Nonlinear Optical Refractive Index Research Articles

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.

Synthesis and characterization of F-doped CdS thin films by spray pyrolysis for photovoltaic applications

A simple and inexpensive spray pyrolysis method has been employed to synthesis a reproducible pure and F:CdS thin films onto a pre-heated glass substrate. The x-ray diffraction studied reveals that the sprayed pure and F:CdS films exhibit cubic structure. The optical parameters of the sprayed pure and F:CdS films such as the linear refractive index n as well as the optical band gap, Eg were evaluated as a function of the F doped content. The dispersion parameters of the sprayed pure and F:CdS films were used to determine the nonlinear optical susceptibility, χ (3) and non-linear refractive index n2 as a function of the F doping content in CdS. The sprayed 8 wt% F:CdS thin film exhibit a highest values of the bsorption coefficient and optical conductivity as compared to other films. Thus, the concentration of 8 wt% F:CdS has been chosen to fabricate the Al/p-Si/F:CdS/Au heterojunction. The addition of fluorine to the CdS films raises the efficiency of the fabricated heterojunction from 1.92 to 2.63%.

Nanorod films of bisbenzimidazo[2,1-a:2′,1′-a′]anthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-10,21-dione7 (BI-diisoQ) for highly optoelectronic devices

Nanostructure thin films of bisbenzimidazo[2,1-a:2′,1′-a′]anthra[2,1,9-def:6,5,10-d′e′f′]diisoquinoline-10,21-dione7 (BI-diisoQ) were prepared by using vacuum thermal evaporating procedure under vacuum of 2.45 ×10− 5 mbar with thickness of 150 nm. Structural and optical properties for the as-deposited and the annealed BI-diisoQ thin films were carried out in the temperature range of (373–623 K). The X-ray diffraction (XRD) examination of BI-diisoQ confirmed that the annealed films were a mixture of amorphous and crystalline structure, whilst the as-deposited films are utterly amorphous. Scanning Electron Microscopy (SEM) images showed a clear shape of nanorods of BI-diisoQ with diameter of 40 nm at 632 K. The optical characteristics of nanostructure thin films of BI-diisoQ were investigated by measuring transmittance and reflectance spectrum versus the incidence of visible light in the range of 190–2500 nm. Our conception dissected that the optical transition type of BI-diisoQ nanorod films is indirect allowed transition with optical and fundamental energy gaps equal to1.54 eV and 3.54 eV respectively, which decreased to 1.36 eV and 3.45 eV at the annealed temperature of 623 K. The oscillation energy, E o , and the dispersion energy, E d , were investigated by using the ideation of single oscillator model (SOM). Moreover, the non-linear optical susceptibility, χ(3), and non-linear refractive index, n 2 , were found to be temperature annealing dependence. The optical investigation of BI-diisoQ nanorod films indicated that these films have excellent optical characteristics, and thus can be recommended as a potential material for integrated highly optical applications.

Impurity-related optical properties of a laser-driven quantum dot

In this paper, we explore theoretically the effect of an on-center Gaussian impurity on the optical properties of a laser-driven parabolic quantum dot system under uniform magnetic field. Laser radiation with circular polarization has been treated within the framework of high-frequency Floquet approach. The linear and third-order nonlinear optical absorption coefficients and refractive index changes have been examined by means of the compact-density matrix approach. Numerical results reveal that the position and magnitude of the resonant peaks of absorption coefficients and refractive index changes are sensitively affected by magnetic field, the depth and the range of the impurity potential. Besides, the presence of intense laser field causes a red-shift in the positions and reduction in the amplitudes of the resonant peaks of optical characteristics.

