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Abstract In this present work a detailed theoretical study on the influence of the static electric, magnetic, and non-resonant intense THz laser fields on the nonlinear optical properties such as nonlinear optical rectification (NOR) and second harmonic generation (SHG), of a quantum well that has the Woods-Saxon potential profile. The static electric and high-frequency intense THz laser fields are applied along the growth-direction of the structure whilst the static magnetic field is applied perpendicular to them. The outcome of the numerical calculation demonstrates that, both the peak potions of the NOR and SHG coefficients exhibit a blue-shift with the increment of the static electric and magnetic fields, but their peak amplitudes increases with the magnitude of the electric field whilst decreases with the magnitude of the magnetic field. However, the peak positions of the NOR and SHG coefficients exhibit firstly a blue-shift, and then a red-shift with the increment of the laser intensity, but their peak amplitudes increases. We hope that these theoretical results will be useful for designing new optoelectronic devices with a performance tailored by the adjustment of the applied fields. Highlights • The magnitude of the NOR and SHG increase with the static electric field and ILF. • The magnitude of the NOR and SHG decrease with the static magnetic field. • The applied external fields have to important effects on the optical properties of Woods-Saxon QW. [ABSTRACT FROM AUTHOR]

Abstract In the present paper, we theoretically investigate the effect of applied external fields, such as electric, magnetic, and intense terahertz laser fields on the optical absorption and the relative refractive index change coefficients of triple δ -doped quantum well structures. To investigate the applied external field effects, we perform the calculation of the allowed subband energy levels and their corresponding eigen-functions using the diagonalization method within the framework of the effective-mass approximation. The effects of the applied external fields on the nonlinear optical properties of the quantum well structure are treated within the compact-density-matrix approach via the iterative method. The numerical results obtained are presented for two different values of electric, magnetic, and intense terahertz laser fields. These results show that changing the intensity of the external electric, magnetic, and intense terahertz laser field. It is concluded that the nonlinear optical response of the triple δ -doped structure can be significantly changed through the changes in the configuration of the external probes. [ABSTRACT FROM AUTHOR]

Tb3+ doped GeO 2 -Na 2 O glasses have been fabricated by conventional melt quenching technique using 0.3, 1, 3, and 5 %mol of terbium ions. The optical properties were studied by means of steady-state photoluminescence (excitation and emission spectra), and emission decay time. Under excitation of 355 nm and as the concentration of dopant increases, the glasses show an enhancement of the emission intensity from 5D 4 level accompanied by a decrease on the emission intensity from 5D 3 level. This phenomenon can be attributed to an energy transfer process that occurs through cross-relaxation mechanisms between Tb3+ ions. The aim of this study is to report an experimental technique to study the cross-relaxation of 5D 3 level decay curves of Tb3+ ions under simultaneous temporal and spatial pulsed excitation using UV and visible light (355 nm + 488 nm), allowing to limit the occurrence of cross-relaxation mechanisms and increase luminescent efficiency. Upon simultaneous UV + Vis excitation, the emission from 5D 3 level in enhanced, as the energy of the 488 nm pulse is increased. Additionally, the energy transfer efficiency between Tb3+ ions was analyzed with the Inokuti-Hirayama (IH) model, as function of the excitation pulse energy at 488 nm, keeping fixed the energy of the 355 nm pulse, determining a dipole–dipole interaction as the dominant interaction mechanism. [ABSTRACT FROM AUTHOR]

Abstract: In this work we are studying the intense laser effects on the electron-related linear and nonlinear optical properties in GaAs–Ga1−x Al x As quantum wells under applied electric and magnetic fields. The calculated quantities include linear optical absorption coefficient and relative change of the refractive index, as well as their corresponding third-order nonlinear corrections. The nonlinear optical rectification and the second and third harmonic generation coefficients are also reported. The DC applied electric field is oriented along the hererostructure growth direction whereas the magnetic field is taken in-plane. The calculations make use of the density matrix formalism to express the different orders of the dielectric susceptibility. Additionally, the model includes the effective mass and parabolic band approximations. The intense laser effects upon the system enter through the Floquet method that modifies the confinement potential associated to the heterostructure. The results correspond to several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation. They suggest that the nonlinear optical absorption and optical rectification are nonmonotone functions of the dimensions of the heterostructure and of the external perturbations considered in this work. [Copyright &y& Elsevier]

