Third-order nonlinear optical properties of Bi2S3 nanocrystals doped in sodium borosilicate glass studied with Z-scan technique

The third-order nonlinear optical properties of Bi₂S₃ nanocrystals doped in sodium borosilicate glass are measured by Z-scan technique. The microstructures of the glass are characterized by means of X-ray diffraction, transmission electron microscopy, scanning transmission electron microscopy, energy dispersion X-ray spectra, and high-resolution transmission electron microscopy. The results show that the Bi₂S₃ nanocrystals ranging from 10 to 30 nm are determined to be of the orthorhombic crystalline phase, and the third-order optical nonlinear refractive index γ, absorption coefficient β, and susceptibility χ⁽³⁾ of the glass are determined to be 2.56 × 10⁻¹⁶ m² W⁻¹, 4.13 × 10⁻¹⁰ mW⁻¹, and 1.43 × 10⁻¹⁰ esu, respectively.     

Exceptionally large third-order optical susceptibility in Ag:SrBi2Nb2O9 composite films

Thin films of SrBi₂Nb₂O₉ with and without the inclusion of Ag nanocrystals were prepared on MgO (001) substrates by alternative pulsed laser ablation of SrBi₂Nb₂O₉ ceramic and Ag metal in a nitrogen atmosphere. The size of the Ag nanocrystals can be brought down to ca. 5.0 nm, as revealed by transmission electron microscopy and X-ray diffraction. We measured the third-order susceptibility χ⁽³⁾ of the deposits by single beam z-scan technique at a wavelength of 532 nm. It is found that SrBi₂Nb₂O₉ is an effectively nonlinear optical medium, exhibiting a very large χ⁽³⁾. With the inclusion of Ag nanocrystals the χ⁽³⁾ was nearly doubled (Reχ⁽³⁾ = 8.052 × 10^− 7 esu, and Imχ⁽³⁾ = − 1.717 × 10^− 7 esu), which comes very close to the maximum value available in the current time. This indicates that the Ag:SrBi₂Nb₂O₉ composite structure can be an excellent candidate for nonlinear optical applications. A general approach for further enhanced third-order susceptibility by tailoring the dielectric constant of the metal inclusion is briefly discussed.     

The third-order optical nonlinearity of Bi3.25La0.75Ti3O12 ferroelectric thin film on quartz

Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin film was prepared on quartz substrates using chemical solution deposition. The sign and magnitude of both real and imaginary parts of third-order nonlinear susceptibility χ⁽³⁾ of the BLT thin film have been determined by the Z-scan technique performed at 800 nm with a femtosecond laser. The nonlinear refractive index coefficient γ and the nonlinear absorption coefficient β of the BLT thin film are − 1.915 × 10^− 12 cm² / W and − 6.764 × 10^− 8 m/W, respectively, the real part and imaginary part of the third-order nonlinear susceptibility χ⁽³⁾ of the BLT thin film are − 5.81 × 10^− 18 m² / V² and − 1.31 × 10^− 18 m² / V², respectively. Both the real and the imaginary parts of the third-order nonlinear susceptibility χ⁽³⁾ contribute to the nonlinearity of the film. These experimental results show that BLT thin film is a promising material for applications in nonlinear optical devices.     

Nonlinear optical properties of laser deposited CuO thin films

In this work we investigate the third-order optical nonlinearities in CuO films by Z-scan method using a femtosecond laser (800 nm, 50 fs, 200 Hz). Single-phase CuO thin films have been obtained using pulsed laser deposition technique. The structure properties, surface image, optical transmittance and reflectance of the films were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV-vis spectroscopy. The Z-scan results show that laser-deposited CuO films exhibit large nonlinear refractive coefficient, n₂ = − 3.96 × 10^− 17 m²/W, and nonlinear absorption coefficient, β = − 1.69 × 10^− 10 m/W, respectively.     

