Third-order Optical Susceptibility Research Articles

Conversion of preferred crystalline orientation by annealing and its impacts on the structural, electronic, and optical properties of pulsed laser-deposited CdO thin films

The impact of annealing on the preferred crystalline orientation as well as the structural, electronic, and optical properties of pulsed laser-deposited 150 ± 3 nm thick cadmium oxide (CdO) films was studied. X-ray diffraction analysis revealed that the annealed CdO films have smaller crystallite sizes, as their molecules at the grain boundaries possessed enough kinetic energy to rearrange their preferred crystalline orientation between (111) and (200). The atomic force microscopy and field emission scanning electron microscopy analyses revealed an enhancement in the active surface area with optimized grain boundaries by annealing which facilitates gas adsorption/desorption. DC electrical conductivity depends on the annealing process and reveals two different conduction mechanisms. The direct optical energy gap was decreased from 3.41 eV to 2.76 eV by annealing at 473 K which is greater than the theoretical value, i.e. 2.2 eV, for bulk CdO. The findings agree with the Burstein-Moss effect as a result of the increased carrier concentration following the generation of numerous oxygen vacancy sites and Cd interstitials. However, mutual charge carrier-impurity interaction and charge carrier Columb interaction contributed to narrowing the band gap by increasing the annealing temperature. The enhanced values of Urbach energy, optical packing density, dispersion parameters, optical conductivity, dissipation factor, oscillator strength, and lattice dielectric constant supported the effectiveness of the annealing process on tailoring optoelectronic responses in the infrared region for the CdO thin films for use in optoelectronic devices. Moreover, the calculated linear optical susceptibility, and nonlinear constants (i.e. third-order optical susceptibility and nonlinear refractive index) were the highest for CdO films annealed at 473 K. The improved value of the figure of merit, solar material protection factor, and solar skin protection factor for the CdO films, annealed at 473 K supports its use in several photovoltaic applications, including solar cells.

Styrene monomer as potential material for design of new optoelectronic and nonlinear optical polymers: density functional theory study

Using density functional theory, we have studied the intrinsic properties of styrene. First, we determine the optimized structures, structural parameters and thermodynamic properties to make our simulations more realistic to experimental results and check the stability. Second, we investigate optoelectronic, electronic and global descriptors, transport properties of holes and electrons, natural bond orbital analysis, absorption and fluorescence properties. Finally, we study nonlinear optical (NLO) properties: first- and second-order hyperpolarizability, second and third-order optical susceptibilities, hyper-Rayleigh scattering hyperpolarizability, electro-optical Pockel effect, direct current Kerr effects and quadratic refractive index. The bandgap energy E g = 5.146 eV and dielectric constant ε r = 3.062 show that styrene is a good insulator with an average electric field value of 4.43 × 10 8 Vm −1 . Thermodynamic findings show that our molecule is thermodynamically and chemically stable. Electron and hole reorganization energies of 0.393 and 0.295 eV, respectively, show that styrene is more favourable to hole transport than electron transport. Styrene is transparent with linear refractive index n = 1.750 and quadratic n 2 = 1.748 × 10 −20 m 2 W −1 . At the NLO, styrene has a non-zero value of β H R S , which confirms the existence of first-order NLO activity. Globally the study shows that the styrene monomer is suitable for the architecture design of new polymer materials for NLO applications and optoelectronic by functionalization.

Design and realization of plasmonic nanostructures with large third-order optical nonlinearity

We designed an optical structure comprising plasmonic and dielectric materials that exhibits large third-order optical susceptibility and low-power consumption. Finite-difference time-domain simulation results were used to select tightly-packed gold nanosphere (AuNS) film, indium tin oxide (ITO) films, and gold (Au) thin film to construct AuNS/ITO/Au sandwiched nanostructures. Local-field enhancement factors up to 425 and large third-order optical susceptibility (χ(3)) with an amplitude order of 4.4 × 10−2 esu were achieved under an excitation power of 0.1 mW. These χ(3) results are exceptionally high, thereby rendering AuNS/ITO/Au a promising material for future applications in optical switches and related nonlinear optical devices.

Enhanced double resonance Raman scattering in multilayer graphene with broadband coherent anti-Stokes Raman spectroscopy.

