HMC Physics Colloquium

Tuesdays at 16:30 in Shanahan Center for Teaching and Learning, Room B460

Oskar Painter


Nano-opto Mechanics: Utilizing Light Forces Within Guided-Wave Nanostructures

Feb. 24, 2009

The fact that light carries momentum and can exert a mechanical force was first proposed by Kepler and Newton. The interaction of light with sound waves, in the form of Brillouin and Raman scattering, has been known since the 1920s and has many practical applications in the fields of spectroscopy and optoelectronics. With the advent of the laser in 1960s, it became possible to manipulate micron-scale dielectric particles using optical "tweezers" as pioneered by Art Ashkin. This was also the beginning of the use of laser beams for the trapping and manipulation of gas-phase atoms, which ultimately led to the demonstration of atomic Bose-Einstein Condensates. More recently, it has been realized that laser light, with its very low intrinsic noise, may be used as an effective method of cooling a macroscopic mechanical resonant element, with hopes of reaching effective temperatures suitable for measuring inherently quantum mechanical behavior. In duality to the cooling effect, it has also been demonstrated that optical amplification from a continuous-wave laser beam can be used to form regenerative mechanical oscillators. With these developments, interest in the new field of cavity-optomechanics has been piqued, with myriad of different materials, devices, and techniques currently being developed. In this talk I will describe some of the on-going work at Caltech to create nano-mechanical structures strongly coupled to internally guided light beams through gradient optical forces. These structures enter physical regimes not possible in more macroscopic devices, with motional mass and effective optomechanical coupling length many orders of magnitude smaller than in Fabry-Perot or whispering-gallery resonators which rely on radiation pressure. I will present recent results on a so-called "zipper" photonic crystal cavity which shows an optical spring effect many times that of the intrinsic mechanical spring, resulting in interesting mechanical mode-mixing and extremely high motion sensitivity. Finally, I will also discuss some of the potential applications of these devices to photonics, sensing, and to an area of particular interest within my group, cavity-QED.