Fig. 4
From: Reconfigurable optomechanical circulator and directional amplifier
Transmission matrices. a The transmission matrix of an ideal circulator: T1→2 = T2→3 = T3→4 = T4→1 = 1, and all remaining matrix elements are 0. A circulator requires an asymmetric transmission matrix with regard to the dashed line, which breaks the reciprocity. Conversely, b shows a symmetric transmission matrix measured without a control field, representing a reciprocal device. c, d Transmission matrices for the demonstrated circulator and directional amplifier, respectively. The control power is 7.8 mW for the circulator and 6.9 mW for the directional amplifier, corresponding to Ccw = 4.6 and −4.0. The values of all transmission matrices are provided in Supplementary Tables 1 and 2. e Identical I of the circulator, directional amplifier and add–drop filter as a function of Ccw. The lines are the results of theoretical calculations based on the parameters κ/2π = 16.2 MHz, ωm/2π = 90.47 MHz, and γ/2π = 22 kHz. See Supplementary Note 2 for more details of calculation
