Nonlinear Optical Rectification Research Articles

Strain-induced modulations in nonlinear optical rectification of core/shell quantum dots within an MEH-PPV polymer matrix under electric field: a 3D finite-element modeling study

This research aims to explore how the MEH-PPV polymer matrix and the strength of the applied field (EF) affect an electron confined within strained CdSe/ZnSe spherical core/shell quantum dots (CSQDs). By solving the Schrödinger equation using the element method (FEM) and effective mass approximation we calculated eigenenergy values and their corresponding wavefunctions. Through a compact density matrix approach, we examined how the MEH-PPV polymer matrix, QDs size and electric field intensity impact nonlinear rectification (NOR), in both unstrained systems. By considering factors such as the surrounding polymer matrix and size confinement we analysed computed coefficients related to EF intensity, peak locations and shifts. Our key findings suggest that understanding NOR in relation to parameters and surrounding materials can provide insights, for improving future optoelectronic and photonic devices.

Effects of hydrostatic pressure, temperature, and position-dependent mass on the nonlinear optical properties of triple delta-doped GaAs quantum well

In this study, we thoroughly investigate the impacts of hydrostatic pressure, temperature, and position-dependent mass (PDM) on the nonlinear optical properties of asymmetric triple δ-doped GaAs quantum wells. Our analysis covers total optical absorption coefficients, relative refractive index changes, nonlinear optical rectification, second harmonic generation, and third harmonic generation. Initially, we employ PDM to solve the time-independent Schrödinger equation using the diagonalization method under effective mass and parabolic band approaches, considering pressure and temperature dependencies. Utilizing the first four energy eigenvalues and eigenfunctions, we apply the compact density matrix method to compute the system’s nonlinear optical properties numerically. The results indicate a shift in optical property peak positions toward lower (higher) energy spectra with increasing hydrostatic pressure (temperature). Furthermore, the influence of PDM shifts the system’s optical properties toward the higher energy spectrum, resembling the effect of temperature. From an experimental and theoretical perspective, one of the topics that researchers work on most is GaAs-based δ-doped systems (δ-doped heterojunction bipolar transistors, δ-doped field effect transistors, δ-multiple independent gate field effect transistors, etc.). We believe these findings will provide valuable insights for the researchers involved in GaAs-based δ-doped optoelectronic device design.

Modulation of nonlinear optical rectification, second, and third harmonic generation coefficients in n-type quadruple δ-doped GaAs quantum wells under external fields

The paper theoretically explores the variations in nonlinear optical rectification (NOR), second (SHG), and third harmonic generation (THG) coefficients of an n-type quadruple δ-doped GaAs quantum well in the presence of electric, magnetic, and THz laser fields. The energies of subbands and associated wave functions are derived through the solution of the Schrödinger equation, utilizing effective mass and parabolic band approximations. The findings indicate that the applied external electric and magnetic fields significantly influence both the magnitudes and the positions of the peaks in NOR, SHG, and THG concerning the incident photon energies. In addition to the influences of electric and magnetic fields, subjecting the system to an intense laser field results in noticeable changes in the THG, SHG, and NOR coefficients. These numerical findings regarding the optical properties of quadruple δ-doped quantum wells in the presence of external fields could offer valuable guidance for experimental studies.

Nonlinear optical rectification in symmetric double-graded quantum wells dressed by non-resonant laser field under electric and magnetic fields

Nonlinear optical rectification in symmetric double-graded quantum wells dressed by non-resonant laser field under electric and magnetic fields

Effects of anisotropy on the electronic structure and nonlinear optical rectification in a quantum dot with hydrogen molecular ion

In this study, the effects of anisotropy and quantum dot size on energy levels and nonlinear optical rectification of a D_{2}^{ + } molecular complex confined to a two-dimensional quantum dot are investigated. The energy eigenvalues and corresponding eigenfunctions of the resulting eigenvalue equation are obtained using the adiabatic approach and the two-dimensional diagonalization method. We conclude that the evolution of the energy spectrum depends predominantly on the anisotropy-induced change of geometric confinement size. In addition, it has been determined that the peak position of the nonlinear optical rectification shifts to lower or higher energies as the asymmetry of the system increases, depending on whether the QD is in the oblate or prolate case. This feature can be considered an advantage in tuning the nonlinear optical properties of systems based on two-dimensional semiconductor heterostructures.

