Impedance matching in RF excited fast axial flow CO2 laser: The role of the capacitance due to laser head

Impedance matching in an indigenously developed 2 kW RF-excited fast axial flow (RF-FAF) CO2 laser was seen to be significantly influenced by the capacitance formed between the laser head and the electrodes. We find in the published literature that this capacitance is generally assumed to be negligible while designing the matching network in the RF-FAF CO2 lasers. It is shown that this capacitance could have a significant value and consequently would modify the design of the matching network remarkably for a specific laser design studied in the present case. The widely used discharge load model for capacitively coupled RF (CCRF) discharge excited CO2 laser plasma is extended to include this capacitance. The method of measurement of this capacitance using a bridge and the ANSYS software based simulation of its formation due to the laser head structure are discussed.

► Impedance matching in RF-FAF CO2 laser. ► Identified the role of laser head capacitance in impedance matching. ► Impedance matched by inclusion of this capacitance in the network design. ► Existing load model modified to include the laser head capacitance. ► The values of this capacitance from experiments and direct measurement were close.