Third-harmonic Generation Coefficient Research Articles

Optical third-harmonic generation of spherical quantum dots under inversely quadratic Hellmann plus inversely quadratic potential

The third-harmonic generation (THG) coefficient for a spherical quantum dot system with inversely quadratic Hellmann plus inversely quadratic potential is investigated theoretically, considering the regulation of quantum size, confinement potential depth and the external environment. The numerical simulation results indicate that the THG coefficient can reach the order of 10−12 m2 V–2, which strongly relies on the tunable factor, with its resonant peak experiencing a redshift or blueshift. Interestingly, the effect of temperature on the THG coefficient in terms of peak location and size is consistent with the quantum dot radius but contrasts with the hydrostatic pressure. Thus, it is crucial to focus on the influence of internal and external parameters on nonlinear optical effects, and to implement the theory in practical experiments and the manufacture of optoelectronic devices.

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.

Effects of external fields and structural parameters on third harmonic generation of GaAs/AlGaAs Manning-like double quantum well structure

In this theoretical work, we investigate how external fields like as electric, magnetic, and intense laser fields, as well as structural factors, affect the third harmonic generation (THG) coefficient of an AlGaAs/GaAs Manning-like double quantum well heterostructure. To achieve our goals, we numerically solve the time-independent Schrödinger equation using the diagonalization approach with the effective mass approximation and then derive the subband energy levels and corresponding wave functions of the structure. After that, we derive the mathematical expression of the THG coefficient by using the compact density matrix method. According to our results, the resonance peaks of the THG coefficient show shifting to the high-energy region with an increase in the field’s magnitude in cases where external fields (electric, magnetic, and intense laser) are applied separately. At the same time, increasing the depth (width) of the quantum well structure causes the THG peaks to shift to the high (low) energy region. We believe that the findings from this search will have a substantial impact on existing experimental device designs and applications.

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.

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.

Third Harmonic Generation in Al0.3Ga0.7As/GaAs Quantum Dots: the Influence of the Structure Parameter, Static Electric, and Magnetic Field

Herein, the nonlinear third harmonic generation (THG) distribution of Al0.3Ga0.7 As/GaAs quantum dots is studied under the combined influence of hydrostatic pressure and structural parameters, considering the presence of an electrostatic field and magnetic field. Hydrostatic pressure is introduced into the system as an environmental condition in the form of effective mass. When the hydrostatic pressure changes within a certain range, the peak shift and resonance peak of the THG coefficient change significantly, reflecting its application effect elegantly. Interestingly, the effects of these application modes on nonlinear optical properties have different effects, whether it is hydrostatic pressure, structural parameters, or electromagnetic fields.

Ultrahigh-level enhancement on nonlinear optical susceptibility of cubic quantum dots achieved by THz laser and electric field.

Multi-physics coupling, composed of an intense THz laser and electric field, serves as a new approach to realize the ultrahigh-level enhancement on third-harmonic generation (THG) of cubic quantum dots (CQDs). The exchange of quantum states caused by anticrossing of intersubbands is demonstrated by the Floquet method and finite difference method with the increasing laser-dressed parameter and electric field. The results show that the rearrangement of the quantum states excites the THG coefficient of CQDs four orders of magnitude higher than that achieved with a single physical field. The optimal polarization direction of incident light that maximizes the THG exhibits strong stability along the z axis at high laser-dressed parameter and electric field.

Electric field effect on anisotropic nonlinear optical properties of GaN/AlN quantum dots with multitype-tunable shape

A new investigation on anisotropic nonlinear optical properties of GaN/AlN quantum dots with multitype-tunable shape under electric field have been performed in the effective mass approximation. By means of the finite difference method, the results show that continuously graded elliptic-like quantum dots have higher polarization stability on nonlinear coefficients. The enhancement and abort of the second-harmonic generation, the optical rectification and third-harmonic generation coefficients strongly depend on the asymmetry of quantum dots, the electric field strength and direction, and polarization direction of incident wave.

