs or (B) GaAs/AlGaAs. A higher degree of carrier confinement in structure B results in superior lasing characteristics at elevated temperatures. However, at temperatures below 130 K these devices demonstrate inhomogeneously broadened gain spectra, resulting in lasing over a much wider energy range than for structure A. The results are consistent with inefficient, low temperature interdot carrier transport in devices based on structure B. © 2002 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Oxadiazole-containing material with intense blue phosphorescence emission for organic light-emitting diodes

Fushun Liang, Lixiang Wang, Dongge Ma, Xiabin Jing, and Fosong Wang

Appl. Phys. Lett. 81, 4 (2002); http://dx.doi.org/10.1063/1.1491288 (3 pages) | Cited 25 times

Online Publication Date: 25 June 2002

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2-(2-hydroxyphenyl)-5-phenyl-1, 3, 4-oxadiazole (HOXD), characteristic of excited state intramolecular proton-transfer (ESIPT), was synthesized and found to emit strong blue phosphorescence in the solid state at room temperature and at low temperature (77 K). The photoluminescent spectrum measurement in solution showed that there are two kinds of emission: fluorescence originated from the singlet state and phosphorescence derived from the triplet state in HOXD formed by ESIPT. For the photoluminescent spectrum in the solid state, only phosphorescence emission with the lifetime of 66 μs was observed. Multiple-layer light-emitting diodes with the configuration of ITO/NPB/HOXD/BCP/Alq3/Mg:Ag were fabricated using HOXD as emitter and the maximum brightness of 656 cd/m2 and the luminous efficiency of 0.14 lm/W was obtained. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Bq Liquids

Three-dimensional imaging of a silicon flip chip using the two-photon optical-beam induced current effect

E. Ramsay, D. T. Reid, and K. Wilsher

Appl. Phys. Lett. 81, 7 (2002); http://dx.doi.org/10.1063/1.1491301 (3 pages) | Cited 18 times

Online Publication Date: 25 June 2002

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We describe two- and three-dimensional imaging of a flip-chip silicon integrated circuit using backside optical probing and femtosecond two-photon excitation at a laser wavelength of 1.275 μm. Using a ×50 microscope objective, we typically achieved micron resolutions or better in both lateral and axial directions. Using axial scanning and a peak-detection algorithm we have demonstrated optical depth profiling across components on the chip. © 2002 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
06.60.Jn High-speed techniques (microsecond to femtosecond)
78.47.-p Spectroscopy of solid state dynamics
72.40.+w Photoconduction and photovoltaic effects
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
07.79.Fc Near-field scanning optical microscopes

Organic-film photovoltaic cell with electroluminescence

B. Chu, D. Fan, W. L. Li, Z. R. Hong, and R. G. Li

Appl. Phys. Lett. 81, 10 (2002); http://dx.doi.org/10.1063/1.1488699 (3 pages) | Cited 21 times

Online Publication Date: 25 June 2002

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An organic-film photovoltaic (PV) cell, in which N,N′-bis-(1-naphthyl)- N,N′- diphenyl- 1,1′- biphenyl-4,4′-diamine (NPB) and tris(acetylacetonato)-(monophenothroline) yttrium [Y(ACA)3phen] were used as electron-acceptor and donor, respectively, has been fabricated. Under UV light (4 mW/cm2), the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF) and the overall power conversion efficiency of the optimum PV cell were 46 μA/cm2, 2.15 V, 0.30%, and 0.7%, respectively. The photocurrent response region of the cell parallels the adsorption of NPB. The PV effect is attributed to exciplex formation at the interface between the two organic films. The PV cell described displays electroluminescence (EL) emission of blue light upon application of a dc voltage. The maximum luminance was 750 cd/m2 at 15 V driving voltage. © 2002 American Institute of Physics.
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85.60.-q Optoelectronic devices
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
78.60.Fi Electroluminescence

Tunable terahertz generation using femtosecond pulse shaping

J. Y. Sohn, Y. H. Ahn, D. J. Park, E. Oh, and D. S. Kim

Appl. Phys. Lett. 81, 13 (2002); http://dx.doi.org/10.1063/1.1490140 (3 pages) | Cited 22 times

Online Publication Date: 25 June 2002

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Femtosecond pulse shaping and photomixing methods are combined to make a tunable terahertz source. Grating-pair pulse shaper selects two main frequency components to produce pulses that are modulated with a period which is inversely proportional to the frequency separation. The shaped pulse is then photomixed in semi-insulating GaAs under external bias. Terahertz (THz) emission frequency follows the modulation frequency of the excitation pulses, from 0.5 to 3 THz. Contrary to cw photomixing, this method can easily be combined with electro-optic and photoconductive sampling detection methods. © 2002 American Institute of Physics.
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07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
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