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19 Jan 1998

Volume 72, Issue 3, pp. 269-391

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Near diffraction-limited laser emission from a polymer in a high finesse planar cavity

A. Schülzgen, Ch. Spiegelberg, M. M. Morrell, S. B. Mendes, B. Kippelen, N. Peyghambarian, M. F. Nabor, E. A. Mash, and P. M. Allemand

Appl. Phys. Lett. 72, 269 (1998); http://dx.doi.org/10.1063/1.120709 (3 pages) | Cited 23 times

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We report near diffraction-limited laser emission from the conjugated polymer BEH:PPV in a cavity made with two dielectric mirrors providing a high finesse planar cavity. The laser has a sharp intensity threshold, a strong directionality, and a high degree of polarization. These emission characteristics are compared with those of a single polymer layer without optical feedback. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Bh Lenses, prisms and mirrors

Nonlinear optical effects in ferrofluids induced by temperature and concentration cross coupling

Tengda Du and Weili Luo

Appl. Phys. Lett. 72, 272 (1998); http://dx.doi.org/10.1063/1.120710 (3 pages) | Cited 25 times

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Both experiment and numerical calculation were performed to study the nonlinear optical (NLO) effects in ferrofluids consisting of magnetic particles suspended in an organic solvent. We show that, in contrast to all the mechanisms responsible for NLO phenomena known so far, the novel NLO effects in ferrofluids in the zero applied field can be explained by the cross coupling between the temperature of the system and the concentration of particles through thermophoresis, which in turn leads to the spatial distribution of the refractive index. This NLO effect is enhanced by applying a moderate magnetic field whose mechanism is unclear so far. © 1998 American Institute of Physics.
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42.65.-k Nonlinear optics
75.50.Mm Magnetic liquids
75.50.Tt Fine-particle systems; nanocrystalline materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.20.Ls Magneto-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Mapping of the lateral polar orientational distribution in second-order nonlinear thin films by scanning second-harmonic microscopy

Jan Vydra and Manfred Eich

Appl. Phys. Lett. 72, 275 (1998); http://dx.doi.org/10.1063/1.120711 (3 pages) | Cited 17 times

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We present a nondestructive experimental technique for the determination of the lateral distribution of the polar order in second-order nonlinear optical thin films. The sample, which consists of a poled polymer film is scanned through the focus of an infrared laser beam in a second-harmonic generation setup and the second-harmonic intensity is monitored stepwise. In combination with a conventional electro-optic (EO) characterization it is possible to create an EO-coefficient map of the sample. The resolution of this mapping technique can be significantly increased by using high numerical aperture microscope optics for the illumination of the poled polymer. This method, for instance, allows the evaluation of poling inhomogeneities due to high-field poling and field distortions at the edges of poling electrodes. © 1998 American Institute of Physics.
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61.41.+e Polymers, elastomers, and plastics
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.66.Qn Polymers; organic compounds
42.70.Jk Polymers and organics
68.55.-a Thin film structure and morphology
78.20.Jq Electro-optical effects

Fiber array targets for producing long media of high gain in recombination-pumped soft-x-ray lasers

Tsuneyuki Ozaki and Hiroto Kuroda

Appl. Phys. Lett. 72, 278 (1998); http://dx.doi.org/10.1063/1.120712 (3 pages) | Cited 1 time

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We demonstrate a target for recombination-pumped soft-x-ray lasers, consisting of an equally spaced array of parallel fibers. This target is capable of producing long media of several centimeters, and can also generate high gain due to the initial two-dimensional expansion of the plasma. Numerical simulations show that amplification occurs after the plasma expansion changes from a cylindrical to a slablike one, as a result of collisions with plasma produced from neighboring fibers. Initial gain measurements using graphite-coated fiber array targets reveal Balmer α gain coefficients of 4.1 cm−1. © 1998 American Institute of Physics.
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42.55.Vc X- and γ-ray lasers
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems

Improvement of short pulse operation of AlGaAs quantum-well lasers by temperature increase

I. Y. Khrushchev, I. H. White, and R. V. Penty

Appl. Phys. Lett. 72, 281 (1998); http://dx.doi.org/10.1063/1.120748 (3 pages)

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A theoretical model has been formulated using lumped rate equations to analyze the temperature dependence of the Q-switched (i.e., saturable absorber operated) and gain-switched operation of a quantum-well laser. The results are found to agree with experimental results obtained from AlGaAs quantum-well devices, and show that improvement in the pulse energy in Q-switched and gain-switched lasers can be achieved by optimizing the operating temperature above room temperature. With increasing temperature, the pulse energy increases due to the pulses broadening while the peak power remains approximately constant. The effect is mainly attributed to the decrease of the gain with temperature. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Wide-band suppression of photon-number fluctuations in a high-speed light-emitting diode driven by a constant-current source

M. Kobayashi, M. Kohno, Y. Kadoya, M. Yamanishi, J. Abe, and T. Hirano

Appl. Phys. Lett. 72, 284 (1998); http://dx.doi.org/10.1063/1.120713 (3 pages) | Cited 10 times

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We demonstrate experimental results on the generation of sub-Poissonian photon fluxes emanating from an AlGaAs light-emitting diode, which manifest a wide-band (0–100 MHz) noise suppression below the standard quantum limit level despite low current density ( ∼ 38 A/cm2) operation at room temperature. The experimental noise power spectrum is well fitted in terms of the theoretical curve estimated with the quantum mechanical Langevin equations. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
02.50.-r Probability theory, stochastic processes, and statistics
85.30.De Semiconductor-device characterization, design, and modeling
42.50.Lc Quantum fluctuations, quantum noise, and quantum jumps

Many-body optical gain of wurtzite GaN-based quantum-well lasers and comparison with experiment

Seoung-Hwan Park and Shun-Lien Chuang

Appl. Phys. Lett. 72, 287 (1998); http://dx.doi.org/10.1063/1.120714 (3 pages) | Cited 36 times

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The optical gain of wurtzite InxGa1−xN/In0.02Ga0.98N and GaN/AlxGa1−xN quantum well (QW) lasers taking into account many-body effects is investigated. The valence band structures are calculated as a function of strain and well thickness. The inclusion of compressive strain shows better lasing performance because of the increase of the subband energy separation in the valence band. Our theoretical gain spectra of In0.15Ga0.85N/In0.02Ga0.98N QW lasers are in good agreement with measured ones reported by Nakamura, IEEE J. Sel. Top. Quantum Electron. 3, 712 (1997). It is also shown that there is a universal relation governing the dependence of the band-gap renormalization on the two-dimensional carrier density for GaN-based QW lasers as there is for the infrared III-V systems. © 1998 American Institute of Physics.  
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42.55.Px Semiconductor lasers; laser diodes
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.60.Bs Mechanical and acoustical properties
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