Third order nonlinear optical properties and optical limiting behaviour of sodium penta borate

Studies on third order optical nonlinearity of solution grown inorganic single crystal of sodium penta borate (NaB5) was carried out by z-scan technique with Nd:YAG laser (532 nm, 50 mW). The closed aperture z-scan measurement results peak valley pattern in normalized transmittance indicates the negative nonlinear refractive index due to self-defocusing nature and the nonlinear absorption is regarded as saturable absorption due to maximum transmittance lies near the focus in open aperture curve. The third order nonlinear optical parameters refractive index, nonlinear absorption coefficient and nonlinear susceptibility were found to be −1.28 × 10− 10 cm2/W, −7.91 × 10− 6 cm/W and 2.07 × 10− 7 esu. The optical constants (refractive index (n), reflectance (R), extinction coefficient (K), optical and electrical conductivity) of NaB5 crystals were determined by theoretical calculations from UV–Visible studies. The optical limiting property also studied for grown crystal and the limiting threshold values was found to be 35 mW.

Dependence of Nonlinear Optical Response of Anatase TiO2 on Shape and Excitation Intensity**Supported by the National Natural Science Foundation of China under Grant Nos 11404410 and 11504105.

Nonlinear optical (NLO) properties of anatase TiO2 with nanostructures of nanoparticle (NP), nanowire (NW) and annealed nanowire (NWA) are studied by open-aperture and closed-aperture Z-scan techniques with a femtosecond pulsed laser at wavelengths of 532 nm and 780 nm simultaneously. At 532 nm, when increasing excitation intensity, NLO absorption of TiO2 NPs transforms from saturable absorption to reverse-saturable absorption. However, NWs and NWAs exhibit the opposite change. At 780 nm, all samples show reverse-saturable absorption, but have different sensitivities to excitation intensity. Due to the larger surface-to-volume ratio of NPs and less defects of NWAs by annealing, nonlinear optical absorption coefficients follow the order NPs NWs NWAs. The results also show that these shape and annealing effects are dominant at low excitation intensity, but do not exhibit at the high excitation intensity. The NLO refractive index of NPs shows a positive linear relationship with the excitation intensity, whereas NW and NWAs exhibit a negative linear relationship. The results could provide some foundational guidance to applications of anatase TiO2 in optoelectronic devices or other aspects.

Combined effects of the intense laser field, electric and magnetic fields on the optical properties of n-type double δ-doped GaAs quantum well

In the present work, the effects of the non-resonant intense laser field, electric and magnetic fields on the optical properties, such as linear, third order nonlinear and the total optical absorption coefficient and refractive index changes associated with the intersubband transitions between the ground and the first excited states in the n-type double δ-doped GaAs quantum well is theoretically studied by solving the Schrödinger equation in the laser-dressed confinement potential within the framework of effective mass approximation. 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. Our numerical results show that the optical absorption coefficient and refractive index change are quite sensitive to the applied external fields, such as non-resonant intense laser field, electric and magnetic fields. The obtained results can be applied for the design of various optoelectronic devices based on the intersubband transitions of electrons.

Different modifier oxides effect on the photoluminescence and photoinduced piezooptics of Er3+-doped fluorotellurite glasses

Novel fluorotellurite glasses with composition 70TeO2·5MxOy·10P2O5·10ZnO·5PbF2 (mol %) containing 600 ppm Er2O3, where MxOy = (MgO, PbO, Bi2O3, Nb2O5, TiO2, BaO, WO3, SrO, CdO) have been prepared using the conventional melt-quenching method. Studies of the nonlinear optical refractive index and photoinduced piezooptics were carried out. The Mid-Infrared spectroscopy, optical transmission, photoluminescence and photoinduced changes of diagonal piezooptics and nonlinear optics refractive indices coefficient measurements were applied to determine the appropriate glass modifier to achieve the desirable optical properties and high performance. The glasses may be useful for operation by high-intensity laser pulses.

