Stark Level Structure and Optical Transition Intensities of Activator Ions in Laser Crystals

Author(s):  
Alexander A. Kaminskii
2006 ◽  
Vol 959 ◽  
Author(s):  
Liudmila A Pozhar ◽  
Gail J Brown ◽  
William C Mitchel

ABSTRACTThe Hartree-Fock (HF), restricted open shell HF (ROHF), configuration interaction (CI), complete active space (ICASCF), and multiconfiguration self-consistent field (MCSCF) methods provide sophisticated fundamental theory-based, computational tools to study structure, composition,chemistry and electronic properties of small artificial molecules composed of semiconductor compound atoms. These tools are used to synthesize virtually several prismatic In-N and Zn-O artificial molecules whose structure is derived from that of the symmetry elements of the respective wurtzite bulk lattices. Applications of spatial constraints to the atomic coordinates allow modeling molecular synthesis in quantum confinement, to obtain pre-designed molecules with tunable electronic properties. Relaxation of these constraints, or optimization, leads to the corresponding molecules synthesized in “vacuum”. The development of computational templates of the studied artificial molecules synthesized in confinement reflects effects of quantum confinement on the electronic level structure, bonding, the direct optical transition energy, and charge and spin density distributions of the molecules. Comparison of the structure and properties of these molecules to those of their vacuum counterparts leads to a conclusion that a small changes in atomic positions in otherwise structurally similar molecules cause a significant change in their electronic properties. Thus, the electronic properties of artificial molecules can be tuned by changing their synthesis conditions that are defined by atomistic details of quantum confinement where the molecules are synthesized.


2001 ◽  
Vol 323-324 ◽  
pp. 763-767 ◽  
Author(s):  
I.R. Martı́n ◽  
Y. Guyot ◽  
M.F. Joubert ◽  
R.Yu. Abdulsabirov ◽  
S.L. Korableva ◽  
...  

2006 ◽  
Vol 955 ◽  
Author(s):  
Liudmila A Pozhar ◽  
William C Mitchel

ABSTRACTIn the work reported here the Hartree-Fock (HF), restricted open shell HF (ROHF), and multiconfiguration self-consistent field (CI/CASSCF/MCSCF) methods are used to predict electronic properties of several artificial molecules of InAsN and indium nitride whose structure and composition have been derived from those of the corresponding symmetry elements of the zincblende and wurtzite bulk lattices. Both quantum-confined and “vacuum” clusters (whose geometry has been optimized without any spatial constraints applied to the atomic positions) were studied focusing on the electronic energy level structure, direct optical transition energy (OTE), and charge and spin distributions. The obtained results indicate that inclusion of “impurity” atoms (such as As atoms) may enhance stability of both vacuum and confined pyramidal In-N molecules and provide for manipulations of the OTE in a wide range of its values. The CI/CASSCF/MCSCF OTEs of the studied wurtzite-based clusters may also vary in a wide range, from 1.7440 eV for the smallest pre-designed prismatic molecule In6N6 to 6.9780 eV for its almost perfect prismatic “vacuum” counterpart. These evaluations closely correlate with experimental data available in literature.


2020 ◽  
Vol 92 (2) ◽  
pp. 20101
Author(s):  
Behnam Kheyraddini Mousavi ◽  
Morteza Rezaei Talarposhti ◽  
Farshid Karbassian ◽  
Arash Kheyraddini Mousavi

Metal-assisted chemical etching (MACE) is applied for fabrication of silicon nanowires (SiNWs). We have shown the effect of amorphous sheath of SiNWs by treating the nanowires with SF6 and the resulting reduction of absorption bandwidth, i.e. making SiNWs semi-transparent in near-infrared (IR). For the first time, by treating the fabricated SiNWs with copper containing HF∕H2O2∕H2O solution, we have generated crystalline nanowires with broader light absorption spectrum, up to λ = 1 μm. Both the absorption and photo-luminescence (PL) of the SiNWs are observed from visible to IR wavelengths. It is found that the SiNWs have PL at visible and near Infrared wavelengths, which may infer presence of mechanisms such as forbidden gap transitions other can involvement of plasmonic resonances. Non-radiative recombination of excitons is one of the reasons behind absorption of SiNWs. Also, on the dielectric metal interface, the absorption mechanism can be due to plasmonic dissipation or plasmon-assisted generation of excitons in the indirect band-gap material. Comparison between nanowires with and without metallic nanoparticles has revealed the effect of nanoparticles on absorption enhancement. The broader near IR absorption, paves the way for applications like hyperthermia of cancer while the optical transition in near IR also facilitates harvesting electromagnetic energy at a broad spectrum from visible to IR.


1994 ◽  
Vol 04 (C4) ◽  
pp. C4-573-C4-577 ◽  
Author(s):  
Y. KALISKY ◽  
S. R. ROTMAN ◽  
G. BOULON ◽  
C. PEDRINI ◽  
A. BRENIER

1993 ◽  
Vol 329 ◽  
Author(s):  
Frederick G. Anderson ◽  
H. Weidner ◽  
P. L. Summers ◽  
R. E. Peale ◽  
B. H. T. Chai

AbstractExpanding the crystal field in terms of operators that transform as the irreducible representations of the Td group leads to an intuitive interpretation of the crystal-field parameters. We apply this method to the crystal field experienced by Nd3+ dopants in the laser crystals YLiF4, YVO4, and KLiYF5.


2015 ◽  
Vol 7 (3) ◽  
pp. 1923-1930
Author(s):  
Austine Amukayia Mulama ◽  
Julius Mwakondo Mwabora ◽  
Andrew Odhiambo Oduor ◽  
Cosmas Mulwa Muiva ◽  
Boniface Muthoka ◽  
...  

 Selenium-based chalcogenides are useful in telecommunication devices like infrared optics and threshold switching devices. The investigated system of Ge5Se95-xZnx (0.0 ≤ x ≤ 4 at.%) has been prepared from high purity constituent elements. Thin films from the bulk material were deposited by vacuum thermal evaporation. Optical absorbance measurements have been performed on the as-deposited thin films using transmission spectra. The allowed optical transition was found to be indirect and the corresponding band gap energy determined. The variation of optical band gap energy with the average coordination number has also been investigated based on the chemical bonding between the constituents and the rigidity behaviour of the system’s network.


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