Third-order Nonlinear Refractive Index Research Articles

Electric field-induced modulation of electronic and optical properties in doped CdTe/CdS core/shell quantum dots embedded in an oxide matrix

This work presents a theoretical analysis of a CdTe/CdS core/shell quantum dots embedded in a dielectric oxide matrix under the influence of hydrogenic impurity and the applied electric field intensity. The eigenstates and their corresponding eigenfunctions are computed by solving the Schrodinger equation using the finite element method within the effective mass approximation. The first-order linear and third-order nonlinear optical absorption coefficients as well as the refractive index changes are computed based on the compact density matrix approach. The obtained result shows that the first-order linear and third-order nonlinear optical properties are more pronounced with the electric field, surrounding oxide matrix and the donor impurity effects. However, the first-order linear and third-order nonlinear optical absorption coefficients and refractive index changes can experience a red or blue shift under the influence of electric field, oxide matrix and hydrogenic impurity. In addition, under all conditions, the height peaks of these optical properties can be raised (fall). Our findings demonstrate the critical importance of considering the roles of electric field, the presence of donor impurity, and the capped dielectric oxide matrix in the design and fabrication of core–shell-based optoelectronic devices.

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.

Novel third order nonlinear optical stilbazolium crystal replaced with 3-methoxy benzaldehyde as donor for optical device applications

A novel organic nonlinear optical stilbazolium group single crystal of 1-methyl-2-[2-(3-methoxystyryl)]-pyridinium iodide (subsequently referred to as MSMI) was grown by the solution growth technique using the method of slow evaporation at ambient temperature. The Single-crystal XRD investigation indicates that the MSMI crystal belongs to a monoclinic crystal system with a centrosymmetric space group. CHN elemental analyser confirms the weight percentage of carbon (C = 51.00 %) hydrogen (H = 4.55 %) and nitrogen (N = 3.94 %) in the MSMI crystal structure. The presence of 16 hydrogen atoms and 15 carbon atoms in the MSMI was affirmed by the Nuclear Magnetic Resonance (NMR) spectroscopic analysis. Fourier Transform Infrared (FTIR) studies confirmed the fundamental vibrations for different functional groups found in the MSMI crystal. The Hirsfeld surface analysis figured out the hydrogen bond interaction and π…π interaction which supports the stability of the crystal structure. The crystal is found to exhibit transmittance of wavelength above 400 nm and has a band gap of 3.05 eV ascertained from UV–Vis-NIR spectroscopic analysis. Photoluminescence (PL) studies reveal that the title crystal has an emission wavelength of 572 nm. The surface characteristics of the title crystal were examined by Atomic Force Microscopy (AFM), and etching studies. The value of Meyer's number is n = 1.8 which is determined by the Vickers microhardness studies. The value of the third-order nonlinear refractive index (n2) is 4.662×10−8 cm2/W, the nonlinear absorption coefficient (β) is 1.305×10−3 cm/W, nonlinear susceptibility (χ(3)) is 9.297×10−5 esu and the optical limiting threshold is 11.43 J/cm2 was ascertained form the Z-scan technique. The results indicate that the MSMI crystal is a potential optical limiter and has promising applications in nonlinear optical devices.

Investigation and structural of phosphate glasses at low photon energy through: optical and attenuation properties

This paper presents a novel low-cost phosphate glass preparation by using the melt quenching technique. It was investigated for use in diagnostic protective applications. The range of UV-VIS wavelength is used to estimate the optical energy gap. The MAC denotes the mass attenuation coefficients of the present glass were computed at low photon energies between 15 and 200 KeV using the MIKE program. The manufactured glasses parameters viz; the mean free path, half value layer, tenth value layer, effective atomic number, effective electron density, and linear attenuation coefficient denotes as follows; 𝑀𝑀𝑀𝑀𝑀𝑀, 𝐻𝐻𝐻𝐻𝐻𝐻, 𝑇𝑇𝑇𝑇𝑇𝑇, 𝑍𝑍𝑒𝑒𝑒𝑒𝑒𝑒, 𝑁𝑁𝑒𝑒𝑒𝑒𝑒𝑒, 𝑎𝑎𝑎𝑎𝑎𝑎 𝐿𝐿𝐿𝐿𝐿𝐿 were determined. Furthermore, the molar volume, oxygen molar volume, and optical packing density of fabricated glass were assessed. The third-order susceptibility (χ(3) and non-linear refractive index of the present glass were determined. From previous results, it can be concluded that the glass has unique attenuation characteristics, therefore, can be used for radiation protection at low energy 15 to 200 KeV.

