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Simultaneous contribution of saturation in absorption and nonlinear photoacoustic effects in CuTPP under blue laser irradiation
摘要： The nonlinear optical responses of CuTPP are studied in toluene under the irradiation of a blue laser beam focused using a convergent lens. The z-scan setup is applied in order to determine nonlinear optical responses. Besides the nonlinear absorption response, which indicates reversed saturable absorption, intensity dependence photoacoustic waves are created in both hearable sound and ultrasonic waves. Hearable sound is recorded by a microphone and analyzed by Fourier transform analyzes in order to calculate the sonic frequencies. Because of the high absorption of dye molecules, a dilute solution is prepared to enhance transmittance from the cell to analyze profile of the passing beam. Diffraction rings pattern is observed with about 30 dense rings, in which the number of rings depends on the beam intensity that could be attributed to the higher frequency photoacoustic waves and the corresponding refractive grating induced by the waves. The nonlinear refraction of the solution is a simultaneous contribution of thermal lensing and photoacoustic effects, in addition to the saturation in absorption process which influences the nonlinear absorption behavior. This compound can be proposed as a good candidate in mode locking, Q-switching devises, and short pulse generators where we need a pattern from the activity of the saturable absorber at the cross section of the beam.
关键词： OPAZ-Scan,CuTPP,Photoacoustic,Saturation in absorption,Z-scan,Diffraction rings pattern
更新于2025-09-23 15:19:57
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Dynamics of Instability in Plasmonic Response of Nanostructured Gold Thin Films on Ambient Ageing
摘要： Instability in the plasmonic response of nanostructured gold (Au) thin films on ambient ageing has been investigated. Different types of Au nanostructures (island, percolated, and continuous thin film) are obtained at the early stage of thin film growth by variation in film thickness using sputtering technique. Absorbance spectra of as-deposited island Au film shows a systematic blue-shift in the localized surface plasmon resonance (LSPR) peak position on ageing. The rate of blue-shift in the LSPR peak position is fitted with single-exponential decay function to analyze the dynamics of the plasmonic response. The as-deposited percolated Au film displays a transformation of broadened plasmonic response into a wavelength independent absorbance profile on ageing. The immersion of a new plasmonic band in the absorbance spectra is noted for continuous Au thin film on ageing. The change in plasmonic responses of nanostructured Au thin films on ambient ageing is found to be directly correlated with the re-organization of the surface morphology. Finally, ageing-induced solid-state dewetting and crystallization are found to be the main responsible processes of the underlying mechanism for morphological re-organizations, leading to change in the plasmonic response of the nanostructured Au thin films.
关键词： X-ray reflectivity,Grazing incidence X-ray diffraction,Localized surface plasmon resonance,Thin film ageing,Transmission electron microscopy
更新于2025-09-23 15:19:57
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Laser frequency shift up to 5 GHz with a high-efficiency 12-pass 350-MHz acousto-optic modulator
摘要： We demonstrate a novel laser frequency shift scheme using a 12-pass 350-MHz acousto-optic modulator (AOM). This AOM system shows better performance compared to ordinary acousto-optic modulation schemes. The frequency of the incident laser beam is shifted by 4.2 GHz with the total diffraction efficiency as high as 11%, and the maximum frequency shift is 5 GHz. Combining the ±1st order diffraction, laser signals with up to 10 GHz frequency difference can be obtained, which fulfill most frequency shift requirements of laser cooling and coherent manipulation experiments with alkali metal atoms.
关键词： frequency stability,diffraction efficiency,acousto-optic modulator,multi-pass AOM,laser frequency shift
更新于2025-09-23 15:19:57
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Development and characterization of TlGaSe2 thin film-based photodetector for visible-light photodetector applications
摘要： In current work a thermal evaporation technique has been employed to fabricate the thin films from the grown TlGaSe2 single crystal and investigated. X-ray diffraction study revealed the formation of polycrystalline films of monoclinic crystal system. The crystallite size was estimated to be 11 nm. Atomic force and scanning electron microscopy studies shows the nanocrystalline film fabrication and the size of grain was estimated. Optical study shows that the grown film is about 55% transparent in 800–1500 nm region and possess a sharp absorption edge. The direct energy gap of TlGaSe2 films was estimated around 2.31 eV. The photo current of the fabricated TlGaSe2 photodetector increases about 6 times compare to dark when exposed under 5 mW/cm2 illumination. The fabricated detector possesses high external quantum efficiency of 158% and also the detectivity reached to 5.16 ? 1010 at V ? 10 V. The on/off behaviour of the device was also studied and found that the response time for growth and decay is 88 ms and 90 ms, respectively.
