Cw Ar Ion Laser Research Articles

Influence of substrate temperature and oxygen pressure on the structural and optical properties of polycrystalline BaTiO3 thin films grown by PLD

The effect of substrate temperature and oxygen pressure on linear and nonlinear optical properties of pulsed laser deposited barium titanate BaTiO3 (BTO) thin films is reported in the present manuscript. BTO thin films have been deposited on n-type Si (100) and quartz substrates in the range of substrate temperatures from 400 to 700 °C and oxygen pressures from 0.005 to 1 mbar. The root means square (RMS) surface roughness is observed to decrease with the rise in substrate temperature and increased with an increase in oxygen pressure. The optimum background pressure and the substrate temperature are observed to be around ∼0.1 mbar and 700 °C, respectively. All the BTO thin films are found to be in the preferential (110) plane, from X-ray Diffraction (XRD), indicating the pseudocubic phase. Raman analysis also confirms the pseudocubic phase of BTO for all the thin films. The crystallite size, measured from XRD analysis is found to be increased with the increase in substrate temperature and is also affected by the background oxygen pressure. The thickness, linear absorption coefficient, and refractive index of the thin films are determined from UV–Visible–NIR spectroscopy. Transmission is observed to be 75–85% for all the thin films in the spectral range of 400–2000 nm. Nonlinear optical properties (NLO) are studied by an in-house assembled modified Z-scan set-up using continuous-wave (cw) Ar-Ion laser (λ = 488 nm) and found to be (57.54 ± 0.05) cm/W at the optimum deposition parameters.

Second Order Nonlinear Optical Polarization at Different Wavelengths for Zinc-Blende Crystals

Second order nonlinear optical polarization P(2) has been calculated theoretically for several crystals having zinc-blende symmetries. Three distinct wavelengths 457 nm, 488 nm and 514 nm emitted from a continuous wave (cw) Ar-ion laser have been considered for the estimation of the second order nonlinear optical polarization. The study reveals nonlinear dependence of the second order nonlinear optical polarization on the applied electric field intensities at various wavelengths.

Single beam Z-scan for the calculation of nonlinear refractive index (n2) for poly(2,5-dimethylaniline)

An experimental work has been done to measure the nonlinear refractive index of poly(2,5-dimethylaniline) (PDMA). In this work, a continuous wave (cw) Ar-ion laser has been used to calculate n2 for a novel polymer; poly(2,5-dimethylaniline): synthesized from 2,5 dimethylaniline. The single beam Z-scan technique was used with laser beams of 514 and 488 nm wavelengths, taking PDMA in methanol solvent at different concentrations. The order of n2 was found to be of the order of ~ 10-14 esu.

Photoacoustic spectroscopy and optothermal window as analytical tools to quantitate carotenes in margarines

Photoacoustic spectroscopy (PAS) and optothermal window (OW) with a cw Ar ion laser used as a radiation source at 476.5, 488 and 496 nm were applied to quantify total carotenes (TC) in margarines. Both techniques, being rapid and extremely simple, allow for direct measurement without any pretreatment of the sample. The PAS has proven precise and sensitive enough to allow quantitation of TC in margarines containing 1–9 mg TC/kg, in applications such as the quality control of intermediate and final products. The sensitivity of OW is lower than that of PAS but the approach can still be used for quantitation of TC in margarine matrices at much higher concentrations.

Fabrication and photoluminescence characteristics of Er3+-doped optical fiber sensitized by Si particles

We report for the first time the development of Er3+/Si-doped optical fiber amplifier operating at 1550nm upon 512nm pumping. Er3+-doped silica glass optical fibers incorporated with silicon particles as the sensitizer were fabricated by the modified chemical vapor deposition and the solution doping technique. The effect of silicon incorporation into the fiber core on the optical absorption and photoluminescence properties was investigated. Upon pumping with the CW Ar-ion laser at 512nm, a photoluminescence band appeared near 770nm and 1560nm. The peak intensity of the photoluminescence at 1560nm in the Er3+/Si-doped fiber was found to enhance by about 70% compared to the Er3+-doped fiber.