Investigation of linear and nonlinear optical properties in quantum dots: Influence of magnetic and AB flux fields

In the present work, analytical expressions for the energy eigenvalues and eigen functions are obtained by solving the radial Schrödinger equation for inverse quadratic Hellmann plus Yukawa (IQHY) potential using Nikiforov-Uvarov functional analysis method. As an application part of this work, expressions for the linear and third-order nonlinear absorption coefficients and refractive index changes are computed to study the optical properties of the spherical GaAs quantum dots. We extend the investigation of the IQHY potential by incorporating the effects of magnetic and Aharonov–Bohm (AB) flux fields. Our results reveal that the optical properties of the GaAs quantum dots are strongly influenced by variations in the dot radius, potential height and intensity of incident photons. Specifically, we observe that the introduction of magnetic and AB flux fields significantly alters the energy eigenvalues and eigenfunctions, leading to distinct optical characteristics. The results of present study are found in consistent with other theoretical studies available in the literature.

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.

Opto-Electrical Properties of Graphene Oxide Liquid Crystal Films

Graphene Oxide Liquid Crystal (GOLC) was prepared using the improved Hummer’s method. A particular purification methodology is used to reduce the disadvantages of the common purification methods. The thin films of GOLC were prepared using a wasteless low-cost drop-casting method. The optical parameters are determined for GOLC films of different thicknesses in the range from 400 nm to 2000 nm. The spectral distribution of transmittance and reflectance of GOLC films was investigated in the wavelength range from 300 nm to 2000 nm. The refractive index of GOLC films was analyzed according to the single oscillator model. The oscillator and dispersion energies are estimated using the Wemple-DiDomenico (WDD) method. The allowed transitions in GOLC films are found to be indirect, with the energy gap decreasing gradually with increasing film thickness in the investigated range. The optical and electrical conductivities as functions of photon energy are explored. Also, the third-order susceptibility and non-linear refractive index are calculated.

Impact of intense laser Bessel beam on excitonic complexes in ellipsoidal quantum dot

This theoretical study investigates the response of a strongly oblate GaAs ellipsoidal quantum dot to an intense laser field with a Bessel intensity profile at non-resonant extreme violet and simultaneously resonant mid-infrared laser irradiation. Mainly, the linear and nonlinear optical properties of biexcitons in quantum dot are observed. Due to the complexity of the considered particle, all calculations are performed in the framework of the variational method. Biexciton variational function is constructed on the one-particle wave functions, which are correlated with each other by exponents with variational parameters. The biexciton energies for different values of applied intense laser field magnitude on the small geometrical parameter of ellipsoidal quantum dot are calculated. The nonlinear optical properties, including the oscillator strength, third-order nonlinear susceptibility, absorption coefficient, and refractive index change, are evaluated. Numerical results reveal the dependence of the exciton and biexciton energies on the intensity of the laser field and the geometrical parameters of the quantum dot. Additionally, the dependencies of the third-order susceptibility, absorption coefficient, and induced refractive index change on photon energy near the one-photon resonance and two-photon resonance are analyzed. The two-photon absorption coefficient of the biexciton in GaAs ellipsoidal quantum dot is computed, and the spectra of refractive index changes induced by biexciton transitions between ground states are analyzed for different magnitudes of the intense laser field. Biexciton recombination radiative lifetime on the small semiaxis of the ellipsoidal quantum dot for the different values of the laser field influence is estimated. Finally, the visualization of the localization region of biexciton in the ellipsoidal quantum dot is performed.