Third-harmonic generation in spherical quantum dots under Deng–Fan–Eckart potential: Effects of hydrostatic pressure, temperature and Al-concentration

In this work, third-harmonic generation (THG) of GaAs/Ga1−xAlxAs spherical quantum dots (QDs) affected by Deng–Fan–Eckart (DFE) potential are carefully analyzed for different applied tuning parameters (pressure, temperature and Al-concentration). The eigensolutions of the radial Schrödinger equation are obtained using Factorization method within the effective mass approximation. The results show that the energies and dipole matrix elements are strongly dependent on DFE potential parameters and applied tuning factors. Moreover, we find that these parameters have a significant effect on the position and magnitude of resonant peak of THG coefficient.

The second and third-harmonic generation of spherical quantum dots under modified Kratzer plus screened Coulomb potential

We report the second harmonic generation (SHG) and third harmonic generation (THG) of GaAs/GaAlAs spherical quantum dots (QDs) with the modified Kratzer (MK) plus screened Coulomb (SC) potential in the presence of hydrostatic pressure and temperature. The eigen energies and wave functions can be deduced under the frame work of Nikiforov–Uvarov (NU) method. Then we calculate the SHG and THG coefficients within the framework of the density matrix method. Numerical calculations revealed that the SHG coefficient has two formants and THG coefficient has three formants depend on the energies and parameters of our system. The results indicate that these parameters bring about significant changes on the SHG and THG coefficients.

Building-block approach to the discovery of Na8Mn2(Ge2Se6)2: A polar chalcogenide exhibiting promising harmonic generation signals with a high laser-induced damage threshold

A new polar quaternary chalcogenide, Na8Mn2(Ge2Se6)2, has been synthesized using the building-block approach by reacting preformed Na6Ge2Se6 and MnCl2 at 750 °C. The structure consists of layers of [Na(1)Mn(Ge2Se6)]3– stacked perpendicular to the c-axis and sodium ions occupying the interlayer space. An indirect bandgap of 1.52 eV has been calculated using density functional theory, which is expectedly underestimated compared to the observed optical bandgap of 1.95 eV derived from diffuse reflectance spectroscopic measurements in the UV/Vis/NIR region. Magnetic measurements confirm the paramagnetic nature of Na8Mn2(Ge2Se6)2 with an experimental magnetic moment of 5.8 μB in good agreement with the theoretical spin only moment of 5.92 μB for high spin Mn2+. Na8Mn2(Ge2Se6)2 exhibits a potentially wide region of transparency in the measured range of 2.5–25 µm. Na8Mn2(Ge2Se6)2 shows a modest second-harmonic generation (SHG) response but with a high laser-induced damage threshold (LIDT) of ~9x AgGaSe2. Third harmonic generation (THG) measurements indicate that Na8Mn2(Ge2Se6)2 displays a high THG coefficient (1.9x AgGaSe2) at λ = 1800 nm.

Second and third harmonic generation in linear, concave and convex conical GaAs quantum dots

Second harmonic generation (SHG) and third harmonic generation (THG) in quantum dots with cylindrical geometry are studied by solving the Schrödinger equation within the effective mass approximation. The cylindrical nanostructures are a linear cone, convex cone and a concave cone compared with the solid cylindrical quantum dot. Results show that for the different cylindrical quantum dots of the same base radius, peaks of both the SHG and THG coefficients occur at different photon energies, and in order of increasing photon energy: solid cylinders, convex cones, linear cones and the concave cones. Additionally, peaks of both SHG and THG coefficients in conical quantum dots are more separated in energy than those associated with a purely solid cylindrical quantum dot. Potential applications and other features are discussed.

