Nonlinear Optical Refractive Index Research Articles

Rashba spin-orbit coupling effects on the optical properties of double quantum wire under magnetic field

We investigate the effects of Rashba spin-orbit interaction on the optical absorption coefficients and refractive index changes associated with transitions between the first two lower-lying electronic levels in double quantum wire. The wire system represented by a symmetric, double quartic-well confinement potential is subjected to a perpendicular magnetic field. The analytical expressions of the linear and third-order nonlinear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism and iterative scheme. Optical properties are investigated as a function of structural parameter, magnetic field, Rashba spin-orbit interaction and photon energies. Numerical results reveal that competing effects between spin-orbit interaction and magnetic field modify strongly the optical properties and can be altered by these parameters.

Effect of Si δ-Doping on the Linear and Nonlinear Optical Absorptions and Refractive Index Changes in InAlN/GaN Single Quantum Wells**Supported by the Deanship of Scientific Research of University of Dammam under Grant No 2015134.

In the framework of effective mass approximation, we theoretically investigate the electronic structure of the Si δ-doped InAlN/GaN single quantum well by solving numerically the coupled equations Schrödinger–Poisson self-consistently. The linear, nonlinear optical absorption coefficients and relative refractive index changes are calculated as functions of the doping concentration and its thickness. The obtained results show that the position and the amplitude of the linear and total optical absorption coefficients and the refractive index changes can be modified by varying the doping concentration and its thickness. In addition, it is found that the maximum of the optical absorption can be red-shifted or blue-shifted by varying the doping concentration. The obtained results are important for the design of various electronic components such as high-power FETs and infrared photonic devices.

Effect of compositional dependence on physical and optical parameters of Te17Se83−xBix glassy system

In the present paper we have studied the effect of Bi addition on the physical and optical properties of thermally evaporated Te17Se83−xBix thin films. With Bi addition the density, mean coordination number, mechanical constraints, glass transition temperature increases. The other parameters theoretical energy gap, lone pair electron, deviation from stoichiometry decreases. Transmission spectra have been taken in the spectral range 400 nm–2500 nm using ultraviolet–visible–near infrared spectrophotometer. The fundamental absorption edge shifts towards longer wavelength with Bi incorporation. Optical energy gap and linear refractive index have been determined using transmission spectra. A good correlation has been drawn between the optical and theoretical parameters. Using linear optical parameters, the nonlinear optical susceptibility and nonlinear refractive index have been estimated.

Anisotropically Enhanced Nonlinear Optical Properties of Ensembles of Gold Nanorods Electrospun in Polymer Nanofiber Film.

Polymeric nanofibers containing gold nanorods (GNRs) are aligned in a uniform orientation through electrospinning. The dispersive and absorptive parts of the third-order optical nonlinear optical refractive index of the composite film measured by polarization dependent z-scan method are demonstrated to be anisotropically enhanced. Anisotropic optical response of the aligned GNRs and its connection with the ultrafast electron dynamics are discussed in light of the results of resonant femtosecond pump-probe experiments. The significant appearance of anisotropic nonlinear optical properties of ensembles of GNRs is attributed to the sensitive excitation of longitudinal surface plasmon resonance (LSPR) of highly aligned GNRs. For the macroscopic applications of ensembles of GNRs, such as passive mode-locking and all-optical switching, the experimental results demonstrate that the alignment of GNRs through electrospinning should be very high efficient, and economic.

The effect of hydrostatic pressure, temperature and magnetic field on the nonlinear optical properties of asymmetrical Gaussian potential quantum wells

In this study, simultaneous effects of hydrostatic pressure, temperature and magnetic field on the linear and nonlinear intersubband optical absorption coefficients (OACs) and refractive index changes (RICs) in asymmetrical Gaussian potential quantum wells (QWs) are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy eigenvalues and their corresponding eigenfunctions of the system are calculated with the differential method. Our results show that the position and the magnitude of the resonant peaks of the nonlinear OACs and RICs depend strongly on the hydrostatic pressure, temperature and external magnetic field. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons.