Computational, structural, spectral, optical and Hirshfeld surface analysis of (E)-2-(3,4,5-trimethoxybenzylidene) hydrazinecarbothioamide (ETMBHC): Third order NLO single crystal

By using a slow evaporation solution growth technique, single crystals of (E)-2-(3,4,5-trimethoxybenzylidene) hydrazine carbothioamide (ETMBHC) have been produced. The crystalline compound has the following properties: a = 7.471 (3), b = 9.705 (4), c = 11.168 (4), = 73.200(11)°, = 70.633 (10)°, = 70.334 (10)°; it belongs to the triclinic system with space group P. The ETMBHC chemical is a member of the P-1 triclinic system. Fourier transformations and Fourier transform infrared (FT-IR) The functional groups have been identified by Raman spectrum research. To understand how charge transfer occurs inside molecules and to establish that the title crystal is appropriate for NLO applications, the HOMO and LUMO energies for the grown crystal were computed. TGA-DTG analysis was used to study the melting point and thermal stability. Z-scan analyses were used to determine the grown crystal's nonlinear absorption coefficient and third-order nonlinear refractive index.

Harmonic-Gaussian Symmetric and Asymmetric Double Quantum Wells: Magnetic Field Effects

In this study, we considered the linear and non-linear optical properties of an electron in both symmetrical and asymmetrical double quantum wells, which consist of the sum of an internal Gaussian barrier and a harmonic potential under an applied magnetic field. Calculations are in the effective mass and parabolic band approximations. We have used the diagonalization method to find eigenvalues and eigenfunctions of the electron confined within the symmetric and asymmetric double well formed by the sum of a parabolic and Gaussian potential. A two-level approach is used in the density matrix expansion to calculate the linear and third-order non-linear optical absorption and refractive index coefficients. The potential model proposed in this study is useful for simulating and manipulating the optical and electronic properties of symmetric and asymmetric double quantum heterostructures, such as double quantum wells and double quantum dots, with controllable coupling and subjected to externally applied magnetic fields.

Theoretical investigation of laser field effect on nonlinear optical properties of quantum dots

In this work, we have theoretically investigated the effects of a high-frequency intense laser field on the nonlinear optical properties of a two-dimensional Gaussian quantum dot system. A non-resonant monochromatic intense laser field with circular polarization applied to the system is considered in the framework of a non-perturbative approach. The nonlinear optical properties of the system have been investigated by using the compact-density matrix approach and iterative procedure. The laser field effect on the linear and the third-order nonlinear absorption coefficients and refractive index changes have been examined. Results reveal that the optical characteristics of the two-dimensional Gaussian quantum dot system are considerably influenced by the strength of the intense laser field in addition to structure parameters.

Linear and nonlinear optical properties of Bi12GeO20 single crystal for optoelectronic applications

The present paper aims at presenting linear and nonlinear optical properties of Bi12GeO20 single crystals grown by Czochralski method. Transmission and reflection measurements were performed in the 400–1000 nm region. The recorded spectra were analyzed considering well-known optical models. Spectral dependencies of absorption coefficient, skin depth, refractive index, real and imaginary components of dielectric function were presented. The analyses performed on absorption coefficient showed direct bandgap and Urbach energies as 2.56 and 0.22 eV, respectively. The first- and third-order nonlinear susceptibilities and nonlinear refractive index of the crystal were also reported in the present work. The results of the present paper would provide valuable information for optoelectronic device applications of Bi12GeO20.

Investigation of linear and nonlinear optical absorption coefficients and refractive index changes of a zigzag quantum well with structure parameters and applied external fields

In this study, we have investigated some linear and nonlinear optical properties of GaAs/GaAlAs zigzag quantum well structures under different electric and magnetic field intensities. We also examined the effect of adjustable structural parameters as well as width on the optical response of the system. The diagonalization method has been the tool to numerically solve the effective mass approximation Schrödinger equation obtaining the energy levels and related wave functions needed to evaluate the expressions of linear, third-order nonlinear, and total optical absorption coefficients and relative refractive index changes derived within the compact density matrix method. Results show that the optical response becomes blue-shifted with the applied electric and magnetic fields’ increment.

