arXiv subjects

Priscila Romagnoli

Publications and source records attributed to Priscila Romagnoli.

3 recordsLinked to original sources

arXiv2022

Controlling the motional quality factor of a diamagnetically levitated graphite plate

Researchers seek methods to levitate matter for a wide variety of purposes, ranging from exploring fundamental problems in science, through to developing new sensors and mechanical actuators. Many levitation techniques require active driving and most can only be applied to objects smaller than a few micrometers. Diamagnetic levitation has the strong advantage of being the only form of levitation which is passive, requiring no energy input, while also supporting massive objects. Known diamagnetic materials which are electrical insulators are only weakly diamagnetic, and require large magnetic field gradients to levitate. Strong diamagnetic materials which are electrical conductors, such as graphite, exhibit eddy damping, restricting motional freedom and reducing their potential for sensing applications. In this work we describe a method to engineer the eddy damping while retaining the force characteristics provided by the diamagnetic material. We study, both experimentally and theoretically, the motional damping of a magnetically levitated graphite plate in high vacuum and demonstrate that one can control the eddy damping by patterning the plate with through-slots which interrupt the eddy currents. We find we can control the motional quality factor over a wide range with excellent agreement between the experiment and numerical simulations.

physics.app-ph↗

arXiv2020

Polarization-Controlled Cavity Input-Output Relations

Cavity input-output relations (CIORs) describe a universal formalism relating each of the far-field amplitudes outside the cavity to the internal cavity fields. Conventionally, they are derived based on a weak-scattering approximation. In this context, the amplitude of the off-resonant field remains nearly unaffected by the cavity, with the high coupling efficiency into cavity modes being attributed to destructive interference between the transmitted (or reflected) field and the output field from the cavity. In this Letter, we show that, in a whispering gallery resonator-waveguide coupled system, in the strong-scattering regime, the off-resonant field approaches to zero, but more than 90% coupling efficiency can still be achieved due to the Purcell-enhanced channeling. As a result, the CIORs turn out to be essentially different than in the weak-scattering regime. With this fact, we propose that the CIOR can be tailored by controlling the scattering strength. This is experimentally demonstrated by the transmission spectra exhibiting either bandstop or bandpass-type behavior according to the polarization of the input light field.

physics.optics↗

arXiv2020

Fabrication of Optical Nanofibre-Based Cavities using Focussed Ion-Beam Milling -- A Review

Nanofibre-based optical cavities are particularly useful for quantum optics application, such as the development of integrated single-photon sources, and for studying fundamental light-matter interactions in cavity quantum electrodynamics (cQED). Although several techniques have been used to produce nanofibre-based optical cavities, focussed ion beam (FIB) milling is becoming popular; it can be used for the fabrication of complex structures directly in the nanofibre. This technique uses a highly accelerated ion beam to remove atoms from the target material with high resolution. However, it is challenging to mill insulating materials with highly-curved structures and large aspect ratios, such as silica nanofibres, due to charge accumulation in the material that leads to mechanical vibrations and misalignment issues. In this article, we highlight the main features of nanofibres and briefly review cQED with nanofibre-based optical cavities. An overview of the milling process is given with a summary of different FIB milled devices and their applications. Finally, we present our technique to produce nanofibre cavities by FIB milling. To overcome the aforementioned challenges, we present a specially designed base plate with an indium tin oxide (ITO)-coated Si substrate and outline our procedure, which improves stability during milling and increases repeatability.

physics.optics↗