The distribution and nonuniformity of the electric field have been simulated in the active medium of CO2 laser using successive-over-relaxation numeric method. The different configurations of UV preionization have been considered as spark array, surface corona, plasma cathode, and sliding discharge. The electric field distribution and field deviation (FD) is compared in various configurations to obtain an insight into the electrical field uniformity. The numerical simulation results show that the minimum FD is related to the plasma cathode and sliding discharge configurations regarding boundary conditions. For the sliding configuration, a slight increase in the FD was observed in comparison with plasma cathode. The FD of surface corona configuration is about two percent lower than the spark array.
The construction of a surface corona UV pre-ionized TEA CO2 laser is described and dependence of its average output energy of the laser to gas mixture, discharge voltage and repetition rate is investigated. The electric circuit diagram and geometry of the pre-ionization system are presented. Configuration of circuit has been designed to produce only impulsive voltage difference between the laser electrodes. Also, the triggering configuration of trigatron is prepared for fast operation to minimize the arc occurrence as much as possible. Some data of current, voltage, laser pulses and average output energy versus gas mixture and applied voltages are given. IR spectrometer is used for measurements of central output wavelength of the laser. Operation of the laser on two adjacent vibrational-rotational transitions of CO2 molecule has been observed that shows the ability of this laser for working on multi-line in a same time for special applications.
A single longitudinally excited CW CO2 laser, designed based on gas flow mechanism has been used for small signal gain measurements. By inserting a ZnSe stack polarizer set at Brewster angle inside the laser cavity the absorption loss at the critical condition was obtained. The small-signal gain measurements were performed under various laser operational conditions such as gas pressure and input electric power. At the same experimental conditions, the values of the saturation intensity were calculated from the output power and the measured small-signal gain values. The results are compared with those reported previously by other researchers.
Operation of a TEA CO2 laser with parallel spark array pre-ionization is investigated. Low repetition rate pulsed laser has been made having integrated pre-ionization and peaking circuits. The effect of gas mixture, applied voltage and capacity of the main, peaking and preionization capacitors on output power of the laser are presented. Total efficiency up to 7% was obtained and although the fraction of the He in gas mixture was only 58% stability of discharge was good (2 arc in 55 discharges).
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