Abstract: A study of the electronic and optical properties of coupled double quantum wells is presented. Within the framework of the effective mass and parabolic-band approximations we have calculated the electron–hole and photoluminescence energy transitions under simultaneous effects of electric and magnetic fields. For that purpose, a variational procedure has been used, taking into account the effect of hydrostatic pressure. The electric field is taken to be oriented along the growth direction of the heterostructure whereas for the magnetic field both in-plane and in-growth directions have been considered. The results show that hydrostatic pressure is a useful tool to tune the direct and indirect exciton transitions in such heterostructures. It is shown that the photoluminescence peak energy transitions strongly depend on the external fields and hydrostatic pressure studied here. Furthermore, our numerical outcome is in good agreement with previous experimental findings at zero pressure in double quantum wells under applied electric and magnetic fields. [Copyright &y& Elsevier]

The purpose of this paper is to present a new spectroscopic experimental technique to study the contributions of the different cross-relaxation mechanisms observed in Dy3+ doped TeO 2 -GeO 2 -ZnO glasses, based on the luminescence decay curves from 4F 9/2 → 6H 13/2 (at 573 nm) transition of Dy3+ ions under spatial and temporal simultaneous UV (6H 15/2 → 6P 7/2) and IR (6H 15/2 → 6F 3/2, 6H 15/2 → 6H 7/2 and 6H 15/2 → 6H 9/2) excitations, for which the results are reported. The spectroscopic characterization was carried out through Raman, optical absorption, luminescence decay time profiles, and energy transfer as a function of Dy3+ ions content (0.5–5%). Emission spectra measurements indicated that concentration quenching is active in the samples. The lifetime decay of emission at 573 nm (4F 9/2 level) was studied under excitation at 355 nm. At lower concentration of Dy3+, the temporal behavior of the emission at 573 nm is exponential, however, it becomes non-exponential as the concentration increases. The emission decay curves at 573 nm were fitted to Inokuti-Hirayama model and an energy transfer process dominated by an electric dipole-dipole interaction was deduced. A shortened lifetime was observed as the dysprosium ion content increased, which is attributed to non-radiative energy transfer between Dy3+ ions through the cross-relaxation mechanism. The analysis of the 4F 9/2 → 6H 13/2 (573 nm) emission decay s , obtained under simultaneous excitation at 355 nm and at different infrared excitations 6H 15/2 → 6F 3/2 (905 nm), 6H 15/2 → 6H 7/2 (1100 nm) and 6H 15/2 → 6H 9/2 (1285 nm), allowed the determination of the dominant process in the cross-relaxation mechanism at high and low concentrations of Dy3+. It was possible to infer that in the glass with low concentration of Dy3+ the mechanism occurs predominantly by 4F 9/2 + 6H 15/2 → 6F 11/2 + 6F 3/2 channel, and for high concentration of Dy3+, the channels 4F 9/2 + 6H 15/2 → 6F 11/2 + 6F 3/2 , F 9/2 + 6H 15/2 → 6F 5/2 + 6F 9/2 + 5H 7/2 , and 4F 9/2 + 6H 15/2 → 6F 3/2 + 6F 11/2 + 5H 9/2 have a similar contribution to the Dy3+-Dy3+ resonant energy transfer. Image 1 [ABSTRACT FROM AUTHOR]

We explore the impact of external fields on the absorption coefficients and relative refractive index changes in a quantum cascade laser profile-like heterostructure that consists of a triple asymmetric quantum well. Firstly, we solve numerically the time-independent Schrödinger equation by using the diagonalization method under the effective mass and parabolic band approaches, to obtain the energy levels and wavefunctions. Then, we evaluate the optical coefficients from the analytical expressions derived from the compact density matrix method. The obtained results put forth that the resonant peaks of optical coefficients shift to higher (lower) energies by increasing the value of the electric (magnetic) field. These results indicate that it would be possible to adjust the optical properties of these structures to the desired range with external fields. As a result, we hope that new optoelectronic devices based on asymmetric triple quantum wells can be developed using the features found here. [ABSTRACT FROM AUTHOR]

