A microstructured wavefront filter for the Darwin nulling interferometer

The European Space Agency's space-based Darwin mission aims to directly detect extrasolar Earth-like planets using nulling interferometry. However, in order to accomplish this using current optical technology, the interferometer input beams must be filtered to remove local wavefront errors. Although short lengths of single-mode fibre are ideal wavefront filters, Darwin's operating wavelength range of 4 - 20µm presents real challenges for optical fibre technology. In addition to the fact that step-index fibres only offer acceptable coupling efficiency over about one octave of optical bandwidth, very few suitable materials are transparent within this wavelength range. Microstructured optical fibres offer two unique properties that hold great promise for this application; they can be made from a single-material and offer endlessly single-mode guidance. Here we explore the advantages of using a microstructured fibre as a broadband wavefront filter for 4 - 20 µm

Microstructured fibers for broadband wavefront filtering in the mid-IR

The European Space Agency's space-based Darwin mission aims to directly detect extrasolar Earth-like planets using nulling interferometry. However, in order to accomplish this using current optical technology, the interferometer input beams must be filtered to remove local wavefront errors. Although short lengths of single-mode fiber are ideal wavefront filters, Darwin's operating wavelength range of 4 - 20 µm presents real challenges for optical fiber technology. In addition to the fact that step-index fibers only offer acceptable coupling efficiency over about one octave of optical bandwidth, very few suitable materials are transparent within this wavelength range. Microstructured optical fibers offer two unique properties that hold great promise for this application; they can be made from a single-material and offer endlessly single-mode guidance. Here we explore the advantages of using a microstructured fiber as a broadband wavefront filter for 4 - 20 µm

A General Model of the Atmospheric Scattering in the Wavelength Interval 300 - 1100nm

We have presented and developed new theoretic-empirical models of the extinction coefficients of the molecular scattering in the lower, close to the ground troposphere. We have included the indicatrices of backscattering. The models have been presented using general analytical functions valid for the whole wavelength interval 300-1100 nm and for the whole interval of visibility from 0.1 km up to 50 km. The results have been compared in quantity with the model and experimental data of other authors. The modeling of troposphere scattering is necessary for the analysis and design of all optoelectronic free space systems: atmospheric optical communication systems, location systems for atmospheric research (LIDAR), optical radiometric systems