Optical Homogeneity of a Ultraviolet-Preionized CO_2 Laser Discharge

A single-filament schlieren method for flowing characteristic measurements in the pulsed gas lasers

“…There have been lots of methods applied in repetitively pulsed gas lasers to study the characteristics of the flow field after energy deposition such as pressure probe measurements [7,11,14], interferometry [9,15,16] and Schlieren method [1,14,17]. The pressure probe has been employed on the chamber wall to record the temporal evolution of the pressure fluctuation amplitude.…”

“…The previous studies have shown three acoustic waves families differentiated by their direction of propagation [9]. More detailed characteristics such as density variation resulting from acoustic waves [9,16] and density distribution after heated gas expansion [15] can be obtained from the interference pattern. However, heated gas with high density gradient was formed in the ArF excimer laser in the case of high gas pressure and narrow electrodes width, so the probing beam was totally deflected away after passing through the heated gas region, and the interferometry was difficult to measure the flowing characteristics after discharge in the ArF excimer laser.…”

“…Though spatial pattern can be given in just one-shot by the conventional Schlieren method, temporal evolution can only be recovered by sequential sampling from many repeated pulses, and a CCD camera is usually used which complicates the experimental setup. A single-filament schlieren system that consists of a helium-neon (He-Ne) laser beam passing through the cavity on to a knife edge has been proposed to measure the acoustic disturbances in real time based on the fast response of the photodiode [16]. This method is based on the beam deflection through inhomogeneous media.…”

“…However, the mixture used in Ref. 16 and Ref. 18 mainly contains of helium, not the working gas of excimer laser, so the residual energy deposition and the flowing characteristics in the chamber were different.…”

Note: Measurement for the disturbance of discharge medium in pulsed gas laser

“…There have been lots of methods applied in pulsed lasers to measure the disturbance of the gas medium after discharge, e.g., pressure probe measurements, 2 interferometry, [9][10][11] and schlieren method. 4 The pressure probe has been assembled in the chamber wall to record temporal evolution of the acoustic waves.…”