<title>Investigation of beam pointing stability, far-field divergence angle and power density distribution of a high-power CO<formula><inf><roman>2</roman></inf></formula> laser</title>

Abstract

A high power C02-laser beam, sampled by a diffraction grating, is monitored simultaneously by a Hartmann sensor to measure the wavefront and by a pyroelectric matrix camera to obtain the far field distribution. The maximum sampling frequency of the Hartmann sensor is 1 kl-Jzwith a resolution of 10 psad for the measurement of the beam direction. The data of the pyrocamera can be analysed with a maximum frequency of 5 Hz and the beam direction in the far field can be measured with an angular resolution of 50 jirad.Both methods reveal a periodic change ofthe beam direction with an amplitude ofnearly 50 grad and a periodic change of the beam divergence with an amplitude of about 1 50 trad. Far field profiles measured with the matrix camera show that the angular stability is limited by fluctuations of the power density distribution. These changes of the transverse beam profile are dosely connected to fluctuations of the laser gas pressure, which are due to the gas pressure regulation system.

Laser pointing stability measured by an oblique-incidence optical transmittance difference technique

“…Laser beam pointing stability is typically determined by measuring the displacement of the beam position in the focal plane of a suitable lens system [1][2][3]. The beam displacement (positional stability) is measured with a four-quadrant position sensitive detector.…”

Laser beam quality and pointing measurement with an optical resonator

“…Usually, position sensitive detectors ͑PSDs͒ are used to measure the transverse shift of the beam at one position along the beam axis. [13][14][15][16] The angular tilt has to be transformed by a lens into a transverse shift in order to be measured. This transverse shift can then be detected with a second PSD at the focal plane of the lens.…”