Comparison of Noise Properties of Laser Sources Intended for Multidimensional Interferometric Tools

This work is oriented towards investigation of displacement measurement uncertainty contribution of different laser sources that are suitable for powering multidimensional interferometric positioning system for local probe microscopy. Main aim of this work was to find a suitable laser source for this measuring system. Most common 633 nm He-Ne lasers were compared with 532 nm frequency-doubled Nd:YAGs of different construction (external cavity doubling, ring configuration laser). We investigated amplitude and frequency noise of several lasers intended for micro- and nano-CMMs (coordinate measurement machines) and compared their noise properties together with the aim to find the best option. Amplitude noise measurements were done directly with the help of low noise photodetector, frequency noise of tested lasers was measured by two approaches - first with the help of Fabry-Perot resonator, which was used as a frequency discriminator converting a frequency (phase) noise into the amplitude one and second directly with the help of interferometer - measuring of interferometric fringe signal and position evaluation - another type of frequency discriminator. Both frequency noise and also amplitude noise measurements were done simultaneously to have a chance to compare both approaches and results.