Fig. 3: Time-reversal symmetry and optical non-reciprocity of the optomechanical ring resonator (OMR).
From: Optomechanical ring resonator for efficient microwave-optical frequency conversion
The OMR is measured with different configurations in the four quadratures made of photon and phonon propagation directions. The TE2 output signal is measured and plotted as the normalized intensity in arbitrary units (a.u.). a and f are the cases where the photon and phonon are counter-propagating, thus in the second and fourth quadrature, respectively. They are time-reversal of each other. b and e are cases where the photon and phonon are co-propagating, thus in the first and third quadrature, respectively. They are also time-reversal of each other. c and d are cases when only photons circulate in the OMR with no phonons, thus on the x-axis. (a and b), (e and f) are the optical reciprocal of each other. The non-reciprocal output is due to the symmetry-breaking by phonons. The device schematics in each quadrature illustrate the selected input port for the specific propagation directions. The TE2 transmission is normalized to cases (c) and (d). The solid lines are Lorentzian fitting, and the open circles are measured data.
