Ne Laser Beam Research Articles

Experimental study on the non-equilibrium condensation of a liquid film after shock wave in a vertical diaphragmless shock tube

In this study, the physical characteristics of ethanol vapor behind the incident and reflected shock waves in a vertical diaphragmless shock tube are measured. To verify the excellent properties of the vertical diaphragmless shock tube, the experimental data are compared with the theoretical Rankine-Hugoniot curves. Combined with the shock wave visualization imaging, it is verified that the designed shock tube can be effectively used for investigating the phase-change heat transfer behind the shock waves. According to measurements based on a He–Ne laser beam optical interference system, the growth rate of the liquid film behind the reflected shock wave (Vfr) is smaller than that behind the incident shock wave (Vfi). The experimental value of condensation parameter is approximately 0.025, which is in good agreement with the theoretical value determined using the molecular dynamics approach. When the Mach number of the incident shock wave (Mi) is employed as a factor influencing liquid film growth, it is observed that when all the other parameters remain constant, the larger the Mi, the faster the growth of condensed liquid film. The vertical diaphragmless shock tube facilitates strong reproducibility of results under the same conditions, which can increase the accuracy of experiments such as phase-change heat transfer.

Ammonium iodide salt-doped polyvinyl alcohol polymeric electrolyte for UV-shielding filters: synthesis, optical and dielectric characteristics

Polyvinyl alcohol (PVA) incorporated with various amounts of ammonium iodide salt (NH4I) composite polymer electrolyte films were prepared via the casting process. The XRD analysis, as a tool for structural investigation, confirms the polymer electrolytes formation. The transmittances of the studied samples are decreased with increasing NH4I fillers. The UV–Vis absorption spectra are shifted to the higher wavelengths, which indicate their importance for light shielding devices. The bandgaps decrease with the increase in NH4I content, attributed to the increase in the crystallite size. The calculated Urbach energy was found to increase with increasing NH4I salt fillers. The samples' optical limiting is carefully investigated using a He–Ne laser beam of wavelength = 632.8 nm. This result enhances light absorption behavior and makes the material suitable for optical UV-protection devices. The correlation between dielectric properties and conductivity is also understood and discussed. The dielectric permittivity e' of the samples is associated with the dipole, and polarization increased with the addition of NH4I salt content as the particle size increased according to XRD analysis. AC impedance spectroscopy was carried out to disclose the PVA doped with NH4I polymer electrolyte films as a function of various NH4I salt fillers. The analysis via complex electric modulus gives abnormal behavior by adding NH4I salt content, where the minimization of the electrode polarization can be achieved. Our results indicate that the newly designed composite polymeric electrolyte films are commonly appropriate for electronic and optoelectronic devices.

Controlling the light wavefront through a scattering medium based on direct digital frequency synthesis technology* *Project supported by the National Key Research and Development Program of China (Grant Nos. 2016YFB0401902 and 2016YFB0402001) and Key-Area Research and Development Program of GuangDong Province, China (Grant No. 2019B010926001).

Phase modulation is a crucial step when the frequency-based wavefront optimization technique is exploited to measure the optical transmission matrix (TM) of a scattering medium. We report a simple but powerful method, direct digital frequency synthesis (DDS) technology to modulate the phase front of the laser and measure the TM. By judiciously modulating the phase front of a He–Ne laser beam, we experimentally generate a high quality focus at any targeted location through a 2 mm thick 120 grit ground glass diffuser, which is commercially used in laser display and laser holographic display for improving brightness uniformity and reducing speckle. The signal to noise ratio (SNR) of the clear round focus is ∼ 50 and the size is about 44 μm. Our study will open up new avenues for enhancing light energy delivery to the optical engine in laser TV to lower the power consumption, phase compensation to reduce the speckle noise, and controlling the lasing threshold in random lasers.

