Refractive Nonlinear Coefficient Research Articles

Structural, linear/nonlinear optical characteristics and radiation shielding effectiveness of Cu4O3/Cu2O dual-phase thin films: Influence of oxygen flow rate in reactive sputtering process

In the present work, we investigated the impact of oxygen flow rate on the structural, linear, and nonlinear optical characteristics while also evaluating the radiation shielding effectiveness during reactive radio frequency (rf) sputtering in the deposition of Cu4O3/Cu2O dual-phase thin films. Microstructural analysis revealed distinct changes with increased OFRs, switching from a Cu2O cubic structure phase to a Cu4O3 tetragonal structure phase. The XRD patterns revealed good crystallinity, and the crystallite size of the film reduced from 28 nm to 22 nm, and the microstrain exhibited an opposing trend as the oxygen flow rate increased. In contrast, investigating the optical properties of dual-phase Cu4O3 and Cu2O thin films using UV–Vis–NIR spectroscopy revealed intriguing trends in the absorbance spectra, absorption coefficient, and extension index. The apparent bandgap increases from 2.0 eV to 2.62 eV with increasing oxygen flow rates. In addition, nonlinear optical parameters, including the nonlinear refractive index n2 linear, nonlinear sensitivity (χ1 and χ3), and nonlinear absorption coefficient βc were calculated to demonstrate the applicability of these materials. The dual-phase structure of the films enhances their potential for effective radiation shielding. Our findings provide valuable insights into the design of properties of Cu4O3/Cu2O dual-phase thin films for applications ranging from photoelectric and nonlinear optical devices to radiation shielding effectiveness.

Measurement of nonlinear refraction and absorption coefficient in BaGa2GeSe6 crystal

The coefficients of nonlinear absorption and nonlinear refraction of the quaternary barium chalcogenide crystal BaGa2GeSe6 at a wavelength corresponding to half the band gap, as well as their dependence on the pulse repetition rate and peak on-axis irradiance, were measured for the first time. The third-order nonlinear optical properties were studied using the single-beam Z-scan technique. An Nd: YLF laser at 1.053 μm with a pulse duration of approximately 5.2 ns was used as a radiation source. In addition, a thermal Z-scan was carried out to investigate thermal lensing in the BaGa2GeSe6 crystal, employing a continuous wave Nd: YAG laser at 1064 nm. These studies represent an important step in comprehending the nonlinear optical properties of barium chalcogenide crystals and their behavior at different pulse intensities. The results might be significant for the modelling and design of mid-infrared optical systems.

Investigating the nonlinear optical response of virgin cherry kernel oil and its application to detecting adulteration

The nonlinear optical (NLO) response of materials is the basis for their use in various applications including optical switching, optical data storage, and optical limiting. Additionally, it can be used as an innovative authentication method. In this study, the NLO properties of virgin cherry kernel oil (VCKO) were investigated by observing of spatial self-phase modulation (SSPM) diffraction rings using a 532nm continuous-wave laser beam. Based on the intensity-dependent number of symmetric diffraction rings, the nonlinear refraction coefficient and thermo-optical coefficient of VCKO were estimated to be 3.81×10−6cm2/W and 5.34×10−4K−1, respectively, for the first time, according to the authors’ knowledge. Furthermore, we employed the SSPM technique for adulteration detection in the VCKO sample by analyzing its NLO properties. To accomplish this, we prepared different adulterated samples by mixing VCKO with cheaper commercial oils, such as virgin sunflower oil (VSFO) and virgin canola oil (VCO) at various concentration ratios. In the mixed VCKO adulterated samples, the measured NLO parameters were highly correlated with the amount of adulteration. The results confirmed the ability of the SSPM technique to determine the degree of adulteration in oil samples by measuring and comparing their NLO properties. In addition, our results indicate that cherry kernel oil can be a viable candidate as a nonlinear medium for optical applications.

Novel polymorph of 2-amino-6-methyl pyridinium-4-methyl benzoate (2A6MP4MB) single crystals: Synthesis, crystal structure, optical, spectroscopic and self-defocusing capabilities for nonlinear optical applications

By using the slow evaporation solution growth technique, the 2-amino 6-methyl pyridinium 4-methyl benzoate (2A6MP4MB) is crystallized in a single, high-quality crystal. Single crystal X-ray diffraction (SXRD) was used to determine the crystal structure. The different functional groups of the substances were identified using Fourier Transform Infrared Spectroscopy (FTIR) analysis. The 2A6MP4MB crystal exhibits a significant optical transmittance throughout the complete visible spectrum and a lowered UV cutoff wavelength, according to studies conducted using UV-Vis spectrometers. The optical band gap energy (Eg) of a single crystal of 2A6MP4MB is 4.768[Formula: see text]eV. The compound’s photoluminescence (PL) spectrum in the title illustrates the green emission technique. We analyze the produced single crystal’s dielectric tensorial behavior at various frequencies. The produced 2A6MP4MB crystal’s third-order susceptibility, nonlinear refraction, and nonlinear absorption coefficient were evaluated using the [Formula: see text]-scan technique. A Vickers hardness tester was used to assess the created crystal’s mechanical stability.

