Dr. Michele Bonaldi Profile

Dr. Michele Bonaldi

at Istituto Nazionale di Fisica Nucleare

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Publications (4)

PROCEEDINGS ARTICLE | May 21, 2015

Low loss optomechanical cavities based on silicon oscillator

Proc. SPIE. 9517, Smart Sensors, Actuators, and MEMS VII; and Cyber Physical Systems

KEYWORDS: Mirrors, Oscillators, Silicon, Coating, Optical coatings, Reflectivity, Microfabrication, Computer aided design, Semiconducting wafers, Cryogenics

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In an optomechanical cavity the optical and mechanical degree of freedom are strongly coupled by the radiation pressure of the light. This field of research has been gathering a lot of momentum during the last couple of years, driven by the technological advances in microfabrication and the first observation of quantum phenomena. These results open new perspectives in a wide range of applications, including high sensitivity measurements of position, acceleration, force, mass, and for fundamental research. We are working on low frequency pondero-motive light squeezing as a tool for improving the sensitivity of audio frequency measuring devices such as magnetic resonance force microscopes and gravitational-wave detectors. It is well known that experiments aiming to produce and manipulate non-classical (squeezed) light by effect of optomechanical interaction need a mechanical oscillator with low optical and mechanical losses. These technological requirements permit to maximize the force per incoming photon exerted by the cavity field on the mechanical element and to improve the element’s response to the radiation pressure force and, at the same time, to decrease the influence of the thermal bath. In this contribution we describe a class of mechanical devices for which we measured a mechanical quality factor up to 1.2 × 106 and with which it was possible to build a Fabry-Perot cavity with optical finesse up to 9 × 104. From our estimations, these characteristics meet the requirements for the generation of radiation squeezing and quantum correlations in the ∼ 100kHz region. Moreover our devices are characterized by high reproducibility to allow inclusion in integrated systems. We show the results of the characterization realized with a Michelson interferometer down to 4.2K and measurements in optical cavities performed at cryogenic temperature with input optical powers up to a few mW. We also report on the dynamical stability and the thermal response of the system.

PROCEEDINGS ARTICLE | May 17, 2013

Multi-modal vibration based MEMS energy harvesters for ultra-low power wireless functional nodes

Proc. SPIE. 8763, Smart Sensors, Actuators, and MEMS VI

KEYWORDS: Microelectromechanical systems, Electronics, Microsystems, Resonators, Silicon, Energy harvesting, Modal analysis, Finite element methods, Electromagnetism, Instrument modeling

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PROCEEDINGS ARTICLE | May 17, 2013

Design strategies of opto-mechanical micro oscillators for the detection of the ponderomotive squeezing

Proc. SPIE. 8763, Smart Sensors, Actuators, and MEMS VI

KEYWORDS: Mirrors, Oscillators, Resonators, Silicon, Coating, Optical coatings, Reflectivity, Radiation effects, Semiconducting wafers, Cryogenics

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The interaction of the radiation pressure with micro-mechanical oscillators is earning a growing interest for its wide-range applications (including high sensitivity measurements of force and position) and for fundamental research (entanglement, ponderomotive squeezing, quantum non-demolition measurements). In this contribution we describe the fabrication of a family of opto-mechanical devices specifically designed to ease the detection of ponderomotive squeezing and of entanglement between macroscopic objects and light. These phenomena are not easily observed, due to the overwhelming effects of classical noise sources of thermal origin with respect to the weak quantum fluctuations of the radiation pressure. Therefore, a low thermal noise background is required, together with a weak interaction between the micro-mirror and this background (i.e. high mechanical quality factors). The device should also be capable to manage a relatively large amount of dissipated power at cryogenic temperatures, as the use of a laser with power up to a ten of mW can be useful to enhance radiation pressure effects. In the development of our opto-mechanical devices, we are exploring an approach focused on relatively thick silicon oscillators with high reflectivity coating. The relatively high mass is compensated by the capability to manage high power at low temperatures, owing to a favourable geometric factor (thicker connectors) and the excellent thermal conductivity of silicon crystals at cryogenic temperature. We have measured at cryogenic temperatures mechanical quality factors up to 105 in a micro-oscillator designed to reduce as much as possible the strain in the coating layer and the consequent energy dissipation. This design improves an approach applied in micro-mirror and micro-cantilevers, where the coated surface is reduced as much as possible to improve the quality factor. The deposition of the highly reflective coating layer has been carefully integrated in the micromachining process to preserve its low optical losses: an optical finesse of F = 6×104 has been measured in a Fabry-Perot cavity with the micro-resonator used as end mirror.

PROCEEDINGS ARTICLE | September 29, 2004

Dual detectors of gravitational waves

Proc. SPIE. 5500, Gravitational Wave and Particle Astrophysics Detectors

KEYWORDS: Signal to noise ratio, Fabry–Perot interferometers, Optical amplifiers, Oscillators, Resonators, Sensors, Interference (communication), Amplifiers, Transducers, Prototyping

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