Optical nonlinearities of Au nanocluster composite fabricated by 250 keV ion implantation

Metal nanocluster composite glass prepared by 250 keV Au ions into silica with dose of 1 × 10¹⁷ ions/cm² has been studied. The microstructural properties of the nanoclusters are characterized by optical absorption spectra and transmission electron microscopy (TEM). Third-order optical properties of the nanoclusters are studied by the Z-scan technique under 1064 nm and 532 nm excitations. The nonlinear refraction index, nonlinear absorption coefficient, and the real and imaginary parts of the third-order nonlinear susceptibility are deduced. The results of the investigation of nonlinear refraction using the off-axis Z-scan configuration are presented and the mechanisms responsible for the nonlinear response are discussed. The third-order nonlinear susceptibility χ⁽³⁾ of this kind of sample was determined to be 1.6 × 10⁻⁷ esu at 532 nm and 1.3 × 10⁻⁷ esu at 1064 nm.     

Nonlinear optical properties of Ag nanocluster composite fabricated by 200 keV negative ion implantation

Metal nanocluster composite glass prepared by 200 keV Ag ions' implantation into silica with dose of 2 × 10¹⁷ ions/cm² has been studied. The formation of sandwiched nanocluster-nanovoid-nanocluster structures has been evidenced by in situ transmission electron microscopy experiment (TEM). Fast nonlinear optical refraction and nonlinear optical absorption coefficients were measured at 532 nm and 1064 nm of wavelength by the Z-scan technique. The third-order nonlinear susceptibility χ⁽³⁾ of this kind of sample was determined to be 4.0 × 10⁻⁸ esu at 532 nm and 9.0 × 10⁻⁸ esu at 1064 nm, respectively.     

Nonlinear optical properties of p-(N,N-dimethylamino)dibenzylideneacetone doped polymer

A bis-chalcone derivative, p-(N,N-dimethylamino) dibenzylideneacetone was synthesized. Its third-order nonlinear susceptibility was determined to be as high as 10⁻¹² esu by employing single beam Z-scan and degenerate four wave mixing techniques using Nd:YAG 7 ns laser pulses at 532 nm. The compound was doped in to poly(methylmethacrylate) matrix and the third-order nonlinearity was investigated by using Z-scan technique. The nonlinear refractive index of the doped polymer is found to be negative, and its magnitude is of the order of 10⁻¹⁰ esu. The results show that the compound exhibits strong reverse saturable absorption and a good optical limiting property and hence may be used as a promising dopant material. The study on concentration dependence of nonlinear optical parameters has been presented.     

Crystal structure and third-order nonlinear optical property study of a copper complex constructed by DMIT ligand

A copper complex constructed by the ligand: 1,3-dithiole-2-thione-4,5-dithiolato (DMIT) has been synthesized and its crystal structure has been determined by means of X-ray single crystal diffraction. The central copper(II) ion coordinates with two DMIT which constructed a square environment. Intermolecular C–H?S hydrogen bonds between cation groups and ligands lead to the formation of a two-dimensional supramolecular network. Its third-order nonlinear optical property has been studied using Z-scan technique at different peak laser irradiance with 20 picosecond (ps) pulses at wavelength 1064 nm. Its molecular second hyperpolarizability γ was determined to be 4.03 × 10⁻⁵⁷ m⁴ C V⁻³.     

Gold nanoparticles incorporated mesoporous silica thin films of varied gold contents and their well-tuned third-order optical nonlinearities

Gold nanoparticles (NPs) incorporated mesoporous silica thin films (MSTFs) of varied gold contents from 4.64 to 29.15 wt.% were synthesized through a refined chemical modification to the mesopore surface using different amounts of silane with amino end group. The microstructures of the composite thin films were characterized and the off-resonant third-order optical nonlinearities of the composite thin films were investigated by Z-scan technique at 1064 nm. The resultant composite thin films showed increased third-order optical nonlinear susceptibility (χ⁽³⁾) from 4.26 × 10⁻¹¹ to 9.24 × 10⁻¹⁰ esu at increased gold contents. The dependence of χ⁽³⁾ on gold content have been discussed, which can be described by an exponent function y = y₀ + Ae^−x/t when the gold contents of the composite thin films were below 30 wt.%.     