Angle- and polarization-dependent reflection and backscattering from FS-LIPSS covered stainless steel surfaces: experimental study

Large double-scale random rough surfaces covered by femtosecond laser-induced periodic structures are produced experimentally. Irradiation circumstance is considered as the main approach for manufacturing various samples. Fabricated surfaces on the steel substrate are full of high spatial frequency ripples which are crossed by deeper grooves. A polarized He–Ne laser beam is utilized to illuminate the complex surfaces and probe their optical features. Intensities of the reflected and backscattered beams at various incident angles (from small values to large amounts) are monitored in this regard. Results show that the linearly polarized probe beam is scattered diffusely and also de-polarized significantly after striking the irradiated surfaces. However, the amounts of de-polarization of the reflected/backscattered lights are dependent on characteristics of the surface as well as the initial polarization and incident angle of the probe beam. Besides, a relation between the optical response and orientation of the samples is also observed. Finally, at last section, discussions concerning the physical phenomena that are playing a role in the optical response of the samples are presented in detail. Our experimental results reveal that photo-ablation with ultrashort laser systems is highly sensitive and fast enough method for fabrication of surfaces with applications in industry and medical fields in which controlled light reflections or backscattering are needed.

Nonlinear optical re-orientation and photoacoustic properties of indium tin oxide nanoparticles

Abstract The nonlinear optical Kerr effect of indium tin oxide (ITO) nanoparticles (NPs) was investigated using continuous wave laser beams. ITO NPs were synthesized using the sol-gel method and were prepared as a colloid and a thin film. The structural and optical properties of the synthesized particles were characterized by X-ray diffraction analysis, transmission electron microscopy and UV–visible spectroscopy. The energy band gap was found to be 3.45 eV. The nonlinear optical properties of these NPs were measured by two sources: one He–Ne laser beam and a diode laser beam at wavelengths of 632.8 nm and 450 nm, respectively. For the He–Ne laser beam, the obtained nonlinear refractive index was found to be n 2 = + 1.7 × 10 − 7 c m 2 W , which its plus sign indicates that the main nonlinear refractive phenomenon involved was the optical re-orientation effect due to the electric dipole moment of the particles. The high nonlinear absorption of the particles at both wavelengths leads to the creation of intensity-dependent photoacoustic (PA) signals that are mainly in the audible range of sound frequencies. The sonic waves were within a frequency interval of 2–19 KHz. The ITO particles were present as NPs, which simultaneously show optical re-orientation and PA responses under continue wave (CW) laser irradiations. This research thus finds that ITO NPs are a good candidate for electro-optical sensors and applications.

Ag/PVP nanocomposite thin film with giant optical nonlinearity

Ag/PVP nanocomposites were prepared by a chemical reduction process. Then, a drop-casting method was employed to deposit the Ag/PVP nanocomposite thin film on the glass substrate. To study the optical and structural properties of the prepared sample, different characterization methods including UV–Vis absorption spectroscopy, scanning electron microscopy, XPS, and Raman spectroscopy were employed. The optical nonlinearity of the prepared thin films was evaluated by the Z-scan technique using a He–Ne laser beam (632 nm). Results showed that the nonlinear refraction index (n2 ~ 10−6 cm2/w) and nonlinear absorption coefficient (β ~ 10−1 cm/w) of the prepared Ag/PVP nanocomposite thin film are higher than the previously reported values. A weak thermal optical nonlinearity was also observed and the nonlinear response dominantly resulted from the electronic origin.

Optically tunable feedback operation of silicon nanowire transistors

In this study, we present an optically tunable feedback field-effect transistor (FBFET) with two independent gates and a p+-i-n+ silicon nanowire. Because of the feedback operation, the FBFET features extremely steep switching characteristics with subthreshold swings <4 mV dec−1, and it can be reconfigured as a p- or n-type transistor by controlling the gate-voltage biases. When the FBFET is exposed to a He–Ne laser beam (λ = 633 nm), photogenerated carriers accumulate in the potential wells and reduce the potential-barrier height. The optically tunable feedback operation is attributed to the lowering of the potential barrier caused by the light. The triggering voltages can be modulated according to illumination, even when feedback is being provided. This optically tunable transistor with excellent switching characteristics opens up possibilities for application in future optoelectronic devices.

