Fiber-optic gyroscope for rotational seismic ground motion monitoring of the Campi Flegrei volcanic area.

The real-time monitoring of densely populated areas with high seismic and volcanic risk is of crucial importance for the safety of people and infrastructures. When an earthquake occurs, the Earth surface experiences both translational and rotational motions. The latter are usually not monitored, but their measurement and characterization are essential for a full description of the ground motion.

All-fiber high-resolution incoherent broadband spectrometer.

Portable optical spectrometers are crucial devices for bio-chemical sensing and spectroscopic applications whereby robust, compact and cost-effective set-ups are desirable. However, existing miniaturized instruments typically struggle to achieve broad wavelength operation and high spectral resolution at the same time. Here, an all-fiber optical spectrometer based on two cascaded Bragg gratings is devised and demonstrated, showing a record resolution and a wavelength span-to-resolution ratio larger than that of most miniature broadband spectrometers reported to date.

Automatic Alignment Method for Controlled Free-Space Excitation of Whispering-Gallery Resonances.

Whispering-gallery mode microresonators have gained wide popularity as experimental platforms for different applications, ranging from biosensing to nonlinear optics. Typically, the resonant modes of dielectric microresonators are stimulated via evanescent wave coupling, facilitated using tapered optical fibers or coupling prisms. However, this method poses serious shortcomings due to fabrication and access-related limitations, which could be elegantly overcome by implementing a free-space coupling approach; although additional alignment procedures are needed in this case.

Liquid Droplet Microresonators.

We provide here an overview of passive optical micro-cavities made of droplets in the liquid phase. We focus on resonators that are naturally created and suspended under gravity thanks to interfacial forces, illustrating simple ways to excite whispering-gallery modes in various slow-evaporation liquids using free-space optics. Similar to solid resonators, frequency locking of near-infrared and visible lasers to resonant modes is performed exploiting either phase-sensitive detection of the leakage cavity field or multiple interference between whispering-gallery modes in the scattered light.

Ionizing radiation detectors based on Ge-doped optical fibers inserted in resonant cavities.

The measurement of ionizing radiation (IR) is a crucial issue in different areas of interest, from environmental safety and industrial monitoring to aerospace and medicine. Optical fiber sensors have recently proven good candidates as radiation dosimeters. Here we investigate the effect of IR on germanosilicate optical fibers.