Optoelectronic cooling of mechanical modes in a semiconductor nanomembrane

Abstract

Optical cavity cooling of mechanical resonators has recently become a research frontier [1][2][3]. The cooling has been realized with a metal-coated silicon microlever via photo-thermal force [4] and subsequently with dielectric objects via radiation pressure [5][6][7]. Here we report cavity cooling with a crystalline semiconductor membrane via a new mechanism, in which the cooling force arises from the interaction between the photo-induced electron-hole pairs and the mechanical modes through the deformation potential coupling. The optoelectronic mechanism is so efficient as to cool a mode down to 4 K from room temperature with just 50 µW of light and a cavity with a finesse of 10 consisting of a standard mirror and the sub-wavelength-thick semiconductor membrane itself. The laser-cooled narrow-band phonon bath realized with semiconductor mechanical resonators may open up a new avenue for photonics and spintronics devices.