Graphene's unique gapless band structure and remarkably large third-order optical susceptibility have drawn significant attention to its nonlinear optical response, particularly in the context of coherent anti-Stokes Raman scattering (CARS). Under the combined influence of phononic and electronic resonances, the CARS response of graphene has been observed to exhibit a distinctive feature of time-resolved dip-to-peak evolution. Here, we report a greatly enhanced double resonance Raman mode beyond the G mode of multi-layer graphene with broadband CARS measurements. The significant difference in the intensity ratio between CARS and SR for this mode may be attributed to the preferential activation of low-frequency phonons in the impulsive stimulated Raman scattering process (ISRS) and a lower dephasing rate. Our results build on a foundation towards a deeper exploration of the coherent Raman response of two-dimensional materials.

Optical, magneto-optical properties and fiber-drawing ability of tellurite glasses in the TeO2–ZnO–BaO ternary system

The presented work is focused on the optical and magneto-optical characterization of TeO2-ZnO-BaO (TZB) tellurite glasses. We investigated the refractive index and extinction coefficient dispersion by spectroscopic ellipsometry from ultraviolet, λ ≈ 0.193 μm, up to mid-infrared, λ ≈ 25 μm spectral region. Studied glasses exhibited large values of linear (n632 ≈ 1.91–2.09) and non-linear refractive index (n2 ≈ 1.20–2.67×10−11 esu), Verdet constant (V632 ≈ 22–33 radT−1m−1) and optical band gap energy (Eg ≈ 3.7–4.1 eV). The materials characterization revealed that BaO substitution by ZnO leads (at constant content of TeO2) to an increase in linear and nonlinear refractive index as well as Verdet constant while the optical band gap energy decreases. Fiber drawing ability of TeO2–ZnO–BaO glassy system has been demonstrated on 60TeO2–20ZnO–20BaO glass with presented mid-infrared attenuation coefficient. Specific parameters such as dispersion and single oscillator energy, Abbe number, and first-/third-order optical susceptibility are enclosed together with the values of magneto-optic anomaly derived from the calculation of measured dispersion of the refractive index.

Determination of optical constants via the single oscillator Drude-Voigt dispersion model in fluoroborate glass for optical lenses: Nonlinear optical properties

In this work, a new fluoroborate (B2O3+AlF3+NaF + CaF2) glass has been fabricated using the melt-quenching technique. Glass sample has been characterized via X-ray diffraction, scanning electron microscope, and optical spectrophotometric measurements for absorption, transmission, and reflection in the range of 350–750 nm. The optical absorption of this transparent glass is used to determine the absorption coefficients, which are then used to estimate the extinction coefficients. The refractive indices as a function of wavelengths are estimated using extinction coefficients and reflectance data of fluoroborate glass. Very important parameters such as density, molar volume, and molar polarizability have been extensively studied. Using these data, fundamental optical parameters such as average oscillator strength (6.42) and inherent absorption wavelength (119 nm) are evaluated using the Drude-Voigt single oscillator model. Compared with previously studied oxide-based glasses, the fluoroborate glass possesses a relatively high refractive index of 1.74 and an Abbe number of 49 in the visible region of 587.6 nm. The relationship between inherent absorption wavelength and Abbe number values is also discussed. Moreover, the values of refractive index and linear optical susceptibility are used to evaluate the third-order optical susceptibility (11.56 × 10−14 esu) and nonlinear refractive index (2.50 × 10−12 esu). These results suggest that fluoroborate glass is a potential material for optical lenses and nonlinear devices in the visible range.

Electronic, nonlinear optical, UV–vis and NBO analysis of methyl methacrylate for optoelectronic and optical applications: DFT study and impact of conformation

Using Density Functional Theory (DFT) and time-dependent DFT (TD-DFT), we studied a compound widely used in daily life, namely: Methyl Methacrylate (MMA) monomer in its two stable isomers, cis-MMA and trans-MMA. The impact of conformation on the optical and electronic properties of MMA was highlighted. Structural parameters and thermodynamic properties were also assessed, and allowed to discuss the stability and reactivity of this compound. In addition, analysis of optoelectronic and electronic properties, global reactivity descriptors, natural bond orbital (NBO), and hole and electron reorganization energies was performed. The absorption and fluorescence properties, as well as the linear and nonlinear optical (NLO) properties of MMA were also investigated. The findings show that MMA is an insulator due to its wide band gap of 6.20 eV. It also exhibits good optoelectronic properties with high average electric field values of about 5.90 × 109 Vm−1 for cis-MMA and 5.42 × 109 Vm−1 for trans-MMA and high electric displacement values of at least 14.65 × 10-2 cm−2 for cis-MMA and 14.33 × 10-2 cm−2 for trans-MMA, suggesting a potential use for the design of piezoelectric and pyroelectric materials. In addition, trans-MMA has a dielectric constant close to that of good insulators; while cis-MMA exhibits a dielectric behaviour close to that of polymeric substances. Further, these materials are thermodynamically stable in its two conformations, with a good reactivity which can lead to good ability of polymerization. The analysis of the UV–vis spectra revealed that both forms of MMA absorb and emit mainly in the UV and that the Stokes shift of MMA is low, reducing its potential use in devices such as solar cells. At NLO level, MMA isomers exhibit weak optical properties such as second- and third-order optical susceptibility and cannot suitable for second and third harmonic generation; however, the conformation enhances second-order NLO response by at least 2 times when moving from cis- to trans-MMA, whereas the third-order response is almost unaffected. In addition, the conformation also affects the electronic and optoelectronic properties of MMA.

