Copper Bromide Vapor Laser Research Articles

Statistical approach in planning experiments with a copper bromide vapor laser

To improve the planning of experiments, the statistical analysis of a large amount of experimental data obtained for a copper bromide laser emitting at 510.6 nm and 578.2 nm was performed. Various statistical methods such as factor analysis, method of principal components, multiple regression and others were applied for studying the influence of the ten basic input laser parameters on the output laser power. It was found that the most important parameters are the inside diameter of the laser tube, the diameter of internal rings, the length of the active area and the input electrical power.

Statistical analysis of the CuBr laser efficiency improvement

A new approach for improving the efficiency of a copper bromide vapour laser with wavelengths of 510.6 and 578.2 nm is implemented. Multi-factor and regression analyses of a large amount of experimental data have outlined the parameters with highest impact on the laser efficiency. They are electric input power, inside diameter of the rings, distance between the electrodes, inside diameter of the laser tube, hydrogen pressure and electric input power per unit length. The results obtained allow discovery of the internal structure of dependences among parameters, to better account for the physical processes that influence efficiency, to improve the planning of further experiments and laser production technology.

Metal and metal halide vapor lasers: new opportunities

The influence of minor H2 and HBr additives on the generation characteristics of some copper bromide vapor lasers is experimentally investigated. It is demonstrated that at optimal concentrations of both admixtures, the average generation power increases by five times for lasers with small active element diameters, and by two times for lasers with major diameters. For the maintenance of an adjusted concentration of the admixture, the original construction of the HBr generator is developed, which in the reversible regime removes not only the HBr surplus from active volume of the laser, but also at least some of harmful products of the working laser. The obtained results are applied to the development of a sealed-off self-heating copper bromide vapor laser with an integral HBr generator, operating in the automatic regime.

Modeling the plasma kinetics mechanisms of CuBr laser with neon–hydrogen additives

A mathematical model describing the discharge kinetics and lasing characteristics of copper bromide vapor laser with neon and hydrogen additives has been developed. The suggested model is based on a “zero-dimensional” model and offers simple mechanisms to explain discharge kinetics mechanisms, different physical processes and hydrogen additive effects on the copper bromide vapor laser. The model estimates the temporal evolution of discharge voltage and current, population densities, laser beam density, electron temperature and radial distribution of pressure and buffer gas temperature. The suggested mechanism assumes that the electron detachment from negative hydrogen ions does not contribute to the copper ionization process. Numerical solutions of a nonlinear rate equation system predict the generation of nanosecond pulses. The calculated maximum values of discharge voltage, current, average output laser power, electron temperature, etc. are in good agreement with other reported calculated and experimental data.

A copper bromide vapour laser with a high pulse repetition rate

The results of an experimental study of a copper bromide vapour laser with a discharge-channel diameter above 2.5 cm and a high pump-pulse repetition rate are presented. A TGU1-1000/25 high-power tacitron used as a switch made it possible to obtain for the first time a fairly high output radiation power for pump-pulse repetition rates exceeding 200 kHz. At a maximum pump-pulse repetition rate of 250 kHz achieved in a laser tube 2.6 cm in diameter and 76 cm long, the output power was 1.5 W. The output powers of 3 and 10.5 W were reached for pump-pulse repetition rates of 200 and 100 kHz, respectively. These characteristics were obtained without circulating a buffer gas and (or) low-concentration active impurities through the active volume.

Method of Measuring Electron Density in Pulse Metal Vapor Lasers Using Microwave Technique

A method of measuring the electron density kinetics in the plasma of pulse-periodic metal vapor and metal compound vapor lasers using microwave technique within the wavelength region of 78–142 GHz is realized. The method is based on the dependence of the absorption efficiency of a probe microwave radiation on the frequency of electron collisions and also on the dependence of the “cut-off” or the critical density on the frequency of the probe radiation. In a quasioptical translucence scheme the plasma of a copper bromide vapor laser is studied within an interpulse time interval in a gas-discharge tube of 20 mm in inner diameter and with a 300 mm long active heated region excited by a capacitor discharge with a pulse repetition rate of 10 kHz. It is shown that under operational conditions typical for metal vapor lasers the absorption of the probe radiation within the interpulse intervals is totally determined by Coulomb electron–ion collisions. This allows one to measure both the density kinetics and the electron temperature. Probable measurement errors are analyzed and it is shown that they result in a systematic error for the absolute value of the electron density but have a slight influence on the density kinetics.

