Search

Measurement results of a high speed, low power single channel optical link operating at 1060 nm are presented. The link is composed of low power VCSEL devices fabricated and provided by Furukawa Electric Co. Ltd. and a low cost OM2 fiber. Clear eye openings are observed at 20 Gbps with a 2 mA DC bias. A modulation voltage of 150 mVp-p results in a -4.1 dBm OMA at the fiber output in a back-to-back configuration, with 0.19 unit amplitude eye opening and 32 ps total jitter extrapolated to a 10-12 bit error ratio. The insertion of a 100 m-long OM2 fiber causes a small signal degradation due to low attenuation and dispersion. For an ideal index profile optimized for dual wavelength operation (850 and 1300 nm), the minimum modal dispersion of the fiber is in the vicinity of the current operation wavelength.

While the thermomechanical properties of sapphire make it an excellent candidate of test mass for advanced laser interferometers, its optical quality is not well understood or well controlled. We have studied the results from high-resolution measurements of scattering, absorption, and birefringence in test-mass samples to better understand issues of quality. Samples show large-scale scattering structures clearly linked to the crystal-growth process. Samples characterized by the presence of point defects have significantly lower scattering (except at the point defects). In general on a large scale, high scattering also correlates with higher absorption and higher average birefringence inhomogeneity. However, on a smaller scale there is not a clear point-to-point correlation between scattering and absorption. Often a large-scale scattering structure is spatially displaced by tens of millimeters from a similar absorption structure, indicating that quite separate microscopic mechanisms give rise to scattering and absorption. The spatial displacements indicate that absorption centers and scattering centers are laid down during crystal growth at different distances from the solid-liquid interface. We suggest that absorption may be linked to F centers, while scattering may be linked to impurities such as iron.

DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. It aims at detecting various kinds of gravitational waves between 1 mHz and 100 Hz frequently enough to open a new window of observation for gravitational wave astronomy. The pre-conceptual design of DECIGO consists of three drag-free satellites, 1000 km apart from each other, whose relative displacements are measured by a Fabry-Perot Michelson interferometer. We plan to launch DECIGO in 2024 after a long and intense development phase, including two pathfinder missions for verification of required technologies.