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 1 p m / H z   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-In this Letter, we study optical properties of all-solid microstructured optical fiber made of soft glass. Such fibers have various interesting features including good geometrical stability, low fundamental transmission losses, high Kerr nonlinearity, and large solubility of rare-earth ions. By investigating the transmission mechanism, mode structure, and numerical aperture of the fibers and confronting the results with theoretical calculations we demonstrate that the fibers have optical properties similar to those observed in air-silica microstructured optical fibers. This makes the all-solid soft-glass microstructured fibers very attractive for many potential applications. [10]. While sophisticated structures of MOFs are responsible for unique properties of the fibers, they also make them very sensitive to any fluctuations of waveguide geometry. In fact, one of the major challenges of MOFs is the preservation of optical properties of the fibers along their length. This becomes particularly challenging for air-glass MOFs, as the capillaries of the fiber preform tend to collapse during fiber drawing [11]. In order to prevent such a collapse, pressure is applied during fiber fabrication. Although this technique limits sizable capillary contraction, it does not fully eliminate fluctuations in the fiber geometry, in particular, distortions of air-glass interface, which often introduce light-power losses and alter dispersion of the waveguide [11].The problem of the instability of optical properties of MOFs may be relaxed by fabrication of all-solid (AS) MOFs [11]. In that case, the geometry deviations are reduced by the application of two or more types of glass with properly matched thermal and chemical properties. A significant difference between refractive indices of glass may provide a sufficient contrast between the core and cladding allowing for the total-internal-reflection (index) guidance or the photonic-bandgap light guidance.In this Letter, we investigate optical properties of the AS MOF made of two types of soft glass (F2 and NC-21) with the respective refractive indices n F2 =1.619 and n NC =1.533, similar to those investigated in [12]. The fiber possesses hexagonal structure with the lattice constant Λ ≈ 2.5µm and d/Λ ≈ 0.65, where d is the diameter of the F2-glass rods (Fig. 1). Its core was formed by replacing seven central F2 rods with a single NC-21 rod and was surrounded by eight rings of the F2 rods constituting a microstructured cladding of the fiber [ Fig. 1(a)]. The fiber has an attenuation of ~13.1dB/m at 855nm [12]. All measurements presented in this paper were performed with a fiber of 18cm in length. (c) Scheme of the experimental setup. Depending on the investigated property, we used a diode laser operating at 795nm (the transverse mode profile and the numerical aperture measurements) or a supercontinuum source (the photonic-bandgap determination). The light was delivered to the investigated MOF trough a polarization-maintaining PANDA fiber. Detector denotes one of three types of...

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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.