ABSTRACT
This paper describes a novel, to the best of our knowledge, approach to build ultrastable interferometers using commercial mirror mounts anchored in an ultralow expansion (ULE) base. These components will play a critical role in any light particle search (ALPS) and will also be included in ground testing equipment for the upcoming laser interferometer space antenna (LISA) mission. Contrary to the standard ultrastable designs where mirrors are bonded to the spacers, ruling out any later modifications and alignments, our design remains flexible and allows the alignment of optical components at all stages to be optimized and changed. Here we present the dimensional stability and angular stability of two commercial mirror mounts characterized in a cavity setup. The long-term length change in the cavity did not exceed 30 nm and the relative angular stability was within 2 µrad, which meet the requirements for ALPS. We were also able to demonstrate 1pm/Hz length noise stability, which is a critical requirement for various subsystems in LISA. These results have led us to design similar opto-mechanical structures, which will be used in ground verification to test the LISA telescope.
ABSTRACT
We report on the absorption measurements of the liquid-filled pure-silica microstructured optical fibers. The measurements concentrate on spectroscopic analysis of the water solutions of a cationic dye, oxazine 725 perchlorate which, when filling the fiber, demonstrates much stronger absorption signals than observed in bulk with regular cuvettes. The effect is also seen in another cationic dye, but not in anionic dyes. Our investigations reveal that the effect originates from the adsorption of the dye molecules on the fiber inner walls. This effect also significantly enhances the sensitivity of spectroscopic measurements enabling the detection of molecules at very low concentrations. In particular, the detection of a 1 nM concentration of oxazine 725 perchlorate was demonstrated.