Investigation of nonlinear optical rectification within multilayer wurtzite InGaN/GaN cylindrical quantum dots under the impact of temperature and pressure

We have looked numerically at variations of the nonlinear optical rectification (NOR) for an impurity donor localized in a wurtzite Inx0Ga1−x0N/GaN multilayer cylindrical quantum dots (MLCQDs), which is under the effect of hydrostatic pressure and temperature. Using the effective mass approximation, the compact density matrix formalism, we have solved the Schrödinger equation by the finite element method (FEniCS Project) . Firstly, we consider the impact of altering the polarization direction of the incident electromagnetic radiation. Specifically, we explore two distinct scenarios: axial, along the growth axis of the structure, and circular, across the cross-section of the cylinder. From our investigation, we found that the nonlinear optical rectification is determined by two main parameters: the transition energy, which is mainly related to quantum confinement, and the geometrical factor that depends on the distribution of the electron wave functions. The NOR experiences a blueshift with an increase in hydrostatic pressure or indium composition, and a redshift with an increase in temperature or quantum dot radius, where the impurity is located in the center of the upper QD. Furthermore, the results show that the amplitude and resonance peak position of NOR are significantly influenced by varying the impurity’s position and the barrier width.

Influence of structural variables and external perturbations on the nonlinear optical rectification, second, and third-harmonic generation in the InP/InGaAs triple quantum well structure

Influence of structural variables and external perturbations on the nonlinear optical rectification, second, and third-harmonic generation in the InP/InGaAs triple quantum well structure

High harmonic generations triggered by the intense laser field in GaAs/AlxGa1-xAs honeycomb quantum well wires

Under constant electric and magnetic fields, the potential profile of the honeycomb quantum well wire (HQWW) is studied for varying intense laser fields to trigger and optimize high harmonics (nonlinear optical rectification, second and third harmonic generation coefficients). The finite element method has been used to simulate wavefunctions and their corresponding energy levels under effective mass approximation. We have shown that an intense laser field reshapes the potential profile of the HQWW, and this results in maximum and minimum for dipole moment matrix elements and energy differences. The increase and decrease of energy differences create blue and red shifts in the optical spectrum. In the end, we have calculated nonlinear optical rectification as 11.1x10−5 m/V. The second harmonic generation coefficient is found as 18.4x10−7 m/V which is three times and a lot bigger than bulk GaAs and GaAs/AlGaAs superlattice. The third harmonic generation coefficient is calculated as 6.2x10−15 m2/V2. As a conclusion, we have shown that HQWW can be used in harmonic generation-based optical devices.

Influence of spatial extension of impurity on the nonlinear optical properties of doped GaAs quantum dot in presence of noise

This work examines the role of spatial impurity extension (SIE) on a few nonlinear optical (NLO) properties of impurity-doped GaAs quantum dot (QD). The NLO properties considered are the nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG). The study also includes 1 (GWN) which has been incorporated into the doped QD through additive and multiplicative pathways. The study uncovers the delicate interplay between GWN and SIE which ultimately fabricates the said NLO properties. NOR, SHG and THG manifest red-shift with enhancement of SIE both with and without GWN. The study also shows possibilities of attaining maximum NLO response by prudently applying GWN in a particular pathway. Depending upon the particular NLO property concerned, the presence of noise and its mode of application can either deplete or amplify it to different extents with respect to the noise-free situation.

High harmonic generations in GaAs/AlGaAs superlattice: Effect of electric and magnetic field

In this study, we have examined the nonlinear optical rectification (NOR), the second harmonic generation (SHG), and the third harmonic generation (THG) coefficients of the AlxGa1-xAs/GaAs superlattice with a periodically increased barrier width under magnetic field (B) and electric field (F). All calculations are completed using the finite element method under the effective mass approximation. The electric field's polarity (±) changes the probability density of wavefunctions. For B = 0, F = −5 kV/cm (particularly for the difference between energy levels (Efi)) is a critical value. Whereas the Efi value decreases between −40 <F < −5 kV/cm, then it increases in the range of −5<F < 40 kV/cm. This change causes a red or blue shift in the optical spectrum. We also see that F = 40 kV/cm causes a change in the transition energies of the structure more than F = −40 kV/cm. The confinement of electrons under applied magnetic fields occurs in the center of the superlattice. The NOR, SHG, and THG coefficients can be adjusted over a wide energy range and size of the resonance peak with changes in the F and B values. It is believed that with the combined effect of the electric and magnetic fields, the electro-optical properties of the superlattices can be tuned for the desirable property of semiconductor optical device applications.