Large third-order nonlinear susceptibility of newly synthesized 3-amino-1H-1,2,4-triazolium p-toluene sulfonate (TPTSA) single crystal measured by the open and closed aperture of the Z-scan technique

The researchers employed the Slow Evaporation Solution Technique (SEST) to grow a third-order nonlinear optical 3-amino-1H-1,2,4-triazolium p-toluene sulfonate (TPTSA) crystal and subsequently conducted an X-ray structural examination. The resulting solution's monoclinic structure (P21/c space group) was confirmed and refined using the SHELXS 2018/3 program, and this marks the first instance of a TPTSA single-crystal structure being reported. To further investigate the optical qualities of the TPTSA crystals, including reflectance (R), bandgap (Eg), refractive index (n), and extinction coefficient (K), we utilized a UV–Vis–NIR spectrophotometer, which demonstrated a transmittance of 82%. Moreover, photoluminescence spectrum analysis revealed that the crystal emits light at 294 and 471 nm. Thermal properties of the TPTSA single crystals were also studied, and it was determined that TPTSA remains stable up to 197 °C. A Hirshfeld surface study showed various inter and intra molecular interactions within the TPTSA compound. Based on the crystal's Z-scan parameters, such as absorption coefficient (β = 1.02412 × 10−4 m/W), nonlinear refractive index (n2 = 9.7348 × 10−12 m2/W), and third-order linear optical susceptibility (χ3) of TPTSA, which was found to be 3 × 10−8 esu, it is evident that the nonlinear properties of this crystal make it suitable for third harmonic generation applications. The comprehensive structural analysis and physical characteristics of the TPTSA crystal demonstrate its potential for applications in harmonic generation.

Structural, morphological, and non-linear optical properties of thermally evaporated neodymium doped zinc oxide thin films

The thermal evaporation procedure has been used in the current work to synthesize various compositions of neodymium-doped zinc oxide thin films with varied thicknesses on glass substrates. The Films have a hexagonal wurtzite structure, according to x-ray Diffraction (XRD) study, and the structure has not changed after doping of Neodymium. Raman spectroscopy revealed peaks at 100.49, 331, 434,574, and 581 cm−1 that supported the ZnO phase, and the intensity of the peaks reduced as the number of dopants rose. FTIR analysis verified that Nd had completely dispersed in ZnO. The calculations of the bandgap (Eg) and absorption coefficient (α) are done using absorption spectra. The Z-Scan method has been employed to assess nonlinear optical characteristics for all Nd-doped ZnO thin films. The samples show the change from saturable absorption (SA) to reverse saturable absorption (RSA), the process of focusing to self-defocusing, and vice versa. This is due to the fact that the two-photon process is more potent than the one-photon process. The acquired value of the third-order optical non-linear susceptibility χ (3) is of the order of 10−5 to 10 −6 (e.s.u.) that makes the samples suitable for use in various photonic applications like using as an optical limiter and/or optical switch due to higher values of optical non-linear parameters.

Effective model for studying optical properties of lead halide perovskites

We use general symmetry-based arguments to construct an effective model suitable for studying optical properties of lead halide perovskites. To build the model, we identify an atomic-level interaction between electromagnetic fields and the spin degree of freedom that should be added to a minimally coupled $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ Hamiltonian. As a first application, we study two basic optical characteristics of the material: the Verdet constant and the refractive index. Beyond these linear characteristics of the material, the model is suitable for calculating nonlinear effects such as the third-order optical susceptibility. Analysis of this quantity shows that the geometrical properties of the spin-electric term imply isotropic optical response of the system, and that optical anisotropy of lead halide perovskites is a manifestation of hopping of charge carriers. To illustrate this, we discuss third-harmonic generation.