关键词： A. Thin film,D. optical properties,C. X-ray diffraction,B. thermal evaporation,D. electrical properties,D. photodetector
更新于2025-09-23 15:19:57
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A Report on Growth And Spectroscopic Studies on The L-Tartaric Acid Doped Potassium Dihydrogen Phosphate Non-Linear Optical Single Crystals
摘要： In recent years study of non-linear optical (NLO) materials is gaining rapid momentum due to their needs in several device applications. Potassium Dihydrogen Phosphate (KDP) is a well-known NLO material, whose non-linearity is enhanced by doping with amino acids. In this present study, single crystal of L-Tartaric acid doped potassium Dihydrogen phosphate (LTKDP) have been grown by slow evaporation method at room temperature. Good quality transparent crystals were obtained with 27-30 days. The crystallinity and cell parameters were characterized by X-ray diffraction analysis (XRD), the shifts in frequency assignments of various functional groups of KDP due to the addition of L-Tartaric acid was analysed by Fourier transform infrared (FTIR) and Fourier transform Raman spectroscopic studies. The dielectric constant and the dielectric loss of the single crystals were studied as a function of frequency. Kurtz- Perry power technique was employed to determine the Second Harmonic Generation (SHG) efficiency of LTKDP single crystal.
关键词： X-ray diffraction,SHG efficiency,L-Tartaric acid,slow evaporation method,FT-Raman,Potassium Dihydrogen Phosphate,FTIR,non-linear optical materials
更新于2025-09-23 15:19:57
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Growth of Ag(1?1?1) on Si(1?1?1) with nearly flat band and abrupt interface
摘要： Growth of Ag films of up to 30 nm thickness on Si(1 1 1) 7 × 7 at room temperature is investigated by low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). LEED revealed the coexistence of Ag and Si spots starting with 1 monolayer (ML) of Ag deposited. The Ag lattice constant, starting with 25 ML, is slightly higher than for bulk Ag and increase linearly with Ag thickness, reaching about 4.2 nm for the thickest films. The average terrace widths detected from LEED spot profile analysis are about 30 nm for clean Si(1 1 1) 7 × 7 and about 5.5 nm for the thickest Ag(1 1 1) film, in agreement with STM observations. The intensity variation of core levels analyzed by XPS is taken into account by a model assuming the initial formation of Ag islands with linear variation of coverage vs. the amount of Ag deposited, followed by growth in a quasi layer-by-layer mode. The interface barrier is in the range of 0.4 eV, lower than all values reported previously. Ag deposited on Si(1 1 1) 7 × 7 at room temperature provides flat Ag(1 1 1) for synthesis of 2D materials, and may be used for low barrier Schottky diodes.
关键词： Scanning tunneling microscopy,Low energy electron diffraction,X-ray photoelectron spectroscopy,Ag/Si(1 1 1),Molecular beam epitaxy,Surface barrier height
更新于2025-09-23 15:19:57
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Optical properties of ZnO thin films deposed by RF magnetron
摘要： We have grown ZnO thin films on glass substrate by RF magnetron sputtering using metallic zinc target. The influences of some parameters on thin film optical properties were assessed. They exhibited extremely high resistivity of 1012 ?.cm, an energy gap of 3.3 eV at room temperature. It was found that a RF power of 50 W, a target to substrate distance of 70 mm, very low gas pressures of 3.35 x 10-3 Torr of argon and oxygen mixed gas atmosphere gave ZnO thin films with a good homogeneity and a high crystallinity. All the films are transparent in the visible region (400 to 800 nm) with average transmittance above 80%. The optical transmittance and refractive index, calculated from the spectra of optical absorbance, show a significant dependence on the growth parameters. As for the sample grown at 100°C, the average transmittance is about 80% in the visible wavelength range and the refractive index is estimated to be 1.97.