Role of external fields on the nonlinear optical properties of a n-type asymmetric $$\delta$$-doped double quantum well

The effects of in-growth applied electric fields and in-plane (x-oriented) magnetic fields on the nonlinear optical rectification (NOR), second harmonic generation (SHG) and third harmonic generation (THG) of n-type asymmetric double $$\delta$$ -doped GaAs quantum well are theoretically investigated. One-dimensional Schrodinger equation is solved by considering effective mass and parabolic band approximations to obtain subband energy levels and their related wave functions. The variations in the NOR, SHG and THG coefficients are determined by using the iterative solutions of the compact density matrix approach. Obtained results indicate that the applied electric field leads to optical red-shift on NOR, SHG and THG coefficients while the magnetic field causes optical blue-shift on that coefficients. Hence we can conclude that applied electromagnetic fields can be used to tune optical properties of devices working within the region of infrared electromagnetic spectrum.

The laser field controlling on the nonlinear optical specifications of the electric field-triggered Rosen-Morse quantum well

We consider, for the first time, optical specifications such as the nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG) of quantum well (QW) that has the Rosen-Morse potential confinement and is generated by GaAs/GaAlAs heterostructure. To do this, QW structure is firstly asymmetrized by applying an external electric field, as 10 kV/cm. Therefore, the electric field-triggered (F=10 kV/cm) Rosen-Morse QW (eftRMQW) is taken into consideration throughout the study. In this study, it is elucidated that how to control NOR, SHG and THG optical responses through monochromatic linearly polarized intense laser field (ILF). In order to be able to investigate the ILF effects, the time-dependent of ILF is removed to potential energy term of the wave equation by using Kramers-Henneberger (KH) and the dipole approximations, building the laser-dressed potential. Then, the bound state energies and the wave functions of eftRMQW are obtained using the diagonalization method within the effective mass approach and the parabolic approximation. The influences of the ILF and structural parameters of eftRMQW on NOR, SHG and THG coefficients are discussed in detail. The optimum of structure is ferreted out for devices design and applications that will consider eftRMQW, and for this optimum the alternative parameter analysis is carried out.

The effect of intense laser field on the nonlinear optical features in asymmetric multiple step and inverse V-shaped multiple step quantum wells

For asymmetric multiple step quantum wells (AMS QWs) and asymmetric inverse V-shaped multiple step quantum wells (AIVSMS QWs), the nonlinear optical features, such as the nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG) coefficients are analyzed as according on the intense laser field (ILF). The found consequences indicate that the ILF parameter confirms a vital influence on the shape and height of the confined potential profile of both AMS QWs and AIVSMS QWs, and the alterations of the dipole moment matrix elements and the energy levels are adhered on the profile of the confined potential. According to the results, the potential profile and height of the AIVSMS QWs compared to AMS QWs were affected differently from ILF intensity. These results indicate that NOR, SHG, and THG coefficient of AMS QWs and AIVSMS QWs may be regulated in a preferred energy range and the magnitude of the resonance peak (RP) by tuning the ILF parameter. By varying the ILF parameter, it is feasible to classify blue or red shifts in RP locations of NOR, SHG and THG coefficients. Our results can be valuable in investigating new ways of manipulating the opto-electronic properties of semiconductor QW devices.Highlights•The electro-optical properties of AMS QWs and AIVSMS QWs vary by increasing ILF.•The change of AIVSMS QWs compared to AMS QWs is more affected by ILF.•NOR, SHG, and THG coefficients change with rising ILF.•RP spectrums show blue or red shifts as according to ILF.

Depending on the intense laser field of the nonlinear optical rectification, second and third harmonic generation in asymmetric parabolic-step and inverse parabolic-step quantum wells

The nonlinear optical rectification (NOR), the second harmonic generation (SHG) and the third harmonic generation (THG) coefficients in asymmetric parabolic-step quantum wells (APSQW) and asymmetric inverse parabolic-step quantum wells (AIPSQW) are considered as depending on the intense laser field (ILF). The found consequences indicate that ILF parameter approves a dynamic influence on the shape, width and height of the confined potential profile of both APSQW and AIPSQW, and the alterations of the dipole moment matrix elements and the energy levels (ELs) are followed on the profile of the confined potential. The potential profile and height of the AIPSQW compared to APSQW were affected differently from ILF intensity. With and without the ILF, the ELs in the APSQW are smaller than in the AIPSQW. These results designate that NOR, SHG, and THG coefficient of APSQW and AIPSQW may be controlled in a chosen energy range and the magnitude of the resonance peak (RP) by increasing ILF value. By modifying the ILF parameter, it is possible to classify red or blue shifts at the RP positions of the NOR, SHG and THG coefficients. We hope that our results will offer significant development of optical devices in many potential device applications for the appropriate selection of ILF values.

