Third-order Nonlinear Optical Absorption Coefficients Research Articles

Nonlinear optical properties in AlGaAs/GaAs symmetric coupled quantum wells

Based on the density matrix approach and iterative method, we calculated the analytic forms of linear and third-order nonlinear optical absorption coefficients and refractive index changes for symmetric coupled quantum wells (SCQWs) considering a two-level system, and gave the corresponding numerical results. The calculated results show that the optical properties of SCQWs are significantly better than those of asymmetrically coupled quantum wells, and the optical absorption coefficient and refractive index change are affected by the structure parameters of the SCQWs and the incident optical intensity. Their physical mechanisms are elucidated.

Enhancement of optical limiting performance in nanocrystalline La3+ doped ZnO film

Zn1-xLaxO nanofilms were prepared on the glass substrate at 723K using the chemical spray pyrolysis technique. All deposits are hexagonal wurtzite structures with intense plane along the (101) plane. The films doped with 3% La3+ ion showed the least crystalline size with maximum dislocation density. The surface morphology of the deposits changed from fibrous to needles like structure with increased dopant concentration. Both red and blue shifts of absorption edge were noticed as a function of dopant in highly transparent deposited films. A systematic variation of the extinction coefficient and the refractive index was noticed with the incorporation of La3+ in the deposits. Various defects oriented in the films were confirmed by photoluminescence spectra. However, white light emission was found for 4% doped film. Third-order nonlinear optical absorption coefficient (β), susceptibility (χ3) and refractive index (n2) values are 15 × 10−1cm/W, 6.11 × 10−4esu, and −0.34 × 10−5cm2/W, respectively for 3% doped film. It was noticed that Zn0.97La0.03O nanofilm is a more suitable optical limiter application.

The effect of impurity position and doping concentration on the binding energies and total optical absorption coefficients in a $${\delta }$$-doped quantum well

In this present work, for different impurity position and ionized doping concentrations, we have theoretically investigated the linear, third-order nonlinear, and total optical absorption coefficients corresponding to the $$(1\rightarrow 2)$$ intersubband transitions between the ground and first-excited conduction band states in a single $$\delta $$ -doped GaAs well, with and without the presence of a donor impurity. Impurity binding energies were calculated using the effective-mass and parabolic band approximations within a variational scheme. The linear, third-order nonlinear, and total optical absorption coefficients for the intersubband transitions are calculated within the compact density matrix approach. The obtained results show that adding an impurity positioned at the symmetry center of the well, as well as the increase in the ionized donor concentrations, shifts the total optical absorption coefficients to higher photon energies. However, the off-center positions of impurities together with the varying ionized donor concentrations lead to blue or red shifts in relation to the values of binding energies. The results in this study may be useful for the design and applications of the devices based on the $$\delta $$ -doped structures.

Optical properties of spherical quantum dot in the presence of donor impurity under the magnetic field

In this study, the binding energies of an on-center and off-center hydrogenic donor impurity in a spherical quantum dot with finite confinement potential under an applied external magnetic field are investigated in detail by using the matrix diagonalization method in the effective mass approximation. Depending on the calculated energies and wave functions, the linear, third-order nonlinear and total optical absorption coefficients between the ground and several excited states are examined by the iterative method in the compact density matrix approximation for the two-level system. The combined effect of donor position, magnetic field and dot size on binding energies and optical absorption coefficients is observed. The results show that these effects cause significant changes on donor binding energy and optical absorption coefficients.

Electron-related nonlinear optical properties of cylindrical quantum dot with the Rosen–Morse axial potential

We present a theoretical study on the effects of intense laser field (ILF) and static electric field on the linear and nonlinear optical properties of a cylindrical quantum dot with Rosen–Morse axial potential under the framework of effective mass and parabolic band approximations. This study also takes into account the effects of the structure parameters (η, V1, and R). The analytical expressions of the linear, third-order nonlinear and total optical absorption coefficients (TOACs) and the relative refractive index changes (RRICs) are obtained by using the compact-density-matrix approach. The results of numerical calculations show that the resonant peak position of the TOACs and RRICs shifts towards lower energies and the magnitude of the peak increases with the effect of the static electric field and ILF. In addition, it is observed that while the resonant energies of the TOACs and RRICs of system shift towards the higher (lower) energies with the enhancement of η, V1, they decrease with the augmentation of R. Thus, the findings of this study show that the optical properties of the structure can be adjusted by changing the magnitude of structure parameters and applied external fields.

