Argon Laser Radiation Research Articles

Combined effects of a topical fluoride treatment and 445 nm laser irradiation of enamel against a demineralization challenge: A light and electron microscopic ex vivo study.

This study investigated the caries-preventive effect of 445 nm laser radiation in combination with fluoride on the prevention of white spot lesions. Previously, several studies have indicated the ability of 488 nm argon ion laser irradiation to reduce early enamel demineralization. A diode laser (445 nm) could be an alternative technology for possible caries-preventive potential. Each sample of a group of seventeen caries-free bovine teeth was treated in four different ways on four different zones of the labial surface: control/no treatment (C), laser irradiation only (L) (0.3 W, 60 s and applied dose of 90 J/cm2), amine fluoride application only (10,000 ppm and pH 3.9) (F), and amine fluoride application followed by laser irradiation (FL). After treatment, the teeth were subjected to a demineralization solution (pH 4.3 for 48 h at 37 °C) to induce subsurface lesions. After sectioning, the teeth were examined by light microscopy. Three teeth were analyzed by scanning electron microscopy (SEM). The depths of the subsurface lesions in the C, L, F, and FL groups were 103.01 (± 13.04), 96.99 (± 14.51), 42.59 (± 17.13), and 24.35 (± 11.38) μm, respectively. The pairwise group comparison showed the following results: p < 0.001 for FL versus C, FL versus L, F versus C, and F versus L, p = 0.019 for FL versus F and p = 0.930 for L versus C. The SEM micrographs support the light-microscopic examination. The results of the current study have shown that using relatively low irradiation settings of 445 nm laser on fluoridated enamel may be effective for prevention of white spot lesions.

Pulse modulation of multicolored radiation of an argon laser

A method for calculating the parameters of a pulsed acousto-optic modulator of multicolored laser radiation is developed. The parameters make it possible to determine the optimal conditions for the modulation of a specified light spectrum at the maximum sound frequency. The method is experimentally confirmed using an acousto-optic modulator based on paratellurite designed for the modulation of argon laser radiation in the blue–green spectral range.

Pulsed modulation of multi-color argon laser radiation

Pulsed modulation of multi-color argon laser radiation

Polarized Raman Spectra of α Quartz

The purpose of this experiment was to observe the Raman shift to assign the symmetry character of the obtained vibrational modes of α-quartz (which has 9 atom per unit cell) using the selection rules for Raman Effect. We observed the Raman spectra varying the polarization of the incoming beam and the orientation of the crystal. And we used monochromatic radiation of argon laser of wavelength 540 nm for our Raman spectroscopy. We observed the intensity of light rotating the polarizer to vertical position from its horizontal position with respect to the plane of the optical table where the laser is placed and measured the Raman spectra over an energy from 50 to 1250 cm-1 using the laser power of 1W and an acquisition time of 10 sec. averaging over 2 acquisitions. From our experiment we can see that here is 4symmetry for A1 which is predicted on our vibrational modes. However for E symmetry mode we have observed 14 vibrational modes but as E is doubly degenerate there should be 16 vibrational modes on the Raman active modes in the α quartz, as we can see that there are two vibration missing ,it happens may be due to noise on the surroundings. We got different peaks due to the different intensities and the different orientation of the laser beam hitting the sample on different angle. The different intensities of the peaks for the different orientation might be due to the laser beam hitting the samples at different angles due to differences in the orientation of the surfaces. We also found that the biggest amount of the re-radiated light was vibrating horizontally, i.e. in the same direction as the laser beam hitting the sample.

Polarized Raman Spectra of α Quartz

The purpose of this experiment was to observe the Raman shift to assign the symmetry character of the obtained vibrational modes of α-quartz (which has 9 atom per unit cell) using the selection rules for Raman Effect. We observed the Raman spectra varying the polarization of the incoming beam and the orientation of the crystal. And we used monochromatic radiation of argon laser of wavelength 540 nm for our Raman spectroscopy. We observed the intensity of light rotating the polarizer to vertical position from its horizontal position with respect to the plane of the optical table where the laser is placed and measured the Raman spectra over an energy from 50 to 1250 cm-1 using the laser power of 1W and an acquisition time of 10 sec. averaging over 2 acquisitions. From our experiment we can see that here is 4symmetry for A1 which is predicted on our vibrational modes. However for E symmetry mode we have observed 14 vibrational modes but as E is doubly degenerate there should be 16 vibrational modes on the Raman active modes in the α quartz, as we can see that there are two vibration missing ,it happens may be due to noise on the surroundings. We got different peaks due to the different intensities and the different orientation of the laser beam hitting the sample on different angle. The different intensities of the peaks for the different orientation might be due to the laser beam hitting the samples at different angles due to differences in the orientation of the surfaces. We also found that the biggest amount of the re-radiated light was vibrating horizontally, i.e. in the same direction as the laser beam hitting the sample.

