Pulsed Copper Vapor Laser Research Articles

Two-frequency pulsed laser irradiation to stimulate the development of coniferous trees

The possibility of using radiation from a two-frequency pulsed copper vapor laser with wavelengths of 510.6 nm and 578.2 nm with an exposure of 30 to 120 s to stimulate the development of coniferous trees (spruce, pine, larch) with a single seed irradiation is shown. The stimulation effect manifests itself at various early stages of development, such as the awakening of seeds in the aquatic environment in the first hours of the experiment (according to electron absorption spectroscopy data), seed germination, and seedling growth under stressful cultivation conditions. Possible causes of light exposure to plant seeds are discussed.

Numerical investigation of vessel heating using a copper vapor laser and a pulsed dye laser in treating vascular skin lesions

A computer simulation technique was employed to study the selective heating of a tissue vessel using emission from a pulsed copper vapor laser and a pulsed dye laser. The depth and size of vessels that could be selectively and safely removed were determined for the lasers under examination.

Laser ablation of magnesium in water and investigation of optical nonlinearity by the Z-scan technique

Magnesium hydroxide structures were formed by a pulsed copper vapor laser ablation of a magnesium target in water. These structures were characterized by x-ray powder diffraction, scanning electron microscopy, and the Z-scan technique. The measurements of nonlinear optical properties of Mg(OH)2 structures have been performed using a nanosecond Nd:YAG pulse laser at 532 nm by the Z-scan technique. The nonlinear refractive index (n2) and absorption coefficient (β) of Mg(OH)2 structures were obtained from closed and open aperture Z-scans of the order of 10−13 cm2/W and 10−7 cm/W, respectively. The third-order nonlinear optical susceptibility, χ(3), of Mg(OH)2 structures was measured of the order of 10−11 esu. The results suggest that Mg(OH)2 structures, in comparison with other materials that are candidates for the nonlinear optical devices, are cheaper and may be promising candidates for nonlinear optical applications.

Excitation and relaxation of metastable atomic states in an active medium of a repetitively pulsed copper vapour laser

The influence of a pre-pulse population of copper atom metastable states and their sub-population at a current pulse edge on the copper vapour laser pulse energy is studied under optimal temperature conditions. Experiments have been performed with active elements of a commercial laser having an internal diameter of a discharge channel of 14 and . It is found that at a pulse repetition frequency of , corresponding to a maximal output power, the reduction of the energy due to a residual population of metastable states is by an order of magnitude less than due to their sub-population at a current pulse edge. The modelling based on the experimental results obtained has shown that in the case of an active element with an internal diameter of , a decrease in the pulse leading edge from to does not reduce the laser pulse energy up to the repetition frequency of at an average output power of and efficiency of .

Note: A novel and robust circuit for jitter reduction in copper vapor laser system.

A novel circuit scheme is presented to improve timing jitter performance of high voltage pulse power supply utilizing semiconductor switches and magnetic pulse compressors, for pumping pulsed copper vapor lasers. The circuit effectively handles reflected energy from the laser load and achieves better jitter performance. The proposed circuit scheme had typical jitter value of ±2 ns whereas the standard circuit used earlier had jitter of more than ±10 ns under similar conditions. Performance of the circuit scheme is studied on a copper vapor laser operating at average laser power of 40 W.

Broadband infrared light-emitting patterns in optical glass by laser-induced nanostructuring of NiO-doped alkali-gallium germanosilicates

In this Letter, we show functionalization of NiO-doped 7.5Li(2)O·2.5Na(2)O·20Ga(2)O(3)·35SiO(2)·35GeO(2) glass by space-selective nanocrystallization via exposure to the focused beam of a pulsed copper vapor laser (510.6 and 578.2 nm) at temperature close to the glass transition point (570°C). Irradiated areas drastically change their color, caused by electronic transitions of Ni(2+) dopant ions, without any alteration of the optical quality. Importantly, irradiated regions acquire broadband infrared luminescence (centered at about 1400 nm and possessing 400 nm effective bandwidth) typical of Ni(2+) ions in crystalline environment, and by positive change of refractive index (more than 10(-3)). Spectroscopic and diffractometric data of the irradiated regions indeed resemble those previously observed in thermally nanocrystallized glass, with Ni(2+) ions embedded in γ-Ga(2)O(3) nanocrystals. The results demonstrate the possibility of laser writing nanocrystallized multifunction patterns in germanosilicate glasses for the fabrication of active integrated devices.