Effects of external electric and magnetic field on the nonlinear optical rectification, second, and third-harmonic generations in GaAs/AlGaAs asymmetric triple quantum well

Effects of external electric and magnetic field on the nonlinear optical rectification, second, and third-harmonic generations in GaAs/AlGaAs asymmetric triple quantum well

The second, third harmonic generations and nonlinear optical rectification of the Mathieu quantum dot with the external electric, magnetic and laser field

In this study, the nonlinear optical properties of the InxGa1−xAs/GaAs Mathieu quantum dot (MQD) are investigated for the first time, focusing on the nonlinear optical rectification (NOR), second harmonic generation (SHG), and third harmonic generation (THG). The effects of external fields such as the electric field, magnetic field, and laser radiation field on the nonlinear optical properties of MQD are examined, along with structural parameters such as quantum dot depth and width determined by the indium concentration. The motivation of the study is to explain the NOR, SHG, and THG characteristics of MQD in response to changes in external fields and structural factors. To investigate the effects of the laser field, the time-dependent part of the laser field is transferred to the potential energy term of the wave equation using the Kramers–Henneberger (KH) and dipole approximations, creating a laser-dressed potential. Then, the effective potential wave equation is solved using the tridiagonal matrix method. The effects of external fields and structural parameters of MQD on the NOR, SHG, and THG coefficients are discussed in detail. The optimality of the structure for device design and applications considering MQD is revealed, and alternative parameter analysis is conducted for this optimality.

Hydrogen molecular ion-related nonlinear optical rectification in quantum dots

Hydrogen molecular ion-related nonlinear optical rectification in quantum dots

Nonlinear optical rectification of GaAs/GaAlAs quantum dot under tangent square potential

We have investigated in detail the effects of the depth and range of the limiting potential, the quantum size parameter, temperature and hydrostatic pressure on the nonlinear optical rectification (NOR) coefficient in GaAs/GaAlAs parabolic quantum dots (QDs) with a tangent square potential. Firstly, we add the tangent-square potential of the system along the z-axis to the original parabolic QD, and then the corresponding Schrödinger equation of the modified system can be solved to find the analytical forms of different splitting energy levels and envelope wave functions. Finally, the analysis and conclusions of the numerical simulations indicate that the above parameters have significant effects on the nonlinear optical properties of the modified system.

Tailoring of the nonlinear optical rectification in vertically and laterally coupled InxGa1-xAs/GaAs quantum dots for Tera-hertz applications: Under In/Ga inter-diffusion, indium segregation, and strains effects

We numerically investigate the Nonlinear Optical Rectification (NOR) of two laterally coupled lens-shaped InxGa1-xAs/GaAs quantum dots and two layers of InxGa1-xAs/GaAs coupled QDs along the growth axis. In addition, we have examined the impact of applying an external electric field, hydrostatic pressure, and temperature on the NOR under indium segregation inside the wetting layer (WL) and In/Ga inter-diffusion in the QD region. The three-dimensional Schrödinger equation (3D) is solved numerically using the finite difference method (FDM) within the framework of the effective mass. We have used the compact density matrix formalism to compute the NOR coefficient. Our findings reveal that the indium segregation and inter-diffusion phenomena significantly affect the NOR coefficient and should be considered appropriately. It is also found that the lateral and vertical coupling thicknesses significantly impact the NOR coefficient, and the structure under investigation has a resonant behavior in the terahertz domain (0.1–10 THz). Moreover, obtained results reveal that the applied electric field orientation and intensity significantly affect the NOR magnitude. Therefore, the NOR intensity reaches the maximum value, χ(0)(2)=50.10-7m/V, for a negative applied electric field, F = −10 kV/cm. Additionally, it was shown that the increase in the hydrostatic pressure shifts the NOR spectrum to higher energies (blue-shift), whereas increasing temperature has the contrary effect. It is worth noting that the NOR magnitude and its attributed resonance energy can be adjusted for THz devices with a good choice of the external factors mentioned above.