Fabrication and photoluminescence characteristics of Er 3+ -doped optical fibre sensitised by silicon

Er 3+ -doped optical fibres co-doped with silicon particles were fabricated by the modified chemical vapour deposition and the solution doping technique. Peak intensity of the photoluminescence at 1560 nm upon pumping by a CW Ar-ion laser at 512 nm was enhanced by about 70% after the silicon incorporation

Energy transfer and optical gain studies of FDS: Rh B dye mixture investigated under cw laser excitation

Radiative and non-radiative (Forster type) energy transfer processes in a dye mixture of FDS and Rh B in methanol under cw Ar ion laser excitation were investigated for fixed donor concentration and varying acceptor concentration. It is found that most of the pump power absorbed by FDS is transferred to Rh B as a useful pump power. Transfer probability (PDA), transfer efficiency both radiative (ηR) and non-radiative (ηNR) and optical gain (G) of the system were studied for various pump powers. The gain characteristics of Rh B are found to alter due to the change in the effective fluorescence lifetime caused by energy transfer reaction. Theoretical calculations were also done to find the total transfer efficiency (ηT) at various acceptor concentrations to identify the appropriate energy transfer mechanism responsible for gain enhancement in Rh B. Both radiative and non-radiative transfer processes are taken into consideration in all the calculations. Various energy transfer parameters viz. radiative rate constant (KR), non-radiative rate constant (KNR), critical concentration (C0), critical radius (R0) and half quenching concentration ([A]1/2) are calculated by using the Stern–Volmer plots and concentration dependence of radiative and non-radiative transfer efficiencies. Concentration and pump power dependence of the peak gain and lasing wavelengths of the energy transfer dye lasers (ETDL) have also been studied. The experimental results show that the dominant mechanism responsible for the efficient excitation transfer in this mixture is of radiative nature, whereas the long range dipole–dipole (d–d) interaction (Forster type) is comparatively smaller.

CW Argon-ion Laser Crystallization of a-Si:H Thin Films

ABSTRACTThin a-Si:H films, with a thickness of 1 µm, with different hydrogen concentrations, prepared by hot wire deposition were crystallized by 514.5 nm cw Ar ion laser radiation, with a power density between 150 and 270 kW/cm2. The crystallization was continuously monitored by Raman spectroscopy for exposures up to hours. The analysis of crystallization process using Johnson-Mehl phenomenological equations showed an apparent crystallization energy of around 0.5 eV and low dimensional crystal growth. The mean value of the crystal size decreases with increasing irradiation energy and initial hydrogen content and varies between 3 and 6 nm.

210 ホログラフィー干渉法を用いた水中放電による衝撃波の観測(GS-10 計測)

The shock wave generated by a spark discharge in water was observed with holographic interferometry. Double-exposure interferogram of the shock front was recorded by the use of AOM from CW Ar ion laser. A shock speed of 1495m/s was obtained from the recorded interferogram, and yields 9MPa of the shock front pressure.

Collisional coalescence of photoexcited midgap states in anMXchain compound

The pumping-power dependence of the time decay of the long-lived photoinduced midgap absorption has been studied in an MX chain compound $[{\mathrm{Pt}(\mathrm{en})}_{2}]{[\mathrm{Pt}(\mathrm{en})}_{2}{\mathrm{Cl}}_{2}{](\mathrm{B}\mathrm{F}}_{4}{)}_{4},(\mathrm{en})$ being ethylenediamine. The 476.5 nm light of a cw Ar-ion laser is used as the pumping light source. In addition to an extremely nonexponential time decay, the life time of the midgap band is found to vary as ${K}_{0}^{\ensuremath{-}2}$ with the absorption intensity ${K}_{0}$ induced by the laser pumping. This decay behavior is explained well in terms of the Torney-McConnell survival-probability function, $S(\ensuremath{\zeta}{)=e}^{8\ensuremath{\zeta}}\mathrm{erfc}\sqrt{8\ensuremath{\zeta}}$ with $\ensuremath{\zeta}{=A}_{0}^{2}Dt,$ peculiar to the geminate coalescence of unequilibrated states in one dimension, where ${A}_{0},$ D, and t are the initial density of the unequilibrated states, diffusion coefficient, and time, respectively. The observed midgap states are confirmed from this finding to collapse through diffusion-limited mutual collisions in locally disordered PtCl chains. Our previous data on temperature and sample dependencies are reviewed within the framework of this collisional geminate coalescence model.