A novel confocal optical pulse stretcher for laser pulses

We present an analytical and experimental study of a novel confocal optical pulse stretcher (COPS). The simple and passive pulse stretcher consists of two concave mirrors and a scraper beam-splitter and its optical configuration ensures a perfect spatial overlapping of laser pulses at the beam-splitter. The pulse stretcher is compact and suitable for laser pulses of large divergences. The confocal optical pulse stretcher is demonstrated on a pulsed copper vapour laser to convert a 40 ns (1/ e 2 % points) pulse into a 55 ns with reduction of peak power by a factor of 1.375 without loss of pulse energy.

Correlation of prepulse plasma parameters with metastable level population and their effect on lasing characteristics of the pulsed copper vapor laser

The effect of the prepulse electron density and population of the lower laser (metastable) level on lasing characteristics of the pulsed copper vapor laser is considered. In the analysis of their effect, attention is paid to the need to consider the correlation of these parameters. It is emphasized that the effect of the prepulse electron density depends on the electron heating rate at the beginning of the excitation pulse. The conditions controlling the electron heating rate and methods for reducing the effect of this parameter are considered.

Formation of periodic structures by laser ablation of metals in liquids

Experimental results are presented on ablation of metals (W, Cu, brass and bronze) in a liquid environment (e.g., ethanol or water) by irradiation with either a pulsed copper vapor laser (0.51 μm) or a pulsed Nd:YAG laser (1.06 μm). The target material is ejected into surrounding liquid in the form of nanoparticles. In a certain range of laser parameters (fluence and number of laser shots) the surface of the solid target is composed of micro-cones having a regular structure. The distance between neighboring micro-cones in the structure depends on the laser spot size. The structures allow the observation of up-conversion of the laser frequency due to generation of the second harmonics in the eye retina.

Formation of Core-Shell Nanoparticles by Laser Ablation of Copper and Brass in Liquids

Experimental results are presented on the ablation of copper and brass targets in a liquid environment: ethanol, acetone, or water by irradiation with either a pulsed copper vapour laser (0.51 μm) or a pulsed Nd:YAG laser (1.06 μm). The ablated material was ejected into the surrounding liquid as nanoparticles of average size 20 nm. The nanoparticle composition depends on the nature of the liquid. Ablation of 60%Cu, 40%Zn brass in ethanol results in formation of core-shell nanoparticles. Brass nanoparticles were characterized by a well-defined plasmon peak at 510-520 nm.

On the simulation of a copper vapour laser with hydrogen admixtures

The results of computer simulation of a pulsed copper vapour laser with hydrogen admixtures presented in [1–4] are discussed. It is pointed out that the simulation technique used in these papers has a number of serious drawbacks. In particular, it is shown that the prepulse electron temperature obtained with its help is much lower than the temperature of the wall of the gas-discharge tube, which is in direct contradiction with the thermodynamics. Possible reasons for the erroneous results obtained in these works are discussed.

Micromachining and dicing of sapphire, gallium nitride and micro LED devices with UV copper vapour laser

Gallium nitride (GaN) and sapphire are important materials for fabricating photonic devices such as high brightness light emitting diodes (LEDs). These materials are strongly resistant to wet chemical etching and also, low etch rates restrict the use of dry etching. Thus, to develop alternative high resolution processing and machining techniques for these materials is important in fabricating novel photonic devices. In this work, a repetitively pulsed UV copper vapour laser (255 nm) has been used to machine and dice sapphire, GaN and micro LED devices. Machining parameters were optimised so as to achieve controllable machining and high resolution. For sapphire, well-defined grooves 30 μm wide and 430 μm deep were machined. For GaN, precision features such as holes on a tens of micron length scale have been fabricated. By using this technique, compact micro LED chips with a die spacing 100 and a 430 μm thick sapphire substrate have been successfully diced. Measurements show that the performances of LED devices are not influenced by the UV laser machining. Our results demonstrate that the pulsed UV copper vapour laser is a powerful tool for micromachining and dicing of photonic materials and devices.

Numerical study on the terminating mechanisms of copper vapor laser pulse

A self-consistent physical model describing the kinetic process of the longitudinal pulsed discharge-excited copper vapor laser was established, and numerical solutions of the model were obtained. The terminating mechanisms of the copper vapor laser pulse have been further analyzed according to the simulation results. It is shown that the important factors resulting in the termination of laser pulse are the processes of stimulated emission transition, the electron impact excitation of the lower laser level and the depopulation of the upper laser level to the higher excitation levels by electron collisions.

The effect of pulse-periodic laser radiation on polyvinylchloride

Changes in the conductivity, permittivity, and dielectric loss tangent are registered for ten polyvinylchloride-based organic dielectrics (polymers), caused by the exposure for 3–5 s to the unpolarized radiation of a pulsed copper-vapor laser with a wavelength of 510.6 nm. The duration of light pulses is 20 ns, and their repetition frequency, 8.5 kHz.