Influence of Proton Ion Irradiation on the Linear–Nonlinear Optoelectronic Properties of Sb40Se20S40 Thin Films at Different Fluences for Photonic Devices

This study investigates the effects of 30 keV proton ion irradiation on the structural, morphological, and linear–nonlinear optoelectronic properties of Sb40Se20S40 thin films. The retention of an amorphous nature and vibrational bonding rearrangements caused by ion irradiation demonstrate structural tailoring. The cumulative decrease in roughness with an increase in ion dose decreases the surface energy and optical absorption loss. With the blue shifting of the absorption edges, proton irradiation increased the optical transmittance and reflectance. The variation of fluence changes the optical bandgap and Urbach energy, which are induced by local structural changes caused by defects and disorder. The refractive index decreased considerably, which supports the Moss rule. Proton irradiation reduced the interband transition and average band energy gap of the system. However, ion irradiation increased optical losses while decreasing optical conductivity and dielectric characteristics. The third-order nonlinear susceptibility and nonlinear refractive index decreased significantly as the fluence increased. Such materials with optical tuning capabilities via ion fluence are essential for cutting-edge photonic and optoelectronic applications.

Mid-infrared ultra-broadband optical Kerr frequency comb based on a CdTe ring microresonator: a theoretical investigation.

Microresonator Kerr frequency combs are coherent light sources that emit broadband spectrum of evenly spaced narrow lines in an optical microresonator, which provide breakthroughs in many technological areas, such as spectroscopy, metrology, optical telecommunications, and molecular sensing. The development of mid-infrared (MIR) optical frequency comb (OFC) based on microresonators could pave the way for high performance spectroscopy in the MIR "molecular fingerprint" region. However, the generation of microresonator MIR OFC, especially towards the long-wavelength MIR (>10 µm) region, is prohibited by the transmission window of the commonly used Kerr optical media such as Si and Si3N4, and low nonlinearity at long wavelengths. Here, we seek the possibility to realize an ultra-broadband frequency comb operating in the long-wavelength MIR region based on a cadmium telluride (CdTe) ring microresonator. CdTe features a broad transmission range covering the wavelengths of 1∼25 µm, a flat dispersion profile, and an extraordinary third-order nonlinear refractive index (∼1.4 × 10-17 m2W-1 at 7 µm) which is 2-order greater than that of Si3N4, making it a promising platform to realize MIR Kerr frequency comb. Based on the above excellent optical properties, we design a CdTe/cadmium sulfide (CdS)/Si heterojunction microring resonator to generate an ultra-broadband MIR OFC. Through the numerical simulation, the geometric parameters (width, height, and radius) of the microresonator, polarization, wavelength of the pump, and quality factor are investigated and optimized. As a result, a MIR OFC covering 3.5∼18 µm is numerically demonstrated by using the pump wavelength of 7 µm and a pump power of 500 mW. This is the first simulation demonstration of Kerr OFC with the spectral range extending beyond 10 µm, to the best of our knowledge. This work provides new opportunities for the realization of ultrabroad microresonator frequency combs based on novel Kerr optical medium, which can find important applications ranging from calibration of astronomical spectrographs to high-fidelity molecular spectroscopy.

The nonlinear optical properties of GaAs/GaAlAs triple quantum well: Role of the electromagnetic fields and structural parameters

Being relevant to the field of device applications, multiple semiconductor quantum wells are systems that exhibit remarkable optical and electronic properties. These can be properly tuned by suitably modifying the composition, structural parameters, and the application of external probes. Here, the electronic and optical properties of a GaAs/GaAlAs triple quantum well have been investigated under the influence of applied electric and magnetic fields, as well as the change of well and barrier widths. We have used the diagonalization method to numerically solve the Schrödinger equation under the effective mass approximation for obtaining the subband energy levels and related electronic wave functions. The expressions used for evaluating linear, third-order nonlinear, and total optical absorption coefficients (TOACs) and relative refractive index changes (RRICs) were previously derived within the compact density matrix method. According to our results, whilst an increment in the applied electric field causes a red shift in TOACs and RRICs, a blue shift of the optical responses occurs with increasing the applied magnetic field. Besides, a blue shift is observed as well by changing the width of the central well (LwL), whilst a red shift is noticed when changing left and right wells (LwL and LwR) and barrier (LbL and LbR) widths for zero fields. We believe that our study could make a contribution to designing new quantum-well-based optoelectronic devices.