关键词： X-ray diffraction,RF sputtering magnetron,refractive index,ZnO,transmittance
更新于2025-09-23 15:19:57
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Studies on structural, surface morphology and optical properties of Zinc sulphide (ZnS) thin films prepared by chemical bath deposition
摘要： Zinc sulphide (ZnS) thin films have been prepared by chemical bath deposition method. X-ray diffraction (XRD) is used to analyze the structure and crystallite size and scanning electron microscopy is used to study the particle size and morphology of ZnS thin film. Optical studies have been carried out using UV-Visible-NIR absorbance spectrum. The band gap value of the film is calculated and it is found to be 3.45 eV. The dielectric properties of ZnS thin films have been studied in the different frequency at different temperatures.
关键词： scanning electron microscopy (SEM),Zinc sulphide (ZnS) thin films,dielectric studies,X-ray diffraction (XRD)
更新于2025-09-23 15:19:57
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Substitution Effect on Near Infrared Absorbance Based Selective Fluoride Sensing of Indole Functionalized Thiourea Molecules
摘要： A series of six new symmetrically functionalized thiourea based indole conjugated ligands (S1–S6) are synthesized in good yields and their anion recognition/sensing ability in the solution as well as in solid state is explored. Chemosensors S1–S6 show selective colorimetric sensing of fluoride by stable NIR signatures at 942 nm, 956 nm, 825 nm, 890 nm, 948 nm, and 1160 nm with corresponding spectral shifts (Δλ) of 592 nm, 588 nm, 603 nm, 485 nm, 610 nm, and 800 nm by virtue of position, conjugation and electronic effect of different functional groups attached to indole unit. To the best of our knowledge the peak shift of a chemosensor by magnitude of 800 nm (from UV to NIR region) in the presence of fluoride represents the highest of its kind. The changes in absorption spectra in the presence of various anions follow the Hofmeister series of anions. All the chemosensors show a bathochromic shift in the absorption spectra of the ligands in the presence of acetate, benzoate, di-hydrogen phosphate and hydrogen pyrophosphate due to hydrogen bonding interactions with the indole and thiourea-NH groups. The single-crystal X-ray structures evidence in favour of planar structures of the free sensors (S1, S4, and S5) and strong hydrogen bonding interactions between phosphate anion and indole–thiourea NH groups.
关键词： X-ray diffraction,NMR titration,Fluorides,UV/Vis titration,Sensing
更新于2025-09-23 15:19:57
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RBS/C, XRR, and XRD Studies of Damage Buildup in Er‐Implanted ZnO
摘要： Accumulation and transformation of defects formed in bulk ZnO crystals at room temperature upon 300 keV Er ions bombardment have been thoroughly examined using complementary techniques: Rutherford Backscattering Spectrometry in ion Channeling mode (RBS/C), X-Ray Reflectivity (XRR), and X-Ray Diffraction (XRD). Evaluation of RBS/C spectra has been performed using Monte Carlo (MC) simulations (McChasy software). Two defect types have been indicated: point defects (randomly displaced atoms, RDA) and extended ones (edge dislocations, DIS). Depth-distributions of RDA and DIS turned out to be shifted toward deeper regions of ZnO crystals (relative to Er-ions range) while DIS are localized even deeper than RDA. The MC simulations reveal three regions of defects accumulation separated by two regions of rapid defects transformation occurring at a certain critical Er fluence. Strain, suggested to be a driving force of defect transformation, has been determined using simulations of the XRD profiles based on the dynamical theory of X-ray diffraction (MROX software). The presented research can help to better understand the interaction between impurity Er ions and ZnO target atoms during the implantation process. Hence, implantation conditions, for example, for luminescence purpose may now be more efficiently chosen based on the results discussed.
关键词： Monte Carlo simulations,defects analysis,X-ray reflectivity,ion channeling,dynamical theory of X-ray diffraction
更新于2025-09-23 15:19:57