The detection of ultra high energetic cosmic neutrinos provides a unique means to search for extragalactic sources that accelerate particles to extreme energies. It allows to study the neutrino component of the GZK cut-off in the cosmic ray energy spectrum and the search for neutrinos beyond this limit. Due to low expected flux and small interaction cross-section of neutrinos with matter large experimental set-ups are needed to conduct this type of research. Acoustic detection of cosmic rays may provide a means for the detection of ultra-high energetic neutrinos. Using relative low absorption of sound in water, large experimental set-ups in the deep sea are possible that are able to detect these most rare events, but it requires highly sensitive hydrophones as the thermo-acoustic pulse originating from a particle shower in water has a typical amplitude as low as a mPa. It has been shown in characterisation measurements that the fibre optic hydrophone technology as designed and realised at TNO provides the required sensitivity. Noise measurements and pulse reconstruction have been conducted that show that the hydrophone is suited as a particle detector.

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Various space telescope array systems are being considered to investigate other terrestrial planets orbiting around nearby stars in order to find extra-terrestrial life. One of them is the DARWIN mission of the European Space Agency (ESA). The required technology is the nulling interferometer. The challenge of nulling is making the null in the interferometric signal sufficiently deep to cancel the light from the bright star during the collection of light from its surrounding planets. The performance of the nulling is limited by the wavefront quality of the beams. The wavefront error can be reduced by filtering using a single mode fiber. For the DARWIN mission, the operational wavelength range is 6.5-20μm. Within the current ESA project, this is covered by a dual-band fiber system. A chalcogenide glass fiber based on the Te-As-Se (TAS) composition is selected to be used for the short wavelength band. For the long wavelength band up to 20 μm, Tellurium based glass is proposed. Different samples of various composition based on Te glass are manufactured and tested. The fibers are designed by TNO and different prototypes have been manufactured by the University of Rennes. Test setups are developed to demonstrate/investigate the single mode operation. Cladding modes are found to disturb the single mode operation. The effect of cladding modes is modeled. Solutions to eliminate the cladding modes are investigated and tested.

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