Hybrid quantum dot-graphene layers with improved optical properties in the terahertz spectrum region

Recently, it has been shown that the graphene plasmonic (GP) effect can enhance the optical properties of quantum dots (QDs) through the Purcell's effect. This can happen when the electromagnetic field is concentrated tightly in a region where the ground state (S-state) and the first excited state (P-state) of electron are present, and the S-to-P transition frequency falls onto the frequency of plasmonic resonance of graphene layers. Here, we use a hybrid composition of graphene layers, consisting of a disk and four L-shaped layers, and a QD aimed to enhance the linear and third-order optical susceptibilities of QD in the terahertz (THz)/far infrared (FIR) spectrum region. Unlike the previous works, where much more graphene layers were used, in this work, we use fewer layers beneath the wetting layer and with a noticeably simpler scheme, we achieve comparable results in transition dipole moments (TDMs) and optical properties. By changing the Fermi's energy of graphene, we could reach 90-fold enhancement for TDM and 8 × 10 3 - and 6 × 10 7 -fold enhancements, respectively, for linear and third-order susceptibilities. Our scheme can noticeably reduce the difficulties in fabricating hybrid graphene-QD systems. • Graphene flakes in nanodisk and L-shaped geometry have been placed in conic-shaped InAs/GaAS quantum dots (QDs). • The emission of QDs has been tuned with graphene plasmonic (GP). • With use of GP effect, S-to-P transition dipole moment (TDM) of QD has been enhanced 120 times. • Linear susceptibility of QD has been multiplied by a factor of 8 × 10 3 . • Third-order susceptibility of QD has been multiplied by a factor of 6 × 10 7 . • GP has been used as a passive method to enhance significantly the optical properties of QDs.

Appreciably optimization of PVA/PVP nanocomposite blend for enhanced optoelectronics properties and multifunctional applications

The optical and electrical properties of PVA/PVP were manipulated by optimizing the blend ratio between those polymers. The (40/60) wt.% of PVA/PVP achieved the lowest energy gap and the highest electrical conductivity. After that, the optical and electrical properties of blend films were engineered using Ni(OAc)2 for enhanced optoelectronic properties. The doping impact on the semicrystalline and molecular structures of the prepared blend was investigated. The optical properties of the doped blend films were examined using optical transmission and absorption spectra measurements. The nonlinear optical parameters such as nonlinear refractive index and third-order optical susceptibility were estimated. The prepared films showed a pronounced laser cut-off performance. The electrical properties of the fabricated films showed a tunable behavior with the variation of doping level. The engineered doped polymer blend films exhibited good sensitivity to visible light with promising values of responsivity and specific detectivity ∼5.89 mA/W, and 4.31 × 109 Jones, respectively.

Estimation of structural and optical properties of transparent PS/ZnO nanocomposite foils for UV shielding and photonic applications

The structural and optical characteristics of polystyrene (PS) and ZnO nanoparticles embedded in polystyrene as polymeric nanocomposite foils (PS/ZnO) were examined. The sol–gel process was utilized to make ZnO nanoparticles with a diameter of less than 50 nm. The solution casting process was used to prepare pure PS and PS/ZnO nanocomposite foils. The PS/ZnO nanocomposite foils were very transparent in the visible region as-synthesized, but due to substantial absorption in the UV area, absorbent peaks were formed at 264 nm and 364 nm, and these foils serve as UV absorbers. X-ray diffractometer (XRD) of ZnO embedded polystyrene nanocomposite foils studied the crystal structure of the flexible foils. Optical properties and optical constants including band gap were studied by transmittance, absorbance, and reflectance spectra that are obtained by UV–Vis spectrophotometer. The Wemple DiDomenico single oscillator model was used to estimate the dispersion energy parameters ([Formula: see text], [Formula: see text], [Formula: see text], optical moments ([Formula: see text], [Formula: see text], the density of states ([Formula: see text]/[Formula: see text]), dispersion of refractive index ([Formula: see text], and plasma frequency ([Formula: see text] of the investigated foils. Semi-empirical relations were used to estimate the nonlinear index of refraction ([Formula: see text] and third-order optical nonlinear susceptibility ([Formula: see text]. PS/ZnO nanocomposite foils operate as UV absorbents and are a promising preference for photonic applications due to their optical characteristics.

