Improvement in metal vapor laser performance with reduction in localized electric field at electrodes

Abstract

Electrode geometry plays a vital role in metal vapor laser performance. It has been observed that by modifying the electrode geometry, the electric field enhancement near the electrode can be reduced. Reduction in the localized electric field causes reduction in the phantom current in the metal vapor laser. On replacing the electrode geometry having eight pins with an electrode having the zero-pin configuration, a 10% decrease in the phantom current and a 23% increase in optical output power are observed. The low phantom current is responsible for higher efficiencies, large specific average output power, and improved beam characteristics of that laser in reference to a conventional copper vapor laser. It was also observed that reduction in field enhancement causes reduction in the thermal loading at the cathode fall and in the probability of thermal instability, thereby improving the discharge stability and jitter in metal vapor lasers. This simple and effective technique can also be applied to the systems requiring high current and high-volume stable discharge.

Analysis of the discharge plasma impedance of copper vapor laser

“…The conductivity increment leads to localized high current and temperature, which in turn increases the pressure locally and the gas further expands, leading to a drop in gas density. The constriction of discharge increases the probability of discharge instability as reported in our previous paper [17]. The 0-pin electrode offers the highest resistance, which increases the power coupling due to impedance matching.…”

“…We have reported in our previous papers that the electrode pins cause localized electric field enhancement near the electrode [14,17]. The high electric field causes a greater amount of charge carrier generation and increases the electron temperature, which reduces the recombination rate as per equation ( 6) and leads to high remnant electron density (phantom current).…”

“…A CVL discharge tube (36 mm and 1.8 m long) in leakfree condition delivers an average output power of 30 W (plane-plane resonator configuration) and serves as the load to the pulse power supply. The complete details of the PGU, the laser head and the measurement setup are reported in detail in our previous publications [14][15][16][17]. A schematic of the pulse discharge circuit and the laser head is shown in figure 1.…”

“…The PGU consists of a resonant charging circuit, pulse transformer, Insulated Gate Bipolar Transistor (IGBT) and the magnetic pulse compression (MPC) stages [15]. The pulse voltage across the laser head is 13 kV and the pulse current through the laser head is in the order of 450-500 A, depending on the laser head discharge condition [14,17].…”

“…The high electric field causes a greater amount of charge carrier generation and increases the electron temperature, which reduces the recombination rate as per equation ( 6) and leads to high remnant electron density (phantom current). It has been reported that with the increase in the number of pins, the shielding factor becomes dominant, which reduces the electric field enhancement [14,17,20]. It was shown that the phantom current (the remnant electron density) is highest with the 8-pin electrode configuration and lowest with the 0-pin electrode configuration.…”