Nonlinear optical response of silica doped with copper nanoclusters under 1064 nm laser excitation

Metal nanocluster composite glass was formed by Cu ion implantation into silica using metal vapor vacuum arc (MEVVA) ion source. The microstructural properties of the nanoclusters were analyzed by optical absorption spectra and transmission electron microscopy (TEM). Third-order nonlinear optical properties of the nanoclusters were measured at 1064 nm excitations using Z-scan technique. The nonlinear refraction index, nonlinear absorption coefficient, and the real and imaginary parts of the third-order nonlinear susceptibility were deduced. The mechanisms responsible for the nonlinear response were discussed. Third-order nonlinear susceptibility χ⁽³⁾ of this kind of sample was determined to be (4.2 ± 1.0) × 10⁻⁸ esu.     

Intense low threshold nonlinear absorption and nonlinear refraction in a new organic–polymer nanocomposite

Intense reverse saturable absorption is reported for the first time in solid films of a new organic–polymer nanocomposite, cast by doping Biebrich Scarlet dye in a vinyl polymer host polyvinyl alcohol for various concentrations, as studied employing the Z-scan technique at 442 nm under different peak incident intensities ranging from 9.37 × 10² to 104.18 × 10² W cm⁻². The sample also exhibited nonlinear refraction under the experimental conditions. The estimated values of the effective coefficients of nonlinear absorption β_eff(0.27 × 10⁻² to 45.5 × 10⁻² cm W⁻¹) as well as nonlinear refraction n₂ (−1.5 × 10⁻⁷ to −2.75 × 10⁻⁷ cm² W⁻¹) measured up to the highest reported ones for low power continuous wave excitation. The composite films were characterized as nanoclusters consisting of dye molecules encapsulated between larger molecules of the amorphous polymer and having a low average roughness (≈1 nm) for the surface. These results, together with the simple and flexible processing method for the dye–polymer composite, imply that BS–PVA composite films have promising optical properties as an efficient low threshold nanocomposite material for potential applications in nonlinear optical devices.     

Low-resistance p-type ohmic contacts for high-power InGaAs/GaAs-980 nm CW semiconductor lasers

In this paper, the optimization of ohmic contacts for semiconductor lasers based on InGaAs/GaAs/GaAlAs layers is reported. Transmission electron microscopy (TEM) and electrical methods were used to study extensively the Pt/Ti/Pt/Au metallization system. The contact fabrication technology was optimized towards achieving the lowest electrical resistance. The technological control and optimization concerned the contact annealing temperature and thickness of metallic layers that form the contact. The average specific contact resistance was below 5×10⁻⁶ Ω cm² (with the record value of 8×10⁻⁷ Ω cm²) for the 10 nm Pt/20 nm Ti/30 nm Pt/150 nm Au system. The presented system was used in fabrication of continuous wave (CW) operated laser diodes. The chips mounted on passively cooled copper block achieved optical powers over 1 W, threshold current density values of 140-160 A/cm² and differential efficiencies above 1 W/A. The value of the characteristic temperature T₀ for discussed lasers varied in the range of 180-200 K.     

Tungsten-doped ZnO transparent conducting films deposited by direct current magnetron sputtering

Highly conducting and transparent thin films of tungsten-doped ZnO (ZnO:W) were prepared on glass substrates by direct current (DC) magnetron sputtering at low temperature. The effect of film thickness on the structural, electrical and optical properties of ZnO:W films was investigated. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The electrical resistivity first decreases with film thickness, and then increases with further increase in film thickness. The lowest resistivity achieved was 6.97 × 10⁻⁴ Ω cm for a thickness of 332 nm with a Hall mobility of 6.7 cm² V⁻¹ s⁻¹ and a carrier concentration of 1.35 × 10²¹ cm⁻³. However, the average transmittance of the films does not change much with an increase in film thickness, and all the deposited films show a high transmittance of approximately 90% in the visible range.     