High temperature Raman spectra of sodium disilicate crystal, glass and its liquid

Raman spectra of Na 2Si 2O 5 in solid and liquid states from room temperature to 1773 K were measured to observe phase transition and analyze the temperature-dependent variations of the structure units, five kinds of SiO 4 tetrahedrons, which are defined as Q 4, Q 3, Q 2, Q 1 and Q 0 species corresponding to the number of bridging oxygen binding to each Si. A pulsed copper vapor laser was used as laser source coupled with time resolved detection system to eliminate the dense thermal emission background while temperature was >1273 K. Temperature-dependent Raman spectra can clearly indicate melting point of a crystal around 1143 K. Gaussian deconvolutions of complex stretching vibrational bands of crystal and amorphous states (glass and liquid) were described. Raman sensitivity factors were introduced to calculate the mole fractions of the different SiO 4 tetrahedrons. There is a decrease of Q 3 species and an increase of Q 4 and Q 2 species with increasing temperature. And after melting, the ratio of the components remain unchanged. Q 3 species decomposes again after about 1573 K. More Q n species would form with increasing temperature. Although the Q n distribution of the glass is similar to that of the liquid of melting temperature, T m ∼1143 K, the liquid structure has a greater disorder than that of the glass.

Light scattering from deformed droplets and droplets with inclusions I Experimental results

We provide experimental results from the scattering of light by deformed liquid droplets and droplets with inclusions. The characterization of droplet deformation could lead to improved measurement of droplet size as measured by commercial aerodynamic particle-sizing instruments. The characterization of droplets with inclusions can be of importance in some industrial, occupational, and military aerosol monitoring situations. The nozzle assembly from a TSI Aerodynamic Particle Sizer was used to provide the accelerating flow conditions in which experimental data were recorded. A helium-neon laser was employed to generate the light-scattering data, and an externally triggered, pulsed copper vapor laser provided illumination for a droplet imaging system arranged orthogonal to the He-Ne scattering axis. The observed droplet deformation correlates well over a limited acceleration range with theoretical predictions derived from an analytical solution of the Navier-Stokes equation.

Experimental observations of the stepped Cu-atom ionization in the active medium of a Cu laser

An optogalvanic effect in a pulsed copper-vapor laser is discovered and investigated. It is found that the generalized deexcitation rate constant of the resonance level to the ionization state of the active medium is ∼ (3±1)·10−7 cm3·s−1. An optothermal effect caused by the hysteresis of the optogalvanic phenomenon is found experimentally. The feasibility of measuring the stepped ionization constants of resonance and metastable states for a number of metal atoms in a pulse-discharge plasma is discussed.

Large-grained polycrystalline silicon on glass by copper vapor laser annealing

We crystallized 400 nm thick amorphous silicon films on low cost glass substrates using a pulsed copper vapor laser. The moderate pulse energy (60 μJ) and high repetition rate (20 kHz) of the laser allow crystallization scanning rates up to 10 mm/s. The resulting polycrystalline silicon films show large elongated grains 3 μm wide and several tens of microns in length.

Cooled and uncooled single-channel deformable mirrors for industrial laser systems

A study was made of bimorph mirrors intended for industrial laser systems. The technical characteristics of cooled single-channel deformable mirrors were investigated in detail. Preliminary tests were made on uncooled bimorph mirrors in industrial laser systems based on a cw CO2 laser with an output power in excess of 2 kW and on a pulsed copper vapour laser with an average power of 35 W.

The puzzle of whip cracking - uncovered by a correlation of whip-tip kinematics with shock wave emission

During whip cracking the whip-tip reaches a supersonic velocity for a period of about 1.2 ms, thereby emitting a head wave with a parabolic-shaped geometry. A detailed study of this mechanism which encompasses the motion analysis of the whip-tip as well as the determination of the local origin of the shock emission requires a sophisticated recording technique. A pre-trigger framing high-speed video camera system was used which was triggered by an acoustical sensor and synchronized with a pulsed copper-vapour laser. The phenomena were visualized by the direct shadowgraph method and recorded cinematographically as digital images at a frame rate of 9 kHz using a CCD-matrix with \(256{\rm (H)}\times 128{\rm (V)}\) pixels. The resulting series of frames allowed, for the first time, (i) a reconstruction of the whip-tip trajectory, (ii) a determination of the tuft velocity and acceleration, (iii) a correlation of whip-tip kinematics with shock wave emission, and (iv) a motion analysis of the turning and unfolding mechanism of the tuft. The tuft at the whip-tip was accelerated within a distance of about 45 cm from a Mach number of \(M=1\) to a maximum of \(M=2.19\), thereby reaching a maximum acceleration of 50,000 g. The shock is emitted at the moment when the cracker, arriving at the turning point of the lash, is rapidly turned around. After emission of the shock wav \(M<1\) within a short distance of only 20 cm.