Effect of silver nanoparticles size on the ultrafast optical nonlinear and optical limiting properties of Nd3+ doped antimony borate glasses

Nd3+ ions containing borate glasses embedded with silver (Ag) nanoparticles (NPs) were prepared by melting and quenching process. Thermal treatment at 450 °C for different holding durations has been performed to tune the size of the NPs embedded in the glass. The influence of growth of NPs on nonlinear optical (NLO) and optical limiting (OL) properties of glasses has been evaluated in the near–infrared spectral provenience under femtosecond pulse regime. The NLO and OL attributes evaluated using Z–scan configuration disclose the enhanced trend of two–photon absorption and nonlinear refraction coefficients and a decrease behaviour of OL threshold with the augment of thermal holding time. This enhancement in NLO coefficients and OL performance with thermal annealing duration is ascribed to the enhancement of the local field with the size of the NPs. The outcomes acknowledge the Nd3+ ions bearing borate glasses embedded with bigger Ag NPs are preferable for nanophotonic applications and optoelectronic functionalities.

Optical and Dielectric Characteristics of Poly (Methyl Methacrylate)/Polyethylene Oxide/Carbon Nanoparticle Composites Loaded with Nano NiFe2O4

The current study proposes a simple, low-cost, and functional method of doping a pure matrix of poly (methyl methacrylate)/polyethylene oxide/carbon nanoparticles (PMMA/PEO/CNPs) with nano nickel ferrite (NiFe2O4) as a filler. To create NiFe2O4 nanoparticles, a straightforward chemical growth, sol-gel auto-combustion system was used. Next, environmentally friendly and cost-effective, undoped and blended polymers doped with NiFe2O4 using a solution-casting method were synthesized. Rietveld refinement analysis was used to investigate the structure and microstructure of the NiFe2O4. Transmittance electron microscopy was used to confirm the nano nature of the filler. X-ray diffraction was used to verify the crystallite nature of the undoped and doped PMMA/PEO/CNPs blends with NiFe2O4. The linear optical characteristics of the proposed blends were obtained using a diffuse reflectance spectrophotometer. The measured optical parameters included transmittance, absorbance, reflectance, direct and indirect optical bandgaps, absorption coefficient, linear refractive index, extinction coefficient, dielectric constant, energy loss functions, in addition to optical and electrical conductivities. Also, nonlinear optical constants for the synthesized blends, such as the linear and third nonlinear susceptibilities, nonlinear refraction coefficient and nonlinear absorption coefficient, were calculated. The direct and indirect optical band gap energies of the PMMA/PEO/CNPs blends were 4.97 and 4.8 eV, respectively. As the NiFe2O4 doping level increased in the blend to 2.5 wt%, the optical band gap energy values decreased to 4.54 and 4.64 eV, respectively. The fluorescence spectra of the undoped and doped PMMA/PEO/CNPs blended polymers with nano NiFe2O4 were also explored. The effect of NiFe2O4 doping amount on the energy density, electric dielectric constant, ac conductivity and electric moduli of the host blend was also studied. In conclusion, the considered NiFe2O4-doped PMMA/PEO/CNPs blends have an effective and promising role in optoelectronic applications.

Nonlinear optical properties of lanthanum titanate glasses prepared by levitation melting

Lanthanum titanate glasses (17 La2O3-83 TiO2) are fabricated via aerodynamic levitation melting. Nonlinear refraction and absorption were measured with the Z scan technique using ∼550 ps optical pulses at 532 nm wavelength with peak intensities in the range of 0.25–2.5 GW/cm2. The two-photon absorption coefficient (β) and the effective nonlinear refraction coefficient (n2eff) are found to be, respectively, 2.19 cm/GW and 152 × 10−16 cm2/W (85 × 10−13 esu). The Raman gain is measured to be 106 × 10−11 cm/W. The nonlinearity strength is found to be nearly 60 times larger in lanthanum titanate glasses relative to silica.