The impact of high-dose implantation into manganin on its thermo-resistance properties under high pressure

Using high-dose implantation into manganin of 253 MeV Kr ions (a surface dose of 2.5×10¹⁵ ion/cm²), as well as 250 keV Bi ions (a surface dose of 10¹⁷ ion/cm²) and 250 keV Kr ions (a surface dose of 10¹⁶ ion/cm²), the pressure and temperature sensitivities of manganin foil have been investigated. It was found that the pressure sensitivity of manganin increased (α=2.45×10⁻⁵ MPa⁻¹ before implantation and α_imp=4.60×10⁻⁵ MPa⁻¹ after complex implantation with 250 keV of Bi and Kr ions, the accuracy of estimation does not exceed 0.01×10⁻⁵ MPa⁻¹) and its temperature sensitivity remained appreciably reduced.     

Low power CW optical limiting properties of bis(2-aminopyridinium)-succinate-succinic acid (2APS) single crystal

The increase in the usage of low power CW lasers in various applications needs for the design of optical limiters with low thresholds. The optical limiting properties and nonlinear refractive index (n₂ = −2.4189 × 10⁻⁸ cm²/W) of transparent organic crystal bis(2-aminopyridinium)-succinate-succinic acid (2APS) single crystal using continuous wave He-Ne laser excitation following Z-scan method have been evaluated. The sample exhibited negative (defocusing) nonlinearity. This thermally induced defocusing nature of 2APS crystal can be used to design the low power optical limiters. As the origin for this nonlinearity is thermal, a complete thermal transport properties such as thermal diffusivity (α_s = 5.97 ± 0.03 × 10⁻³ cm²/s), thermal effusivity (e_s = 1.94 ± 0.02 × 10⁻² J/cm²-K-s^1/2), thermal conductivity (k_s = (4. 66 ± 0.04) × 10⁻³ W/cm-K)) and specific heat capacity (C_ps = (5.61 ± 0.05) × 10⁻¹ J/g-K) of the material were studied following the photopyro electric (PPE) technique.     

Plasma oxidation of electron beam evaporated cadmium thin films

Thin films of pure cadmium have been deposited using electron beam evaporation technique. Effect of radio frequency (RF) plasma oxidation on structural, optical and electrical properties of cadmium thin films has been investigated. It was found that the RF plasma treatment affects on the physical properties of the oxidized cadmium films. Transmittance values of 87% in the visible region and 90% in the near infrared region have been obtained for cadmium oxide (CdO) film oxidized at a plasma-processing power of 600 W. The optical energy gap, E_g, was found to increase as the RF plasma-processing power increases. The resistivity values of 3 × 10^− 3 and 5 × 10^− 3 (Ω cm) have been obtained for CdO films oxidized at RF plasma-processing powers of 550 and 600 W respectively.     

Study of GeYSi1 − Y:H films deposited by low frequency plasma

In this work, we report a study of the optical properties measured through spectral transmission and spectroscopic ellipsometry in Ge:H and Ge_YSi_1 − Y:H (Y ≈ 0.97) films deposited by low frequency (LF) PE CVD with hydrogen (H) dilution. The dilution was varied in the range of R = 20 to 80. It was observed that H-dilution influences in a different way on the interface and bulk optical properties, which also depend on incorporation of silicon. The films with low band tail characterized by its Urbach energy, E_U, and defect absorption, α_D, have been obtained in Ge:H films for R = 50 with E_U = 0.040 eV and α_D = 2 × 10³ cm^− 1 (hν ≈ 1.04 eV), and in Ge_YSi_1 − Y:H films for R=75 with E_U = 0.030 eV and α_D = 5 × 10² cm^− 1 (hν ≈ 1.04 eV).     

