PMC

(a) Traditional magnetic-optical isolator with a reflection mirror at the output port.(b) On-chip optical diode system with a reflection mirror at the output port. The absence of the reflection signal at the input port can indicate the isolation property of the system.

The system involves in-plane signal channel A and B, and in-plane side-way and off-plane dissipation channels C. The latter one holds the key to optical isolation.

(a) Scanning electron microscope images of our on-chip optical diode structure and (b) doubled-diode structure.(c) Experimental results of the forward (black line), backward (blue line), and round-trip (red line) transmission spectra. (d) Experimental round-trip transmission spectra with changed length L of the center connection waveguide. The experiment confirms the existence of a significant isolation effect in agreement with the theoretical prediction.

(a) Schematic geometry of a doubled-diode structure with a mirror-reflection symmetry with respect to the total reflection mirror, which is used to model the round-trip transmission of an isolator.Inset is the corresponding single-diode structure where the forward and backward transmissions are noted. (b) Calculated forward (black line), backward (blue line), and round-trip (red line) transmission spectra of the diode. The performance of the optical isolator is evaluated by comparing the round-trip transmissivity with the forward transmissivity. Our calculation shows that the former is more than two orders of magnitudes smaller than the latter.