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Lasing Threshold (lasing + threshold)

Distribution by Scientific Domains

Polymers and Materials Science	57%

Selected Abstracts

Integration of a Rib Waveguide Distributed Feedback Structure into a Light-Emitting Polymer Field-Effect Transistor

ADVANCED FUNCTIONAL MATERIALS, Issue 9 2009
Michael C. Gwinner
Abstract Ambipolar light-emitting organic field-effect transistors (LEFETs) possess the ability to efficiently emit light due to charge recombination in the channel. Since the emission can be made to occur far from the metal electrodes, the LEFET structure has been proposed as a potential architecture for electrically pumped organic lasers. Here, a rib waveguide distributed feedback structure consisting of tantalum pentoxide (Ta2O5) integrated within the channel of a top gate/bottom contact LEFET based on poly(9,9-dioctylfluorene- alt -benzothiadiazole) (F8BT) is demonstrated. The emitted light is coupled efficiently into the resonant mode of the DFB waveguide when the recombination zone of the LEFET is placed directly above the waveguide ridge. This architecture provides strong mode confinement in two dimensions. Mode simulations are used to optimize the dielectric thickness and gate electrode material. It is shown that electrode absorption losses within the device can be eliminated and that the lasing threshold for optical pumping of the LEFET structure with all electrodes (4.5,µJ cm,2) is as low as that of reference devices without electrodes. These results enable quantitative judgement of the prospects for realizing an electrically pumped organic laser based on ambipolar LEFETs. The proposed device provides a powerful, low-loss architecture for integrating high-performance ambipolar organic semiconductor materials into electrically pumped lasing structures. [source]

Low Thresholds in Polymer Lasers on Conductive Substrates by Distributed Feedback Nanoimprinting: Progress Toward Electrically Pumped Plastic Lasers

ADVANCED MATERIALS, Issue 7 2009
Ebinazar B. Namdas
A light-emitting transistor (LEFET) architecture with a distributed feedback (DFB) resonator structure nanoimprinted into the gain medium offers a route to achieving an electrically pumped plastic laser. A 2D DFB laser provides lower lasing thresholds than a 1D DFB laser under identical conditions. The 2D DFB lasers exhibit excellent characteristics with lasing threshold and slope efficiency of 32,nJ/pulse and 1.2%, respectively. [source]

Gain characteristics and lasing of Ga(NAsP) multi-quantum well structures

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2009
C. Lange
Abstract Lasing is demonstrated for a Ga(NAsP) multi quantumwell structure grown pseudomorphically on GaP using metal-organic vapour-phase epitaxy. For a series of temperatures ranging from 8 K to 290 K, the sample emission characteristics are determined. With increasing pump power, a spectral narrowing of the emitted light along with a blue-shift is observed as the lasing threshold is approached. Above the threshold, the emission splits up spectrally into a pattern of clearly distinguishable modes. In addition, the potential of this material concerning roomtemperature lasing is investigated by means of a variable stripe-length experiment, where a modal gain of 10 cm,1 is observed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

E-beam pumped resonant periodic gain GaInP/AlGaInP VCSEL

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2005
V. Yu.
Abstract 25-period Ga0.5In0.5P/(Al0.7Ga0.3)0.5In0.5P quantum well structure was grown by MOVPE on GaAs substrates misoriented by 100 from (001) to (111)A and fabricated into a microcavities with dielectric oxide mirrors. The structure period and mirror design were chosen to provide resonant periodic gain. A non-uniformity of 5% in the total structure thickness across the 2 inch wafer was used for studying laser characteristics depending on mismatching structure period from resonance condition. The laser wavelength, threshold and output power was found to depend critically on the alignment of QW period with both the cavity and the MQW gain spectrum. Lasing in the 625,650 nm spectral range with output power up to 9 W (0.45 MW/cm2) was achieved under scanning electron beam longitudinal pumping at room temperature. The minimum threshold current density for a 40 keV electron energy was 8 A/cm2 (0.32 MW/cm2). In order to control the lasing threshold to within 10 % of its minimum, the MQW period should be tuned to the optimum value with an accuracy of about 1 %. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optical Gain Enhancement Using a Carbosiloxane Dendrimer in Dilute Solution of Rhodamine B

CHEMPHYSCHEM, Issue 6 2007
Mei-Ling Zheng
Enhancing emission: The addition of a carbosiloxane dendrimer to rhodamine B in methanol solution efficiently enhances emission by changing the microenvironment around rhodamine B molecules due to the site-isolation effect of the dendrimers (see picture). This effect results in a lower lasing threshold, a narrower width of the lasing peak and higher energy conversion. [source]

Electrically Controllable Omnidirectional Laser Emission from a Helical-Polymer Network Composite Film

ADVANCED MATERIALS, Issue 7 2009
Byoungchoo Park
A liquid-crystal/polymer composite is used to produce a photonic bandgap system. Films of the composite show a large field-induced reversible color shift of the reflection band of over 150 nm. Intensity-controllable laser emission at relatively low lasing thresholds is generated from composite films doped with dye. Moreover, the laser exhibits omnidirectional emission propagation on application of an electric field. [source]