Asymmetric encryption by optical Kerr nonlinearities exhibited by electrochromic NiO thin films.

Herein is analyzed how an electric field can induce a band gap shift in NiO films to generate an enhancement in their third-order optical nonlinearities. An electrochromic effect seems to be responsible for changes in absorbance and modification in off-resonance nonlinear refractive index. The optical Kerr effect was determined as the dominant physical mechanism emerging from the third-order optical susceptibility processes present in a nanosecond two-wave mixing configuration at 532 nm wavelength. Absence of any important multi-photonic absorption was validated by the constant trace of high-irradiance optical transmittance in single-beam mode. The inspection of nonlinear optical signals allowed us to propose an exclusive disjunctive logic gate assisted by an electrochromic effect in an optical Kerr gate. Asymmetric encryption by our XOR system with the influence of a switchable probe beam transmittance and electrical signals in the sample was studied. Immediate applications for developing multifunctional quantum systems driven by dynamic parameters in electrochromic and nonlinear optical materials were highlighted.

Linear and Nonlinear Optical Properties of a Doubly Clamped Suspended Monolayer Graphene Nanoribbon Nanoresonator

We studied the optical properties of a hybrid structure that was composed of a semiconductor quantum dot and a doubly clamped suspended graphene nanoribbon nanoresonator. We obtained analytical results for the linear and third-order optical susceptibilities of the hybrid system. The spectrum of the linear susceptibility exhibited a single resonance, and its position depended on the value of the on-resonance exciton energy and the exciton–nanoribbon resonator coupling strength coefficient; the amplitude of the resonance was independent of the values of these parameters. The third-order optical susceptibility spectrum exhibited a sharp resonance arising at low frequencies of the probe field, the position of which depended only on the frequency of the fundamental flexural phonon mode. It also presented a broader resonance arising at higher frequencies of the probe field, the position of which was determined both by the coupling strength coefficient and by the exciton frequency; its amplitude depended solely on the exciton–photon coupling strength.

Modification of the structural, linear and nonlinear optical properties of zinc oxide thin films via barium and magnesium doping

In the current work, the structural, linear and nonlinear optical properties of zinc oxide thin films have been modified via barium/magnesium doping for modern optoelectronic applications. Ba/Mg-doped and undoped ZnO thin films were successfully prepared by the spray pyrolysis route. The surface morphology, structures' modification and structural parameters were explored using a field emission scanning electron microscope, FT-IR spectrophotometer and X-ray diffraction techniques, respectively. The XRD analysis shows that Ba/Mg-doped and undoped ZnO thin films possess a crystalline nature with a hexagonal wurtzite structure. The crystallite size of the undoped ZnO nanoparticles is 18.5 nm and varies to 21.4 nm (Ba:ZnO), 23.1 nm (Ba/Mg:ZnO) and 16.4 nm (Mg:ZnO). The optical properties (transmittance, absorbance and reflectance) were measured using a UV–visible spectrophotometer. The optical bandgap (Eg) of ZnO thin film decreases from 3.42 eV to 3.35 eV (Ba:ZnO), 3.25 eV (Ba/Mg:ZnO) and 3.31 eV (Mg:ZnO). The decrease in the Eg values of the doped ZnO films as compared with that of the undoped one is mainly attributed to the created defects and localized states in the bandgap of the host ZnO due to Ba/Mg-doping. Moreover, the major optical parameters (refractive index, distinction coefficient, dielectric constant) are also affected as a result of Ba/Mg-doping. Furthermore, a great effect of Ba/Mg-doping on the nonlinear optical constants (third-order optical susceptibility (χ(3)) and nonlinear refractive index (n2)) and first-order linear optical susceptibility (χ(1) is achieved. The obtained results show that the linear and nonlinear optical properties of ZnO film could be enhanced via Ba/Mg-doping for updated applications in multifunctional modern optoelectronics and high-speed communications.

Non-Linear Optical Properties of Biexciton in Ellipsoidal Quantum Dot.