Influence of Welding Current and Focal Position on the Resonant Absorption of Laser Radiation in a TIG Welding Arc

Abstract The work presents the influence of welding current and focal position on the resonant absorption of diode laser radiation in a TIG welding arc. The laser beam is guided perpendicular to the electrical arc to avoid an interaction with the electrodes. Laser power measurements have shown a reduction of the measured laser power up to 18% after passing the electrical arc. This reduction results from the interaction of argon shielding gas atoms and laser radiation at 810.4 nm and 811.5 nm. The interaction is strongly affected by the adjusted welding current and the adjustment of the laser beam and the electrical arc. Lowering the welding current or shifting the laser beam out of the centerline of the electrical arc reduces the ionization probability. An increased ionization is necessary to decrease the resistance of the electrical arc.

The limiting possibilities of interference photolithography implemented in the visible region on thin films of glassy chalcogenide semiconductor

This paper presents the results of investigating the parameters (minimum repetition period of the elements and porosity) of structures obtained under the action of argon laser radiation on thin films of glassy chalcogenide semiconductor deposited on layers of x-ray-amorphous chromium. It is shown that thin films of a three-component glassy semiconductor exposed by radiation with wavelength 0.488 µm can be used in the method of interference photolithography to obtain structures with a minimum period of 260 nm and a minimum size of the structural element of 65 nm. It is established that the minimum size of a structural element can be reduced to 50 nm when the repetition period of the elements is increased to 600 nm by using the “two-mask” technology of interference photolithography.

Photoluminescence properties of β-FeSi2 grains on Si with coating Au layer

We have investigated the growth of β-FeSi2 grains on Si(001) substrates with 90-nm-thick gold layer and its photoluminescence (PL) property. X-ray diffraction and scanning electron microscopy observations revealed that coarse island β-FeSi2 grains with sizes from several to tens of micrometers were formed on the Si surface. A clear PL spectrum for the β-FeSi2 grains was observed on as deposited sample by argon-ion laser irradiation to the Si substrate side. The values of the activation energy for a non-radiative recombination path were large, and indicated the formation of high-crystal-quality β-FeSi2 with a low-level non-radiative center without post-annealing.

Facile synthesis and patterning of silver nanoparticles for surface plasmon generation

A facile single step strategy for the synthesis and large area patterning of silver nanoparticles via photodecomposition of a photoactive silver nitrite aliphatic amine complex was developed. Decomposition of the silver complex was facilitated using either a UV or an Argon ion laser (514.5 nm) irradiation. The synthesis was performed both in solution and thin films. The silver nanoparticles displayed characteristic localized surface plasmon resonance in the absorption spectrum. Utilizing laser beam interference, silver nanoparticles were synthesized and, as well, patterned in a single step.

Assaying Total Carotenoids in Flours of Corn and Sweetpotato by Laser Photoacoustic Spectroscopy.

This study describes the application of the laser photoacoustic spectroscopy (PAS) for quantification of total carotenoids (TC) in corn flours and sweetpotato flours. Overall, thirty-three different corn flours and nine sweetpotato flours were investigated. All PAS measurements were performed at room temperature using 488-nm argon laser radiation for excitation and mechanical modulation of 9 and 30 Hz. The measurements were repeated within a run and within several days or months. The UV–Vis spectrophotometry was used as the reference method. The concentration range that allows for the reliable analysis of TC spans a region from 1 to 40 mg kg−1 for corn flours and from 9 to 40 mg kg−1 for sweetpotato flours. In the case of sweetpotato flours, the quantification may extend even to 240 mg kg−1 TC. The estimated detection limit values for TC in corn and sweetpotato flours were 0.1 and 0.3 mg kg−1, respectively. The computed repeatability (n = 3–12) and intermediate precision (n = 6–28) RSD values at 9 and 30 Hz are comparable: 0.1–17.1% and 5.3–14.7% for corn flours as compared with 1.4–9.1% and 4.2–23.0% for sweetpotato flours. Our results show that PAS can be successfully used as a new analytical tool to simply and rapidly screen the flours for their nutritional potential based on the total carotenoid concentration.

