ADVANCED PHOTONICS USB ISOLATOR FREE

We demonstrated unidirectional transmission of optical pulses with isolation bandwidth of 700 MHz. With only 300 mW of RF power, up to 98% of light is transmitted in the forward direction, while 90% of the backward light is absorbed. In the backward direction, however, the device retains a single resonance and absorbs the incoming light. The strong mode coupling creates Rabi mode splitting and a transparency window at the center wavelength. The strong acousto-optic modulation induces indirect interband transition between the two optical modes in the forward direction, where the phase matching is satisfied.

A pair of transverse electric (TE) and transverse magnetic (TM) optical modes are designed with closely spaced frequency and momentum that match the effective acoustic wave. When driving the three piezoelectric actuators with rotational relative phases, an effective rotating acoustic wave is generated that carries in-plane momentum. 5 Bulk acoustic waves are launched vertically, which modulate the Si 3N 4 optical waveguide through the stress-optic effect. Our team was able to break Lorentz reciprocity and time-reversal symmetry via spatio-temporal modulation 4 of an integrated Si 3N 4 microring resonator with three monolithically integrated aluminium nitride (AlN) piezoelectric modulators. These approaches, however, are limited by dynamic reciprocity, high required optical pump power or narrow bandwidth. Magnetic-free operation is thus highly desired, and has been extensively studied based on optical nonlinearities, stimulated Brillouin scattering and optomechanically induced transparency. 3 Such a system, which requires a bulky external magnet, is still challenging for chip-scale integration. Traditionally, optical nonreciprocity is based on the Faraday effect of magneto-optic materials under an external magnetic field. 2ĭespite these advanced functionalities, nonreciprocal integrated optical devices have posed challenges. Meanwhile, high-quality-factor Si 3N 4 microresonators have recently been used in integrated semiconductor lasers with linewidths comparable to those of commercial fiber lasers. 1 Si 3N 4 has been widely used for Kerr frequency combs, microwave photonics and photonic computing networks. Over the past decade, Si 3N 4 has become a leading material platform for integrated photonics, benefiting from record low loss, large Kerr nonlinearity and compatibility with foundry processes.

ADVANCED PHOTONICS USB ISOLATOR FREE

In recent work, we have developed a key building block for future compact systems: an integrated silicon nitride (Si 3N 4) optical isolator free of the need for external magnetic fields.

Moreover, tight confinement of light in optical waveguides allows the exploration of optical nonlinearities, including optical-frequency-comb, second-harmonic and supercontinuum generation. Advances in nanofabrication technology have enabled the integration of important building blocks, from integrated laser sources to optical modulators to photodetectors. The compactness, robustness and low power consumption of integrated photonics offer an elegant way to bring tabletop optical systems from the research lab to daily life. Strong acousto-optic modulation allows indirect interband transition between a pair of strongly coupled (TE and TM) optical modes in only one direction. A Si 3N 4 microring resonator with three monolithically integrated AlN piezoelectric modulators breaks optical transmission reciprocity without an external magnetic field.

Advanced photonics usb isolator