Intense laser field effects on the intersubband optical absorption and refractive index change in the [formula omitted]-doped GaAs quantum wells

In this paper, we have investigated the effects of the non-resonant intense laser field on the electronic and optical properties such as linear, nonlinear and the total optical absorption coefficient and refractive index change for transitions between two lower-lying electronic states in the GaAs-based δ-doped quantum well. Within the effective mass approximation, we calculated the eigenvalues and corresponding eigenfunctions as a function of the intense laser parameter by solving the Schrödinger equation in the laser-dressed confinement potential. The analytical expressions of the linear and third-order non-linear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism. The obtained results show that the separation between ground and first excited energy levels in the δ-doped quantum well decreases in energy by the increase of the laser field intensity and this effect leads to an optical red-shift in the intersubband transitions. This behavior gives us a new degree of freedom in tunability of different device applications based on the optical transitions.

Influence of image charge effect on impurity-related optical absorption coefficients and refractive index changes in a spherical quantum dot

We have investigated the influence of an image charge effect (ICE) on the energies of the ground and first few excited states of a hydrogen-like impurity in a spherical quantum dot (QD) in the presence of an external electric field. The oscillator strengths of transitions from the 1s-like state to excited states of 2px and 2pz symmetries are calculated as the functions of the strengths of the confinement potential and the electric field. Also, we have studied the effect of image charges on linear and third-order nonlinear optical absorption coefficients and refractive index changes (RICs). The results show that image charges lead to the decrease of energies for all the hydrogen-like states, to the significant enhancement of the oscillator strengths of transitions between the impurity states, and to comparatively large blue shifts in linear, nonlinear, and total absorption coefficients and refractive index changes. Our results indicate that the total optical characteristics can be controlled by the strength of the confinement and the electric field.

The effect of position-dependent mass on nonlinear optical absorption coefficients and refractive index changes in a quantum well

The influence of position-dependent mass (PDM) on nonlinear optical absorption (OA) coefficients and refractive index changes (RICs) is theoretically studied, within the framework of the iterative method and the compact-density-matrix approach. Through solving Schrödinger equation, the eigenfunctions and energy eigenvalues are obtained. The analytic expressions of the optical absorption coefficients and the refraction index changes are derived theoretically. The results reveal that the OA coefficients and the RICs are strongly affected by PDM, and both the peaks of them increase when considering PDM.

Crystal structures and third-order optical properties of three manganese(II) complexes constructed from N-heterocyclic and polycarboxylate ligands

Abstract Three new manganese(II) complexes, {[Mn(PTP)]2[Mn(PTP)(H2O)]}(BTA)2·2H2O (1), [Mn(PTP)(ODA)]2 (2), and [Mn(FTP)(ODA)]2·H2O (3), were synthesized by the reactions of manganese acetate and polycarboxylic acid in the presence of N-heterocyclic ligands (where PTP=4′-phenyl-2,2′:6′,2″-terpyridine, H3BTA=benzene-1,3,5-tricarboxylic acid, H2ODA=4,4′-oxydibenzoic acid, FTP=4′-(furan-2-yl)-2,2′:6′,2″-terpyridine). In complex 1, each BTA ligand serves as a μ 3-bridge to link three Mn(II) centers, whereas each Mn(II) center is coordinated by two BTA ligands. This connection mode results in a grid sheet. Complexes 2 and 3 have very similar molecular structures with Mn(II) centers connected by ODA ligands to result in ring-like arrays. We investigated the third-order nonlinear optical (NLO) properties of the three complexes by single beam Z-scan techniques. Complexes 1–3 exhibit strong third-order NLO reverse saturable absorption with NLO absorptive indices β=1.32×10−6, 3.01×10−6, and 9.42×10−6 m W−1, respectively. In addition, complex 1 shows all excellent self-focusing effect with an NLO refractive index of γ=1.25×10−12 m2 W−1. The third-order NLO susceptibility χ (3) of the three complexes were calculated as 47.55×10−8, 4.85×10−8, and 15.16×10−8 esu, respectively.