Effect of Low-Level Laser Therapy versus Electroacupuncture on Postnatal Scanty Milk Secretion: A Randomized Controlled Trial

Postnatal scanty milk secretion is a common complaint. Some physical and medical interventions were advocated to help milk production. These interventions should be effective and safe for the mother and the infant. This study aimed to compare the effects of low-level laser therapy and electroacupuncture on postnatal scanty milk secretion. A randomized controlled study conducted on 60 healthy primiparous mothers with insufficient lactation. They were randomly divided into three equal groups: group A (control), group B (those who received low-power He-Ne laser beam on both breasts), and group C (those who received faradic current stimulation at Spleen 6, Liver 3, and Small Intestine 1 acupuncture points on both sides). All participants received 10 mg Domperidone three times a day and were given advice about lactation, nutrition, and fluid intake. Evaluation was done before and after the treatment program. The mean serum prolactin, infant weight, and visual analog scale (VAS) score were significantly increased in the three groups posttreatment when compared with their corresponding levels pretreatment. Posttreatment serum prolactin was significantly elevated in group C more than the other two groups (p = 0.001 and 0.012, respectively). Also, it was significantly elevated in group B more than in group A (p = 0.001). The mean value of infant weight was significantly elevated in group C when compared with its corresponding values in both groups A (p = 0.001) and B (p = 0.029). The VAS score was significantly increased in both groups B and C when compared with group A (p = 0.001). Electroacupuncture is more effective than low-level laser therapy in increasing postnatal scanty milk secretion. NCT03806062.

Single and multiphoton absorption induced photoluminescence in pulsed laser deposited Zn1−xAlxO(0 ≤ x ≤ 0.10) thin films

In the present paper, single and multiphoton absorption induced photoluminescence in pulsed laser deposited Zn1−xAlxO (0 ≤ x ≤ 0.10) thin films, is reported. All the films were observed to be preferentially c-axis oriented in the 002 plane as indicated by the X-ray diffraction. A clear emergence of the dominating E2(high) peak in the Raman spectra further confirmed the formation of Wurtzite phase. Single photon induced photoluminescence spectra of all the samples exhibited strong near band edge emission. Multiphoton absorption (MPA) induced photoluminescence (PL) in the thin films was experimentally observed by exciting with a cw He:Ne laser beam operating at a wavelength of 632.8 nm. A blue shift in the UV-PL spectra was observed in the films till x = 0.05 and beyond that it retraced to red-shift. The Intensity of the PL emission was found to be increased in the ZnO film with Al content up-to x = 0.05 due to the improvement in crystalline structure and it decreased with further increase in Al content. Logarithmic plot of the MPA PL intensity and excitation intensity displayed a slope, m, in the range of 1 <m < 2 confirming two photon absorption induced PL emission in these films.

Photochemical Synthesis and Characterization of Xenon(VI) Hexafluoridomanganates(IV)

Reactions between XeF2, MnF3 and UV‐irradiated elemental F2 in anhydrous HF have yielded [XeF5]2[MnF6] and XeF5MnF5; meanwhile, [XeF5]4[Mn8F36] has been observed as a minor phase upon the crystallization of the product obtained by fluorination of an n(XeF2)/n(MnF3) = 1:3 mixture in the presence of an UV source. The crystal structure of [XeF5]2[MnF6] is isotypic with the known [XeF5]2[PdF6]. Its asymmetric structural unit consists of two crystallographically unique [XeF5]+ cations and a [MnF6]2– anion. The single‐crystal structure determination of XeF6·2MnF4 reveals that it is better formulated as [XeF5]4[Mn8F36]. Discrete octameric [Mn8F36]4– anions are built from eight MnF6 octahedra, each sharing three vertices, in the shape of a ring, which is different from the previously known cubic [Ti8F36]4– anion. The main structural feature of the anionic part of the crystal structure of [XeF5][MnF5] (determined from both X‐ray single‐crystal and synchrotron X‐ray powder diffraction data) is infinite zigzag chains of distorted MnF6 octahedra that share cis vertices. [XeF5][MnF5] is paramagnetic in the 296–200 K temperature range, with a Curie constant of C = 1.87 emu K mol–1 (µeff = 3.87 µB) and a Curie–Weiss temperature of θ = –9.3 K. Below 100 K, there is weak antiferromagnetic coupling between the MnIV ions, with a coupling constant of J = –1.3 cm–1. Raman spectra showed that [XeF5]2[MnF6] decomposes at ambient temperature in a He–Ne laser beam (power &gt; 1.7 mW) to [XeF5][MnF5], with further decomposition to MnF3.

