Modal Gain (modal + gain)

Distribution by Scientific Domains


Selected Abstracts


Optical gain and gain saturation of blue-green InGaN quantum wells

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2010
Dmitry Sizov
Abstract Using varied stripe length method we systematically studied optical gain properties of blue-green 3,nm InGaN QWs grown on c -plane and (11,22) semipolar substrates. We determined that for such structures when the product of modal net gain at peak and stripe length exceeds factor 5 the gain saturation occurs due to depletion of pumped carriers. We then focused our attention on the gain in unsaturated conditions. We observed strong gain peak position blue shift with increase of pumping power for both substrate orientations due to quantum well state filling and for c -plane due to piezoelectric field screening. Thus in order to increase lasing wavelength, minimizing optical losses, and maximizing modal gain are essential. We then found that for the semipolar QWs the gain at ,500,nm was 2× higher with the stripe along [,1,123] direction despite the fact that at low pumping level the polarization switching of spontaneous emission resulted predominant E||[,1,123]. Finally we compared the semipolar and c -plane QWs and found that the gain increase with pumping power of c -plane QW is slower than that for semipolar QW in high gain direction while the transparency pumping power is lower for c -plane. [source]


Device characteristics and metal,dielectric high reflectivity coating analysis of ,,,,1.3,µm InGaAsP/InGaAsP MQW PBH lasers

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010
J. W. Leem
Abstract The cavity length-dependent characteristics of compressively strained InGaAsP/InGaAsP multiple quantum well planar buried heterostructure lasers operating at ,,,,1.3,µm were investigated under continuous-wave mode. The uncoated 600,µm long laser exhibits Pmax,=,33.6,mW and Ith,=,12.9,mA at 25,°C with d,/dT,=,0.35,nm/K and d,/dPe,=,0.044,nm/mW, leading to stable beam characteristics of 19.7° (parallel),×,24.1° (perpendicular). From the inverse slope efficiency versus cavity length plot, the loss parameters of internal differential efficiency (,i) and internal optical loss (,i) were extracted, i.e., ,i,=,78% and ,i,=,10.6,cm,1. The transparent current density of Jtr,=,0.12,kA/cm2 and modal gain of G,=,49.5,cm,1 were also estimated from cavity length-dependent threshold current density measurements. Metal,dielectric Au/Ti/SiO2 layers for high reflectivity (HR) coating were analyzed using theoretical calculations and experimental results. For the HR-coated 600,µm long laser with Au (150,nm)/Ti (5,nm)/SiO2 (250,nm), Pmax increased up to 61,mW at 25,°C with a reduced Ith of 10.6,mA compared to the uncoated laser, providing an HR of about 94%. [source]


Effect of stack number on the threshold current density and emission wavelength in quantum dash/dot lasers

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2009
D. Zhou
Abstract InAs quantum dash and dot (QDH and QD) lasers grown by molecular beam epitaxy on InP substrate are studied. The grown lasers with active zone containing multiple stacked layers exhibit lasing wavelength at 1.55 ,m. On these devices, the experimental threshold current density reaches its minimum value for a double stacked QDH/QD structure. Other basic laser properties like gain and quantum efficiency are compared. QD lasers exhibit better threshold current densities but equivalent modal gain per layer than QDH. Finally, the analysis of the modal gain on QD laser structures shows a promising potential for improvement of the laser properties. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Optical properties and modal gain of InGaN quantum dot stacks

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009
Joachim Kalden
Abstract We present investigations of the optical properties of stacked InGaN quantum dot layers and demonstrate their advantage over single quantum dot layer structures. Measurements were performed on structures containing a single layer with quantum dots or threefold stacked quantum dot layers, respectively. A superlinear increase of the quantum dot related photoluminescence is detected with increasing number of quantum dot layers while other relevant GaN related spectral features are much less intensive when compared to the photoluminescence of a single quantum dot layer. The quantum dot character of the active material is verified by microphotoluminescence experiments at different temperatures. For the possible integration within optical devices in the future the threshold power density was investigated as well as the modal gain by using the variable stripe length method. As the threshold is 670 kW/cm2 at 13 K, the modal gain maximum is at 50 cm,1. In contrast to these limited total values, the modal gain per quantum dot is as high as 10,9cm,1, being comparable to the IIVI and III-As compounds. These results are a promising first step towards bright low threshold InGaN quantum dot based light emitting devices in the near future (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [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]