Enhancement of nonlinear optical effects of pure and Mn-doped CsPbBr3 perovskite films by external voltage

CsPbBr3 and Mn:CsPbBr3 nanocrystal (NC) films were prepared on indium tin oxide (ITO) glass by a slow solvent evaporation method. The ITO layer was applied a voltage to enhance the nonlinear optical (NLO) properties of CsPbBr3 and Mn:CsPbBr3 nanocrystal (NC) films. When the voltage is zero, the Z-scan results show that the nonlinear absorption (NLA) coefficients β of CsPbBr3 and Mn:CsPbBr3 NC films are 1.60 × 103 cm/GW and 1.54 × 104 cm/GW, respectively. The nonlinear refraction (NLR) coefficients γ of CsPbBr3 and Mn:CsPbBr3 NC films are 2.07 × 10−5 cm2/W and 2.48 × 10−5 cm2/W, respectively. Subsequently, the voltages of 5.03–13.42 V were applied to the ITO layer. Finally, when the voltage is 13.42 V, the β values of CsPbBr3 (1.75 × 104 cm/GW) and Mn:CsPbBr3 (3.98 × 104 cm/GW) NC films are 10.9 and 2.6 times higher than those without the applied voltage, respectively. The γ values of CsPbBr3 and Mn:CsPbBr3 NC films are 3.73 × 10−5 cm2/W and 3.88 × 10−5 cm2/W, respectively. This research proposes an effective method to improve the third-order NLO performances of CsPbBr3 and Mn:CsPbBr3 NC films by applying voltage.

Thermal and electric field effects on the nonlinear optical response of a cyanobiphenyl liquid crystal doped with carbon dots

The present study is devoted to the investigation of the nonlinear optical response of a cyanobiphenyl liquid crystal (8CB) doped with carbon dots derived from dansyl chloride (CD-DsCl). Using the time-resolved z-scan technique, it is investigated how the CD-DsCl addition affects the nonlinear refractive coefficient of planar liquid crystal samples. The temperature dependence of nonlinear optical responses of pristine and doped samples are analyzed close to smectic-A - nematic and nematic - isotropic phase transitions. Furthermore, the effects of an external electric field are analyzed. Our results show that doped 8CB samples may exhibit an enhanced nonlinear optical response, which depends on the strength of the external field.

Saturable absorption and third-order nonlinear refraction of 2D CdSe nanoplatelets resonant with heavy-hole excitonic transitions

We report on the nonlinear optical response of CdSe nanoplatelets and CdSe/CdS core/shell nanoplatelets in the heavy-hole resonant excitonic transition spectral regions with femtosecond pulses. The nonlinear refraction and saturable absorption coefficients were obtained using the Z-scan technique, and the results were explained theoretically. The nonlinear optical response under nonresonant excitation has been previously examined; comparing with the results presented in this work, at least a one order of magnitude increase in the nonlinear refraction coefficient is evident.

Cubic Nonlinearity of Graphene-Oxide Monolayer.

The cubic nonlinearity of a graphene-oxide monolayer was characterized through open and closed z-scan experiments, using a nano-second laser operating at a 10 Hz repetition rate and featuring a Gaussian spatial beam profile. The open z-scan revealed a reverse saturable absorption, indicating a positive nonlinear absorption coefficient, while the closed z-scan displayed valley-peak traces, indicative of positive nonlinear refraction. This observation suggests that, under the given excitation wavelength, a two-photon or two-step excitation process occurs due to the increased absorption in both the lower visible and upper UV wavelength regions. This finding implies that graphene oxide exhibits a higher excited-state absorption cross-section compared to its ground state. The resulting nonlinear absorption and nonlinear refraction coefficients were estimated to be approximately ~2.62 × 10-8 m/W and 3.9 × 10-15 m2/W, respectively. Additionally, this study sheds light on the interplay between nonlinear absorption and nonlinear refraction traces, providing valuable insights into the material's optical properties.

Nonlinear optical properties of methyl green investigated by the femtosecond Z-scan technique

The third-order optical nonlinearities of methyl green in aqueous solution are studied by the Z-scan technique using a femtosecond laser at 800 nm. The valley shape in the open aperture measurements reveals the presence of reverse saturable absorption effect, which is ascribed to the three-photon absorption process. The closed aperture Z-scan traces demonstrate a negative sign for the nonlinear refractive coefficient, indicating the self-defocusing optical nonlinearity. Furthermore, the magnitudes of the nonlinear refractive index n 2, the three-photon absorption coefficient α 3, and the real part of the third-order nonlinear optical susceptibility Re χ (3) are determined and found to be linearly proportional to the dye concentration within the investigated range. Our results suggest that methyl green may be a hopeful candidate for applications in nonlinear optics.

