Nonlinear Optical Absorption Coefficients Research Articles

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.

Linear and nonlinear optical properties of asymmetric triple quantum wells under intense laser field

For asymmetric triple quantum wells (ATQW) the linear and nonlinear optical absorption coefficient (OAC) and the optical refractive index change (ORIC) are analyzed according to the intense laser field (ILF). The obtained results show that the ILF parameter () has an important effect on the shape and height of the confined potential profile of the ATQW, and alterations in the energy levels and the dipole moment matrix elements depend on the shape of the confinement potential. For = 10 nm (according to the parameters used in this study), ATQW turns into an asymmetric wider double confinement potential. As a consequence of the energy difference between the energy states, the absorption spectrum of (1–2) and (1–3) optical transitions initially shows a redshift (up to = 6 nm and = 4 nm, respectively) and then indicates a blueshift by increasing the ILF. For the (2–3) transition, the optical absorption spectrum continuously shows a blueshift and displays an oncoming shift toward the higher energies. Thus, the linear and nonlinear OAC and ORIC may be adjusted by modifying the ILF parameter. Our results are of use in the investigation into new ways of manipulating the optoelectronic properties of triple quantum well devices.Highlights• The electronic and optical properties of ATQW vary with increasing ILF value.• The effect of ILF on the quantum well (QW) differs depending on the shape of the QW.• OAC and ORIC change with rising ILF.• The absorption spectrum shows blueshifts or redshifts depending on the ILF.

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.

Synthesis, growth and characterization of a long-chain π-conjugation based methoxy chalcone derivative single crystal; a third order nonlinear optical material for optical limiting applications

Organic material (chalcone derivative 4-[(1E)-3-(4-methoxyphenyl)-3-oxoprop-1-en-1-yl]phenyl 4-methylbenzene-1-sulfonate {4MPMS}) has been grown by solvent evaporation technique. The structural properties have been carried out by powder XRD and single crystal XRD data. The linear optical properties (band gap, extinction co-efficient, optical conductivity and complex dielectric constant) were studied by UV-VIS-NIR spectrometer. In addition, defect states were identified and analyzed by creation of color center mechanism using photoluminescence spectroscopy. In Thermal analysis, crystal (4MPMS) is found to be stable up to 158 °C. Hence it may be used for the fabrication of device below the melting point. The electrical properties (dielectric constant and dielectric loss factor) have been carried out. The electronic polarizability is the major contribution for the high frequency dielectric constant values. Therefore, using theoretical aspects, the electronic polarizability values were calculated using Clausius–Mossotti relation as well as band structure approach of Penn model. Laser damage threshold for 4MPMS crystal was determined by using Nd:YAG laser with 532 nm. The nonlinear optical absorption coefficient and third order nonlinear optical susceptibility (χ(3)) values are reasonably larger than those of the other chalcone derivative crystals. High second order molecular hyperpolarizability enhances the third order optical nonlinear efficiency. Increased χ(3) and coupling factor (less than 1/3) indicates that the optical nonlinearity is electronic in origin. The behavior of nonlinear optical absorption curve confirms that the mechanism belongs to reverse saturable absorption (RSA).

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.

The third order nonlinear optical properties of graphene oxide–zinc (II) naphthalocyanine hybrids and amino graphene oxide–zinc (II) naphthalocyanine hybrids

Novel tetracarboxylic zinc naphthalocyanine-graphene oxide (ZnNcC4-GO) and tetracarboxylic zinc naphthalocyanine-amino graphene oxide (ZnNcC4-NGO) hybrids have been prepared with a covalent functionalization method. A series of characterizations have been used to prove the structures of ZnNcC4-GO and ZnNcC4-NGO hybrids. The third order nonlinear optical properties were investigated using the Z-scan technique at 532 nm with 4 ns laser pulses. Either ZnNcC4-GO or ZnNcC4-NGO exhibited much larger nonlinear optical absorption coefficients than GO and ZnNcC4 as a result of the covalent link between GO and ZnNcC4. ZnNcC4-NGO hybrids perform the enhanced NLO properties than ZnNcC4-GO, attributed to the increased excited state absorption from the extended sp2 carbon configurations of the NGO moiety in ZnNcC4-NGO hybrids along with the partial reduction of NGO nanosheets, and the stronger PET/ET process between NGO and ZnNcC4. Moreover, the Z-scan curve of ZnNcC4-NGO shows a deeper RSA valley and the larger β value compared to that of ZnPcC4-NGO because the π-conjugated system of ZnNcC4 is larger relative to that of ZnPcC4.

