Magnetic-Free Silicon Nitride Integrated Optical Isolator

Abstract

Integrated photonics has enabled signal synthesis, modulation and conversion using photonic integrated circuits (PIC). Many materials have been developed, among which silicon nitride (Si${}_3$N${}_4$) has emerged as a leading platform particularly for nonlinear photonics. Low-loss Si${}_3$N${}_4$ PIC has been widely used for frequency comb generation, narrow-linewidth lasers, microwave photonics, photonic computing networks, and even surface-electrode ion traps. Yet, among all demonstrated functionalities for Si${}_3$N${}_4$ integrated photonics, optical non-reciprocal devices, such as isolators and circulators, have not been achieved. Conventionally, they are realized based on Faraday effect of magneto-optic materials under external magnetic field. However, it has been challenging to integrate magneto-optic materials that are not CMOS-compatible and that require bulky external magnet. Here, we demonstrate a magnetic-free optical isolator based on aluminum nitride (AlN) piezoelectric modulators monolithically integrated on ultralow-loss Si${}_3$N${}_4$ PIC. The transmission reciprocity is broken by spatio-temporal modulation of a Si${}_3$N${}_4$ microring resonator with three AlN bulk acoustic wave resonators that are driven with a rotational phase. This design creates an effective rotating acoustic wave that allows indirect interband transition in only one direction among a pair of strongly coupled optical modes. Maximum of 10 dB isolation is achieved under 100 mW RF power applied to each actuator, with minimum insertion loss of 0.1 dB. The isolation remains constant over nearly 30 dB dynamic range of optical input power, showing excellent optical linearity. Our integrated, linear, magnetic-free, electrically driven optical isolator could become key building blocks for integrated lasers, chip-scale LiDAR engines, as well as optical interfaces for superconducting circuits.

References in corpus (10)

• All-optical signal processing platforms for CMOS compatible integrated nonlinear optics
• Monolithic Ultrahigh-Q Lithium Niobate Microring Resonator
• Non-Reciprocal Brillouin Scattering Induced Transparency
• Nonreciprocity and magnetic-free isolation based on optomechanical interactions
• Brillouin scattering induced transparency and non-reciprocal light storage
• Laser soliton microcombs on silicon
• Frequency-encoded photonic qubits for scalable quantum information processing
• Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies
• Electrically driven linear optical isolation through phonon mediated Autler-Townes splitting
• Quantum coherent microwave-optical transduction using high overtone bulk acoustic resonances

Cited by in corpus (10)

• Gigahertz free-space electro-optic modulators based on Mie resonances
• Integrated Passive Nonlinear Optical Isolators
• Electrically driven linear optical isolation through phonon mediated Autler-Townes splitting
• Tutorial: synthetic frequency dimensions in dynamically modulated ring resonators
• Mirror symmetric on-chip frequency circulation of light
• Self-induced optical non-reciprocity
• A passive bias-free ultrabroadband optical isolator based on unidirectional self-induced transparency
• An Integrated Photon-Pair Source with Monolithic Piezoelectric Frequency Tunability
• Optical isolation by temporal modulation: size, frequency, and power constraints
• Piezoelectric optomechanical approaches for efficient quantum microwave-to-optical signal transduction: the need for co-design