Inductively coupled plasma and laser-induced chemical vapour deposition of thin carbon nitride films

Thin CNx films have been deposited on silicon substrates by inductively coupled plasma chemical vapour deposition (ICP-CVD) and by laser-induced chemical vapour deposition (LCVD) utilizing the focused beam of a copper bromide vapour laser. Different gas mixtures were used: CH4/N2 and CCl4/N2/H2 for ICP-CVD, and CCl4/NH3 for LCVD. Plasma properties (electron temperature, electron and ion densities, plasma potential) were studied by Langmuir probe and optical emission spectroscopy. The growth rates ranged up to 80 nm min−1 for ICP-CVD and 700 μm min−1 for LCVD. The surface morphology was studied using atomic force microscopy for ICP-CVD, and scanning electron microscopy for LCVD. Beside carbon and nitrogen, silicon and oxygen for LCVD and chlorine for ICP-CVD (in the case of the CCl4/N2/H2 system) was detected by Auger electron spectroscopy. Fourier transform infrared (FTIR) spectroscopy was used to determine the chemical bonding structure. Bands assigned to C=C and C=N (graphite-like domains) and to C=H bonds were detected in the films deposited by both processes. In addition, different bands attributed to other types of carbon nitride bonds or to due to the presence of impurity atoms were observed in the FTIR spectra of the CNx films deposited by the ICP-CVD and LCVD. The results of both deposition techniques were compared and discussed on the base of the processes peculiarities.

Laser approaches for deposition of carbon nitride films — chemical vapour deposition and ablation

The deposition of carbon nitride films by laser-induced chemical vapour deposition (LCVD) from the system NH 3 /CCl 4 and by laser ablation of a graphite target in nitrogen atmosphere has been studied. Two types of lasers were used: a copper bromide vapour laser for LCVD and an eximer KrF laser for the ablation process. The first laser source has a set of parameters (wavelengths, repetition rate, pulse duration) which makes it unique in material processing. During the ablation deposition an additional DC discharge (ignited by each shot) or RF discharge (permanent) was utilised to increase the reactivity of the nitrogen. The deposition rate for LCVD is almost one order of magnitude higher than for the laser ablation (0.050–0.350 and 0.025–0.040 nm/pulse, respectively) due to the direct laser impact on the substrate surface. The composition of the layers was studied by Auger electron spectroscopy (AES) and wavelength dispersive X-ray analysis (WDX). For the laser ablation the N/C ratio increases when an additional DC or RF discharge was used compared to the non-assisted process. Maximum values are reached at nitrogen pressures twice lower for RF discharge than for DC discharge assisted deposition. In the case of LCVD the composition depends mainly on the laser power. Chemical bonding was investigated by Fourier transform infrared (FTIR) spectroscopy. The FTIR spectra of the films deposited by LCVD show well defined bands which are superimposed to a broad peak for samples prepared by laser ablation. At higher RF plasma power a weak band around 2200 cm −1 appears in the spectra which can be attributed to the stretching mode of triple bonded C–N. Such a peak is not observed in cases of DC discharge and LCVD.

Effects of Peaking Capacitor in a Copper Bromide Vapor Laser

The performance of a copper bromide vapor laser, continuously excited by a charge transfer circuit at 7 kHz, was studied by varying its peaking capacitor. It was observed that, in contrast to many pulsed gas lasers, a slower risetime in the breakdown voltage for discharge initiation produced an extended quasi-steady discharge regime which increased the input power for laser excitation.

Influence of the addition of hydrogen on the operation of a copper iodide laser

An experimental investigation was made of the influence of the addition of molecular hydrogen on the characteristics of a copper iodide laser. An analysis was made of the weak, compared with a copper bromide vapour laser, influence of the addition of hydrogen on the copper iodide laser parameters.

