He-Ne Laser Beam Research Articles

In situ laser reflectivity to monitor and control the nucleation and growth of atomically thin 2D materials*

The growth of atomically thin two-dimensional (2D) layered and other quantum materials is typically performed without in situ monitoring or control. Here, a simple laser reflectivity approach is demonstrated to provide in situ control over sub-monolayer thickness and growth kinetics during pulsed laser deposition (PLD) of MoSe2 layers. First, the general technique is presented with emphasis on designing the maximum sensitivity of the optical contrast through consideration of Fresnel’s equations with proper choice of layer thickness, substrate, and laser monitoring wavelength, incidence angle, and laser polarization. Then the 632.8 nm optical reflectivity of MoSe2 layers on SiO2/Si substrates was predicted and compared with in situ monitoring of MoSe2 growth by PLD under actual growth conditions using a probe HeNe laser beam. The measurements showed high sensitivity and excellent agreement with MoSe2 surface coverages calculated from atomic resolution STEM analysis of 2D layers deposited in arrested growth experiments. Growth kinetics revealed by these measurements showed sigmoidal nucleation and growth stages in the formation of the 2D MoSe2 layers that are described by a simple model, indicating the promise of the laser reflectivity technique for in situ monitoring and control of 2D materials deposition.

Measurement of evaporation of hydrocarbon droplets by laser absorption spectroscopy

Concentration measurements of evaporated hydrocarbon species by infrared laser absorption spectroscopy at a monodisperse droplet chain are presented. A droplet generator was installed within a flow channel and operated with cyclohexane, iso-octane, n-heptane, n-pentane and 1-butanol. The flow channel was flushed with a laminar flow of air at different temperatures. The absorption of a HeNe laser beam at $$\lambda = 3.39\,\upmu \hbox {m}$$ traversing through the flow channel at varying distances from the droplet chain was exploited to determine the vapor concentrations of the hydrocarbons. Measurements of the absorption cross sections in a heated gas cell ($$T = 300$$–773 K) enabled the quantification of the absorption signals from the droplet chain. Vapor concentrations were determined in planes perpendicular to the droplet chain. From the increase of vapor concentration between the planes, the evaporation rate could be determined. The evaporation rates were measured in dependence of co-flow temperature, droplet velocity, droplet generation frequency and droplet spacing. In the investigated temperature range of the air (313–430 K) the evaporation rates increased linearly with temperature. The order of the fuels with respect to evaporation rates corresponded with the boiling points of the individual fuels. In addition to the presentation of the results, the paper discusses the performance of vapor concentration measurements by laser absorption spectroscopy at droplet chains which has not been tested before in such a configuration. Particular attention was paid to the spatial resolution of the measurement. The results are well suited to validate models and numerical simulations.

Determination the Effect of Gamma Radiation on (CR-39, CN-85) Detectors by Using of Penetration of (He-Ne) Laser Beam

Determination the Effect of Gamma Radiation on (CR-39, CN-85) Detectors by Using of Penetration of (He-Ne) Laser Beam

Optical analysis, optical limiting and electrical properties of novel PbI2/PVA polymeric nanocomposite films for electronic optoelectronic applications

This paper studied the influence of changing the lead iodide (PbI2), concentration in the PVA matrix through the structural, optical and electric measurements. Nanocomposite films have been defined by X-ray diffraction and FT-IR spectrometer which reveal the interaction between PVA and PbI2. The interplanar distance, particle size, and the average inter-crystalline separation were calculated. The optical properties of PbI2/PVA composites have been examined. PVA optical band gap was reduced from 5 to 3.49 in indirect transition and from 5.48 to 4.88 indirect transition to cause an increase in optical conductivity. Dielectric constant, and dielectric loss, and electrical conductivity, σ is increased with increasing PbI2 concentrations. So, the electrical conductivity σ can be controlled by the PbI2 doping percentage. PbI2/PVA showed laser power attenuation for both He-Ne and solid-state green laser beams. The results indicate that the nanocomposites are highly recommended in optoelectronic, radiation detection and many other applications.