Excitonic effects on linear and nonlinear optical absorption coefficients and refractive index changes in one-dimensional quantum dots with linear potential

Excitonic effects on linear and nonlinear optical absorption coefficients (OAC) and refractive index changes (RIC) in one-dimensional quantum dots with linear potential are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. It is found that linear and nonlinear OAC and RIC with excitonic effects in one-dimensional quantum dots are larger than that without excitonic effects. Besides, when excitonic effects are considered, our results show a remarkable dependence of linear and nonlinear OAC and RIC on linear potential.

The effects of pressure and hydrogenic donor impurity on the linear and nonlinear optical properties of a GaAs/GaAlAs nanowire superlattice

The combined effects of hydrostatic pressure, presence and absence of hydrogenic donor impurity are investigated on the linear and nonlinear optical absorption coefficients and refractive index changes of a GaAs/Ga1−xAlxAs nanowire superlattice. The wave functions and corresponding eigenvalues are calculated using finite difference method in the framework of effective mass approximation. Analytical expressions for the linear and third order nonlinear optical absorption coefficients and refractive index changes are obtained by means of compact-density matrix formalism. The linear and third order nonlinear absorption coefficient and refractive index changes are presented as a function of photon energy for different values of hydrostatic pressure, incident photon intensity and relaxation time in the presence and absence of hydrogenic donor impurity. It is found that the linear and third order nonlinear absorption coefficients, refractive index changes and resonance energy are quite sensitive to the presence of impurity and applied hydrostatic pressure. Moreover, the saturation in optical spectrum and relaxation time can be adjusted by increasing pressure in presence of impurity whereas the effect of hydrostatic pressure is negligible in the case of absence of hydrogenic impurity.

Spin–orbit interaction effects on the optical properties of quantum wires under the influence of in-plane magnetic fields

In this work, we studied the effects of in-plane magnetic field and Rashba spin–orbit interaction on the intersubband optical absorption coefficients and changes in refractive index for transitions between the first two lower-lying electronic levels of quantum wire represented by a parabolic confining potential. The analytical expressions of the linear and third-order nonlinear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism and iterative scheme. Optical properties are investigated as a function of quantum wire radius, strength and orientation of magnetic field, strength of Rashba spin–orbit interaction and photon energies. Numerical results reveal that the optical absorption coefficients and refractive index changes are strongly affected and thus can be controlled by these parameters.

Absorption Spectra and Refractive Index Changes of an Exciton in a Core/Shell Quantum Dot

The absorption spectra and the refractive index changes are calculated theoretically for an exciton in a core/shell quantum dot. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The dimensionality effect of exciton quantum dots on the optical absorptions has been studied. It has been found that in the same regime, the optical absorption intensities of excitons are much smaller for the core/shell quantum dots than for the two-dimensional quantum rings. The linear and the nonlinear optical absorption coefficients and refractive index changes have been examined with the change of the confinement potential. The results show that the optical absorptions and the refractive index changes are strongly affected by the repulsive core of core/shell quantum dots. Moreover, the calculated results also reveal that as the inner radius increases, the peak values of the absorption coefficients and the refractive index changes of an exciton will show the optical Aharonov-Bohm oscillation in core/shell quantum dots.

Effect of hydrogenic impurity on linear and nonlinear optical absorption coefficients and refractive index changes in a quantum dot

The analytical expressions of linear and nonlinear optical absorption coefficients and refractive index changes in a quantum dot with a hydrogenic impurity are obtained by using the compact-density-matrix approach and iterative method. The wave functions and the energy levels are obtained by using the variational method. Numerical results show that the optical absorption coefficients and refractive index changes are strongly affected by the hydrogenic impurity.