Studies on synthesis, structural, luminescent and thermal properties of a new non-linear optical crystal: 4-amino-4H-1,2,4-triazol-1-ium-3-hydroxy-2,4,6-trinitrophenolate

A new organic proton transfer complex having NLO activity, 4-amino-4H-1,2,4-triazol-1-ium-3-hydroxy-2,4,6-trinitrophenolate (ATHTP), was crystallized to investigate the factors which stabilize the structure of the crystal. The compound crystallizes in triclinic system with space group P-1. Elemental analysis, thermal analysis, UV–Vis–NIR, FT-IR and NMR spectral analyses were carried out to characterize the crystal. Optical, spectral and thermal properties of the title crystal were analyzed to recommend the material for optical applications. Z-scan was used to measure the effective third-order nonlinear optical susceptibility and nonlinear refractive index. The crystal structure was determined using single crystal XRD method and the structure was optimized using Gaussian 09 program at B3LYP/6-311++G(d,p) level of basis set. This hydrogen bond interactions led to the increase in first-order hyperpolarizability of ATHTP and was 30 times greater than that of urea. Hirshfeld analyses surface analysis was carried out to explore intermolecular interactions in the crystalline state.

Intense laser field-induced nonlinear optical properties of Morse quantum well

Abstractauthoren This paper investigates the effects of an intense laser field and electric field on the optical properties of quantum well represented by Morse potential. The non-resonant, high-frequency intense laser effects upon the system are treated within the framework of non-perturbative approach, modifying the confinement potential associated to the heterostructure. 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. The results for a typical GaAs quantum well correspond to several configurations of the structural parameter, the strengths of the intense laser radiation, and the static electric field. Numerical results reveal the striking influence of the external fields on the magnitude and resonant peak energy positions of the optical absorption coefficients and refractive index changes. Besides, the control of intersubband optical transitions by the structure parameter seems feasible.

Linear and nonlinear optical absorption coefficients and refractive index changes in Morse quantum wells under electric field

In this paper, we investigate theoretically the effects of electric field on the linear and nonlinear optical properties of Morse quantum wells considering a two-level system. The effective mass approximation and the envelope function approach are used to calculate the energy levels and wave functions. The analytical expressions of the optical properties are obtained by using the compact density-matrix approach. The linear and third-order nonlinear optical absorption coefficients and the refractive index changes are investigated as a function of the incident photon energy for several configurations of the structural parameter and the applied electric field. Numerical results, presented for a typical GaAs/AlGaAs quantum well, reveal that the electric field has a significant effect on the optical characteristics of these structures and intersubband transitions can be modified by tuning the structural range parameter of the potential.

Spectrophotometric calculations of optical linearity and nonlinearity of nanostructured Pyronin Y/FTO optical system for optoelectronic applications

Pyronin Y (PY) is an organic dye with semiconducting behavior which can be ascribed as a novel dye in different aspects of material science and device engineering. Thin films of Pyronin Y were prepared using a low-cost spin coating method deposited on FTO substrate. XRD showed that PY thin film has an amorphous structure with crystalline peaks corresponding only to FTO layer/glass. Transmittance, reflectance, and absorbance are measured for Pyronin Y/FTO of thickness around 200nm at the normal incident light in the wavelength range 300–2500nm. PY has an absorption valley in the visible region. Based on the measured transmittance and reflectance, the refractive index n of PY/FTO is calculated by using the Fresnel’s equations. Dielectric constants, dissipation factor, band gap and optical/electrical conductivity were also determined and analyzed. Plotting of (αhν)1/2 versus the incident photon energy is giving the values of the band gap. Three optical band gaps are found, the highest one is designed for FTO layer/glass and equals 3.569eV and the other two band gaps are (1.955 and 1.356eV) for Pyronin Y/FTO film. For PY films on FTO, the value of band gap (1.955eV) is described the fundamental band gap and the second band gap (1.356eV) is described as the trap energy inside the fundamental band gap. The nonlinear optical properties including the third order nonlinear optical susceptibility and nonlinear refractive index of PY/FTO glass were calculated and analyzed by using spectrophotometric data. Hence, Pyronin Y/FTO with a graded band gap have a unique optical constant that useful in multi-device applications for physics and engineering.