Direct electrochemical behavior of cytochrome c on sodium dodecyl sulfate modified electrode and its application to nitric oxide biosensor

Polyacrylamide (PAM), sodium dodecyl sulfate (SDS) and cytochrome c (Cyt c) were immobilized on the surface of a glass carbon electrode (GCE), respectively, to form a Cyt c /SDS/PAM/GCE. The modified electrode was characterized with the electrochemical impedance. The direct electrochemical behaviors of Cyt c on SDS/PAM/GCE were obtained by using cyclic voltammetry. A pair of well-defined and reversible redox peaks could be observed in a 0.10 M pH 7.0 phosphate buffer solution. The anodic and cathodic peak potentials of Cyt c were at 0.051 V and − 0.003 V (vs. Ag/AgCl), respectively. The Cyt c on SDS/PAM/GCE exhibited well electrocatalytic activity to reduction of nitric oxide. The relative electrochemical parameters were obtained. The resulted electrode displayed a rapid amperometric response to the reduction of nitric oxide. The catalytic current is linear to the nitric oxide concentration in the range of 8.0 × 10^− 7 M to 9.5 × 10^− 5 M and the detection limit was 1.0 × 10^− 7 M (Signal/Noise = 3). The proposed biosensor could be used to detect quantitatively nitric oxide.     

Effect of base and oxygen partial pressures on the electrical and optical properties of indium molybdenum oxide thin films

Indium molybdenum oxide thin films were RF sputtered at room temperature on glass substrates with a reference base pressure of 7.5 × 10^− 4 Pa. The electrical and optical properties of the films were studied as a function of oxygen partial pressures (OPP) ranging from 1.5 × 10^− 3 Pa to 3.5 × 10^− 3 Pa. The obtained data show that the bulk resistivity of the films increased by about 4 orders of magnitude (from 7.9 × 10^− 3 to 7.6 × 10¹ Ω-cm) when the OPP increased from 1.5 × 10⁻³ to 3.5 × 10^− 3 Pa, and the carrier concentration decreased by about 4 orders (from 1.77 × 10²⁰ to 2.31 × 10¹⁶ cm^− 3). On the other hand, the average visible transmittance of 30.54% of the films (brown colour; OPP = 1.5 × 10^− 3 Pa) was increased with increasing OPP to a maximum of 80.47% (OPP = 3.5 × 10^− 3 Pa). The optical band gap calculated from the absorption edge of the transmittance spectra ranges from 3.77 to 3.88 eV. Further, the optical and electrical properties of the films differ from those deposited at similar conditions but with a base pressure lower than 7.5 × 10^− 4 Pa.     

Fabrication and infiltration kinetics analysis of Ti-coated diamond/copper composites with near-net-shape by pressureless infiltration

The Ti-coated diamond/copper composites with near-net-shape are manufactured by pressurelessly infiltrating liquid copper into porous Ti-coated diamond preforms. The contact angle between diamond and copper, relative density, thermal conductivity (TC), coefficient of thermal expansion (CTE), leak rate and microstructure are evaluated and characterized. In addition, the numerical analysis of the pressureless infiltration kinetics is also discussed. The results indicate that the relative density, TC and CTE of composites are 99.3%, 385 Wm⁻¹ k⁻¹ and 3–8 × 10⁻⁶ K⁻¹, respectively. It can meet heat-sink package requirement of high-power electronic devices as LED, insulated gate bipolar transistor (IGBT), etc. The liquid copper exhibits a turbulent flow with the Reynolds number in the range of 27.83–49.7. The porosity ? and the pressure drop Δp are the main influence factors controlling the velocity of liquid copper. Moreover, under vacuum condition of 8.7 × 10⁻³ Pa, the maximum theoretical infiltration length L_max of Ti-coated diamond/copper composites is found to be 552 mm.