Extended Data Fig.1.

Detailed schematic of the illumination beam. a, M, mirror; L1-L2, spherical lens with focal length of 20 mm and 80 mm, respectively; Obj1-Obj2, objective lenses (4x/0.1NA). b, The noise floor of the laser light is reduced by about 5 dB after passing through two Bragg filters. c, Extinction spectrum of the Fabry-Perot etalon used in the setup. For frequency component that is about 3.6 GHz (Brillouin shift of water) away from the laser frequency, the etalon can provide about 26 dB suppression. The value of zero in b and c represents the wavelength and frequency of the laser light, respectively.