Recent experiments with optically levitated particles have shown incredible promise for high-precision sensing of accelerations and gravitational fields as well as exploring mesoscopic physics. One barrier that often stands in the way of improved acceleration sensitivity or quantum state coherence time is high particle temperatures due to absorption of the light from the trapping laser. In optically levitated acceleration sensing architectures, one limitation on the precision of such sensors is often the upper limit on the size of the particle that can be trapped: larger particles require more laser power to levitate, but too much absorption of the trapping light can overheat and vaporize the particles. We present a novel, detailed analysis on a levitated optomechanical accelerometer to understand what combinations of acceleration sensitivities and maximum-tolerated accelerations can be reasonably achieved, and we analyze the extent to which anti-Stokes optical refrigeration may solve the problem of overheating particles. We also analyze the effect of blackbody radiation pressure shot noise on a force and acceleration sensor concept involving free-falling particles that are released and recaptured by an optical trap. We find that, while optical refrigeration is likely insufficient to solve the problem of large particles vaporizing in high-power traps, it would help mitigate blackbody radiation pressure shot noise in future accelerometers based on free-falling particles.
Magneto-gravitational traps use the repulsion of diamagnetic materials by magnetic fields combined with the Earth's gravity to create a weak trap for micrometer-scale diamagnetic particles. A single particle levitated in this trap oscillates harmonically in three dimensions and its position can be measured optically. We have previously demonstrated feedback cooling of a trapped particle using radiation pressure from a second light source, but the low frequencies of oscillation appear to make quantum behavior unreachable, at least on long time scales. We report on progress towards observing the quantum limit of the motion by optical measurements of the particle position on time scales short compared to the oscillation period of the motion, making the behavior approach that of a free particle. We also show that classical pulsed measurements on larger trapped particles can reach remarkably high precision and demonstrate the performance by using it to measure vibrations of the system.
Levitated optomechanics in vacuum has shown promise for fundamental tests of physics including quantum mechanics and gravity, for sensing weak forces or accelerations, and for precision measurements. While much research has focused on optical trapping of dielectric particles, other approaches, such as magnetic trapping of diamagnetic particles, have been gaining interest. Here we review geometries for both optical and magnetic trapping in vacuum, with an emphasis on the properties of traps for particles with a diameter of at least one micrometer.
Levitated particles are attractive systems for precision optomechanics due to their extreme isolation from their environment. Here we describe several experiments with microparticles in magneto-gravitational traps, which use a combination of diamagnetism and the earth's gravity. First, the center-of-mass motion of the particle can be cooled to temperatures far below the ambient temperature using feedback. Second, the change in the frequency of oscillation of the particle under the influence of field masses can be used to measure the Newtonian gravitational constant. Finally, the fjrst steps towards producing and trapping silicon carbide microcrystals, which may contain optically-addressable defect centers, are reported.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.