The Comparative Third‐Order Nonlinearities of Titanium Carbide and Tungsten Carbide in the Visible Regain

AbstractThis study investigates the structure and properties of Titanium carbide (TiC) and Tungsten carbide (WC) nanoparticles. The X‐ray diffraction patterns confirm the presence of a hexagonal structure in WC nanoparticles and cubic structure in TiC nanoparticles. Transmission electron microscopy analysis reveals the particle sizes to be within the range of 30–50 nm. The bandgap of TiC and WC nanoparticles are 3.5 and 3.6 eV, respectively based on diffuse reflectance spectroscopy (DRS) along with Kubelka–Munk. Furthermore, the optical phonons and dielectric function of WC and TiC nanoparticles are investigated using the reflectance spectra along with the Kramers–Kronig (KK) method. Furthermore, the Z‐scan technique, employing a Nd:YAG laser operating at a wavelength of 532 nm, is utilized to assess the nonlinear optical (NLO) characteristics of WC and TiC nanoparticles. The open aperture Z‐scan measurements of WC nanoparticles indicate reverse saturable absorption (RSA) behavior and a positive nonlinear refraction (NLR) coefficient. On the other hand, TiC nanoparticles show RSA behavior with a negative NLR effect. The order of NLR, nonlinear absorption coefficient, and the susceptibility of TiC and WC are 10−8 cm2 W−1, 10−4 cm W−1, and 10−6 esu, respectively.

Defect-mediated saturable absorption and carrier dynamics in tin (II) monosulfide quantum dots.

Tin (II) monosulfide (SnS) has attracted considerable attention in emerging photonics and optoelectronics because of high carrier mobility, large absorption coefficient, anisotropic linear and nonlinear optical properties, and long-time stability. In this Letter, we report third-order nonlinear absorption and refraction of SnS quantum dots (QDs). Under excitation with 800-nm femtosecond pulses, QDs exhibit saturable absorption (saturation intensity ∼ 47.69 GW/cm2) and positive refractive nonlinearity (nonlinear refraction coefficient ∼ 1.24 × 10-15 cm2/W). Nonetheless, we investigate charge carrier dynamics using femtosecond transient absorption spectroscopy and propose the presence of midgap defect states which not only dictate carrier dynamics but also give rise to nonlinear optical properties in SnS QDs.

Broadband third-order nonlinear optical response of indium tin oxide in the near infrared spectrum

We reported the broadband optical nonlinearity of indium tin oxide (ITO) films with different thickness in the near-infrared spectrum region. The maximum nonlinear response is obtained at its epsilon-near-zero (ENZ) wavelength, and the measured maximum nonlinear refractive index n2 and nonlinear absorption coefficient β at the ENZ wavelength are 47 times and 28 times larger than the corresponding values at the 1000 nm wavelength, respectively. Meanwhile, a large modulation depth of 9.8% hinted that the ITO has good nonlinear modulation characteristics. In addition, the numerical simulation analysis illustrates the large nonlinear enhancement effect of ITO films, which is attributed to the significant enhancement of electric field due to the ENZ conditions. Our results highlight that ITO is a competitive nonlinear material and has great potential applications in the field of nonlinear optics and all-optical modulators.

Hybrid Silicon Nitride Photonic Integrated Circuits Covered by Single-Walled Carbon Nanotube Films.

The integration of low-dimensional materials with optical waveguides presents promising opportunities for enhancing light manipulation in passive photonic circuits. In this study, we investigate the potential of aerosol-synthesized single-walled carbon nanotube (SWCNT) films for silicon nitride photonic circuits as a basis for developing integrated optics devices. Specifically, by measuring the optical response of SWCNT-covered waveguides, we retrieve the main SWCNT film parameters, such as absorption, nonlinear refractive, and thermo-optic coefficients, and we demonstrate the enhancement of all-optical wavelength conversion and the photoresponse with a 1.2 GHz bandwidth.

Adjusting the nonlinear optical and optical limiting properties of MAPbBr3/PMMA by doping with Zn

Third-order nonlinear optical and optical limiting properties of MAPbBr3/polymethyl methacrylate (PMMA) are adjusted by doping with Zn. X-ray diffraction and photoluminescence are performed to confirm the effective doping of Zn. Typical reverse saturable absorption and self-focusing effects are observed in the undoped MAPbBr3/PMMA and Zn-doped MAPbBr3/PMMA. After Zn doping, the nonlinear absorption coefficient becomes larger but nonlinear refraction coefficient becomes smaller. This may be related to the decreased defect states after Zn doping. Besides, both values of the optical limiting threshold and the clamping normalized transmittance for the Zn-doped MAPbBr3/PMMA are obviously smaller than those of the undoped sample, indicating that its optical limiting property enhances. The reverse saturable absorption properties are caused by one photon absorption-induced excited-state absorption processes, which have been explained by using three-energy-level diagrams. The nonlinear optical and optical limiting properties of the Zn-doped MAPbBr3/PMMA make it show great potentials for application in optical limiter.