The simultaneous effect of static electric and magnetic fields as well as the intense THz laser field on the intersubband nonlinear optical properties of n-type asymmetric triple δ -doped quantum well is theoretically investigated. The calculations are carried out within the framework of the effective-mass and parabolic-band approximations, with the use of a diagonalization technique to determine the electron energies and the wave functions. The analytical expression of the total absorption coefficient and the relative refractive change of the structure have been found by using the compact-density-matrix approach via an iterative method. The obtained results show that the strengthening of the electric and the magnetic fields, as well as the increment of laser field parameter, lead to a blue shift of the resonant peaks of the intersubband optical absorption and the relative refractive index change spectrum. Additionally, the strengthening of the external fields leads to the reinforcement of the total absorption spectrum intensity. Finally, we have found that with the decrease in the number of the well, by keeping the effective width of the structure constant, the blue shift can be observed in the total absorption spectrum. Therefore, the obtained results give an additional possibility to tune the performance of new devices, based on the quantum wells nanostructures. [ABSTRACT FROM AUTHOR]

Being relevant to the field of device applications, multiple semiconductor quantum wells are systems that exhibit remarkable optical and electronic properties. These can be properly tuned by suitably modifying the composition, structural parameters, and the application of external probes. Here, the electronic and optical properties of a GaAs/GaAlAs triple quantum well have been investigated under the influence of applied electric and magnetic fields, as well as the change of well and barrier widths. We have used the diagonalization method to numerically solve the Schrödinger equation under the effective mass approximation for obtaining the subband energy levels and related electronic wave functions. The expressions used for evaluating linear, third-order nonlinear, and total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) were previously derived within the compact density matrix method. According to our results, whilst an increment in the applied electric field causes a red shift in TOACs and RRICs, a blue shift of the optical responses occurs with increasing the applied magnetic field. Besides, a blue shift is observed as well by changing the width of the central well (L w L), whilst a red shift is noticed when changing left and right wells (L w L and L w R) and barrier (L b L and L b R) widths for zero fields. We believe that our study could make a contribution to designing new quantum-well-based optoelectronic devices. [ABSTRACT FROM AUTHOR]

Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure. [ABSTRACT FROM AUTHOR]

Abstract: Optical properties like transmission, omnidirectional reflection and localization of modes are theoretically investigated in hybrid periodic/quasiregular dielectric heterostructures based on porous silicon. It is shown that the fabrication of this class of multilayers would lead to an improvement of the formation of microcavities, the widening of the incidence angular interval for total reflection as well as the appearance of spatial localization of electric field intensity within specific regions of the structures. [Copyright &y& Elsevier]

We present a theoretical simulation of the impact of applied external electric and magnetic fields, as well as of the change in structure parameters, on the nonlinear optical rectification (NOR), second harmonic generation (SHG), and third harmonic generation (THG) in typical GaAs/GaAlAs asymmetric double graded quantum wells (ADGQWs). At first, we have calculated the wave functions and the subband energy levels for the lowest bounded four states confined within the structure by solving the Schrödinger equation using the diagonalization method within the framework of the effective mass and single parabolic band approximations. Then, analytical expressions for the NOR, SHG, and THG that arise from the compact density matrix approach are used to evaluate the corresponding coefficients. The simulation results show that the applied external fields and the structure parameters play an important role in the optical properties of ADGQWs. • The impact of applied external electric and magnetic fields, and change in structure parameters in typical GaAs/GaAlAs ADGQWs. • The wave functions and the subband energy levels for the lowest bounded four states are confined within the structure. • Schrödinger equation solution using diagonalization method within the framework of effective mass and single parabolic band approximations. [ABSTRACT FROM AUTHOR]

In this present work, the effect of applied external fields and well width on the optical absorption and refractive index change coefficient of a GaAs quantum well with Razavy confinement potential is theoretically presented. For this, firstly, the confined subband energy levels of the structure and the envelope wave functions corresponding to these states have been computed using the diagonalization method within the framework of effective mass and parabolic band approximation. Then, by using this information, the coefficients of total – linear plus nonlinear – intersubband optical absorption (TOAC) and relative refractive index changes (RRIC) of the structure are evaluated. The obtained numerical results show that the increase in the magnitude of the applied external fields creates a blue shift in TOAC and RRIC. Also, contrarily to the applied external fields, an increment of the quantum well width have induced a red shift in the TOAC and RRIC. We discuss in detail the variation of the diagonal matrix elements and the energy difference (E2–E1) which are responsible for the change of amplitudes of the calculated coefficients. We believe that the obtained numerical results can be useful in the design and application of the next generation devices used in the optoelectronics field. • The magnitude of the TOACs peak decrease with the static electric field. • The magnitude of the TOACs peak increase with the ILF. • The magnitude of the RRICs decrease with the ILF. • The increase of ILF leads to important effects on the optical properties of Razavy QW. [ABSTRACT FROM AUTHOR]