A Historical Narrative of Study of Fiber Grating Solitons

A brief historical narrative of the study of grating solitons in fiber Bragg grating is presented from the late 1970’s up to now. The formation of photogeneration gratings in optical fiber by sustained exposure of the core to the interference pattern produced by oppositely propagating modes of argon-ion laser radiation was first reported in 1978. One important nonlinear application of fiber Bragg grating is grating solitons, including gap soliton and Bragg soliton. This paper summarily introduces the numerous theoretical and experimental results on this field, each indicating the potential these solitons have in all-optical switching, pulse compression, limiting, and logic operations, and especially important for the optical communication systems.

Experimental Determination of the Raman Sampling Depth in Zirconia Ceramics

This study provides experimentally determined values for the actual micro-Raman spectroscopy sampling depth in zirconia ceramics (ZrO2) via line scans on a wedge-shaped sample. Common instrumental settings with metallurgical objective lenses in dry air, argon-ion, and helium-neon laser radiation of approximately 10 mW were chosen. Under those conditions effective sampling depths, defined as the depth at which 99% of the information is recorded, range from 20 to more than 50 microm, depending on the numerical aperture of the lens and the laser wavelength. These results elucidate the pitfalls of the investigation of surface phenomena in zirconia ceramics such as low-temperature degradation or mechanically induced phase transformations by Raman spectroscopy.

Styrylquinolinium borates as donor–acceptor initiators for sensitized photopolymerization of TMPTA

Several photoredox pairs containing mono- and bicationic hemicyanine dyes have been evaluated as photoinitiators for free radical polymerization induced with an argon-ion laser irradiation. The tested photoredox couples are the pairs composed of the hemicyanine dye cations acting as electron acceptors and n-butyltriphenyl borate anions being the electron donors. The photoinitiating abilities of the series of monochromophoric stilbazolium borates, 4-( p-N,N-dialkylaminostyryl)quinolinium n-butyltriphenylborate, were compared to the photochemistry of structurally related, bicationic styrylquinolinium borates. The obtained results clearly documented that the dicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. Our studies revealed also that the rate of photopolymerization depends on Δ G el of electron transfer between borate anion and styrylquinolinium cation. The relationship between the rate of polymerization and the free energy of activation shows the dependence predicted by the classical theory of electron transfer.

Photopolymerization of trimethylolpropane triacrylate induced by diselenide derivatives

Six diselenides have been evaluated as novel photoinitiators for free radical polymerization induced with an argon-ion laser irradiation. Our studies show that the rate of photopolymerization depends on the structure and concentration of the photoinitiators. The relation between the rate of polymerization and the light intensity shows a linear dependence.

Studies on an argon laser-induced photopolymerization employing both mono- and bischromophoric hemicyanine dye–borate complex as a photoinitiator: Part II

Several photoredox pairs containing dichromophoric hemicyanine dyes have been evaluated as novel photoinitiators for free radical polymerization induced with an argon-ion laser irradiation. The tested photoredox couples are the pairs composed of the hemicyanine dye cations acting as electron acceptors and n-butyltriphenyl borate anions being the electron donors. The photoinitiating abilities of the series of dimmeric dichromophoric stilbazolium borates; 1,2-; 1,3-; and 1,4-bis-[4-( p- N, N-dialkylaminostyryl)pyridinyl]xylene di- n-butyltriphenylborates, were compared to the photochemistry of structurally related, monochromophoric styrylpyridinium borates. The obtained results clearly documented that the dicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. Our studies revealed also that the rate of photopolymerization depends on Δ G el of electron transfer between borate anion and styrylpyridinium cation. The latter value was estimated for all series of styrylpyridinium borate salts. The relationship between the rate of polymerization and the free energy of activation shows the dependence predicted by the classical theory of electron transfer.

Morphology Control of Nanoscale PbS Particles in a Polyol Process

Nanostructured PbS with different morphologies and particle sizes have been prepared through a polyol process. Narrow size distribution for star-shaped, octahedral, tetradecanehedral, and cubic products were achieved by slowly introducing the source materials using a peristaltic pump in the presence of poly(vinylpyrrolidone) (PVP) as additive. Systematic variation of the kinetic factors, including the additive, the reaction temperature, the duration time, the ratio of source materials, the sulfur sources, and the Pb(Ac)2·3H2O concentration, reveals that the morphology depends mainly on the supersaturation degree of the free sulfur ions released from thiourea under elevated temperature. Semiquantitative analysis based on the X-ray diffraction (XRD) patterns of these products gives that the peak area ratio of (200) to (111) increases with the increase of the supersaturation degree within the reaction system. The four types of symmetric morphology showed different oxidation stability toward the 514.5 nm argon ion laser irradiation when the power was set at 12.5 mW.

