The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel
materials when subjected to the synergistic effects of the harsh space environment for several months. In this paper, a
few laser and optical elements from NASA Langley Research Center (LaRC) that have been flown on MISSE 6 mission
will be discussed. These items were characterized and packed inside a ruggedized Passive Experiment Container (PEC)
that resembles a suitcase. The PEC was tested for survivability due to launch conditions. Subsequently, the MISSE 6
PEC was transported by the STS-123 mission to International Space Station (ISS) on March 11, 2008. The astronauts
successfully attached the PEC to external handrails and opened the PEC for long term exposure to the space
environment. The plan is to retrieve the MISSE 6 PEC by STS-128 mission in August 2009.
The result in laser material processing is controlled mainly by the properties of the focused laser beam. Very special requirements have to be taken into account to characterize such a laser beam, which is finally used for laser micromachining. These specific aspects for the design of a beam diagnostics system ready to measure small spots (down the 10 micrometer range) at power densities up to several GW/cm2 will be discussed. Based on a CCD-camera concept, care has to be taken to magnify and to attenuate the beam properly. A special electronics design and algorithms are necessary to optimize the performance and finally to realize such a technical measuring system. Some applications of beam diagnostics within industrial processes (drilling holes, cutting wafers etc.) are demonstrated.
The ISO Standard 11146 has joined the various company specific standards into one set of procedures to determine laser beam propagation parameters. Due to the implementation of the standard, a lot of smaller and some critical measurement problems become visible.
The main part of beam parameter calculation is the determination of the beam width based on the second order moments of the power density distribution. Due to the mathematical definition, the second order moments are sensitive to incorrect determination of the zero level of the detector. The signal to noise ratio also plays an important role.
Other critical points are non-linearity and artifacts of the detector and the optical system itself. An example for an implementation of the ISO 11146 within the design of a real measuring tool is demonstrated. The PRIMES MicroSpotMonitor is a camera-based beam diagnostic system. It is ready to measure automatically even high power beams with dimensions down to the range of several micrometers. The constraints between the demands of the standard and practical application will be discussed.
The market offers a relatively wide range of laser power meters for high power applications, but when it comes to verifying measurements, a lot of know-how is required. Even the comparison of national standards between different countries in some cases has given evidence for discrepancies. For high power measurements, a major drawback has been that the primary standards of all the national calibration institutes are cryogenic radiometers, which are built for low power applications, while industrial applications often require lasers in the 0.1 - 12 kW range, thus creating the need for transfer standards from low to high power range. Primes GmbH currently is setting up a calibration laboratory for high power cw laser power meters in cooperation with the German institute for standards, the PTB, which will allow to trace high power laser measurements back to national standards and extend the measurement range substantially. Certified calibration services will be open to all users and manufacturers of laser power meters for high power applications.