Multireflection Polarimetry in Microfluidics

The field of microfluidics promises new portable, low-cost sensing systems, as well as the capabilities to measure the physical or chemical properties of precious samples, for which only small volumes are available. However, when using microfluidic channels with millimeter to micron scale dimensions, together with optical sensing methods, these configurations result in short path lengths over which the signal can be acquired. Whilst polarimetry would greatly benefit from using small volumes, providing important information on the structure of chiral biomarkers in life sciences, the small interrogation volumes associated with the use of minute samples decreases the numbers of molecules in the light path that cause an optical rotation and reduces the sensitivity of the technique. Here, we show that when an optical beam, passing through a chiral sample, undergoes multiple reflections from suitably aligned external micromirrors, the usual cancelling out of the optical rotation, that occurs when the rotated polarized beam is passed back through a solution following reflection at a single mirror, can be negated. This enables the chirality of molecular species present in a microfluidic sample to be measured with increased sensitivity. This approach was validated experimentally using solutions of D-(+)-glucose as a model system, by investigating the effect of multiple reflections of a linearly polarized He-Ne laser beam and a 403 nm diode laser beam across the microfluidic channel. It was found that there was a 30-fold enhancement in the limit of detection with as few as 11 reflections through the sample.

Optical linearity and bandgap analysis of RhB-doped PMMA/FTO polymeric composites films: A new designed optical system for laser power attenuation

Thin films of PMMA doped with Rhodamine B-dye have deposited successfully on a fluorine-doped tin oxide (FTO) glass substrate as a new optical system by using a spin coating method. This new system is promising to be used in various technological applications as solar energy cells, electronic apparatuses, devices of optical filter properties and optoelectronic tools. X-ray diffraction (XRD) illustrates a uniform and semicrystalline structure in nature for the obtained thin films. A spectrophotometric investigation was applied on the prepared thin films at the range of (300–2500 nm) for the wavelength. Both linear refractive index and absorption index values were measured to be reduced as the wavelength was raised. Tauc’s plot indicated that direct and indirect transitions were displayed by the thin film. Both direct and indirect bandgaps were calculated and analyzed. Continuous waves of the green laser beam (operating at 532), and He-Ne laser beam (operating at 632.8 nm) were used to study the optical properties of the prepared thin films with different dye concentrations. The results illustrated that the polymeric composites films are highly attenuated for the laser beam of 532 nm. The designed RhB-doped PMMA/FTO composites can be extensively appropriate to the optoelectronic applications.

Electro-optics Behaviors of Fe3O4 Ferrofluids: A Preliminary Study

In this paper, we report the experimental observation of electro-optics effect in the ferrofluids comprising of Fe3O4 nanoparticles by a 1 mW He-Ne laser beam. An external electric field was applied perpendicular to the beam. Ferrite ferrofluid was prepared by using a coprecipitation-sonochemical technique. The effect of the electric field on the optical properties of ferrofluid was still too weak as we had expected. One possibility that can be suspected as the cause is that the electric field applied to ferrofluid is still too weak.

A Preliminary Study on the Thermo-optics Characteristics of Chromium Ferrite Ferrofluids

In this paper, we report the experimental observation of temperature influence on optical properties of ferrofluids comprising of chromium ferrite nanoparticles by a 1 mW He-Ne laser beam. An external thermal field was maintained perpendicular to the beam. In this research, the thermal response of chromium ferrite ferrofluids prepared by coprecipitation-sonochemical technique was studied. The preliminary investigation showed that the chromium ferrite ferrofluids have an excellent property as a candidate for a temperature sensor application showing a good response on the temperature treatment. Interestingly, we found a hysteresis phenomenon in one cycle in transmission light originating by varying temperature.

Temporal evolution of photoinduced optical chirality in nanostructured light-sensitive waveguide thin films: Simultaneous excitation of TE and TE1 modes

Optical properties of the self-organized gratings in thin photosensitive waveguide AgCl films on a glass substrate, doped by Ag nanoparticles, in the case of simultaneous excitation of TE0 and TE1 modes are investigated. These gratings are a result of interference of the incident linear polarized He-Ne laser beam with the excited TEn-modes of the AgCl layer. The interference field patterns the re-distribution of the nanoparticles. Each excited mode generates its own grating. The self-organized gratings associated with the TE0 mode appear earlier than that of the TE1 mode. There is a competition between TE0-gratings and TE1-gratings for absorbing the nanoparticles, because their available amount is limited in the interaction area. The competition is due to the positive feedback of the light mechanism. Thus, the TE1-grating removes some Ag nanoparticles from the already generated TE0-grating, which forms some chiral complex building blocks of the gratings. The induced chirality leads to the induction and enhancement of optical activities in the samples. Longer exposure of the samples leads to the variation of induced optical chirality. Generation of the gratings increases anisotropy of the sample, which in turn enhances the chiroptical properties of the Ag/AgCl/Glass system. Changes in absorption spectra, induced dichroism, and induced optical gyrotropy of the samples are measured. Diffraction patterns of the exposed samples confirm the coexistence of TE0- and TE1-associated gratings and their competition. AFM images support the above-mentioned process. It is observed that longer exposure and perfect formation of the induced gratings accompany with the reduction of chiroptical property, due to the destruction of chiral complex silver nanoclusters.