Comment on “Linear and nonlinear optical absorption coefficients and refractive index changes in asymmetrical Gaussian potential quantum wells with applied electric field”

Guo and Du (2013) reported theirs result for the linear and nonlinear optical absorption coefficients and refractive index changes in asymmetrical Gaussian potential quantum wells with applied electric field. We find both the energy and the corresponding wavefunction for the low-lying state are wrong to applied in their works. For the same set of parameters studied by Guo and Du, we obtain new and reliable results via the differential method.

Linear and nonlinear optical absorption coefficients and refractive index changes in GaN/AlxGa(1−x)N double quantum wells operating at 1.55 μm

In the present paper, the linear and nonlinear optical absorption coefficients and refractive index changes between the ground and the first excited states in double GaN/AlxGa(1−x)N quantum wells are studied theoretically. The electronic energy levels and their corresponding wave functions are obtained by solving Schrödinger-Poisson equations self-consistently within the effective mass approximation. The obtained results show that the optical absorption coefficients and refractive index changes can be red- and blue-shifted through varying the left quantum well width and the aluminum concentration xb2 of the central barrier, respectively. These structural parameters are found to present optimum values for carrying out the transition of 0.8 eV (1.55 μm). Furthermore, we show that the desired transition can also be achieved by replacing the GaN in the left quantum well with AlyGa(1−y)N and by varying the aluminum concentration yAl. The obtained results give a new degree of freedom in optoelectronic device applications such as optical fiber telecommunications operating at (1.55 μm).

Linear and nonlinear optical absorption coefficients and refractive index changes in double parabolic-square quantum well as dependent on intense laser field

In this study, for double parabolic-square quantum well (DPSQW) the linear and nonlinear intersubband optical absorption coefficients and the refractive index changes are calculated as dependent on the intense laser field (ILF). Our results show that the location and the size of all absorption coefficients and refractive index changes depend on ILF. Also, we show that ILF provides an important effect on the electronic and optical properties of DPSQW, and the changes of the energy levels and the dipole moment matrix elements are dependent on the shape of the confinement potential. Such effects can provide methods to drive tunable semiconductor lasers, which may be tailored by quantum potential well parameters and by ILF values.

Polaronic effect on linear and nonlinear optical properties of spherical quantum dots under electric field

The polaronic effect on the linear and nonlinear optical properties of spherical quantum dots with a shallow hydrogenic impurity under electric field are studied, taking into account the interactions with both confined and surface optical phonons. In addition, the interaction between impurity and phonons has also been considered. Numerical results on typical Zn1−xCdxSe/ZnSe material show that the polaronic effect or electric field redshifts the peak positions of linear and nonlinear optical absorption coefficients and refractive index changes, but does not significantly affect the peak values of them. The polaronic effect is enhanced with the decreasing quantum dot radius or Zn concentrations. Additionally, it is found that the electric field has an important influence on the polaronic effect especially on the surface optical phonons.

Extended π-conjugated ruthenium zinc-porphyrin complexes with enhanced nonlinear-optical properties.

Zinc porphyrin dimers and trimers, in which the porphyrins are connected via a ruthenium metal core, exhibit large third-order nonlinear optical absorption coefficients and refractive indices. These properties are a result of the presence of multiple porphyrins, which lead to an extension of the π-conjugated system and the octupolar effect.

Defects and Their Distribution in KH2PO4 Crystals with Embedded TiO2 Nanoparticles

ABSTRACTResults from the successful growth of high quality KH2PO4 (KDP) crystals with incorporated TiO2 anatase nanoparticles and the characterization of these crystals using several complementary methods are presented. Transmission and scanning electron microscopy have shown that the anatase nanoparticles were captured mainly by the pyramidal growth sector and, to a considerably lesser extent, by the prismatic growth sector. Energy dispersive x-ray analysis confirms that the growth layer stacks contain the TiO2 particles. Significant variation in the imaginary and real parts of the cubic nonlinear optical susceptibilities and refractive index changes at continuous wave excitation were found in prism and pyramid parts of pure KDP and KDP:TiO2 samples. The identified lines of electron paramagnetic resonance belong to four different centers FeA3+, FeB3+, CrR3+ and CrGB3+. From analysis of line intensities it was concluded that the concentration of non-controlled impurities in nominally pure KDP samples is several times larger than in KDP:TiO2, and that the concentration of non-controlled impurities in the prismatic part of the KDP:TiO2 boule is larger than in the pyramidal part.