Third-order nonlinear optical properties of CsPbCl3 and CsPbBr3 perovskite quantum dots: Effects of particle size and surface traps

Particle size and surface trap effects on the third-order nonlinear optical (NLO) properties of CsPbCl3 and CsPbBr3 perovskite quantum dots (PQD) have been investigated using a femtosecond (fs) z-scan experiment. Firstly, optical, morphological, and structural characterizations of the synthesized PQDs were performed using linear absorption and photoluminescence (PL) spectra, XRD, and TEM methods. Next, NLO properties of CsPbCl3 and CsPbBr3 PQDs were studied at the operating wavelength of 800 nm and 3.564 × 1011 W/cm2 laser intensity. The nonlinear absorption coefficient (β), the nonlinear refraction coefficient (γ), and the third-order susceptibilities (χ(3)) values for both sample types were calculated to be on the order of 10−11 m/W, 10−17 m2/W, and 10−11 esu, respectively. The effects of particle size and surface trap sites on the nonlinear properties of the PQDs were studied thoroughly. γ, χ(3), and the unitless nonlinear figure of merits (FOM) parameters were realized to be proportional to the particle size for both types of materials. In addition, these parameters were improved by decreasing the surface trap sites in the PQDs. These results strongly indicate the significant potential of CsPbCl3 and CsPbBr3 PQDs for numerous nonlinear applications.

Manufacturing-Enabled Tunability of Linear and Nonlinear Epsilon-Near-Zero Properties in Indium Tin Oxide Nanofilms.

Epsilon-near-zero (ENZ) materials have attracted great interest due to their exotic linear and nonlinear responses, which makes it significant to tune ENZ wavelengths for wavelength-dependent applications. However, studies to achieve tunability in a wide spectral range and link the fabrication parameters with linear and nonlinear ENZ properties have been uncovered. ENZ indium tin oxide (ITO) nanofilms are fabricated by magnetron sputtering, through which the control of ENZ properties is demonstrated. Factors in the sputtering process, such as the gas ratio and annealing, have a great impact on the ITO samples. Tunable ENZ parameters are listed to provide a beneficial database for ENZ ITO, mainly attributed to the change of carrier concentration. The influence of ENZ parameters on optical characteristics via annealing treatment is further explored. The ENZ wavelength is blue-shifted by 609 nm, and the intrinsic loss is reduced by 63.2%, while the ITO samples exhibit better linear scattering properties and stronger field intensity enhancement. Additionally, the laser testing system illustrates the change from reverse saturable absorption to saturable absorption with an absolute modulation depth of 21.9%, improved by 222.1%, and the nonlinear refractive index n2 and nonlinear absorption coefficient β are 2.07 × 10-16 m2 W-1 and -3.16 × 10-10 m W-1 for post-annealed ITO samples, respectively. The proposed sputtering protocol offers a feasible technique to control the linear and nonlinear ENZ performance, which has great potential in laser technology and nanophotonics.

Nonlinear refractive index enhancement of Nd3+ ions loaded borate glasses in the near–infrared region by silver nanoparticles

The study presents an evaluation and in–depth discussion of the efficacy of silver (Ag) nanoparticles (NPs) concentration on the third–order nonlinear optical (NLO) proeprties of borate glasses. The optical absorption data revealed Nd3+ ions and Ag NPs to be present in the studied glasses. Measurements carried out on the tested glass through transmission electron microscopy revealed spherical–shaped NPs with a median size of ∼16.53 nm (analyzed using the ImageJ software). Open and closed aperture Z–scan configurations were employed to ascertain the attributes of NLO absorption and refraction, respectively. Open–aperture Z–scan data revelaed two–photon absorption nonlinearity in the studied glasses, while the closed aperture Z–scan data revealed self–focusing nonlinear refraction. With the increase in silver NPs concentration, the nonlinear refraction coefficient was significantly increased compared to the nonlinear absorption parameter. The results instantiate large concentrations of Ag NPs embedded in borate glasses bearing Nd3+ ions are suitable for all–optical switching applications that excel in their functioning in near–infrared spectral range.