Interferometric investigation of the opto-mechanical and structural properties of iPP/TiO2 nanocomposite fibers.

Fibers that missing specific features and functionalities could be innovated and functionalised via nano additives, in particular metal oxides. Titanium oxide (TiO2 ) nanoparticles have been added to isotactic polypropylene (iPP) to form iPP/TiO2 nanocomposite fibers. Three samples of iPP/TiO2 fibers were extruded at three extrusion speeds 25, 50, and 78 m/min were considered in this study. Mach-Zehnder interferometer was used to assess the changes in the opto-mechanical and geometrical parameters of iPP/TiO2 nanocomposite fibers along the fiber axis. The mechanical drawing device along with Mach-Zehnder interferometer was utilized to stretch the filaments to different draw ratios. The effect of mechanical cold drawing and extrusion speed on the optical and physical characteristics of iPP/TiO2 nanocomposite fibers were determined along the fiber axis. The optical and physical variation along the nanocomposite samples were characterized by measuring their refractive indices, birefringence, refractive index profile along the fiber axis. The diffraction of He-Ne laser beam was used to define the variation of the fiber diameter along the fiber axis through their cross-sectional area and shape. A sample of uniform diameter from neat iPP fibers was used as reference material for studying the variation of the iPP/TiO2 fiber diameter along the fiber axis. As result, the iPP/TiO2 nanocomposite fibers exhibited nonuniform diameters. The dispersion of TiO2 particles in nanocomposite fibers influences the properties' consistency along and across the fiber.

Characterization of Tunable Micro-Lenses with a Versatile Optical Measuring System.

In this work, we present the results of the opto–electro–mechanical characterization of tunable micro-lenses, Tlens®, performed with a single-spot optical measuring system. Tested devices are composed of a transparent soft polymer layer that is deposited on a supporting glass substrate and is covered by a glass membrane with a thin-film piezoelectric actuator on top. Near-infrared optical low-coherence reflectometry is exploited for both static and low-frequency dynamic analyses in the time domain. Optical thickness of the layers and of the overall structure, actuation efficiency, and hysteretic behavior of the piezo-actuator as a function of driving voltage are obtained by processing the back-reflected signal in different ways. The use of optical sources with relatively short coherence lengths allows performing interferometric measurements without spurious resonance effects due to multiple parallel interfaces, furthermore, selecting the plane/layer to be monitored. We finally report results of direct measurements of Tlens® optical power as a function of driving voltage, performed by redirecting a He-Ne laser beam on the lens and monitoring the focused spot at various distances with a digital camera.

Analysis of Intensity Distribution in the He-Ne Laser Beam by Gaussian Distribution Function

The purpose of this research is to analyze the distribution of density in the laser beam, both from the experimental and theoretical point of view. I measured the density distribution through the He-Ne laser beam and prepared an attempt to compare it with the Gaussian distribution function. Image profiling can be used to determine the distance of objects depending on the distribution of the laser beam spot surroundings by their width. It can also be used to take pictures of things and define their distances and shape things. As we see, Nubia is very good. From the compatibility analysis found that (the program that made the fitting mention of GNUPLOT).

Statistical Analysis of Instantaneous Effect of Polarized He-Ne Laser Radiation on the Elastic Modulus of Soft Biological Tissue

Introduction: This work is dedicated to investigating the effect of applying polarized He-Ne laser beam (λ= 632 nm, 10 mW, 1 j/cm2) with polarization direction perpendicular to the stress direction on the tensile strength of biological tissue (elasticity index of the Pleura 10*4*0.1 mm). Method and Material: The optimized characteristics of the laser illumination in the minimum times of radiation is detected here through some series of designed experiments and the results are completely applicable to the new investigations. To achieve the purpose, the experiments are designed in full factorial design model to study the effecting factor of viscoelastic modules of the pleura. The employed factor is time duration of the exposure. different irradiation timing is 5 s, 10 s, 15 s and 20 s. Result: Through the variance analysis it is found that time duration of radiation plays very important role on its viscoelastic characteristics. Additionally, it is revealed that a special condition, the time of exposure =10 sec, leads to the highest value of relative elastic modulus, i.e., the most increase in the tensile strength of the Pleura because of dehydration of cells is happened in longer time irradiation than 10s and no effect in less duration than 10s. Conclusion: This conclusion can be useful in dealing with wound scars, reforming the shape of the cornea, cartilage reshaping and et.