Micro-Raman study of diamondlike atomic-scale composite films modified by continuous wave laser annealing

We have modified the properties of diamondlike atomic-scale composite (DLASC) material of various thicknesses (5–70 μm) by means of cw Ar-ion laser annealing using a focused beam (∼2 μm spot size). These DLASC films [amorphous “diamondlike/quartzlike” a-(C:H/Si:O)] constitute a novel class of diamond-related materials. The laser annealing effects were investigated by micro-Raman scattering. The structure of these films can be altered locally from amorphous to nanocrystalline depending not only on the parameters of the annealing process (annealing time, laser intensity) but also the mechanical properties (hardness, stress) of the films. For comparison purposes we also measured the effects of thermal annealing.

レーザ光散乱法によるＳｉウエハ付着微粒子計測装置の開発

This paper describes a system used for detecting the impurity particles on a bare Si wafer surface in a short time, at a wide area, and with a high reliability. The particles are less than 100 nm in diameter. The wafer is illuminated with CW Ar-ion laser beam (diameter : 100μm, power : 600 mW) at an oblique incident angle. The laser beam scattered by the particles is collected and focused at the direction perpendicular to the wafer surface. In order to achieve a uniform illumination in the whole observation area, the laser beam is scanned over the area. The time-integrated image of the surface is taken by a long-time exposure CCD camera. As a result, 37 nm-particles are observed in the image with the signal-to-noise ratio of 2.4. According to the Rayleigh equation, the noise signal is corresponding to 32 nm-particles.

External-field-controlled laser wet etching of polycrystalline Al2O3TiC

Laser-induced etching of polycrystalline Al2O3TiC material by tightly focused CW Ar ion laser has been investigated in both H3PO4 and KOH solutions with influence of an external electric field. It is found that a weak external electric field will change the ions distribution in chemical solutions and cause obvious change in etching behavior. The laser etching in a H3PO4 solution can be enhanced by both positive and negative biases of the substrate. While etching in a KOH solution, a positive bias can enhance the etching reaction, whereas a negative bias can suppress the etching process. It is also found that the external electric field can always enhance the mass transfer between reaction products and fresh etchant in a H3PO4 solution. It is revealed that the supply of H+ ions contributes to the etching process in a H3PO4 solution, while the supply of OH− ions contributes to the etching process in a KOH solution. The electric field can be used to control the etching process to achieve fast tuning and higher accuracy.

Laser-induced etching of polycrystalline Al2O3TiC in KOH aqueous solution

Laser-induced etching of polycrystalline Al2−O3TiC material by a tightly-focused cw Ar ion laser has been investigated in a KOH solution with different concentrations. It is found that the KOH concentration can strongly affect the etching quality where low KOH concentration can result in rough and irregular patterns. Laser-induced etching of polycrystalline Al2O3TiC in a KOH solution is found to be a photothermal reaction in which a threshold laser power exists. With an appropriate set of etching parameters, well-defined grooves can be obtained with clean side walls and with an etching rate up to several hundred micrometers per second. The etching behavior is also found to depend on laser scanning direction. It is also found that the grains in the polycrystalline Al2O3TiC material play an important role in the etching dynamics and etching quality. This etching process is believed to be applicable to the formation of a slider surface of magnetic heads in the future.

Microstructures of Luminescent nc-Si by Excimer Laser Annealing of a-Si:H

AbstractWe have reported for the first time on visible photoluminescence (PL) in crystallized a-Si:H/a-SiNx:H multilayer structures by CW Ar ion laser annealing treatments. In this paper we present new results on visible PL from crystallized a-Si:H by using KrF excimer pulse laser (wavelength 248 nm) irradiating treatments. The transmission electron microscopy and Raman scattering studies reveal the microstructures of crystallized Si films, which depend on the pulse number and the pulse energy density of KrF laser. When the laser pulse energy density is higher than 520 mJ/cm2, the nanosized Si crystallites (nc-Si) can be formed from a-Si:H layers with a thickness of 100 nm and strong PL with a peak wavelength of 610 nm has been observed at room temperature.

