Noise reduction of a mechanical resonator by laser cooling

Several schemes to optically cool a micromechanical resonator are introduced. These schemes are classified into a cavity-assisted type and a cavity-free type, which both lead to damping of a micromechanical resonator with a laser light. The cavity-assisted schemes are based on the optomechanical coupling via the radiation pressure or bolometric effects, whereas the cavity-free scheme uses the optically excited carriers (electron-hole pairs) in a compound semiconductor. These laser cooling schemes allow us to reduce the thermal noise of a micromechanical resonator without using any refrigerant. (author)