Parameters Of Laser System Research Articles

Comparison of Laser Chemical Processing and LaserMicroJet for structuring and cutting silicon substrates

This paper deals with the development of a new cutting method for thin silicon solar wafers with liquid-jet-guided lasers (LaserMicroJet®, LMJ, and Laser Chemical Processing, LCP). Several laser systems with different wavelengths were tested to find the optimum laser system and processing parameters in terms of efficient material removal and deep laser cutting. Water and potassium hydroxide were used as carrier liquids to enhance laser ablation. The ablation efficiency was defined as a target parameter and experimentally determined by performing single laser grooves. It is demonstrated that the ablation process of LMJ is mainly affected by silicon melting and then removing by the liquid-jet momentum for single laser grooves. Best result for deep laser grooves is achieved if evaporation dominates the ablation process. Better surface quality referred to laser-induced crystalline damage is presented for a cut wafer with LMJ in comparison to a standard multiwire slurry saw. This shows a great potential of wafering with liquid-jet-guided lasers although no optimal liquid media was used.

Current Concepts: Laser Treatment of Adult Vascular Lesions

Patients frequently seek treatment of cutaneous vascular lesions for both medical and cosmetic reasons. Advances in the use of lasers and light sources enable physicians to effectively treat vascular lesions that were previously untreatable. Given the plethora of devices available, selecting the appropriate laser system and treatment parameters can be confusing for the laser surgeon. This article reviews current concepts in the treatment of adult vascular conditions. It highlights the different types of lasers and the most common vascular lesions amenable to therapy. Also, the article offers several pearls regarding selection of the laser and of the treatment parameters.

High-power mobile chemical lasers

The prospects of equipping mobile carriers with continuous wave chemical lasers (cw CLs), which continue to be the most powerful sources of laser radiation providing the highest energy efficiency and a high optical quality of the beam, are considered. The technological problems involved in such a procedure, whose solution leads to the determination of real technical parameters of autonomous mobile laser systems, are discussed. It is shown that the technical parameters of real lasers must reflect the features of their installation and exploitation under conditions differing radically from the conditions in laboratories where their investigations are being continued.

X-ray generator based on Compton scattering

Nowadays, the sources of the X-rays based on a storage ring with low beam energy and Compton scattering of intense laser beam are under development in several laboratories. In the paper the state-of-art in development and construction of cooperative project of a Kharkov advanced X-ray source NESTOR based on electron storage ring with beam energy 43–225 MeV and Nd:YAG laser are described. The layout of the facility is presented and latest results are described. The designed lattice includes 4 dipole magnets with combined focusing functions, 20 quadrupole magnets and 19 sextupoles with correcting components of magnetic field. At present, a set of quadrupole magnet is under manufacture and bending magnet reconstruction is going on. The main parameters of developed vacuum system providing residual gas pressure in the storage ring vacuum chamber up to 10 −9 Torr are presented. The basic parameters of the X-ray source laser and injection systems are presented. The facility is going to be in operation from the middle of 2006 and generated X-ray flux is expected to be of about 10 13 phot/s.

Experimental investigation of single voxels for laser nanofabrication via two-photon photopolymerization

We report critical roles that are played by laser system parameters in two-photon laser nanofabrication, which are not significant in rapid prototyping at larger scale, including: (i) polarization-induced lateral deshaping of volume elements, voxels, the primitive building block of micronanostructures, and (ii) lateral size reduction of voxels at low numerical aperture lens focusing due to thresholding effect. Also interesting is (iii) simultaneous recording of zeroth- and higher-order diffraction patterns, which was not hindered by the two-order light intensity difference by taking the advantage of the large dynamic exposure time range of general resins, a concept that is proposed in contrast to dynamic power range.

Analytic model for unstable telescopic resonator with an active medium to a two-dimensional geometrical approximation

The design of an unstable telescopic resonator with an arbitrary configuration of the active medium inside the resonator was evaluated for cases of outcoupling of radiation from a concave mirror or from a convex mirror. The calculation makes it possible to assess routinely the energy parameters of laser systems without using high-performance computers.

Pellet-injection in tokamaks and stellarators based on high-power long-wave lasers

An applicability of high-power long-wave lasers for implementing pellet injection in the systems of a tokamak or stellarator type has been considered. It has been shown that pellets can be accelerated with a CO 2-laser up to velocities of the order of 100 km s −1 while keeping them in a condensed state and required physical conditions in the plasma corona have also been defined. A sufficiently high efficiency for the laser beam energy conversion to that of the pellet mechanical movement was noted with proper choice of optimal conditions. The requirements for the laser system parameters have also been considered.

Analysis and modelling of high power laser beam position sensing

A new theory using a rotating convex mirror to reflect part of a laser beam into a pyro-electric sensor in order to detect the high power laser beam position is addressed in this research. The experiments were performed on the Nd:YAG laser system. The sensing performance was tested with the average power up to 50 W, duration time 1 ms and duration frequency 360 Hz. The results of static experiments show that the sensing system designed and developed in this research may correctly detect the Nd:YAG laser beam with the system parameters varied. The results of dynamic experiments show that the average sensing accuracy of beam position is up to 90% with a wide variation of laser system parameters.