In this study, the influence of structure parameter (η) and intense laser field (ILF) on the optical properties such as the nonlinear optical rectification (NOR) coefficient, second and third harmonic generation (SHG and THG) coefficients related to intersubband transitions in a quantum well with Morse confinement potential are theoretically studied. The energy levels and corresponding wave functions of the system are obtained by solving the one-electron Hamiltonian within the framework of the effective-mass, parabolic-band approximations and Kramers-Henneberger (KH) transformation. The optical properties of the structure are calculated through the compact density matrix approach. Numerical calculations are brought out for a typical GaAs quantum well. The results unveil significant influences of ILF and structure parameters of Morse confinement potential on resonant peak position and peak intensity of the NOR, SHG and THG coefficients. • The magnitude of the NOR increase with the ILF. • The magnitude of the SHG and THG increase with the ILF. • The ILF have to important effects on the optical properties of Morse QW. [ABSTRACT FROM AUTHOR]

In the present study, we present numerical results for the influence of non-resonant intense THz laser radiation as well as the structure parameters, such as well width and central doping concentrations, on the total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) in n -type asymmetric triple δ -doped G a A s quantum well (QW) by using the compact-density-matrix formalism via iterative method. In order to obtain these numerical results, we have first obtained the subband energy spectrum and the electronic wave functions of the structure by using the effective-mass and parabolic band approximation. We have then calculated the nonlinear optical (NLO) properties of the system, by employing these energy eigenvalues and eigenfunctions. The numerical results for these calculations show that; (i) the magnitude of the resonant peak of TOACs decreases and the peak position shifts towards the lower energies when the central doping concentration and the well width are increased; (ii) due to the intense laser field effect, the magnitude of the TOACs resonant peak initially increases and its position shifts towards higher energies and then it decreases, shifting towards lower energies; (iii) by increasing the central doping concentration (well width), the magnitude of the resonant peak of RRICs increases (decreases), and the resonant peak position shifts towards the lower energies; and finally (iv) because of the increase in the intensity of the laser field applied to the structure, the magnitude of the resonant peak of RRICs increases, and the resonant peak position initially shifts towards the higher energies and then shifting towards the lower energies. • The magnitude of the TOACs decrease with the central doping concentration. • The magnitude of the TOACs and RRICs decrease with the well width. • The ILF have to important effects on the optical properties of n-type ATDD QW. [ABSTRACT FROM AUTHOR]

In the present paper, we report a theoretical investigations on the linear and nonlinear optical properties of a GaAs-based quantum well with the Kratzer-Fues confining potential, including the effects of external applied static electric, magnetic, and intense THz laser fields. The electronic structure of this system is obtained by using the effective-mass and envelope wave function approaches. Then, the coefficients of linear, third-order nonlinear, and total optical absorption (OACs) and relative refractive index changes (RICs) are calculated by using the iterative solutions of the compact-density matrix approach (CDMA). The obtained numerical results are reported as functions of the incident photon energy taking into account several values of static electric, static magnetic, and intense THz laser fields. These results show that the nonlinear optical properties of this structure are significantly affected by the magnitude of the external applied fields. [ABSTRACT FROM AUTHOR]

In this study, we use density functional theory to calculate the optical and electronic properties of a black-phosphorene/MoS 2 stack. We have considered different exchange–correlation functionals to account for the effects of van der Waals interaction and examined the impact of stacking order/layers alignment on the opto-electronic properties. Our findings reveal that the heterostructure exhibits a reduction in band gap and a modification of optical properties compared to single monolayers. The optical response was evaluated using an independent particle approximation to get the dielectric function's imaginary part, which showed a strong absorption peak in the visible and ultraviolet regions. This feature could be helpful for optoelectronic applications. Nonetheless, the stacking order has a negligible effect on the electronic and optical properties of the BP/MoS 2 bilayer. [Display omitted] • Phosphorene/MoS 2 exhibits different properties compared with monolayers. • The dielectric function has a broad spectrum of energies. • Phosphorene/MoS 2 exhibits appealing properties for optoelectronic applications. • Stacking order induced negligible modifications in optoelectronic properties. [ABSTRACT FROM AUTHOR]