Investigation of electrical and nonlinear optical properties of colloidal composite nematic liquid crystal

The synthesized TiO2 nanoparticles (NPs) doped to nematic liquid crystals (NLCs) with 1% wt. for both alignments (homeotropic and homogeneous). Dielectric permittivity of samples was measured by LCR meter at different temperatures. TiO2 NPs doped into NLCs show higher permittivity than pure NLCs. According to the obtained results, the permittivity of ε⊥ increases more than ε׀׀ in samples. The magnitude and temperature dependence of the refractive indices of TiO2 NPs doped into NLCs are reported. Investigated electrical behavior of the sample was studied over a wide range of frequency using a complex impedance spectroscopy (CIS) technique. The third-order nonlinear optical properties of TiO2 NPs doped into NLCs which tested by a Z-scan method with continuous wave (CW) He: Ne laser beam, are reported. The Z-scan results revealed that the TiO2 NPs in NLCs exhibit self-focusing nonlinearity and saturable absorption effect for both alignments. The results showed that NLCs doped with a small amount of TiO2 NPs can have significantly improved electro-optic properties.

Nonlinear optical response of liquid crystalline matrix doped with single walled carbon nanotube and graphene sheets

In this work, the nonlinear optical characterization of single-walled carbon nanotubes (SWCN) and graphene in guest-host liquid crystal system have been investigated using z-scan technique and far-field diffraction patterns. The guest materials have been dispersed in 8CB smectic liquid crystal at different concentration and specific thermal conditions. Z-scan measurements with continuous wave (CW) He:Ne laser beam at 632.8nm have been used for determining the nonlinear refractive index (n2) of guest-host system. It was found that n2 depends substantially on the concentration of the SWCN and graphene layers doped in SLCs, and it led to a significant growth in the nonlinear refractive index. Furthermore, the results of far-field optical diffraction patterns under CW HeNe laser illumination have been verified the result of nonlinear properties of Z-scan measurements.

Weak-field H3O+ ion cyclotron resonance alters water refractive index

ABSTRACTHeretofore only observed in living systems, we report that weak-field ion cyclotron resonance (ICR) also occurs in inanimate matter. Weak magnetic field (50 nT) hydronium ICR at the field combination (7.84 Hz, 7.5 µT) markedly changes water structure, as evidenced by finding an altered index of refraction exactly at this combined field. This observation utilizes a novel technique which measures the scattering of a He–Ne laser beam as the sample is exposed to a ramped magnetic field frequency. In addition to the hydronium resonance, we find evidence of ICR coupling to a more massive structure, possibly a tetrahedral combination of three waters and a single hydronium ion. To check our observations, we extended this technique to D2O, successfully predicting the specific ICR charge-to-mass ratio for D3O+ that alters the index of refraction.

All-optical logical gates based on photoinduced molecules reorientation in amorphous polymer films

A type of all-optical logical gate based on two kinds of refractive index grating in azo-dye doped polymer film is studied in this paper. Using interference recording method with two 532[Formula: see text]nm laser beams, the transient refractive gratings can be formed in poly(methyl methacrylate) (PMMA) films containing azo-dye Disperse Red 13 (DR13). The characteristics of the transient gratings in films which are recorded by two 532[Formula: see text]nm laser beams with different polarization states are investigated by monitoring the first-order diffraction intensity of the readout He–Ne laser beam (632.8[Formula: see text]nm). It is found that the transient gratings in the polymeric films can be established and decayed in several seconds. Furthermore, we realize XOR and XNOR all-optical logical operation based on the relationship among the polarization states of the recording beams, the reading beam, and the diffraction beam.

Erythrocyte aggregation under high pressure studied by laser photometry and mathematical analysis

The effects of hydrostatic pressure on erythrocyte aggregation have been studied by laser photometry and analysis based on a phenomenological theory. Samples were prepared by suspending swine erythrocytes in their own plasma. A high-pressure vessel consisting of a stainless-steel block with a hole to hold a sample cell and two sapphire windows to allows the passage of a He–Ne laser beam was used in the experimental setup. The suspension was stirred at 1500rpm to disperse the erythrocytes homogeneously. Immediately after reducing the stirring rate from 1500rpm to 300rpm, the transmitted light intensity (I) was recorded every 10ms under a high pressure of 40–200MPa. The value of I increased with time (t) owing to erythrocyte aggregation. From the phenomenological theory, the equation ΔI(t)=ΔIeq[1−e−Kt/(1−B(1−e−Kt))] was derived for the change in the transmitted light intensity (ΔI) due to erythrocyte aggregation, where ΔIeq is the transmitted light intensity in the steady state, K is a time constant and B is a constant that represents the ratio of the number of interaction sites on erythrocyte aggregates at time t to that in the steady state. The observed time courses of ΔI obtained at all pressures could be closely fitted to the theoretical equation. ΔIeq roughly increased with increasing pressure. On the other hand, K and B abruptly decreased above 120MPa. The growth rate of aggregates decreased above 120MPa. These results suggest a change in the mechanism of erythrocyte aggregation at approximately 120MPa. We discuss the physical meaning of the parameters.