The effects of hydrostatic pressure and temperature on the nonlinear optical properties of shallow-donor impurities in semiconductors in a magnetic field

We present a theoretical study of the nonlinear optical properties of shallow-donor impurities in semiconductors subjected to magnetic fields, hydrostatic pressures, and intense laser illumination within the Voigt configuration. The donor energy levels and their wave functions are obtained using a combination of nonperturbative and variational methods where intense laser field effects are exactly taken into account through a laser-dressed Coulomb potential (LdCP). The combined effects of radiation and magnetic fields, hydrostatic pressures, and temperatures on the linear, third-order nonlinear, and total optical absorption coefficients (OACs) for the 1s→2p± and 2pz transitions are investigated using a compact density-matrix approach. We find that the transition energies and geometric factors can be increased or decreased by changing external fields via the LdCP or by changing hydrostatic pressures and temperatures. In this way, saturable absorption depends not only on the incident optical intensity but also on the laser field, which is more easily realized in the z-polarization direction. The peak positions and magnitudes of the linear, third-order nonlinear, and total OACs can be effectively adjusted with an appropriate choice of these external perturbations. Moreover, hydrostatic pressures and temperatures affect these OACs in an opposite way. This opens a promising route to design new and efficient impurity-based devices manipulated by external perturbations.

Intersubband transitions in spherical quantum dot quantum well nanoparticle

In this paper, we present results about electronic spectra and optical properties of one-electron spherical quantum dot-quantum well (QDQW) structure. Investigated structure consists of CdSe core surrounded by ZnS shell and caped by infinitely high electron potential barrier which can be a good model for any high enough potential barriers. This specific QDQW structure is determined by CdSe and ZnS properties (effective masses and conductive band offset) and the core size and the shell thickness. We present calculation results for one-electron ground (1s) state and the first excited (1p) state transition. For this transition we have calculated oscillator strengths and linear and third-order nonlinear intersubband optical absorption coefficients for various core and shell size i.e. different CdSe core radii and ZnS barrier thickness. Change in core and shell dimensions induces change in one-electron wave function i.e. electron energy states and localization for both 1s and 1p states. As a result, intersubband 1s–1p transition of this system is greatly dependent on the core and shell size. For very small core radii, less than 0.7 nm, and core radii over 1.5 nm the most probable intersubband transition is 1s–1p, but in the region between 0.7 and 1.5 nm core radii, transitions from 1s to other p states dominates. Investigated properties depend mostly on the core radius. These results connect the dot structure and the optical properties of this particular structure. This behavior is than an illustration of similar systems.

Optical Absorption Coefficient on-center donor impurity in a spherical core/shell quantum dots

The polaronic effect on the linear, third-order nonlinear and total optical absorption coefficients have been calculated in the case of GaAs/AlAs core/shell quantum dot, with the impurity is positioned at the central radial position of the GaAs shell. The calculations are realized in the framework of the effective mass approximation and the numerical results are obtained by using a variational method and an infinite confining potential. The results show that the polaronic effect has a great influence on optical properties of core/ shell quantum dot, he causes a red-shift of the nonlinear optical coefficients associated to light absorption. Also, the polaronic effect is enhanced with the decreasing of quantum dot radius.

Giant and Multistage Nonlinear Optical Response in Porphyrin-Based Surface-Supported Metal-Organic Framework Nanofilms.

Benefitting from the strong intrinsic nonlinear optical (NLO) property of the individual porphyrin molecule, the integration of porphyrin molecules into tightly aligned arrays may lead to intuitively promising high-performance materials of tailorable NLO effect. In order to verify this speculation, we prepare crystalline and highly oriented porphyrin-based surface-supported metal-organic framework nanofilms (SURMOFs) and then characterize their NLO performance. Results reveal that porphyrin-based SURMOFs exhibit the highest saturable absorption (SA) yet recorded with a third-order NLO absorption coefficient up to -10-3 cm/W, about 7 orders stronger than porphyrin solvents in which the porphyrin molecules are disordered, under a certain excitation strength. Further increasing the excitation strength shows that the NLO absorption property of the porphyrin-based SURMOFs can be effectively modulated from SA to reverse saturable absorption, followed by a reemerging SA. The multiple-stage NLO switching is assigned to the interplay of simultaneous one-photon SA, two-photon absorption, and two-photon SA effects. The superior and modulatable NLO property as well as the designable and ordered crystalline structure suggest that porphyrin-based SURMOFs might be employed as a new class of high-performance NLO materials with potential applications in novel optical switches or logic gates to realize the all-optical information process.

