The concept that electromagnetic radiation can exert forces on material objects was predicted by Maxwell, and the radiation pressure of light was first observed experimentally more than a century ago. The force F exerted by a beam of power P retroreflecting from a mirror is F=2P/c. Because the speed of light is so large, this force is typically extremely feeble but does manifest itself in special circumstances (e.g., in the tails of comets and during star formation). Beginning in the 1970s, researchers were able to trap and manipulate small particles and even individual atoms with optical forces.
Recently there has been a great surge of interest in the application of radiation forces to manipulate the center-of-mass motion of mechanical oscillators covering a huge range of scales from macroscopic mirrors in the Laser Interferometer Gravitational Wave Observatory (LIGO) project to nano- or micromechanical cantilevers, vibrating microtoroids, and membranes. Positive radiation pressure damping permits cooling of the motion; negative damping permits parametric amplification of small forces. Cooling a mechanical system to its quantum ground state is a key goal of the new field of optomechanics. Radiation pressure also appears in the form of unavoidable random backaction forces accompanying optical measurements of position as the precision of those measurements approaches the limits set by quantum mechanics [18, 19]. The randomness is due to the photon shot noise, the observation of which is a second key goal of the field.
In pioneering work, Braginsky and collaborators first detected mechanical damping due to radiation in the decay of an excited oscillator. Very recently, both measurement and mechanical damping of (the much smaller) random thermal Brownian motion (i.e., cooling of the center-of-mass motion) was achieved by several groups using different techniques.
Gathered by: Sh.Barzanjeh(shabirbarzanjeh@gmail.com)
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