Effects of Applied Magnetic Field on the Optical Properties and Binding Energies Spherical GaAs Quantum Dot with Donor Impurity.

The screened modified Kratzer potential (SMKP) model is utilized to scrutinize the impacts of an applied magnetic field (MF) on the binding energies and linear and nonlinear optical properties spherical GaAs quantum dot with donor impurity (DI). To accomplish this goal, we have used the diagonalization method to numerically solve the Schrödinger equation under the effective mass approximation for obtaining the electron energy levels and related electronic wave functions. The expressions used for evaluating linear, third-order nonlinear, and total optical absorption coefficients and relative refractive index changes were previously derived within the compact density matrix method. It has been shown here that the MF and DI impacts the characteristics of the absorption coefficients and the refractive index changes. This study’s results will find application in optoelectronics and related areas.

Linear and nonlinear optical properties in spherical quantum dots: Modified Möbius squared potential

The optical properties of quantum dots (QDs) in modified Möbius squared (MMS) potential are studied. To obtain the energy expressions and the wave functions, we solved the Schrödinger equation by using Nikiforov-Uvarov (NU) method. We investigated the linear, third-order nonlinear and total absorption coefficients (AC) and refractive index changes (RIC) using the density matrix. The numerical results show that the structure parameters and optical intensity have a strong influence on AC and RIC.

Structural and Optical Properties of Nanocrystalline 3-(2-Benzothiazolyl)-7-(diethylamino) Coumarin (C6) Thin Films for Optoelectronic Application

In the current work, the structural and optical properties of thermally evaporated 3-(2-Benzothiazolyl)-7-(diethylamino) coumarin [Coumarin 6 (C6)] thin films on a pre-cleaned quartz substrate were studied as a function of the annealing temperature. The influence of annealing on the structural, morphological, and molecular structures was investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy, respectively. The XRD and AFM results confirmed that the as-deposited and annealed films have nanostructural features (30.96–45.34 nm). Also, the increase in roughness of the C6 thin film surface resulted from particle agglomeration and coalescence. Optical constants of C6 thin films were derived from the transmittance T(λ) and reflectance, R(λ) measurements in the spectral range of 200–2500 nm. Analysis of the optical absorption coefficient data indicates that the type of electronic transition in these films is an indirect allowed transition. The estimated optical band gap was decreased from 2.12 eV to 2.01 eV as the annealing temperature was increased. Dispersion and dielectric parameters were determined as functions of the annealing temperature. Lastly, nonlinear optical parameters such as the third-order nonlinear susceptibility, χ(3) and nonlinear refractive index, n(2) were estimated and influenced by annealing temperature. The optical properties of C6 thin films were showed that C6 thin films would be used in a wide range of photonic applicationsGraphical

A comprehensive investigation of structural and optical properties of the spray coated Nd-doped ZnO

We report on the synthesis and characterization of Nd3+ doped Zinc oxide (ZnO) thin films fabricated using the chemical spray pyrolysis technique at 723 K. A comprehensive investigation using a combination of experimental techniques is undertaken to unveil the structural, morphological, compositional, electrical, linear, and nonlinear optical characteristics of the Nd-doped (a higher ionic radius dopant) ZnO thin films. The X-ray diffraction reveals a hexagonal wurtzite structure of the polycrystalline deposits with preferred orientation change from (101) to (002) plane at dopant concentrations above 5%. The inclusion of Nd dopants causes the morphology to change from fibrous to needle-like. The oxidation states of the dopant elements were identified by using XPS spectra. The Raman spectroscopy elucidates the deterioration of crystallinity with the increase in the dopant concentrations. The additional absorption band at higher dopant concentrations in the Fourier transform infrared spectra points to a new phase. The optical bandgap and charge carrier concentrations decrease and increase, respectively, with dopant concentrations up to 5 at%, followed by a reversal in the trend at still higher doping. The optical refractive index and extinction coefficient of the doped samples show an increase compared to pure ZnO. The defect-mediated energy transfer from the host ZnO to Nd dopants was identified from photoluminescence spectra. The sign of the third-order nonlinear refractive index changes from negative for pure ZnO to positive with Nd doping.