The effect of temperature, hydrostatic pressure and magnetic field on the nonlinear optical properties of AlGaAs/GaAs semi-parabolic quantum well

In this paper, we explore the optical properties of AlGaAs/GaAs semi-parabolic quantum well (QW) under different temperature, hydrostatic pressure and applied magnetic field. We calculate the nonlinear optical absorption coefficients and the refractive index changes (RICs) with the compact density-matrix approach and iterative method. Then, within the framework of the effective mass and parabolic-band approximations, the energy eigenvalues and the corresponding wave functions for semi-parabolic QW have been obtained by the finite difference method. The theoretical findings show that (1) the energy spectrum depends strongly on temperature, hydrostatic pressure and applied magnetic field; (2) the linear and third-order nonlinear optical absorption coefficients and the RICs are quite sensitive to temperature, hydrostatic pressure and applied magnetic field. Our study provides a theoretical basis for the fabrication of QW structure.

A theoretical study on the optical properties of a quantum well with short-range bottomless exponential potential

The effects of external applied fields on the electron-related optical nonlinear properties in a short-range bottomless exponential potential quantum well are investigated. The potential profile behaves as inverse square root in the vicinity of the origin and vanishes exponentially toward infinity, supporting a finite number of bound states whose energies and wave functions are determined within the effective-mass approximation. The linear, third-order nonlinear and total optical absorption coefficients (TOACs) as well as the coefficient of relative refractive index changes (RRICs) of the system are calculated from the expressions derived in the framework of the compact density matrix approach. The results obtained after numerical calculations show that with the effect of the static electric and magnetic fields (high-frequency THz laser field), the resonant peak position of the optical response shifts toward higher (lower) energies and the magnitude of the peak increases.

Impurity related optical properties in tuned quantum dot/ring systems

ABSTRACTIn this paper, we explore the linear, third-order nonlinear, and total optical absorption coefficient (OAC) and refractive index change coefficient (RICC) of a GaAs doped quantum dot/quantum ring (QD/QR) with parabolic-inverse squared potential in conjunction with modified Gaussian confinement and taking into account the presence of on-centre shallow donor and or acceptor impurity. Calculations are done via the compact density matrix formalism and the iterative method. The two-dimensional parabolic QD/QR is subjected to uniform magnetic field oriented perpendicularly to the plane of the structure. The energy levels and wave function are derived within the framework of effective-mass and parabolic band approximation. The results exhibit that the OACs and RICC are clearly affected by different parameters of the applied confinement, strength of magnetic field, and the presence of impurity. The variation of confinement potential, nature of impurity, dot radius, cyclotron frequency of the parabolic confinement potential, and geometric parameter of the on-centre repulsive potential lead to either a red-shift or a blue-shift of the resonant peaks of the OACs and of the maximum and minimum of the RICC together with significant variations of the magnitudes of these resonant structures.

Influence of image charges on the impurity-related optical properties of near-surface quantum wells under a transverse electric field

The simultaneous effects of an external electric field and image charges on the hydrogen-like impurity-related optical properties of a GaAs/AlGaAs near-surface quantum well with a parabolic potential have been investigated. The oscillator strengths and the linear and the third-order nonlinear optical absorption coefficients have been investigated as the functions of incident photon energy, impurity position, and electric field strength. Numerical results show that the inclusion of image charges leads to an increase in the oscillator strength of about two times for the system under study. This effect is especially notable for large values of an electric field. It is also shown that the influence of image charges leads to a blue shift and a significant increase in peak values of the total absorption coefficient. Our results show a remarkable dependence of optical properties on both the electric field and the impurity position. We believe that a significant increase in the optical characteristics of near-surface quantum wells due to the influence of image charges should be taken into account in future developments.

Non-linear optical properties of nanoscale elliptical ring-shaped at the presence of Rashba spin–orbit interaction and magnetic field

The significant information about the properties of matter can be described with the interaction between light and matter. On this subject, the effect of the applied magnetic field and structural variation on the optical properties of elliptical and circular GaAs quantum rings at the existence of Rashba spin–orbit interaction (RSOI) have been investigated. The effective mass equation for the system containing RSOI and magnetic flux has been solved in cylindrical coordinate with Matrix Diagonalization method for circular quantum ring and with finite difference method for elliptical quantum ring. Also, the linear and third-order nonlinear optical absorption coefficient (AC) and refractive index changes (RIC) are calculated by density matrix. According to the consequence, the geometry of quantum structure plays a significant role in specifying the AC and RIC which provide the methods for fabricating effective application.

