Fig. 2: Characterization of topological edge states using optomechanical read-out.
From: Topological phonon transport in an optomechanical system
a Optical microscope image of triangular topological mechanical cavity (Domain wall: dashed line. Read-out cavities for the measurements in d, f, and g: yellow dots). b, Zoom-in of the topological cavity corner (green box in a). c Experimental setup. Mechanical side-bands are imprinted on a laser beam transmitted through an optical cavity, detecting the NPSD of the mechanical waves. Acronyms: optical wave meter (λ meter), variable optical attenuator (VOA), fiber polarization controller (FPC), optical switch (SW), erbium-doped fiber amplifier (EDFA), photodetector (PD). d, f, g Measured (top) and numerically estimated (bottom) NPSD, respectively, in the bulk of domain 1, on a slanted edge, and on a horizontal edge. Insets in f, and g: Sketches showing read-out positions and the expected local density of states. e Measured NPSD as a function of frequency and read-out position on a slanted edge (highlighted in black in the sketch). Red dashed line corresponds to the spectrum in f. The low-frequency region (dark gray in f and g) harbors modes only inside the slanted edges (cf Fig. 1i). Data calibration is required to compare measurements from different read-out cavities (see Supplementary Note 8 and Supplementary Fig. 6). h Optomechanical coupling for edge states in slanted (top) and horizontal (bottom) domain walls (see Supplementary Note 7).