Femtosecond nonlinear optical refraction of single crystal alumina doped with copper ions

The single crystal alumina was fabricated by the Czochralski method. The copper ions were doped into the alumina sample to form the Cu:Al2O3 composite material. The doping energy is 35keV and the ion concentration is 1.2×1017 ions/cm2. The suppercontinuum spectrum was investigated to show the larger nonlinear refraction of this composite material. The nonlinear optical refractive property of the Cu:Al2O3 composite material was investigated by using the Kerr-lens autocorrelation technique for the first time. The nonlinear optical refractive indices, n2=2.8×10−15cm2/W at 800nm, is larger than the value of the single crystal alumina. The mechanism of the nonlinear optical refraction has been discussed and it is due to the optical Kerr effect.

Enhancement of nonlinear optical properties of composite material based on Al2O3 by iron

We fabricate the Fe:Al2O3 composite material by using the ion implantation technique. The implantation was performed at energy of 35 KeV with ion concentration of . The supercontinuum spectrum was measured to show the nonlinear refractive property of this kind of sample. The Kerr-lens autocorrelation method was used to measure the nonlinear optical refractive index of this Fe:Al2O3 composite material for the first time. The measuring result was at a wavelength of 800 nm. The nonlinear optical refraction of Al2O3 can be dramatically enhanced by Fe ion implantation. The XPS spectrum was measured to analyze the valence state of Fe in the surface of this composite material.

The linear and nonlinear optical properties of a hydrogenic donor impurity in a nanowire superlattice: Effects of laser radiation and hydrostatic pressure

The effects of laser radiation and hydrostatic pressure on the linear and nonlinear optical properties of an impure GaAs/Ga1−xAlxAs nanowire superlattice (NWSL) are analyzed using the finite difference method and compact density-matrix approach. In this regards the transition between ground and first excited states is considered to obtain linear, third order nonlinear and total optical absorption coefficients (ACs) and refractive index (RI) changes. Our calculations show that presence of laser radiation causes an increment in ACs and RI changes and shifts optical spectrum towards lower energies. Additionally, applying pressure leads to a decrement in ACs and RI changes with a small blue shift in the spectrum. Moreover, the nonlinear terms of ACs and RI changes are very sensitive to laser radiation and pressure, and saturation in optical spectrum can be adjusted by magnitudes of laser radiation and pressure.

Synthesis, structures, and third-order nonlinear optical properties of three new copper complexes based on salicylaldehyde phenoxyacetohydrazide ligand

Three copper complexes, [Cu2(Hsa)2(pipe)]·2DMF (1), [Cu(Hsa)(MEA)]n (2), and {[Cu4(Hsa)4(DMF)](DMF)}n (3) (pipe = piperazine; MEA = methenamine, Hsa = (2-hydroxybenzylidene)-2-phenoxyacetohydrazide), have been synthesized in methanol/DMF solution at room temperature and structurally characterized by single-crystal X-ray diffraction. In 1, the copper(II) complexes are bridged by pipe ligands to form binuclear clusters. In 2, the MEA ligands link copper(II) complexes to result in an infinite chain structure. Compound 3 contains tetranuclear clusters, which are bridged by Hsa to give an infinite chain structure. Third-order nonlinear optical (NLO) properties of the compounds were determined by Z-scan technique in DMF solution. All three compounds show very strong NLO absorption properties with absorptive coefficients β(MKS), 1.71 × 10−10 m W−1 for 1, 1.39 × 10−10 m W−1 for 2, and 9.30 × 10−11 m W−1 for 3, respectively. The NLO refractive index value γ(MKS) of 3 is 5.97 × 10−18 m2 W−1. Compound 3 shows strong self-focusing behavior.