The donor-impurity-related optical absorption, relative refractive index changes, and Raman scattering in GaAs cone-like quantum dots are theoretically investigated. Calculations are performed within the effective mass and parabolic band approximations, using the variational procedure to include the electron-impurity correlation effects. The study involves 1 s -like, 2p x -like, and 2p z -like states. The conical structure is chosen in such a way that the cone height is large enough in comparison with the base radius thus allowing the use a quasi-analytic solution of the uncorrelated Schrödinger-like electron states. [ABSTRACT FROM AUTHOR]

In the present study, the effects of electric and magnetic fields on the linear and third-order nonlinear optical absorption coefficients and relative change of the refractive index in asymmetric GaAs/GaAlAs double quantum wells under intense laser fields are theoretically investigated. The electric field is oriented along the growth direction of the heterostructure while the magnetic field is taken in-plane. The intense laser field is linear polarization along the growth direction. Our calculations are made using the effective-mass approximation and the compact density-matrix approach. Intense laser effects on the system are investigated with the use of the Floquet method with the consequent change in the confinement potential of heterostructures. Our results show that the increase of the electric and magnetic fields blue-shifts the peak positions of the total absorption coefficient and of the total refractive index while the increase of the intense laser field firstly blue-shifts the peak positions and later results in their red-shifting. [ABSTRACT FROM AUTHOR]

The results of calculation of intersubband absorption coefficients for either center-, or edge-delta-doped with Phosphorus 10 nm and 20 nm-wide Si 0.8 Ge 0.2 /Si/Si 0.8 Ge 0.2 quantum wells are presented. It is shown, that the absorption for delta-doped structures differs substantially from that of a pure rectangular or uniformly doped ones. There are two main features for delta-doped quantum wells. The first one is the blue-shift for optical transitions between first and others (more pronounced), and second and others (less pronounced) space quantized energy levels. The second one is that edge doping changes the symmetry of the quantum well and forbidden optical transitions for the rectangular structure become now allowed. The influences of temperature, quantum well width, and impurity concentration on the optical absorption are studied. It is shown that the most dramatic changes in comparison with rectangular quantum wells are for wider investigated edge-doped structures with bigger number of ionized impurities. [ABSTRACT FROM AUTHOR]

Abstract: In this present study, we have theoretically investigated the effects of hydrostatic pressure and temperature on the nonlinear optical properties in a typical GaAs/Ga0.7Al0.3As parabolic quantum well under the intense laser field. The energy levels and wave functions are calculated using the effective mass approximation and optical properties are obtained using the compact density-matrix approach. The numerical results show that the confinement potential and the energy difference depend strongly on the intense laser field but weakly on the hydrostatic pressure and temperature. Additionally, it has been found that the linear and nonlinear optical properties in a GaAs/Ga0.7Al0.3As parabolic quantum well under the intense laser field can be tuned by changing the hydrostatic pressure and temperature. [Copyright &y& Elsevier]

Simultaneous effects of electric, magnetic, and non-resonant intense laser field on the nonlinear optical properties of a GaAs quantum well with an anharmonic confinement potential profile are theoretically investigated. Energy eigenvalues and eigenfunctions of the system are determined using the diagonalization method within the framework of the effective mass and parabolic band approximation. Nonlinear optical properties associated to the inter and intra band transitions are evaluated. Our numerical results for the intra-band response show that the resonance peak positions of the total optical absorption coefficients and relative refractive index changes shift towards higher energy levels (blueshift) by increasing the strength of the applied external electric, magnetic, and non-resonant intense laser field. The analysis of inter-band (electron-heavy hole) transitions reveals that the optical coefficients has a pronounced redshift induced by the electric field while a blueshift is caused by the magnetic and laser signals. It is seen that the nonlinear optical properties of such structures can be adjusted according to the purpose by changing the external perturbations and could be used in new optoelectronic device designs. [ABSTRACT FROM AUTHOR]

In this work, we have investigated theoretically the impact of intense laser, electric and magnetic fields on the linear and nonlinear optical properties of a quantum well heterostructure containing triple parabolic barriers (GaAs/AlGaAs). Within the framework of the effective-mass and parabolic band approximations, we have computed the confined lowest energy levels and their corresponding densities of probability, through the use of a finite difference technique to solve the corresponding differential equation. Besides, we evaluate the total optical absorption (TOACs) and relative refractive index change (RRICs) coefficients. The obtained findings show that an increase of the intensity of the intense laser field produces a blue shift at first and then a red shift of the TOACs and RRICs. A specific value of the laser field separating the two kinds of signal displacements is outlined. Contrarily to the intense laser field, an increment of the external static electric and magnetic fields induces only a blue shift in the variation of the TOACs and RRICs. In addition, we have discussed in detail the variation of diagonal and non-diagonal matrix elements which are responsible on the variation of the amplitudes of the TOACs and RRICs. We think that the obtained results can be useful in the design of new device's generation employed in optoelectronic domain. [ABSTRACT FROM AUTHOR]