Donor-impurity-related optical absorption and refractive index changes in GaAs/AlGaAs core/shell spherical quantum dots

In this study, the linear and nonlinear intersubband optical absorption coefficients (OACs) and refractive index changes (RICs) in GaAs/AlGaAs core/shell spherical quantum dots (QDs) are theoretically investigated within the framework of the compact-density-matrix approach and iterative method for both cases with and without on-center impurity. The energy eigenvalues and their corresponding eigenfunctions of the system are calculated by using 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 hydrogenic impurity and QDs radius. It was found that the total OACs indicates saturation at sufficiently high incident intensities. Also we found that the binding energy of the ground and excited states of the impurity depend on the QDs radius.

Nonlinear optical study of 1-(carboxymethyl)-8-hydroxyquinolin-1-ium chloride and 1-(carboxymethyl)quinolin-1-ium chloride salts by Z-scan technique

Z-scan technique was used to investigate the nonlinear optical properties of 1-(carboxymethyl)-8-hydroxyquinolin-1-ium chloride and 1-(carboxymethyl)quinolin-1-ium chloride salts. The new 1-(carboxymethyl)-8-hydroxyquinolin-1-ium chloride and 1-(carboxymethyl)quinolin-1-ium chloride salts were synthesized and characterized using UV–visible, FTIR and NMR measurements and the characterization spectra confirm the expected molecular structure of the prepared salts. Measurements were performed with a CW Diode laser at 635nm wavelength and 26mW power. The nonlinear optical absorption coefficient (β) and nonlinear refractive index (n2) of the 1-(carboxymethyl)-8-hydroxyquinolin-1-ium chloride was affected by OH group. The excited-state absorption cross sections (σex) and the ground -state absorption cross sections (σg) were calculated for the two studied compounds. It was found that the σex is larger than the σg, indicating that the reverse saturable absorption mechanism (RSA) is the dominating mechanism for the observed absorption nonlinearities.Our results suggest that this material should be considered as a promising candidate for future optical devices applications.

Metal-induced efficient enhancement of nonlinear optical response in conjugated azo-based iminopyridine complexes

The nonlinear optical (NLO) properties of conjugated azo-based iminopyridine complexes with zinc and silver metal cations were studied. The processes of second and third harmonic generations in guest-host polymeric films were investigated and NLO parameters were extracted. Obtained second and third order NLO susceptibilities of zinc containing complex exceeds the latter of silver containing one. Using the Z-scan technique the NLO refractive index, NLO absorption coefficient, second order hyperpolarizability and NLO absorption cross section for the azo-based iminopyridine zinc (II) and silver (I) complexes were obtained and analyzed. Estimated nonlinearity/loss figure of merit of these complexes show promise for optical device applications.

Facile synthesis of two-dimensional WS2 with reverse saturable absorption and nonlinear refraction properties in the PMMA matrix

We report a versatile, cost-effective and reproducible solid-state reaction approach to synthesize two-dimensional (2D) WS2 with strong nonlinear optical performances. The reverse saturable absorption and nonlinear refraction properties of 2D WS2 incorporated into PMMA were measured by the z-scan configuration under femtosecond pulses at 800 nm. The figure of merit and the nonlinear optical refractive index n2 were calculated to be ∼0.40 × 10−13 esu cm and ∼3.34 × 10−4 cm2/GW, respectively. Furthermore, optical limiting (OL) effects of the WS2/PMMA composite were observed with OL threshold FOL∼2.4 mJ/cm2, which is lower than those of previously reported OL materials. Such results imply the WS2/PMMA composite as a potential candidate for practical OL applications and the solid-state reaction technology provides a feasible approach for the preparation of 2D WS2 applied in the field of nanophotonics.