Electrically driven optical isolation through phonon-mediated photonic Autler-Townes splitting

Optical isolators today are exclusively built on magneto-optic principles but are not readily implemented within photonic integrated circuits. So far, no magnetless alternative(1-22) has managed to simultaneously combine linearity (that is, no frequency shift), linear response (that is, input-output scaling), ultralow insertion loss and large directional contrast on-chip. Here we demonstrate an electrically driven optical isolator design that leverages the unbeatable transparency of a short, high-quality dielectric waveguide, with the strong attenuation from a critically coupled absorber. Our concept is implemented using a lithium niobate racetrack resonator in which phonon-mediated(13) photonic Autler-Townes splitting(10,16,23,24) breaks the chiral symmetry of the resonant modes. We demonstrate isolators at wavelengths one octave apart near 1,550 nm and 780 nm, fabricated from the same lithium-niobate-on-insulator wafer. Linear isolation is demonstrated with simultaneously <1 dB insertion loss, >39 dB contrast and 10 dB bandwidth up to similar to 200 MHz. Non-magnetic optical isolators are demonstrated using phonon-mediated photonic Autler-Townes splitting. The on-chip lithium niobate devices simultaneously achieve ultralow insertion loss and high contrast.

Automated summary

Optical isolators based on magneto-optic principles have limitations in integration with photonic circuits, but a non-magnetic alternative utilizing phonon-mediated photonic Autler-Townes splitting shows promise in achieving ultralow insertion loss and high contrast on-chip.