Carbon isotope separation by infrared multiphoton dissociation of CF2HCl molecules with a separation reactor in a laser cavity

An investigation was made of isotopically selective multiphoton dissociation of CF2HCl molecules by high-intensity infrared radiation in a separation reactor placed inside the cavity of a TEA CO2 laser. Special attention was paid to the influence of the laser system parameters (linear and nonlinear cavity losses, input energy) on the time and spatial characteristics of the laser radiation, and to the dependences of the characteristics of an elementary isotope separation event (selectivity and dissociation yield) on these laser parameters. The intracavity position of the separation reactor made it possible to reach high energy densities in large volumes, to utilise efficiently the laser radiation, and to achieve high values of the selectivity (in excess of 100) and yield (over 5%) of the multiphoton dissociation process. The conditions of operation of this laser system were optimised in respect of the input energy and the CF2HCl pressure in the separation reactor.

Effects of continuous‐wave laser systems on stapes footplate

Background and Objective The aim of the present study was to clarify which of the presently available continuous-wave laser systems are best suited for application in stapes surgery. Study Design/Materials and Methods Isolated human stapes and bovine compact-bone platelets were used to investigate the connections between the parameters of various laser systems and their effects on bone tissue. The purpose was to optimize the laser parameters required to achieve a perforation measuring 500 μm to 600 μm in diameter. Three different laser systems were applied: the argon and CO2 laser in continuous wave (cw) mode and the CO2 laser in superpulse mode. Results The suitability of the argon laser for stapedotomy is doubtful in view of the lower absorption coefficient of the stapes for the argon beam and the considerable influence which the degree of pigmentation of the irradiated medium exerts on its effect with the resultant poor reproducibility of the perforation diameter. The beam of the CO2 laser is far better absorbed at the footplate than that of the argon laser. This results in higher effectivity, lower thermic side effects, and better reproducibility of the perforation. The two modes of the CO2 laser do not show any appreciable differences. Conclusion The experimental results presented indicate that the CO2 laser in cw and superpulse mode is the most suitable of the systems now clinically applied in stapes surgery. © 1996 Wiley-Liss, Inc.

Frequency-shift mode locking of continuous-wave solid-state lasers

We present the analysis of a new technique for mode locking cw solid-state lasers. The mode-locking mechanism consists of a combination of a laser carrier frequency shift from the center of gain band caused by insertion of a knife-edge into the intracavity prism section and self-phase modulation. It results in the quasi-soliton formation of ultrashort pulses. An investigation of the soliton parameters versus the laser system parameters and a nonlinear analysis of soliton stability are presented that show new possibilities for highly efficient mode locking of solid-state lasers.

2.3 - Performance limits and design procedure for all-weather terrestrial rangefinders

This paper provides an assessment of the maximum all-weather operational range for "single-ping" terrestrial laser rangefinders. It is shown that this range is a function of a single parameter involving the transmitted pulse energy, receiver aperture area, photoelectric quantum efficiency, and operating wavelength. By virtue of this convenient parameter, trade-offs between different laser materials and system parameters can be made by inspection, as well as comparative evaluations of different range-finder designs. The major uncontrollable factor which affects the range performance of these devices is weather conditions; the effects arise from signal loss due to atmospheric extinction and spurious returns due to backscatter from atmospheric particles. A first-order theory for the analysis of the effect of weather on the performance of pulsed laser rangefinders shows that the maximum backscatter varies as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/R^{3}</tex> compared with a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/R^{2}</tex> or <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/R^{4}</tex> dependence of minimum signal. The effects of backscatter can be minimized by incorporation of a time-programmed gain circuit in the receiver. Calculations for the design of optimum time-programmed gain characteristics are given, as well as experimental results with actual systems designed by this procedure.

Performance limits and design procedure for all-weather terrestrial rangefinders

This paper provides an assessment of the maximum all-weather operational range for single-ping terrestrial laser rangefinders. It is shown that this range is a function of a single parameter involving the transmitted pulse energy, receiver aperture area, photoelectric quantum efficiency, and operating wavelength. By virtue of this convenient parameter, trade-offs between different laser materials and system parameters can be made by inspection, as well as comparative evaluations of different range-finder designs. The major uncontrollable factor which affects the range performance of these devices is weather conditions; the effects arise from signal loss due to atmospheric extinction and spurious returns due to backscatter from atmospheric particles. A first-order theory for the analysis of the effect of weather on the performance of pulsed laser rangefinders shows that the maximum backscatter varies as 1/R^{3} compared with a 1/R^{2} or 1/R^{4} dependence of minimum signal. The effects of backscatter can be minimized by incorporation of a time-programmed gain circuit in the receiver. Calculations for the design of optimum time-programmed gain characteristics are given, as well as experimental results with actual systems designed by this procedure.