Effect of Conduction Band Non-Parabolicity on the Nonlinear Optical Properties in GaAs/Ga1-xAlxAs Double Semi-V-shaped Quantum Wells.

In this paper, we investigate the effect of conduction band non-parabolicity (NPBE) on the third harmonic generation(THG), the linear and nonlinear intersub-band optical absorption coefficients (OACs) related with electronic states of double semi-V-shaped GaAs/Ga1−xAlxAs quantum wells(QWs) by using the compact-density-matrix approach. Simultaneously, the work is performed in the position dependent effective mass in order to compute the electronic structure for the system by the finite difference and self-consistent techniques. We also compare the results with and without considering NPBE. It is found that: (1) the NPBE has a significant influence on the sub-band energy levels of double semi-V-shaped QWs, and (2) the amplitude and position of the resonant peaks of the THG and nonlinear OACs in the case of considering NPBE show complicated behavior due to the energy dependent effective mass m*(E) where the energy value was chosen self-consistently.

Enhancement of linear and nonlinear optical absorption coefficients in spherical dome semiconductor nanoshells by surface plasmon resonances

Nonlinear optical effects in semiconductor nanostructures with quantum size regime have aroused great interest due to their giant nonlinearities in contrast to those of bulk counterparts, which is of great importance for developing nonlinear optical nano-devices. Here, using quantum theory, we reveal that surface plasmon resonances of metal nanoparticles greatly enhance the linear and nonlinear optical absorption coefficients of spherical dome semiconductor nanoshells with quantum sizes. These enhanced linear and nonlinear optical effects can be flexibly tuned and amplified by manipulating both the structural parameters of the nanoshells and the distance between nanoshells and metal nanoparticles. Furthermore, the bleaching effects are more clearly observed through the surface plasmon resonances. Our founding make spherical dome semiconductor nanoshells a promising candidate for nonlinear optical nano-devices with the potential for integrated nonlinear optical applications.

Studies on growth and characterization of (E)-N′-[4-(dimethylamino) benzylidene]-4-hydroxybenzohydrazide hemihydrate: a nonlinear optical material

Hydrazone compound (E)-N′-[4-(dimethylamino) benzylidene]-4-hydroxybenzohydrazide hemihydrate (DMABHBH) was synthesized and single crystals of DMABHBH were grown by solvent evaporation method at room temperature. Molecular structure of DMABHBH compound was confirmed by 1H and 13C nuclear magnetic resonance techniques. The presence of functional groups was confirmed by Fourier transform infrared and FT Raman spectral analyses. The X-ray crystal structure was elucidated at 173 K by single crystal X-ray diffraction and the results were compared with the corresponding values obtained at 298 K. The compound crystallizes in the chiral monoclinic space group P21. Mechanical stability of the grown crystals was estimated from the Vicker’s microhardness test. Powder second harmonic generation efficiency of DMABHBH is about 1.1 times that of potassium dihydrogen phosphate. DMABHBH is found to show optical limiting behavior at high input light intensities, the third order nonlinear optical absorption coefficient measured using open aperture Z-scan studies, is 0.95 × 10−11 m/W. Anti-bacterial activity was studied using the well and disc diffusion methods.

Spherical quantum dot in Kratzer confining potential: study of linear and nonlinear optical absorption coefficients and refractive index changes

Linear and nonlinear optical absorption coefficients (ACs) and refractive index changes (RICs) between the ground and the excited states of the GaAs spherical quantum dot (QD) under the effect of Kratzer confining potential and laser field have been investigated theoretically. The electronic energy levels and their corresponding wave functions are obtained by solving Schrodinger equation using finite difference method within the effective mass approximation. The dependency of energies, probability densities, dipole matrix elements on the Kratzer potential parameters and on the size of QD are investigated. The use of density matrix formalism is made to study the variations in linear, nonlinear ACs and RICs with the energy and intensity of the laser field. Also the effect of variation of the QD size and Kratzer potential parameters on linear, nonlinear ACs and RICs are studied.