Development of a time-of-flight low-energy neutral particle analyzer for EAST tokamak

To understand the erosion effect of neutral particles on the first wall, a low energy neutral particle analyzer (LENPA), based on the time-of-flight method, has been developed for the Experimental Advanced Superconducting Tokamak (EAST). The LENPA to be installed in the EAST mid-plane mainly consists of a chopper sub-system, a 3 m long flight tube, two sets of detector assemblies, and data acquisition and processing, vacuum, power supply, and control sub-systems. The neutral outflux is gated in bunches of 1 μs time scale by a slotted rotating disc which is driven by a vacuum compatible motor modified from a turbomolecular pump. A He-Ne laser beam is projected through the disc slit to record the instants of chopper slits opening with an avalanche photodiode module. An on-axis electron multiplier detects chopped neutrals, and a central perforated Cu-Be plate is employed to channel the emitted secondary electrons into an off-axis electron multiplier. The radiation peaks of on-axis electron multiplier caused by UV photons projected through the central hole of the Cu-Be plate provide an alternative way to record the chopper slits' opening time. With an additional 4 TB fast memory card, 1 GS/s sampling rate has been realized by using a GaGe acquisition card continuously. The LENPA data from the EAST together with neutral particle material erosion experiments will be used to benchmark the simulation results for better predictions on future fusion reactors, such as ITER and China Fusion Engineering Test Reactor (CFETR).

Detection of Vegetable Oil Variance Using Surface Plasmon Resonance (SPR) Technique

The difference between coconut oil, corn oil, olive oil, and palm oil has been detected using surface plasmon resonance (SPR) technique. This is a new method in material characterization that can be used to identify vegetable oil variance. The SPR curve was measured by SPR system consisting of optical instruments, mechanical instruments, Main UNIT, and user interface (computer). He-Ne laser beam of wavelength 633 nm was used as light source, while gold (Au) thin film evaporated on half cylinder prism was used as the base so that surface plasmon polariton (SPP) waves propagate at the interface. Tween-80 and PEG-400 are used as surfactant and co-surfactant to make water-oil emulsion from each sample. The sample was prepared with the ratio of oil: surfactant: co-surfactant as 1:2:1 and then stirred on the water to make emulsions. The angle shift was measured by the change of SPR angle from prism/Au/air system to prism/Au/water-oil emulsion. The different SPR angle of each sample has been detected in the various number of spray, a method that was used for depositing the emulsion. From this work, we conclude that the saturated fatty acid component was the most significant component that changes the refractive index in the vegetable oil in water emulsion that can be used to characterize the vegetable oil variance.

Polydyne displacement interferometer using frequency-modulated light.

A radio-frequency Frequency-Modulated (FM) signal is used to diffract a He-Ne laser beam through an Acousto-Optic Modulator (AOM). Due to the modulation of the FM signal, the measured spectra of the diffracted beams comprise a series of phase-synchronized harmonics that have exact integer frequency separation. The first diffraction side-beam emerging from the AOM is selected by a slit to be used in a polydyne displacement interferometer in a Michelson interferometer topology. The displacement measurement is derived from the phase measurement of selected modulation harmonic pairs. Individual harmonic frequency amplitudes are measured using discrete Fourier transform applied to the signal from a single photodetector. Phase signals are derived from the changes in the amplitudes of different harmonic pairs (typically odd-even pairs) with the phase being extracted using a standard quadrature method. In this study, two different modulation frequencies of 5 and 10 kHz are used at different modulation depths. The measured displacements by different harmonic pairs are compared with a commercial heterodyne interferometer being used as a reference for these studies. Measurements obtained from five different harmonic pairs when the moving mirror of the interferometer is scanned over ranges up to 10 μm all show differences of less than 50 nm from the reference interferometer measurements. A drift test was also used to evaluate the differences between the polydyne interferometer and reference measurements that had different optical path lengths of approximately 25 mm and 50 mm, respectively. The drift test results indicate that about half of the differences can be attributed to temperature, pressure, and humidity variations. Other influences include Abbe and thermal expansion effects. Rough magnitude estimates using simple models for these two effects can account for remaining observed deviations.

