Theoretical Performance Of Mid-Infrared Broken-Gap Multilayer Superlattice Lasers

1997 ◽  
Vol 484 ◽  
Author(s):  
Michael E. Flatté ◽  
J. T. Olesberg ◽  
C. H. Grein
Keyword(s):  
Auger Recombination ◽  
Band Edge ◽  
Lasing Threshold ◽  
Spectral Structure ◽  
Material System ◽  
Final State ◽  
Lasing Wavelength ◽  
Edge Structure ◽  
Intersubband Absorption ◽  
Resonance Energies

AbstractWe present calculations of the intersubband absorption and Auger recombination rate of superlattices based on the InAs/GaInSb material system involving more than two layers in the repeating unit cell and strain balanced to match the GaSb substrate. We demonstrate theoretically the presence of final-state optimization in a 4.0 μm strain-balanced brokengap superlattice. This system's band structure is optimized not only at the band edge, where the valence density of states has been reduced, but also at resonance energies, where reside final states for Auger and intersubband processes. The spectral structure of the intersubband absorption, which for some wavelengths near the lasing wavelength can exceed 500 cm−1 at lasing threshold, has been considered when designing this active region. Fortunately, final-state optimized designs which minimize Auger recombination tend to minimize intersubband absorption as well. The effectiveness of final-state optimization is evaluated by considering band structures with identical band edge structure, but different final-state structure.

Ultrafast Carrier Dynamics, Optical Amplification, and Lasing in Nanocrystal Quantum Dots

MRS Bulletin ◽  
2001 ◽  
Vol 26 (12) ◽  
pp. 998-1004 ◽  
Author(s):  
Victor I. Klimov ◽  
Moungi G. Bawendi
Keyword(s):  
Quantum Dots ◽  
Quantum Wells ◽  
Quantum Wires ◽  
Electronic States ◽  
Three Dimensions ◽  
Band Edge ◽  
Lasing Threshold ◽  
Wide Energy Range ◽  
Band Edge Emission ◽  
Edge States

Semiconductor materials are widely used in both optically and electrically pumped lasers. The use of semiconductor quantum wells (QWs) as optical-gain media has resulted in important advances in laser technology. QWs have a two-dimensional, step-like density of electronic states that is nonzero at the band edge, enabling a higher concentration of carriers to contribute to the band-edge emission and leading to a reduced lasing threshold, improved temperature stability, and a narrower emission line. A further enhancement in the density of the band-edge states and an associated reduction in the lasing threshold are in principle possible using quantum wires and quantum dots (QDs), in which the confinement is in two and three dimensions, respectively. In very small dots, the spacing of the electronic states is much greater than the available thermal energy (strong confinement), inhibiting thermal depopulation of the lowest electronic states. This effect should result in a lasing threshold that is temperatureinsensitive at an excitation level of only 1 electron-hole (e-h) pair per dot on average. Additionally, QDs in the strongconfinement regime have an emission wavelength that is a pronounced function of size, adding the advantage of continuous spectral tunability over a wide energy range simply by changing the size of the dots.

X-ray absorption near edge structures in cobalt oxides

1996 ◽  
Vol 11 (9) ◽  
pp. 2242-2256 ◽  
Author(s):  
T. Jiang ◽  
D. E. Ellis
Keyword(s):  
Wave Functions ◽  
Site Symmetry ◽  
Local Geometry ◽  
Final State ◽  
Cluster Technique ◽  
Edge Structure ◽  
X Ray ◽  
Local Electronic Structure ◽  
Edge Features ◽  
X Ray Absorption

Theoretical studies have been made of K-edge x-ray absorption near edge structure (XANES) of Co in CoO, Co(OH)2, CoTiO3, Co3O4, and CoAl2O4. Correlations of experimental near edge features with site symmetry, local geometry, local electronic structure, i.e., atomic configuration, charge transfer, and backscattering from neighboring atomic potentials are interpreted. The self-consistent Discrete Variational Xa Method (DV-Xα) within an embedded cluster technique has been used to generate the crystal potential. A multiple scattering (MS) approach is then used to solve for the final state wave function. The ground state DV wave functions are analyzed in terms of the projected density of states, whereas the final state MS continuum wave functions are analyzed through the concept of photoelectron trapping time.