Detection of Neisseria meningitidis using surface plasmon resonance based DNA biosensor

Herein, we report the development of a surface plasmon resonance (SPR) based biosensor for the detection of Neisseria meningitidis DNA employing Kretschmann configuration. Highly c-axis oriented ZnO thin film of thickness 200nm was deposited on gold coated glass prisms by RF sputtering technique. Single stranded probe DNA was immobilized on the surface of ZnO thin film by physical adsorption method. SPR reflectance curves were recorded as a function of incident angle of He–Ne laser beam using a laboratory assembled SPR setup. The prepared biosensor exhibits a linear response towards target meningitidis DNA over the concentration range from 10 to 180ng/μl with a high sensitivity of about 0.03°/(ng/μl) and a low limit of detection of 5ng/μl. The SPR biosensor demonstrated high specificity and long shelf life thus, pointing towards a promising application in the field of meningitidis diagnosis.

Temporal dispersion induced commercial laser in speckle free intense imaging

Coherent imaging suffers from speckle, which is basically some uncorrelated intensity distribution and bears no obvious relationship to the macroscopic properties of the object illuminated. Reducing the spatial coherence of the illuminating beam, usually improves the quality of imaging by paying the penalty for reducing intensity, and directionality as well. Here, we demonstrate an alternative way of resolving the speckle issue by inducing temporal dispersion onto the commercial He–Ne laser beam, devising with a dispersive slope available near to the edge of the 1-D organic photonic band gap Cholesteric Liquid Crystal (CLC).

Experimental profiling of a non-truncated focused Gaussian beam and fine-tuning of the quadratic phase in the Fresnel Gaussian shape invariant

An especially dedicated homodyne profiler is used for recording the intensity distribution of focused non-truncated Gaussian beams. The spatial distributions are obtained at planes in the vicinity of the back-focal plane of a focusing lens placed at different distances from a He–Ne laser beam with a Gaussian intensity profile. Comparisons of the experimental data with those obtained from the analytical equations for an ideal focusing lens allow us to propose formulae to fine-tune the quadratic term in the Fresnel Gaussian shape invariant at each interface of the propagated field. We give analytical expressions to calculate adequately the propagation of the field through an optical system.

Characterization of thermal diffusivity and optical properties of Ag nanoparticles

Thermal diffusivity of silver nano-fluid synthesized using radiation technique at a concentration of 5.889×10−3M and irradiated with γ-radiation at different doses was measured. The measurements were performed by thermal lens method. A diode laser (λ=532nm) was used as an excitation beam while a He–Ne laser beam (λ=632.8) was utilized as a probe beam. The thermal diffusivity of Ag nano-fluid samples measured at room temperature increase with the increasing nanoparticles size ranging from 44nm to 64nm. A similar behavior of nonlinear refractive index measured using a single beam z-scan are presented and discussed.

Laser microsculpting for the generation of robust diffractive security markings on the surface of metals

We report the development of a laser-based process for the direct writing (‘microsculpting’) of unique security markings (reflective phase holograms) on the surface of metals. In contrast to the common approaches used for unique marking of the metal products and components, e.g., polymer holographic stickers which are attached to metals as an adhesive tape, our process enables the generation of the security markings directly onto the metal surface and thus overcomes the problems with tampering and biocompatibility which are typical drawbacks of holographic stickers. The process uses 35ns laser pulses of wavelength 355nm to generate optically-smooth deformations on the metal surface using a localised laser melting process. Security markings (holographic structures) on 304-grade stainless steel surface are fabricated, and their resulted optical performance is tested using a He–Ne laser beam of 632.8nm wavelength.