Linear and nonlinear optical absorptions in III–V nitrides quantum well with semi-parabolic confining potential

Linear and third-order nonlinear optical absorptions in III–V nitrides semi-parabolic quantum wells are investigated. The analytical expression of linear and third-order nonlinear optical absorption coefficients is obtained by using compact density matrix approach and iterative method. Our results show that the optical absorption coefficients are strongly influenced by confinement frequency and electric fields. Moreover, the optical absorption coefficients also sensitively depend on the relaxation time of the systems. However, the influences of the involved parameters for the linear optical absorption, third-order nonlinear optical absorption, and the total optical absorption are different.

Numerical modelling of electronic and optical properties of isolated and self-assembled InAs/InP quantum dots

In the present work, we are interested for an isolated and self-assembled InAs/InP quantum dots with a dome cross-section. We have tried to study the electronic and optical properties in the quantum dot by using an efficient and simple method. This numerical method is based on the coordinate transformation and the finite difference method (FDM). The influence of the parameters introduced in the mathematical function, is studied on the size, the shape and the number of the quantum dot. The electron, and heavy hole energy levels as well as their interband transition energies are also investigated. The linear, third-order nonlinear and total interband optical absorption coefficients and refractive index changes are investigated as a function of photon energy with varying height dot (H) and the incident optical intensity (I). The analytical expressions of these optical properties are obtained by using the compact-density matrix formalism.

Impurity-related optical properties of a laser-driven quantum dot

In this paper, we explore theoretically the effect of an on-center Gaussian impurity on the optical properties of a laser-driven parabolic quantum dot system under uniform magnetic field. Laser radiation with circular polarization has been treated within the framework of high-frequency Floquet approach. The linear and third-order nonlinear optical absorption coefficients and refractive index changes have been examined by means of the compact-density matrix approach. Numerical results reveal that the position and magnitude of the resonant peaks of absorption coefficients and refractive index changes are sensitively affected by magnetic field, the depth and the range of the impurity potential. Besides, the presence of intense laser field causes a red-shift in the positions and reduction in the amplitudes of the resonant peaks of optical characteristics.

Impact of electron-LO-phonon correction and donor impurity localization on the linear and nonlinear optical properties in spherical core/shell semiconductor quantum dots

In the present work, the linear, third-order nonlinear and total optical absorption coefficients as well as relative refractive index change have been calculated in the case of GaAs/AlAs core/shell quantum dot, taking into account the effects of the interaction with LO-phonon and the presence and localization of a donor impurity center. Our calculations are performed in the framework of the effective mass approximation and the numerical results are obtained by using a variational method and an infinite confining potential. The results are presented as a function of the incident photon energy. It has been seen that: (i) the polaronic effect causes a redshift of the nonlinear optical coefficients associated to light absorption and relative refractive index change (ii) the polaronic effect is enhanced with the decreasing of quantum dot radius (iii) The donor position effects are particularly significant when the Coulombic center is located at the radial positions D=(RS+RC)/2 and D=RS of the shell, where RC and RS the core and the shell radius respectively.

Absorption coefficient and refractive index changes of a quantum ring in the presence of spin-orbit couplings: Temperature and Zeeman effects

Effects of applied magnetic field, temperature and dimensions on the optical absorption coefficients (AC) and refractive index (RI) changes of a GaAs quantum ring are investigated in the presence of both Rashba and Dresselhaus spin-orbit interactions (SOI). To this end, the finite difference method (FDM) is used in order to numerically calculate the energy eigenvalues and eigenstates of the system while the compact density matrix approach is hired to calculate the optical properties. It is shown that application of magnetic field, temperature as well as the geometrical size in the presence of spin-orbit interactions, alter the electronic structure and consequently influence the linear and third-order nonlinear optical absorption coefficients as well as the refractive index changes of the system. Results show an obvious blue shift in optical curves with enhancing external magnetic field and temperature while the increment of dimensions result in red shift.

Combined effects of the intense laser field, electric and magnetic fields on the optical properties of n-type double δ-doped GaAs quantum well

In the present work, the effects of the non-resonant intense laser field, electric and magnetic fields on the optical properties, such as linear, third order nonlinear and the total optical absorption coefficient and refractive index changes associated with the intersubband transitions between the ground and the first excited states in the n-type double δ-doped GaAs quantum well is theoretically studied by solving the Schrödinger equation in the laser-dressed confinement potential within the framework of effective mass approximation. The analytical expressions of the linear and third-order nonlinear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism. Our numerical results show that the optical absorption coefficient and refractive index change are quite sensitive to the applied external fields, such as non-resonant intense laser field, electric and magnetic fields. The obtained results can be applied for the design of various optoelectronic devices based on the intersubband transitions of electrons.