Simulation and initial experiments of a high power pulsed TEA CO₂laser

Abstract

In this paper, the output characteristics of a UV pin array pre-ionized TEA CO 2 laser have been simulated and compared with the associated experimental data. In our simulation, a new theoretical model has been improved for transient behavior analysis of the discharge current pulse. The laser discharge tube was modeled by a nonlinear RLC electric circuit as a real model for electron density calculation. This model was coupled with a six-temperature model (6TM) in order to simulation dynamic emission processes of the TEA CO 2 laser. The equations were solved numerically by the fourth order Runge-Kutta numerical method and some important variables such as current and voltage of the main discharge, resistance of the plasma column and electron density in the main discharge region, were calculated as functions of time. The effects of non-dissociation factor, rotational quantum number and output coupler reflectivity were also studied theoretically. The experimental and simulation results are in good agreement.

Some experimental studies on the UV spark pin-array pre-ionization in TEA CO2 laser

“…These lasers provide output pulses in 9-11 µm spectral range with energies up to several kJ [1,2], time durations varying from ps [3] to µs [4] orders and repetition rates up to several kHz [5] with relatively low costs and without the needs for high-tech facilities. This flexibility in output characteristics are due to novel developments and progresses in various aspects including discharge circuits [6-8], electrodes [9-12] and resonator [13, 14] configurations, gas mixture [15][16][17] and pressure [18][19][20], pulse shaping techniques [21] as well as pre-ionization methods [22][23][24][25][26]. Each of these items plays a key role in achieving stable and longterm operation of the laser especially at high repetition rates and sealed-off regime [27][28][29].…”

“…Each of these items plays a key role in achieving stable and longterm operation of the laser especially at high repetition rates and sealed-off regime [27][28][29]. Therefore, much experimental [25,[30][31][32] and theoretical [31,[33][34][35][36][37] works have been done * Author to whom any correspondence should be addressed. so far to characterize the spatial-temporal properties of the output pulses of the pulsed CO 2 lasers according to their structural and operational conditions.…”

Generalization of the 6-Temperature model for simulation of super-atmospheric pulsed CO2 lasers output

“…They were also the first to add the vibrational states of CO molecules to those of CO 2 and N 2 for prediction of the CO 2 lasers output characteristics by 6-temperature model (6TM). This model provide better simulation results (in respect to 4 and 5-temperature previous models) by taking into account more vibrational energy levels involved in population distribution [3][4][5][6][7]. Nowadays, this model is widely used to theoretical analysis of CW [3,4] and TEA CO 2 [5][6][7] lasers operation, mathematical modeling of the tunable [8] and hybrid [9][10][11] CO 2 lasers, dynamic analysis of Q-switched TEA CO 2 lasers [12] and recently, CW CO 2 laser pulse amplifier [13].…”

Comparative study of spark pin-array and printed circuit board surface plasma pre-ionization systems for transversely excited atmospheric CO2 laser performance

“…Pre-ionization processes contribute very effectively to obtain a stable glow discharge by inducing a remarkable uniform electron density within the discharge volume prior to ignition of the main discharge. Beside the technically complex electron beam [7] Power Supply and x-ray [8] pre-ionization methods, UV radiation-based preionization systems are considered as the most common technics suitable for gas lasers, particularly pulsed CO 2 lasers with atmospheric or higher pressures [9,10]. This superiority can be explained as follows [6]: (a) A high electron density of around 10 8 -10 10 cm −3 is induced in the discharge volume, making it possible to inject large amounts of electric energy into the active volume with a weak dependence on the applied voltage rise time and the delay time between the pre-ionization and main discharges; (b) Because the produced electron density is much higher than the minimum primary electron density required to achieve glow discharge (10 4 cm −3 ), the glow discharge is achievable even in the presence of impurities produced in the discharge volume like as CO, O 2 etc.…”

“…This superiority can be explained as follows [6]: (a) A high electron density of around 10 8 -10 10 cm −3 is induced in the discharge volume, making it possible to inject large amounts of electric energy into the active volume with a weak dependence on the applied voltage rise time and the delay time between the pre-ionization and main discharges; (b) Because the produced electron density is much higher than the minimum primary electron density required to achieve glow discharge (10 4 cm −3 ), the glow discharge is achievable even in the presence of impurities produced in the discharge volume like as CO, O 2 etc. Among different UV pre-ionization methods such as corona discharge [11], mesh cathode configuration [6] and the spark pin-array (SPA) system [9,10,[12][13][14], the latter is the most used method in pulsed CO 2 lasers due to advantages including simplicity of implementation, good uniformity and high stability. However, the SPA pre-ionization systems involve some challenges, such as the high degree of CO 2 molecule dissociation and relatively low UV radiation penetration depth within the CO 2 -N 2 -He active gas mixtures [8,15].…”