Laser and Thermal Annealing Modification of Diamond-Like Atomic-Scale Composite Films Studied by Micro Raman Spectroscopy

AbstractWe have modified the properties of diamond-like atomic-scale composite (DLASC) material of various thicknesses (5 μm – 70 μm) by means of (a) cw Ar-ion laser annealing using a focussed beam (˜ 2 μm spot size) and (b) thermal annealing (400°C≤ T ≤800°C for one hour). These DLASC films [amorphous “diamond-like/quartz-like” a-(C:H/Si:O)] constitute a novel class of diamond-related materials. The annealing effects were investigated by micro-Raman scattering. The laser annealing procedure shows that the structure of these films can be altered locally from amorphous to nano-crystallite depending not only on the parameters of the annealing process (annealing time, laser intensity) but also the mechanical properties (hardness and stress) of the DLASC films.

Stability transfer of stabilized Ar/sup +/ laser on optically pumped I/sub 2/ laser towards a frequency standard around 1.3 μm

A Doppler-free stimulated-emission technique using an optically pumped I/sub 2/ laser with applications in spectroscopy and infrared frequency standards is reported. A single mode CW Ar ion laser, locked on a hyperfine component of the 13P(43-0) line of the B-X electronic transition /sup 127/I/sub 2/ iodine molecule, is used as laser pump. Continuous wave oscillation is observed on transitions belonging to the B-X system into highly excited vibrational levels of the ground state. The long term stability of the Ar laser (/spl Delta//spl nu///spl nu//spl ap/10/sup -13/ in 100 s) can be transferred to the iodine laser. >

Application of Laser Microetching in Formation of Air-Bearing Surface for Magnetic Head Sliders

ABSTRACTLaser-induced etching of polycrystalline Al2O3TiC material by a tightly-focused CW Ar ion laser has been investigated in a KOH solution with different concentrations. It is found that the KOH concentration can strongly affect the etching quality where low KOH concentration can result in rough and irregular patterns. The etching effect is also related to laser power and scanning speed. Laser-induced etching of polycrystalline AI2O3TiC in a KOH solution is found to be a photothermal reaction in which a threshold laser power exists. With an appropriate set of etching parameters, well defined grooves can be obtained with clean side walls and with an etching rate up to several hundred micrometers per second. It is also found that the grains in the polycrystalline Al2O3TiC material play an important role in the etching dynamics and etching quality. This etching process is believed to be applicable to the formation of a slider surface of magnetic heads in the future.

Thermal Conductivity of Single Carbon Fibers Using Photothermal Deflection Techniques

AbstractA modification of the transverse photothermal deflection technique is used to determine the thermal diffusivity of high-conductivity carbon fibers. A chopped, cw Ar-ion laser beam is focused to a point on the fiber to cause localized heating of the fiber and the surrounding transparent fluid medium. The fluid medium immediately adjacent to the fiber sample is probed with a weak He-Ne laser that grazes the fiber surface and is deflected by the synchronous thermal lens produced near the fiber surface. The pump laser is stepped along the length of the fiber to produce a photothermal signal that is proportional to the temperature gradient along the length of the fiber. The theory necessary to predict the magnitude and phase of the probe beam deflection as a function of distance along the fiber is derived. This signal can then be analyzed by a simple method to determine the thermal diffusivity of the carbon fiber.

Direct laser indiffusion of Ti into LiNbO3 single crystals

The successful indiffusion of Ti into single-crystalline LiNbO3 substrates is reported as a result of high-intensity ruby laser irradiation of LiNbO3 samples coated with films of Ti of 400 Å thickness. The experimental data are compared to the results of cw CO2 or Ar ion laser irradiations. We conclude that the Ti indiffusion process starts with the oxidation of Ti and continues in a liquid phase.