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20 Dec 1999

Volume 75, Issue 25, pp. 3905-4030

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Mechanism of efficient ultraviolet lasing in GaN/AlGaN separate-confinement heterostructures

S. Bidnyk, J. B. Lam, B. D. Little, Y. H. Kwon, J. J. Song, G. E. Bulman, H. S. Kong, and T. J. Schmidt

Appl. Phys. Lett. 75, 3905 (1999); http://dx.doi.org/10.1063/1.125489 (3 pages) | Cited 14 times

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We report the results of an experimental study on efficient laser action in an optically pumped GaN/AlGaN separate-confinement heterostructure (SCH) in the temperature range of 10–300 K. The lasing threshold was measured to be as low as 15 kW/cm2 at 10 K and 105 kW/cm2 at room temperature. Strongly polarized (TE:TM ≥ 300:1) lasing peaks were observed over the wavelength range of 358–367 nm. We found high-finesse lasing modes that originate from self-formed microcavities in the AlGaN and GaN layers. Through analysis of the relative shift between spontaneous emission and lasing peaks, combined with the temperature dependence of the lasing threshold, we conclude that exciton–exciton scattering is the dominant gain mechanism leading to low-threshold ultraviolet lasing in the GaN/AlGaN SCH over the entire temperature range studied. Based on our results, we discuss possibilities for the development of ultraviolet laser diodes with a GaN active medium. © 1999 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Direct far-field observation of surface-plasmon propagation by photoinduced scattering

T. Velinov, M. G. Somekh, and S. Liu

Appl. Phys. Lett. 75, 3908 (1999); http://dx.doi.org/10.1063/1.125490 (3 pages) | Cited 3 times

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A tightly focused laser beam is shown to act as a scatterer of surface plasmons. The energy released into free space due to the scattering is collected by far-field optics. Scanning the laser beam over the plasmon field gives a map of their propagation. Evidence is given which shows that the surface-plasmon map gives much more detail of plasmon propagation and film structure than the photothermal image, which monitors the heat deposited during plasmon propagation. © 1999 American Institute of Physics.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
79.20.Ds Laser-beam impact phenomena

Low-loss Al-free waveguides for unipolar semiconductor lasers

C. Sirtori, P. Kruck, S. Barbieri, H. Page, J. Nagle, M. Beck, J. Faist, and U. Oesterle

Appl. Phys. Lett. 75, 3911 (1999); http://dx.doi.org/10.1063/1.125491 (3 pages) | Cited 77 times

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A promising waveguide design for midinfrared (λ = 5–20 μm) unipolar semiconductor lasers is proposed and demonstrated in (Al)GaAs quantum cascade structures. In the latter, the active region is embedded between two GaAs layers, with an appropriate doping profile which allows optical confinement, with low waveguide losses and optimal heat dissipation. Low internal cavity losses of 20 cm−1 have been measured using different techniques for lasers with emission wavelength at ∼9 μm. At 77 K, these devices have peak output power in excess of 550 mW and threshold current of 4.7 kA/cm2. © 1999 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays

Polarization-independent four-wave mixing in a bidirectional traveling-wave semiconductor optical amplifier

G. Contestabile, A. D’Ottavi, F. Martelli, A. Mecozzi, P. Spano, and A. Tersigni

Appl. Phys. Lett. 75, 3914 (1999); http://dx.doi.org/10.1063/1.125492 (3 pages) | Cited 11 times

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In this work, we demonstrate polarization-independent four-wave mixing using a single semiconductor optical amplifier. The result is obtained using a polarization-diversity scheme, in which all the injected fields are split by a polarization beam splitter and the two resulting patterns are injected counterpropagating in the amplifier. The use of two orthogonally polarized pumps allows a conjugate generation with efficiency also independent of the signal-conjugate detuning. A comparison of the amplifier performance with mono- and bidirectional propagation is given. © 1999 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.55.Px Semiconductor lasers; laser diodes
42.79.Fm Reflectors, beam splitters, and deflectors
42.79.Nv Optical frequency converters
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Phase jumps and interferometric surface plasmon resonance imaging

A. N. Grigorenko, P. I. Nikitin, and A. V. Kabashin

Appl. Phys. Lett. 75, 3917 (1999); http://dx.doi.org/10.1063/1.125493 (3 pages) | Cited 49 times

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Conditions at which phase of light demonstrates a markedly different behavior for close values of system parameters as well as the Heaviside jump are discussed and explained in terms of phase topology. On this basis, a method of interferometric surface plasmon resonance imaging is proposed and applied to develop ultrasensitive affinity array sensors with a monoatomic thickness resolution. © 1999 American Institute of Physics.
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07.60.Ly Interferometers
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
87.64.M- Optical microscopy

Light-emitting multifunctional rhenium (I) and ruthenium (II) 2,2′-bipyridyl complexes with bipolar character

Wai Kin Chan, Po King Ng, Xiong Gong, and Sijian Hou

Appl. Phys. Lett. 75, 3920 (1999); http://dx.doi.org/10.1063/1.125494 (3 pages) | Cited 40 times

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A series of multifunctional molecules consisting of hole transport, electron transport, and light-emitting moieties were synthesized and fabricated into single-layer organic light-emitting devices. The light-emitting units were based on 2,2′-bipyridine complexes of rhenium and ruthenium. It was found that, due to the bipolar character of the molecules, the charge carrier mobilities, charge injection barrier, and the device performance were improved. The electron carrier mobilities are on the order of 10−4 cm2 V−1 s−1 and a maximum luminescence of 730 cd/m2 was observed. © 1999 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
73.61.Ph Polymers; organic compounds
73.50.Dn Low-field transport and mobility; piezoresistance
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