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.
Within the EUREKA-project "CHOCLAB" a workshop was organised, where several panners analysed the beam of an industrial CO2 laser device. The goal was to qualify the ISO 1 1 146 standard by using different measurement techniques. This paper compares the results of the determination of the beam propagation factor and beam widths.The following test methods for measuring the beam width were applied: determination of the power density distribution with a rotating pinhole device and subsequent evaluation of beam widths, determination of the power density with a pyroelectric camera and subsequent evaluation of beam widths, moving knife edge method.For the measured data various methods of evaluation were used. These include data processing with different filters, evaluation of averaged power density distributions as well as different algorithms for curve fitting.Despite the different methods of measurement and evaluation the results showed reasonable agreement. This proves the applicability of the ISO 1 1146 standard to an industrial CO2 laser device.
A versatile optical vector signal analyzer based on a differential direct detection scheme is presented. The analyzer measures phase, intensity, eye diagrams and constellations. The performance is demonstrated for a 112 Gbit/s PolMUX DQPSK signal and other formats.
The EUREKA-project CHOCLAB (Characterization of Qptica! Components and Laser eams), which was initiated in 1995, aims to investigate and develop instruments and standard measurement procedures for laser beam and laser optics characterization. From the start of the project, one of the main work items in the field of laser beam characterization has been the determination of the beam propagation parameters (beam width, divergence angle and beam propagation factor). The most common measurement devices for these purposes are 2d-matrix-cameras (i. e. CCD-cameras), id or 2d scanning devices (i. e. scanning pinholes and/or moving knife-edges) -both of them requiring further evaluation of the measured power density distribution to obtain laser beam parameters -and variable transmission/reflectivity optical elements, which allow the direct measurement of beam properties. The advantages and drawbacks of the different types of measurement devices, as well as measures to reduce systematical and statistical errors will be discussed.The instruments and proposed standard measurement procedures are tested by ,,Round Robin" experiments: different laboratories characterize the same laser beam source according to the standards. In 1996 and 1997 four different ,,Round Robin" experiments on laser beam characterization were performed within the CHOCLAB project. The main goal of these ,,Round Robin" experiments was to test the applicability of the proposed standard measurement procedures to different important types of industrial laser devices (in particular high power C02-lasers and pulsed Nd:YAG-lasers). The results of these experiments as well as the current status of CHOCLAB and of the draft international standards concerning laser beam characterization will be briefly reviewed.
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