Cavity opto-mechanical cooling via radiation pressure dynamical backaction enables ground state cooling of mechanical oscillators, provided the laser exhibits sufficiently low phase noise. Here, we investigate and measure the excess phase noise of wi
dely tunable external cavity diode lasers, which have been used in a range of recent nano-optomechanical experiments, including ground-state cooling. We report significant excess frequency noise, with peak values on the order of 10^7 rad^2 Hz near 3.5 GHz, attributed to the diode lasers relaxation oscillations. The measurements reveal that even at GHz frequencies diode lasers do not exhibit quantum limited performance. The associated excess backaction can preclude ground-state cooling even in state-of-the-art nano-optomechanical systems.
The coupling of mechanical and optical degrees of freedom via radiation pressure has been a subject of early research in the context of gravitational wave detection. Recent experimental advances have allowed studying for the first time the modificati
ons of mechanical dynamics provided by radiation pressure. This paper reviews the consequences of back-action of light confined in whispering-gallery dielectric micro-cavities, and presents a unified treatment of its two manifestations: notably the parametric instability (parametric amplification) and radiation pressure back-action cooling. Parametric instability offers a novel photonic clock which is driven purely by the pressure of light. In contrast, radiation pressure cooling can surpass existing cryogenic technologies and offers cooling to phonon occupancies below unity and provides a route towards cavity Quantum Optomechanics
Optical frequency combs provide equidistant frequency markers in the infrared, visible and ultra-violet and can link an unknown optical frequency to a radio or microwave frequency reference. Since their inception frequency combs have triggered major
advances in optical frequency metrology and precision measurements and in applications such as broadband laser-based gas sensing8 and molecular fingerprinting. Early work generated frequency combs by intra-cavity phase modulation while to date frequency combs are generated utilizing the comb-like mode structure of mode-locked lasers, whose repetition rate and carrier envelope phase can be stabilized. Here, we report an entirely novel approach in which equally spaced frequency markers are generated from a continuous wave (CW) pump laser of a known frequency interacting with the modes of a monolithic high-Q microresonator13 via the Kerr nonlinearity. The intrinsically broadband nature of parametric gain enables the generation of discrete comb modes over a 500 nm wide span (ca. 70 THz) around 1550 nm without relying on any external spectral broadening. Optical-heterodyne-based measurements reveal that cascaded parametric interactions give rise to an optical frequency comb, overcoming passive cavity dispersion. The uniformity of the mode spacing has been verified to within a relative experimental precision of 7.3*10(-18).