Enhanced Back-Scatter in double-pass optical links with non-classic turbulence.

The average intensity, as well as the intensity-intensity correlation at one and two points of the He-Ne laser beam passing in the monostatic double-passage (21 meter long in single pass) atmospheric channel with a retro-reflector are measured experimentally. The non-classic turbulence is generated in two different ways: by means of a 1.8-meter long turbulent chamber with 3D distributed non-classic turbulence and a localized hot air jet-stream applied to the beam in a transverse direction. The Enhanced Back Scatterer (EBS) effects produced by the two types of turbulence are compared as turbulence is placed at various locations along the channel. The data reveals the spatial stability of the EBS intensity in the detected beam in both cases, while the whole beam centroid generally appears to be off-centered, due to deterministic and random temperature gradients. The strongest EBS effect was observed with the localized turbulence placed close to the retro-reflector. The studied situations may appear in urban/industrial/coastal atmosphere and are of importance for free-space optical communications with retro-modulation.

Effect of Helium-Neon Laser and Sodium Hypochlorite on Calf Thymus Double-Stranded Deoxyribonucleic Acid Molecule: An in Vitro Experimental Study

Introduction: Low-energy helium-neon (He-Ne) laser beam lightis used in combination with sodium hypochlorite (Na2HOCl3) for clinical purposes. Regarding this, the present study aimed to investigate the effect of He-Ne laser (632.8 nm) and sodium hypochlorite on the calf thymus double-stranded deoxyribonucleic acid (ctdsDNA) molecule. Materials and Methods: For the purpose of the study, ctdsDNA solutions (30µg/ml) were exposed to He-Ne laser (632.8 nm) light in the absence and presence of different concentrations of sodium hypochlorite for up to 60 sec. The levels of nucleic acids released as uncontaminated and contaminated proteins were considered as the markers of DNA damage in terms of hypochromasia (i.e., DNA strand breakage) and hyperchromasia (i.e., of DNA strands separation). Results: The mean concentration of nucleic acids insignificantly (P > 0.05) decreased after exposure to laser light irradiation (hypochromic effect). Furthermore, laser irradiation insignificantly and inconsistency protected the ctdsDNA molecules from the effect of sodium hypochlorite. Sodium hypochlorite at concentrations of 1 and 3 mmol reduced the levels of the nucleic acids released from contaminated protein by 29.2% and 78.3% of the pre-incubated levels (hyporchromasia effect). The He-Ne laser (632.8 nm) irradiation induced hypochromic effect on the uncontaminated and contaminated proteins, while sodium hypochlorite induced a remarkable hyperchromic effect at higher concentrations. Conclusion: As the finding indicated, a short time He-Ne laser light (632.8 nm) irradiation exerted minor significant effect on the ctdsDNA molecule. This laser light did not interact with sodium hypochlorite as a synergistic combination against the ctdsDNA molecule.

Polarization-independent phase modulators enabled by two-photon polymerization

A double-layer polarization-independent liquid crystal (LC) phase modulator is demonstrated and characterized. Using two-photon polymerization process, an ultra-thin partition polymeric film to separate the LC cell into two layers with orthogonal alignment directions is fabricated. Such a thin partition film also helps to reduce the voltage shielding effect. Using a high birefringence and low viscosity LC mixture, 2π phase change at merely 10 V for a He-Ne laser beam is achieved, while keeping a fast response time. Simulation result agrees reasonably well with experimental data.

Laser treatment of Se/Bi heterostructure: Bi2Se3 nanofilm formation

Thin films of Se/Bi heterostructure were obtained by the by thermal vaporization of Se and Bi powders in a vacuum camera. A focused He-Ne laser beam at 632.8 nm is shown to cause local darkening of Se/Bi heterostructure at incident power densities above 3.5 kW/cm2. The possibility of laser recording of diffraction grating by this technique is demonstrated. It is shown that the resistance between the electrical contacts on the heterostructure reduces as the lines between these contacts are recorded. Data obtained from Raman spectra before and after laser treatment indicate that the darkening is accompanied by Bi2Se3 formation.