Fig. 4

Coherent control of a two-port chiral absorber. (a) Schematic diagram of the original one-port perfect absorber, but with two equal input beams from both ports. As a result of scatters that break the chiral symmetry, the CW and CCW are coupled together, hence affecting the output dynamics of both ports. (b) Output spectra of left (upper) and right (lower) ports, in which, the reflection of \(\small {{\alpha }}_{\text{i}\text{n}1}\) (yellow) and \(\small {{\alpha }}_{\text{i}\text{n}2}\)(purple), the transmission of \(\small {{\alpha }}_{\text{i}\text{n}1}\) (blue) and \(\small {{\alpha }}_{\text{i}\text{n}2}\)(red) are depicted separately. Five representative cases of phase modulation results (top: theory, bottom: experiment) are shown in (c)-(g) with various frequency detuning \(\small {\varDelta }_{1}\) of -0.341 GHz, -0.127 GHz, 0, 0.127 GHz, 0.341 GHz, respectively. The incident power of fundamental waves from left and right ports are controlled precisely by a variable optical attenuator such that the reflection of \(\small {{\alpha }}_{\text{i}\text{n}1}\) and the transmission of \(\small {{\alpha }}_{\text{i}\text{n}2}\) can coincide at points c and g in (b). Port 1 input beam: \(\small 16{\mu }\text{W}\). Port 2 input beam: \(\small 7.5{\mu }\text{W}\). When both ports are excited, chiral perfect absorption can be observed in the left port, (c) & (g) due to the complete destructive interference cancellations, meanwhile, there are some remaining transmissions in the right port. The parameters used in the simulation are obtained by fitting the spectrum in (b): \(\small {{\gamma }}_{\text{c}1}=0.6097265\)GHz, \(\small {{\gamma }}_{1}=0.8772764\)GHz, \(\small {\text{J}}_{21}=0.34\)GHz, \(\small {\text{J}}_{21}=0.05\)GHz