Optical absorption via intersubband transition of electrons in GaAs/AlxGa1−xAs multi-quantum wells in an electric field * * Project supported by the National Natural Science Foundation of China (No. 61764012).

Based on the effective mass approximation, the Schrödinger equation and Poisson equation in GaAs/ AlxGa1−xAs multi-quantum wells (MQWs) are self-consistently solved to obtain the wave functions and energy levels of electrons in the conduction band for the ground first excited state by considering a lateral electric field (LEF). Then, the effects of size, ternary mixed crystal, doping concentration, and temperature on linear and nonlinear intersubband optical absorption coefficients (IOACs), and refractive index changes (RICs) due to the transition between ground states and the first excited states of electrons are discussed based on Fermi’s golden rule. The results show that, under a fixed LEF, with increase of Al composition and doping concentration, the IOACs produce a red shift. With increases of both widths of the wells and barriers IOACs appear as blue shifts and their amplitudes increase, but the barrier width change is much more important to affect nonlinear IOACs, whereas increasing the temperature results in a blue shift first and then a red shift of IOACs. When the other parameters are fixed but there is an increase in the LEF, IOACs occur with a blue shift, and the RICs have similar properties.

Laser damage threshold, hardness and third order non-linear optical analysis of potassium dihydrogen phosphate with sodium chloride

Abstract z-scan technique was used to investigate the non-linear optical properties of Potassium dihydrogen phosphate doping sodium chloride (PDPSC) were grown slow evaporation solution growth technique at room temperature. The lattice parameters were calculated from single x-ray diffraction. Laser damage threshold value was found to be 13.48 GW/cm2. The Vickers microhardness test was carried out on the grown crystals and there by Vickers hardness number (Hv), work hardening coefficient (n), yield strength (σy), stiffness constant C11 were calculated. The z-scan technique has been employed to determine the third order nonlinear optical (TONLO) nature of PDPSC crystal at 532 nm. The third order nonlinear optical linear absorption coefficient (α), Nonlinear refractive index (n2), Nonlinear absorption coefficient (β), Real part of the third-order susceptibility [Re (χ|3|)], Imaginary part of the third-order susceptibility [Im (χ|3|)] and Third-order nonlinear optical susceptibility (χ3) has been calculated using the Z-scan data.

Linear and nonlinear optical absorption coefficient and electronic features of triple GaAlAs/GaAs and GaInAs/GaAs quantum wells depending on barrier widths

In the present work, the effect of the barrier widths (BWs) on the linear and nonlinear optical absorption coefficient (OAC) and the electronic features of asymmetric triple Ga1-xAlxAs/GaAs (A structure) and Ga1-xInxAs/GaAs (B structure) quantum wells (QW) was investigated. The wave-functions and energy levels of asymmetric triple quantum wells (ATQW) consisting of inverse semi V-shaped, inverse semi parabolic and semi parabolic quantum well were analyzed by solving the Schrödinger equation, using the effective mass approach. As the electrons in the ground state are mostly located into the semi-parabolic quantum well, they are less affected by BWs. However, the electrons in the second and third states show a great change due to the increase in BW between them. Our results present that the potential height, the energy levels and the energy differences of A structure are always lower than of B structure. Also, the linear and nonlinear OACs depend on BWs. The absorption spectrum of the intersubband indicates blue or red shifts, as the energy interval changes with BWs. Therefore, the variation of these coefficients, which may be suitable for various optical modulators and infra-red optical device applications, can be smoothly achieved by replacing BWs.

Theoretical study of optical absorption in nonpolar AlGaN/GaN step quantum well structures

The linear and nonlinear intersubband optical absorption coefficients (OACs) of nonpolar AlGaN/GaN step quantum well structures (SQWs) were calculated theoretically for various geometrical structures, $$ \delta $$ doping schemes, and material compositions. The results revealed that the absorption frequency of such structures is obviously tunable by changing parameters such as the quantum well width, step barrier width, Al composition in the step barrier layer, and doping position. These characteristics can be attributed to non-polarization-related effects. The doping and Al composition were found to have remarkable effects on the position and magnitude of the peaks in the nonlinear optical absorption spectrum, whereas the geometric parameters of the SQWs, such as the well width and step barrier width, changed the magnitude of the peaks only very slightly. On the other hand, the nonlinear OACs of the SQWs were found to be strongly sensitive to the Al composition x and doping density in the step barrier layer. This study suggests that the step barrier layer in SQWs plays an important role in manipulating their intersubband optical absorption.

