scholarly journals Linear and Nonlinear Intersubband Optical Properties of Direct Band Gap GeSn Quantum Dots

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 124 ◽  
Author(s):  
Mourad Baira ◽  
Bassem Salem ◽  
Niyaz Madhar ◽  
Bouraoui Ilahi
Keyword(s):  
Quantum Dots ◽  
Refractive Index ◽  
Absorption Coefficient ◽  
Electron Energy ◽  
Energy State ◽  
Total Absorption ◽  
Absorption Coefficients ◽  
Third Order ◽  
Index Changes ◽  
Total Absorption Coefficient

Intersubband optical transitions, refractive index changes, and absorption coefficients are numerically driven for direct bandgap strained GeSn/Ge quantum dots. The linear, third-order nonlinear and total, absorption coefficients and refractive index changes are evaluated over useful dot sizes’ range ensuring p-like Γ-electron energy state to be lower than s-like L-electron energy state. The results show strong dependence of the total absorption coefficient and refractive index changes on the quantum dot sizes. The third order nonlinear contribution is found to be sensitive to the incident light intensity affecting both total absorption coefficient and refractive index changes, especially for larger dot sizes.

scholarly journals Gamma?Radiation Absorption Coefficients of Various Materials Allowing for Bremsstrahlung and Other Secondary Radiations

1961 ◽  
Vol 14 (4) ◽  
pp. 443 ◽  
Author(s):  
JW Allison
Keyword(s):  
Absorption Coefficient ◽  
Energy Loss ◽  
Basic Assumption ◽  
Radiation Energy ◽  
Radiation Absorption ◽  
Annihilation Radiation ◽  
Total Absorption ◽  
Absorption Coefficients ◽  
Radiation Energy Loss ◽  
Total Absorption Coefficient

Existing calculations of the total absorption coefficient are generally based on the assumption that all the primary radiation energy which is converted into Comptonscattered radiation escapes from the material without significant absorption. This paper extends this basic assumption to include fluorescent and annihilation radiation and bremsstrahlung, and new values of the photoelectric, Compton, pair production, and total absorption coefficients are determined in the energy range O� 01-100 MeV for hydrogen, nitrogen, oxygen, argon, aluminium, iron, lead, air, and water. For comparison purposes revised values of the total absorption coefficient, allowing for the Compton radiation energy loss only, are also determined for these materials, using the most recent data for the component coefficients.

Nonlinear Intersubband Optical Absorption Coefficient and Refractive Index Changes in Asymmetric Parabolic Double Quantum Wells

2017 ◽  
Vol 6 (1) ◽  
pp. 121-125 ◽  
Author(s):  
Menberu Mengesha Woldemariam
Keyword(s):  
Refractive Index ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Quantum Wells ◽  
Optical Absorption Coefficient ◽  
Double Quantum ◽  
Absorption Coefficients ◽  
Total Change ◽  
Left Handed ◽  
Index Changes

The change in optical absorption coefficients and refractive index in GaAs-AlGaAs asymmetric parabolic double quantum wells (DQWs) with applied electric field are studied in detail. Analytical expressions for the linear, nonlinear and total intersubband absorption coefficient and refractive index changes are obtained by using compact density matrix approach. It is found that the magnitude of the nonlinear part of the change in refractive index and absorption coefficients are larger than the linear part in the given frequency region. The value of the total change in refractive index is negative and the asymmetric DQWs becomes left handed media. This property is of great importance for metamaterials science and can contribute substantially to the present search for simple and inexpensive left handed media. Moreover the negative value of the total change in absorption coefficient may be used for developing optical device such as maser at different frequency regime.

Optical properties of an exciton trapped by an ionized donor in ellipsoidal quantum dots under electric field and hydrostatic pressure

2019 ◽  
Vol 33 (12) ◽  
pp. 1950108 ◽  
Author(s):  
Lei Shi ◽  
Zu-Wei Yan
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Perturbation Theory ◽  
Hydrostatic Pressure ◽  
Electric Field ◽  
Absorption Coefficients ◽  
Third Order ◽  
Ellipsoidal Quantum Dot ◽  
Index Changes ◽  
Shape And Size

The optical properties of an exciton trapped by an ionized donor in an ellipsoidal quantum dot (QD) with both oblate and prolate shapes under applied electric field and hydrostatic pressure have been studied. We have calculated the linear and third-order nonlinear absorption coefficients (ACs) and refractive index changes (RICs) by using a variational method within the perturbation theory. The results show that the QD shape and size have a significant influence on the positions and magnitudes of the peaks of the (ACs) and RICs, moreover, the influence of hydrostatic pressure and electric field under different QD shape is also different.

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