Tailoring the optical properties of quantum ring irradiated by THz laser

ABSTRACTThis study set out to introduce the optical nonlinearities of a intense laser-driven two-dimensional quantum ring subjected to external uniform magnetic field. Inclusion of the effect of non-resonant, high-frequency THz laser radiation is realised by the laser-dressed potential, whereas the total optical absorption coefficients, total relative refractive index changes and third-harmonic generation (THG) coefficient are inferred from the scheme of compact density-matrix formalism and iterative method. Our results reveal that the laser field smoothens the antidot region of the ring that consequences with remarkable modifications in the electronic structure and correspondingly the optical response of the system. We have found that the height and location of the resonant peaks of total optical absorption coefficient, total relative refractive index changes and THG coefficient can be controlled by the externally applied fields and system parameters. The tunability of the intersubband transitions could be beneficial for practical device application relying on the electronic optical transitions.

Using the Purcell effect for the modification of third-harmonic generation in a quantum dot near a metallic nanosphere

We study the modification of third-harmonic generation from a quantum dot close to a metallic nanosphere. We show that the strong variation of the spontaneous decay rate of the quantum dot near the metallic nanoparticle can be used for tailoring the third-harmonic generation coefficient of the quantum dot. Specifically, the strong enhancement or suppression of the quantum dot’s spontaneous emission rate can strongly modify the third-harmonic generation coefficient of the quantum dot depending on the distance of the quantum dot from the surface of the metallic nanosphere and on the direction of the electric dipole moment of the quantum dot. The alteration of the third-harmonic generation coefficient is also strongly dependent on the quantum dot’s pure dephasing rate.

Intense laser-induced electronic and optical properties in double finite oscillator potential

ABSTRACTIn the present paper, a theoretically study of the non-resonant laser field effect on the optical response, such as nonlinear optical rectification (NOR), second (SHG) and third harmonic generation (THG) coefficients in double finite oscillator potential (DFO) quantum wells is performed in the framework of the effective mass approximation. The obtained results reveal that, energy states and optical response is significantly affected by the non-resonant intense laser field (ILF) intensity and symmetry of the structure. Also it was found that the laser field is more effective on the optical response in the DFO potential when the asymmetric character of the confinement potential is strong. Thus, the NOR, SHG and THG coefficients with designated values can be obtained by using a properly adjusted ILF intensity and symmetry parameter of confinement potential.

Nonlinear Optical Rectification, Second and Third Harmonic Generations in Square-Step and Graded-Step Quantum Wells under Intense Laser Field

For square-step quantum wells (SSQWs) and graded-step quantum wells (GSQWs), the nonlinear optical rectification (NOR), second harmonic generation (SHG) and third harmonic generation (THG) coefficients under an intense laser field (ILF) are analyzed. The found results indicate that ILF can ensure a vital influence on the shape and height of the confined potential profile of both SSQWs and GSQWs, and alterations of the dipole moment matrix elements and the energy levels are adhered on the profile of the confined potential. According to the results, the potential profile and height of the GSQWs are affected more significantly by ILF intensity compared to SSQWs. These results indicate that NOR, SHG and THG coefficients of SSQWs and GSQWs may be calibrated in a preferred energy range and the magnitude of the resonance peak (RP) by tuning the ILF parameter. It is feasible to classify blue or red shifts in RP locations of NOR, SHG and THG coefficients by varying the ILF parameter. Our results can be useful in investigating new ways of manipulating the opto-electronic properties of semiconductor QW devices.