The nonlinear optical rectification and second harmonic generation of a single electron confined in a multilayer spherical quantum dot

The nonlinear optical rectification and second harmonic generation of a single electron confined in a multilayer spherical quantum dot

Pressure and temperature influences on the nonlinear optical rectification of an impurity in a symmetrical double quantum dot

Pressure and temperature influences on the nonlinear optical rectification of an impurity in a symmetrical double quantum dot

Comparative studies of terahertz-based optical properties in transmission/reflection modes of GaSe: S and measurement of its scattering losses due to surface roughness for efficient terahertz generation

The paper reports the efficient terahertz generation using nonlinear optical rectification process and comparative studies of optical, dielectric, and surface scattering properties of 1.0 mm thin GaSe: S crystal in transmission/reflection modes. We employed 800 nm wavelength of 140 fs and 50 fs pulse durations obtained from Ti: Sapphire oscillator and amplifier systems at 80 MHz and 1 kHz repetition rates, respectively, and evaluated the THz generation potential and optical properties such as refractive index, absorption coefficients, relative permittivity in transmission mode. In the next step, the crystal was subjected to a commercial THz system of 0.3 picosecond pulses at 100 MHz repetition rate in reflection geometry and once again recorded the similar parameters and compared with the transmission mode data. In addition, these data were used to measure the scattering losses from the surface of the crystal in terms of surface roughness, optical impedance, and Fresnel’s reflection coefficients. The maximum generated THz power was of the order of 4.5 μW with conversion efficiency (η) ∼ 2.2 × 10−3%. The measured THz efficiency was found equivalent to 20 mm thick GaSe crystal used in the difference frequency mixing technique. Finally, we have measured the Rayleigh roughness factor (g) of the crystal surface at different THz frequencies. When g < 1 (for small roughness) the Fresnel reflection loss factor becomes 0.75 at 1.4 THz frequency range which helps to enhance the generated signal.

Optical properties of a single quantum well with Pöschl–Teller confinement potential

In this work, using the compact density matrix approach and iterative procedure, the effects of the two asymmetry parameters of the Pöschl-Teller quantum well (QW) on the nonlinear optical rectification (NOR), second harmonic generation (SHG), third harmonic generation (THG), inter-subband optical absorption coefficient (IOAC), and refractive index change (RIC) are studied. Numerical results reveal that the two asymmetry parameters ν and μ of the Pöschl-Teller QW have a great influence on the NOR, SHG, THG, IOACs, and RICs. The maximum asymmetry of the Pöschl-Teller confinement potential can be gotten by an optimized set of two ν and μ asymmetry parameters. If it is desired to obtain the NOR, SHG, THG, and total RIC (IOAC) with larger values, then a relatively small (large) value of μ / ν should be employed. Significant high-order nonlinear can be obtained via a correct choice of the set of the two asymmetry parameters. The results of our study show that the Pöschl-Teller QW is a promising candidate for optoelectronic device applications. • The asymmetry parameters ( ν and μ ) of the Pöschl-Teller QW have great influences on the NOR, SHG, THG, ACs, and RICs. • The maximum asymmetry of the Pöschl-Teller confinement potential can be gotten by an optimized set of ν and μ . • If it is desired to obtain the NOR, SHG, THG, and total RIC (IOAC) with larger values, then a relatively small (large) value of ν and μ should be employed. • Significant high-order nonlinear can be obtained via a correct choice of the set of ν and μ . • The results of our study show that the Pöschl-Teller QW is a promising candidate for optoelectronic device applications.

Effects of external fields on the nonlinear optical rectification and second harmonic generation of GaAs/GaAlAs zigzag quantum well

For the first time, the impact of externally applied static electric and magnetic field on the nonlinear optical rectification (NOR) and second harmonic generation (SHG) coefficients of GaAs/GaAlAs zigzag quantum well is theoretically investigated in this study. Additionally, we examined the effect of physical parameters such as width and depth of the structure on these coefficients. We have numerically solved the time-independent Schrödinger equation by using the diagonalization method under the effective mass approximation for obtaining subband energy levels and wave functions of the structure, and then we have used the compact density matrix method to obtain the analytical expressions of NOR and SHG coefficients. The obtained numerical results showed that when the magnitude of the externally applied electric and magnetic fields is increased, the peak position of NOR and SHG shifts to blue, and by increasing the width and potential depth of the quantum well, it shifts to red.