Desvitrification on an oxyfluoride glass doped with Tm 3+ and Yb 3+ ions under Ar laser irradiation

Desvitrification in a Tm 3+ and Yb 3+ codoped oxyfluoride glass has been obtained by exciting with a continuous Argon laser radiation increasing the average laser power from 144 to 2900 mW. Excitation spectra inside a locally damaged zone in a 1 mol% Tm 3+ and 2.5 mol% Yb 3+ codoped glass have been measured under excitation in the wavelength range 750–830 nm detecting the 2F 5/2 (Yb 3+) level. This curve is the result of the contribution of two different kinds of centers, the fluoride nanocrystals and the glassy phase of the glass ceramic sample created due to the irradiation. The weight of the contributions of each of the centers depends on the excitation wavelength, and from the analysis of the decay of the luminescence it can be concluded that approximately 80% of the Tm 3+ ions are located in the nanocrystals and therefore less than 20% in the glassy phase.

Polymer-dispersed liquid crystal/layered double hydroxide nanocomposite: A new emerging optical application

Abstract This paper describes the preparation and characterization of polymer-dispersed liquid crystal (PDLC)/layered double hydroxides (LDHs) nanocomposites. In this study, Mg–Al LDH was applied as two-dimensional host material, with the unique properties of higher anionic exchange capacity (AEC) and higher aspect ratio. Preparation of nanomaterials with a uniform, higher crystalline and surface charge density could be performed by a hydrothermal method. SEM and particle diameter analysis measurement, successfully obtained affords smaller crystallites with a higher aspect ratio, having a very narrow distribution of crystallite size. The structure formula [ Mg 2 Al ( OH ) 6 ] NO 3 · 1.2 H 2 O were carried out by ICP-AES, EA and TGA. The major applications of LDHs based on the intercalation or exchange of specific guests as absorbents have been reported. However, it is seldom discussed to apply as optical materials. In this work, we have studied the Mg–Al LDH mixed with nematic liquid crystal and photo-polymer matrix. Photo-polymerization was induced by argon ion laser irradiation on the filled cells, which contain photo-initiator, monomers, liquid crystals and Mg–Al LDHs. Diffraction efficiency makes apparently increasing from 1.4 to 5.6%. When the sample was added 1 phr of Mg–Al LDH, the diffraction efficiency rise to 5.6 from 1.4%, compared with original PDLCs. Polymerization induced the phase separation of polymer and liquid crystal in the PDLC film. Higher diffraction efficiency was observed when PDLC hybridized with inorganic LDH, which will change the polymerization rate of PDLC, and help the formation of the grating effect; therefore, the diffraction efficiency of the whole system was improved. The noteworthy factor of improving diffraction efficiency will be discussed in this paper.

Study on Laser Direct Bonding of Silicon and Glass

Laser direct bonding of glass and silicon has been studied in this paper. After argon ion laser irradiation on single crystalline silicon through Pyrex, the samples were directly bonded together. The bonding requires good physical contact between silicon and glass. After bonding, the silicon surface traced by the laser beams warped like weld bead. The bonding zone is, however, larger than the warping zone. The fact suggests that the glass was heated by the silicon to melt and stick on the silicon. At the time of bonding, as higher laser power, adhesion force became higher mainly because of larger bonding zone. On the other hand, stress of the silicon at the warping zone became higher too. The bonding technique was applied to enclosing a solder-piece in a hole on silicon with glass plate.

Pyrromethene dye sensitized photopolymer—photochemical behavior in polymer matrix and application to photoresist for printed circuit board

The photochemical behavior of the visible light initiating system that consists of a sensitizing dye, 2,6-diethyl-8-phenyl-1,3,5,7-tetramethylpyrromethene BF2 complex (EPP), and a photoacid generator, N-trifluoromethylsulfonyloxy-1,8-naphthalimide (NIOTf), was studied mainly by means of absorption and fluorescence spectrometry not in solution but in a polymer matrix which is a closer medium to the one currently employed in the field of photoresists. Excited singlet electron transfer from EPP to NIOTf was considered as the main reaction pathway in this system. The EPP/NIOTf system was applied to a photoresist for printed circuit board with an appropriate binder polymer which contains an acetal protection group. A pattern profile of the photoresist was exceedingly affected by the amount of photogenerated acids, their diffusion, and amine in the atmosphere. Finally, by controlling exposure energy and the post-exposure bake (PEB) process, a photoresist with a high resolution (8 µm line and space) was obtained under argon ion laser irradiation. Copyright © 2006 John Wiley & Sons, Ltd.