Ultrafast Nonlinear Optical Excitation Behaviors of Mono- and Few-Layer Two Dimensional MoS2

The layered MoS2 has recently attracted significant attention for its excellent nonlinear optical properties. Here, the ultrafast nonlinear optical (NLO) absorption and excited carrier dynamics of layered MoS2 (monolayer, 3–4 layers, and 6–8 layers) are investigated via Z-scan and transient absorption spectra. Our experimental results reveal that NLO absorption coefficients of these MoS2 increase from–27 × 103 cm/GW to–11 × 103 cm/GW with more layers at 400-nm laser excitation, while the values decrease from 2.0 × 103 cm/GW to 0.8 × 103 cm/GW at 800 nm. In addition, at high pump fluence, when the NLO response occurs, the results show that not only the reformation of the excitonic bands, but also the recovery time of NLO response decreases from 150 ps to 100 ps with an increasing number of layers, while the reductive energy of A excitonic band decreases from 191.7 meV to 51.1 meV. The intriguing NLO response of MoS2 provides excellent potentials for the next-generation optoelectronic and photonic devices.

Study of non-linear optical properties of center and edge delta-doped multiple quantum wells

In the present paper, the linear and non-linear optical properties of GaAs/AlGaAs multiple quantum well with on-center and on-edge delta doping are studied within the effective mass approximation. The delta potential is analytically modeled within each quantum well potential to obtain the energy levels and the corresponding wave functions using the robust finite difference method. The linear and non-linear optical absorption coefficients and changes in the refractive index are studied in the presence of a static magnetic and a periodic laser field using the density matrix approach. The obtained results show that the position of resonances and the amplitude of the optical absorption coefficients and the refractive index changes can be modified by varying the magnetic field and strength and position of doping potential. Lastly, an increase of the optical intensity appreciably changes the total absorption coefficient, as well as the total refractive index changes. Obtained results are important for the design of various electronic components such as high-power FETs and infrared photonic devices based on the intersubband transition of electrons in δ-doped multiple quantum wells.

Structural Insights and Third Order NLO Studies of Pseudohalide‐ Based Polymeric and Monomeric Congeners of Halo‐Substituted Parent Schiff Bases

AbstractThe present work focuses on the pseudohalide embodied copper(II) complexes of a tridentate Schiff base (HL) derived from N,N‐dimethylethylenediamine and 3,5‐dichloro‐2‐hydroxyacetophenone. Of them, two are coordination polymers and rest are monomers. The azide in the complex [Cu(L)(N3)]n, adopts an end‐on coordination mode begetting a trans helical propagation while the end‐to‐end bonding fashion of the dicyanamide in [Cu(L)[N(CN)2]n, fostered a meso‐helical chain. The interplay of covalent & non‐covalent forces develop the complexes into supramolecular architectures. Similar forces stitch the monomeric cyanato and thiocyanato complexes to chains. Quantification of intermolecular forces was achieved by surface analysis along with fingerprint plots. Charge‐transfer bands exhibit negative solvatochromic effect while the influence of the solvents on the geometry of the complexes is based on d‐d bands. Further, fluorescence and thermal studies were also done. The third order non‐linear optical (NLO) response of the complexes were recorded. Open aperture scan showed a positive NLO absorption coefficient and closed scan, a negative non‐linear refractive effect. A predominant refractive effect of the complexes make them ideal for optical switching applications.

Nonlinear optical properties of asymmetric double-graded quantum wells

ABSTRACTIn this work, the effects of the structure parameters, such as the central barrier thickness and the aluminium concentrations x, on the linear and nonlinear intersubband optical absorption coefficients and refractive index changes of the asymmetric double-graded quantum wells (ADGQWs) under the presence of an external static electric field are studied theoretically. The nonlinear optical properties of the ADGQWs are obtained using the compact-density matrix approach and iterative method. The numerical results obtained from the present work show that the external static electric field and the structure parameters play an important role in the optical properties of ADGQWs. Depending on the asymmetric nature of the confinement potential, in an electric field of kV/cm, the overlap between electronic wave functions decreases with increasing field whereas it increases for larger field values. The tunability of intersubband transitions can be applied to optical modulators and various device applications based on the optical transitions of electrons.