A. Pontin

Probing deformed commutators with macroscopic harmonic oscillators.

A minimal observable length is a common feature of theories that aim to merge quantum physics and gravity. Quantum mechanically, this concept is associated with a nonzero minimal uncertainty in position measurements, which is encoded in deformed commutation relations. In spite of increasing theoretical interest, the subject suffers from the complete lack of dedicated experiments and bounds to the deformation parameters have just been extrapolated from indirect measurements. As recently proposed, low-energy mechanical oscillators could allow to reveal the effect of a modified commutator. Here we analyze the free evolution of high-quality factor micro- and nano-oscillators, spanning a wide range of masses around the Planck mass mP (≈22 μg). The direct check against a model of deformed dynamics substantially lowers the previous limits on the parameters quantifying the commutator deformation.

Squeezing a Thermal Mechanical Oscillator by Stabilized Parametric Effect on the Optical Spring

We report the confinement of an optomechanical micro-oscillator in a squeezed thermal state, obtained by parametric modulation of the optical spring. We propose and implement an experimental scheme based on parametric feedback control of the oscillator, which stabilizes the amplified quadrature while leaving the orthogonal one unaffected. This technique allows us to surpass the -3  dB limit in the noise reduction, associated with parametric resonance, with a best experimental result of -7.4  dB. While the present experiment is in the classical regime, in a moderately cooled system our technique may allow squeezing of a macroscopic mechanical oscillator below the zero-point motion.

Ultralow-dissipation micro-oscillator for quantum optomechanics

Generating nonclassical states of light by optomechanical coupling depends critically on the mechanical and optical properties of micro-oscillators and on the minimization of thermal noise. We present an oscillating micromirror with a mechanical quality factor

A "low-deformation mirror" micro-oscillator with ultra-low optical and mechanical losses

Q=2.6\ifmmode\times\else\texttimes\fi{}{10}^{6}

Frequency-noise cancellation in optomechanical systems for ponderomotive squeezing

at cryogenic temperature and a finesse of 65 000, obtained thanks to an innovative approach to the design and the control of mechanical dissipation. We predict that, already at 4 K with an input laser power of 2 mW, the radiation-pressure quantum fluctuations become the main noise source, overcoming thermal noise. This feature makes our devices particularly suitable for the production of ponderomotive squeezing.

Inhomogeneous mechanical losses in micro-oscillators with high reflectivity coating

We report on the mechanical losses measured in a “low-deformation mirror” micro-oscillator designed to reduce as much as possible the strain in the coating layer and the resulting energy dissipation. The deposition of the highly reflective coating layer has been fully integrated in the micro-machining process. We measured at cryogenic temperature a mechanical quality factor up to 105 and an optical finesse of about 4×104, and simulations show that the device can manage input powers of a few mW at 4.2 K. These features make the device very promising for quantum optics experiments.

Fabrication of low loss MOMS resonators for quantum optics experiments

Ponderomotive squeezing of the output light of an optical cavity has been recently observed in the megahertz range in two different cavity optomechanical devices. Quadrature squeezing becomes particularly useful at lower spectral frequencies, for example, in gravitational wave interferometers, despite being more sensitive to excess phase and frequency noise. Here we show a phase and frequency-noise cancellation mechanism due to destructive interference which can facilitate the production of ponderomotive squeezing in the kilohertz range and we demonstrate it experimentally in an optomechanical system formed by a Fabry-P´erot cavity with a micromechanical mirror.

Microfabrication of large-area circular high-stress silicon nitride membranes for optomechanical applications

We characterize the mechanical quality factor of micro-oscillators covered by a highly reflective coating. We test an approach to the reduction of mechanical losses that consists in limiting the size of the coated area to reduce the strain and the consequent energy loss in this highly dissipative component. Moreover, a mechanical isolation stage is incorporated in the device. The results are discussed on the basis of an analysis of homogeneous and non-homogeneous losses in the device and validated by a set of finite-element models. The contributions of thermoelastic dissipation and coating losses are separated and the measured quality factors are found in agreement with the calculated values, while the absence of unmodeled losses confirms that the isolation element integrated in the device efficiently uncouples the dynamics of the mirror from the support system. Also the resonant frequencies evaluated by finite-element models are in good agreement with the experimental data, and allow the estimation of th...

Design of wideband acoustic detectors of gravitational waves equipped with displacement concentrators

We present the fabrication and characterization of opto-mechanical micro-resonators developed to detect radiation-pressure coupling between light and a macroscopic body. The major achievements of this work are the development of complex high aspect ratio shapes by using the deep-RIE Bosch process and the integration of a high-reflectivity dielectric mirror. The micro-resonators were used as an end-mirror of a Fabry?Perot cavity, attaining an optical finesse of about 6 ? 104, and at cryogenic temperature (about 10?K) we measured a mechanical quality factor up to 2 ? 106 at about 90?kHz. These features make our devices particularly suitable for experiments on quantum-opto-mechanics.

Imaging Correlations in Heterodyne Spectra for Quantum Displacement Sensing

In view of the integration of membrane resonators with more complex MEMS structures, we developed a general fabrication procedure for circular shape SiNx membranes using Deep Reactive Ion Etching (DRIE). Large area and high-stress SiNx membranes were fabricated and used as optomechanical resonators in a Michelson interferometer, where Q values up to 1.3 × 106 were measured at cryogenic temperatures, and in a Fabry-Perot cavity, where an optical finesse up to 50000 has been observed.