Chemical vapour deposition of BC2N films and their laser-induced etching with SF6

Thin BC2N films have been obtained by chemical vapour deposition (CVD) from BCl3 and CH3CN. The layers were two types according to their appearance: metallic and black. The differences in their morphology, structure and composition were studied by scanning electron microscopy. X-ray diffraction and X-ray photoelectron spectroscopy. Metallic BC2N films were subjected to laser-induced etching with SF6 using copper bromide vapour laser. The etch depths increased with the increase of laser power and SF6 pressure, and with the decrease of scanning speed. The maximum etch rate was 120 μm s★ at 2 W laser power. 100 kPa SF6 and 400 μm s★ scanning speed.

Mass spectrometric investigation of products emitted from polytetrafluoroethylene irradiated with copper bromide vapor laser

Copper bromide vapor laser irradiation of polytetrafluoroethylene (PTFE) in vacuum was studied. The analyses of gaseous phase products were carried out by a quadrupole mass spectrometer. The main products of the decomposition process were C 2F 4 and C 3F 6 together with radicals and atoms. The obtained mass spectra were compared with reference data for excimer- and Nd:YAG-laser-induced decomposition of PTFE. In the case of copper bromide vapor laser-induced decomposition the process is mainly due to pyrolytic effects which resulted in formation of mainly low mass species. A mechanism of the laser destruction was proposed on the basis of the obtained mass spectrometric data. The formation of C 2F 4, C 3F 6 and CF as a function of time and laser scanning speed was studied.

Laser-induced chemical vapor deposition of aluminum from trimethylamine alane

Maskless patterning of aluminum has been achieved by using visible light from a copper bromide vapor laser for pyrolytic decomposition of trimethylamine alane (TMAA) on silicon monocrystalline wafer. The analysis of the resultant stripes included scanning electron microscopy, Auger electron spectroscopy, Talystep, and electrical resistance measurements. The crystalline structure of the layers showed well-defined grains. The Auger electron spectra indicated pure aluminum layers with small quantities of oxygen and carbon. The low resistivities of aluminum stripes deposited from TMAA (up to 4.0 μΩ cm) make it a promising precursor for metallization with aluminum and especially for chemical vapor deposition enhanced with a pulsed visible laser.

LCVD of aluminium stripes obtained by pyrolysis of TMAA and TMA

Maskless patterning of aluminium has been achieved by using visible light from a copper bromide vapor laser for pyrolytic decomposition of trimethylaluminium (TMA) and trimethylamine alane (TMAA). A silicon monocrystalline wafer was used as a substrate. The deposition was carried out at different process parameters (partial pressure of the precursors, laser power and scanning speed). The analysis of the resultant stripes included scanning electron microscopy, Auger electron spectroscopy, Talystep and electrical resistance measurements. The crystalline structure of the layers showed well-defined grains for both precursors. The Auger electron spectra indicated pure aluminium layers with small quantities of oxygen and carbon for stripes deposited from TMAA while those obtained from TMA were more contaminated. The difference in the layers composition for the used precursors resulted in their resistivity values. The low resistivities of aluminium stripes deposited from TMAA (up to 4.0 μΩ.cm) makes it promising precursor for metalization with aluminium and especially for chemical vapor deposition enhanced with pulsed visible laser

An experimental approach for growth rate determination of LCVD-written aluminium stripes

A new experimental approach for growth rate determination of microdimensional aluminium stripes written by laser-induced chemical vapour deposition (LCVD) was developed. The aluminium lines were obtained by pyrolysis of trimethylaluminium (TMA) on (100) silicon monocrystalline wafer using the focused beam of a copper bromide vapour laser. Quantitative determination of the deposit was performed by its chemical removal from the substrate into a solution and further analysis performed using inductively coupled plasma atomic emission spectroscopy. Using this analytical method, dependences of the aluminium quantity on the partial pressure of TMA and the laser power were obtained. The growth rate at direct writing with a pulsed visible laser was calculated on the basis of aluminium quantity determinations. It is demonstrated that the proposed experimental approach could be successfully used for kinetic studies of LCVD processes.