The asymmetric potential profiles are of great interest from the nonlinear optical properties point of view for semiconductor devices. The reason for this statement is because the existing theories on nonlinear optical properties obviously depends on the dipole matrix element for the involved transitions and an complete characterization for asymmetric potential profiles enables to the semiconductor device designers to have possible ranges of implementation and because the dipole matrix elements strongly depends on the asymmetry of the potential profile. Once the potential profile is well defined, with the desired range on operation, the external factors play also an important role on the optical properties tuning. In particular, in this paper we reported the absorption coefficient and the relative refractive index changes for semi-infinite inverse Gaussian-like profile for an Al x Ga 1− x As/GaAs quantum well when is subjected to a z -directed electric field, to an in-plane x -directed magnetic field and finally to a non-resonant intense laser field effect, being the Al concentration the parameter that allows to shape the potential profile. In general, we conclude that the external factor are an efficient way to tune the optical properties that are in the range of the THz spectrum, at least for the intersubband transitions reported here. • The semi-infinite inverse Al x Ga 1− x As/GaAs Gaussian-like profile is investigated. • Electric and magnetic fields induce a blueshift for optical properties in this system. • The non-resonant intense laser field produces a redshift for optical properties. • Intra-band optical properties are in the THz region of the electromagnetic spectrum. • Optical properties could be tuned by combined effects of the studied external fields. [ABSTRACT FROM AUTHOR]

• The BPO with adsorbed gas could be employed as gas sensor. • The O2 induced the transition from semiconductor to conductor of the BPO. • The single oxygen vacancy turns out to be more favorable for adsorption. We report a first-principles study of the electronic and optical properties of BPO (Blue phosphorene oxide) and BPO-V (Blue phosphorene oxide with vacancy) with the adsorption of low molecular weight gases (CH 4 , CO 2 , CO, SO 2 , and O 2). Blue phosphorene oxide -with and without vacancies- shows different optoelectronic compared to blue phosphorene. The BPO has proven to be more energetically, and structurally stable than blue phosphorene under ambient conditions. Our calculations show that: Blue phosphorene oxide -with and without vacancies- exhibits different optoelectronic compared to blue phosphorene. Physical adsorption occurs for all gas molecules. Highest values of adsorption energy are found when the monolayers interact with O 2 and SO 2. This is associated with a modification of conducting nature, which is changed from semiconductor to conductor character, depending on the orientation of adsorbed molecules. By contrast, the coupling with CO and CO 2 molecules leads to the lowest values of the energy of adsorption. The observed features of the electronic properties and optical response of BPO + adsorbed-gas complexes allow to suggest that this phosphorene-based structures could be promising candidates for gas sensing applications. [ABSTRACT FROM AUTHOR]

• DFT-based first principles calculation. • Electronic structure and optical properties of CuGaSe2. • Effects of uniaxial and biaxial strain. • Variation of refractive index with strain. In this study, we have investigated the effect of bi-axial, ϵ ab , and uni-axial, ϵ c , strains on the optoelectronic properties of chalcopyrite semiconductor CuGaSe 2 through first-principles full potential linearized augmented plane wave method. These materials have recently attracted much interest within the materials science community. The results are obtained in the framework of Density Functional Theory (DFT), using the Generalized Gradient Approximation based on the minimization of total energy, together with the modified Becke-Johnson exchange-correlation potential, as implemented in the WIEN2k code. Our results show that unstrained CuGaSe 2 is a direct band gap semiconductor with a energy of 1.16 eV, thus improving the results of some previous DFT calculations, but still below the accepted experimental data. The incorporation of biaxial and uniaxial strain results in a monotonous decreasing behavior of the energy band gap when both ϵ ab and ϵ c change between -8% and +8%, with unstrained value being, approximately, at the middle of the variation range. It is also found that strain causes modifications in the index of refraction of the material, with modifications of its static value that rank above 10% over the entire range of deformations considered. [ABSTRACT FROM AUTHOR]