We have presented a theoretical investigation of exciton and biexciton states for the ground and excited levels in a strongly oblate ellipsoidal quantum dot made from GaAs. The variational trial wave functions for the ground and excited states of the exciton and biexciton are constructed on the base of one-particle wave functions. The energies for the ground and excited levels, depending on the ellipsoidal quantum dot’s geometrical parameters, are depicted in the framework of the variational method. The oscillator strength of the transition from exciton to biexciton states for ground and excited levels is investigated as a function of the ellipsoidal quantum dot’s small and large semiaxes. The third-order optical susceptibilities of ground and excited biexcitons around one-photon and two-photon resonances are calculated as a function of the photon energy. The dependences of third-order optical susceptibilities for the ground and excited levels on the photon energy for different values of the ellipsoidal quantum dot’s semiaxis are revealed. The absorption coefficients in the ellipsoidal quantum dot, both for ground and excited states of exciton and biexciton, are calculated. The absorption coefficients for the ground level of exciton and biexciton for the fixed value of the large semiaxis and for the different values of the small semiaxis are determined. Finally, the two-photon absorption coefficient of the biexciton in the GaAs ellipsoidal quantum dot is computed.

Large third-order optical nonlinear susceptibility in natural dye derived from Clitoria ternatea petal

The third-order nonlinear optical response of Clitoria ternatea (CT) petal’s dye in various solvents were characterized via Z-scan technique with a diode pumped solid state (DPSS) laser at 532 nm. The observations from the closed aperture z-scan showed the dye possess a self-defocusing effect with a negative nonlinear refractive index, n2 with a moderate magnitude of real part of the third-order nonlinear optical susceptibilities, Re χ(3) of the order of 10−10 esu. Open z-scan results showed that the CT dyes samples demonstrate a reverse saturable absorption (RSA) with strong two-photon absorption (TPA) coefficients, β ~ 10−3 cm/W, corresponds to large imaginary parts, Im χ(3) in the order of 10−5 esu. The highest values of n2 and β was observed in CT dye in ethanol and dimethyl sulphoxide, respectively. Not only the linear absorption spectra depends on the type of solvent used, but also the nonlinear characteristics are drastically influenced by it. On the whole, large χ(3) of the dye samples were found to be in order of 10−5 esu. Based on the measured value of nonlinear susceptibility, χ(3), the natural dye derived from CT petals can be a candidate for applications such as optical limiting and switching.

Coupling the graphene plasmonic with terahertz emission of truncated conic-shaped InAs/GaAs quantum dots: A passive approach to enhance the intersubband optical properties

Graphene plasmonic (GP) concentrates the electromagnetic waves in small zones beyond the optical diffraction limit. This effect provides strong interactions of radiation with atomic and molecular systems in the vicinity. Here, in this work, we use GP effect to enhance the intersubband optical response of truncated conic-shaped InAs/GaAs quantum dots (QDs) attached to wetting layer (WL). Monolayer graphene flakes with triangular geometries arranged in various configurations are located in the QDs to intensify the electric field and consequently to couple GP with terahertz radiation of QDs. The results show 120-fold enhancement in S-to-P transition dipole moment (TDM) and 1.3 × 10 4 and 6.5 × 10 7 times enhancements, respectively, in the linear and third-order optical susceptibility of QDs. The optimal QDs are those with height of 5 nm and base length of 10 nm. The results of this work are promising to improve the performance of QD-based lasers, detectors, light emitting diodes (LEDs), etc. • Graphene flakes in triangular geometry have been placed in trancated conic-shaped InAs/GaAS quantum dots (QDs). • The emission of QDs has been tuned with graphene plasmonic (GP). • With use of GP effect, S-to-P transition dipole moment (TDM) of QD has been enhanced 120 times. • Linear susceptibility of QD has been multiplied by a factor of 1.3 × 10 4 . • Third-order susceptibility of QD has been multiplied by a factor of 6.5 × 10 7 .

Phonon-assisted laser-induced third-order optical susceptibility for interband transition in a group II–VI asymmetric quantum well

Exciton–LO phonon interaction of the Fröhlich type is studied in the CdS/CdSe/CdS asymmetric double quantum well under an applied laser field. The intensity of laser effect on the exciton binding energy, oscillator strength, optical transition energies, and third-order harmonic generation are investigated by changing the right well sizes and barrier sizes. The laser-associated confined energies and their corresponding binding energies are brought out with the variation of well sizes. The position-dependent potential is altered by the laser-associated parameter. The laser-field-dependent third-order optical susceptibilities due to interband transitions in the asymmetric well are investigated. The effective Coulomb potential, using the Aldrich and Bajaj polaronic effect, is included in the Hamiltonian. The results show that the laser field considerably affects the confining potential of the quantum well and causes a drastic deformation of the confining potential profile. The obtained optical nonlinearities suffer a redshift in the asymmetric quantum well; also, their peak values are determined by the dipole matrix elements.