Mass spectrometric study of laser induced pyrolytic decomposition of TIBA and TMAA

The composition of the gaseous phases during pyrolytic laser-induced chemical vapor deposition (LCVD) of aluminium from triisobutylaluminium (TIBA) and trimethylamine alane (TMAA) (aluminium trihydride trimethylamine) was determined. The analysis was carried out by means of quadrupole mass spectrometer (QMS) in closed reaction cell. The developed arrangement for sampling allowed in situ analyses during the LCVD process. The decomposition of the aluminium precursors was induced by copper bromide vapor laser on the surface of (111) silicon monocrystalline wafer at different process parameters (partial pressure, laser power and scanning speed). The analyses showed usual gaseous products for the pyrolysis of TIBA and TMAA and additional species. The occurred pyrolysis products were probably due to different ways of decomposition of the precursors caused by pulsed laser irradiation. The results from this study combined with surface analysis of the deposit could help for better understanding of LCVD and for obtaining of high purity aluminium layers

Pyrolytic Lcvd of Silicon Using A Pulsed Visible Laser - Experiment and Modelling

AbstractMaskless deposition of silicon from silane on Si monocrystalline wafer using copper bromide vapor laser (CBVL) is investigated. Morphology and geometric parameters of the stripes obtained are studied and some conclusions for the process mechanism are made. Applying Kirchoff's transform and Green's function analysis nonlinear heat diffusion problem for different pulse shapes was solved. The influence of pulse shape on the temperature distribution and its time evolution was studied. Nonisothermal and non-stationary deposition kinetic models using the obtained results were developed.

Mass spectrometric study of laser‐induced pyrolytic decomposition of TMA

AbstractThe composition of the gaseous phase during pyrolytic laser‐induced chemical vapour deposition (LCVD) of aluminium from trimethylaluminium (TMA) was determined. The analysis was carried out in situ by means of a quadrupole mass spectrometer (QMS) in a closed reaction cell. The decomposition of the aluminium alkyl was induced by a copper bromide vapour laser on the surface of (111) silicon monocrystalline wafer at 0.22 GW m−2 average power density, 120 μm s−1 scanning speed and 100 Pa (1 mbar) partial pressure of TMA. The detected gaseous products of the pyrolysis of TMA were ethane, ethylene, methane and hydrogen. The presence of ethane and ethylene was probably due to the unconventional way of decomposition caused by pulsed laser irradiation. The mass peak dynamics of the created pyrolytic products at m/e = 28, 16 and 2 indicated significant production of ethane + ethylene, methane and hydrogen in the ratio 1:5:1.75.

Active optical systems with a copper bromide vapor amplifier

An experimental demonstration was made of the feasibility of using the active medium of a copper bromide vapor laser with hydrogen admixtures as an image amplifier in active optical systems. Images of microobjects located several meters from the amplifier were obtained in this way. Large (~ 7 cm) fields of vision were achieved in the telescopic system. The power of a beam carrying a negative image exceeded 0.5 W, so that it was possible to project independent images on a screen of more than 5 m2 in area.

Investigation of optical inhomogeneity of the active medium in a CO2laser with hf excitation

An investigation was made of the optical inhomogeneity of the active medium in a fast-flow closed-cycle CO2 laser with a transverse hf capacitative discharge and a 5-liter active volume. A lateral-shear interferometer employing a pulse-periodic copper bromide vapor laser was used in the measurements. Optical inhomogeneity of the wedge type in the flow direction and of the positive lens type in the transverse direction was found to be present at the start of the discharge, and there was a 2-mm-thick layer at the electrodes. The inhomogeneity was considerably smoothed out toward the end of the discharge zone along the flow direction. The gain and gas temperature distributions in the active medium were measured in the discharge current direction. The results obtained prove that the active medium homogeneity in a laser with an hf capacitative discharge is higher than that when a self-sustained discharge is pumped by a dc current.