Unusually Strong Bi-Exciton Repulsion Detected in Quantum Confined CsPbBr3 Nanocrystals with Two and Three Pulse Femtosecond Spectroscopy

2021 ◽  
Author(s):  
jayanta dana ◽  
Tal Binyamin ◽  
Lioz Etgar ◽  
Sanford Ruhman
Keyword(s):  
Cross Section ◽  
Quantum Confinement ◽  
Auger Recombination ◽  
Transient Absorption ◽  
Stimulated Emission ◽  
Band Edge ◽  
High Time Resolution ◽  
Difference Spectra ◽  
The Difference ◽  
Absorption Measurements

Transient absorption measurements were conducted on pristine and on monoexciton saturated<br>CsPbBr3 nanocrystals varying in size within the regime of strong quantum confinement. Once<br>the difference spectra were translated to absolute transient changes in absorption cross section,<br>a single exciton is shown to completely bleach the band edge absorption peak, and induce a<br>new absorption roughly two times weaker ~100 meV to the blue. Difference spectra obtained<br>during Auger recombination of biexcitons demonstrate that addition of a second exciton, rather<br>than double the effect of a first, bleaches the blue induced absorption band without producing<br>net stimulated emission at the band edge. Accompanied by high time resolution transient<br>absorption spectra pumping at the lowest exciton band, these results identify the blue induced<br>absorption as the second transition to 1Se1Sh which is shifted in energy due to unusually strong<br>and promptly rising biexciton repulsion. <br>

Infrared photoreflectance investigation of resonant levels and band edge structure in InSb

2015 ◽  
Vol 40 (22) ◽  
pp. 5295 ◽  
Author(s):  
Xiren Chen ◽  
Jinwook Jung ◽  
Zhen Qi ◽  
Liangqing Zhu ◽  
Sehun Park ◽  
...  
Keyword(s):  
Band Edge ◽  
Edge Structure

Multiple-band-edge quantum-well intermixing in the InGaAs∕InGaAsP∕InGaP material system

2005 ◽  
Vol 86 (24) ◽  
pp. 241117 ◽  
Author(s):  
Erik J. Skogen ◽  
Larry A. Coldren ◽  
James W. Raring ◽  
Steven P. DenBaars
Keyword(s):  
Quantum Well ◽  
Band Edge ◽  
Material System ◽  
Quantum Well Intermixing ◽  
Multiple Band

Coordination “Fingerprints” of Boron Measured by EELS

1990 ◽  
Vol 48 (2) ◽  
pp. 54-55
Author(s):  
H. Sauer ◽  
R. Brydson ◽  
W. Engel ◽  
P.N. Rowley
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Excited Atom ◽  
Core Loss ◽  
High Energy ◽  
Nearest Neighbour ◽  
Final State ◽  
Edge Structure ◽  
Local Symmetries ◽  
Electron Energy Loss

The electron energy-loss near-edge structure (ELNES) associated with a core-loss edge measured using electron energy-loss spectroscopy (EELS) provides, in favourable cases, a “fingerprint” corresponding to the specific nearest-neighbour coordination of the excited atom.Boron atoms in boron-oxygen compounds occur in both trigonal (BO3) and tetrahedral (BO4) coordinations. The B K-ELNES of BO3 and BO4 units (Figs, le and 2b) are remarkably different and arise from the differing local symmetries which determine the final state molecular orbitals. The BK-ELNES of BO3 units exhibit a sharp π∗ peak at ca. 194 eV followed by a broader σ∗ peak some 9-10 eV higher in energy, which may possess a low energy shoulder. BO4 B K-ELNES show no π∗ peak and display solely a σ∗ peak at ca. 199 eV together with a high energy shoulder. Both these spectra may be modelled using multiple scattering calculations.The mineral howlite contains both BO3 and BO4 units and is sensitive to electron-beaminduced damage.

Wavelength Shift of InP-Based InAs Quantum Dot Lasers Above Room Temperature

2007 ◽  
Vol 7 (12) ◽  
pp. 4443-4446 ◽  
Author(s):  
Jin Soo Kim ◽  
Cheul-Ro Lee ◽  
Kyeong Won Seol ◽  
Dae Kon Oh
Keyword(s):  
Quantum Dot ◽  
Room Temperature ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Wavelength Shift ◽  
Material System ◽  
Quantum Dot Lasers ◽  
Lasing Wavelength ◽  
Band Filling ◽  
Inas Quantum Dot

For the InAs quantum dot (QD) lasers based on the InAlGaAs-InAlAs-InP material system, the lasing operation was successfully achieved up to 100 °C. The lasing wavelength was linearly increased with a slope of 0.100 nm/K up to 50 °C and then, decreased with (−)0.419 nm/K above 50 °C. The temperature-induced shift in the lasing wavelength can be attributed to both the band-gap shrinkage and the band-filling effect of carriers, which was well agreed with the characteristic temperatures of the InAs QD laser calculated from the temperature dependence of threshold current density.

Band edge structure of ferroelectric IV–VI compounds

2007 ◽  
pp. 27-48 ◽  
Author(s):  
Günther Bauer ◽  
Wolfgang Jantsch ◽  
Eike Bangert
Keyword(s):  
Band Edge ◽  
Edge Structure
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