We use circular dichroism (CD) in reflectivity from excitonic states as a spatially resolved probe of charge-carrier spin polarization. We report evidence that ferromagnetic order in electrostatically doped, monolayer transition metal dichalcogenide (TMD) semiconductors can be stabilized and controlled at zero magnetic field by local optical pumping. This approach can be replicated in III-V platforms paving the way for high-performance lasers with co-integrated monolithic isolators. While the demonstrated electro-optic polarization rotation rate is approximately 1 rad/cm, the exceptionally low loss of lithium niobate enables non-reciprocal polarization rotators with figures of merit that are 1-2 orders-of-magnitude better than what is possible with magneto-optics. Our demonstration leverages electro-optic inter-polarization scattering around 780 nm in lithium niobate, in which the reciprocity is broken with the help of a radiofrequency stimulus that carries synthetic momentum. Here, we demonstrate that broadband non-reciprocal polarization rotation can be produced using electro-optics in nanophotonic devices. Moreover, magneto-optic materials tend to be highly lossy, and while large (10-100 rad/cm) polarization rotation can be achieved, the key figure of merit (rotation-per-loss) is typically < 1 rad/dB. For integrated photonics foundries, however, there is still no good path to producing low-loss magneto-optic components, which has prompted a search for alternatives that do not use polarization rotation. Non-reciprocal polarization rotation, enabled via the magneto-optic Faraday effect, has been essentially unbeatable for broadband isolators and circulators. #Optical isolator ic 10kv freePolarization is a fundamental degree of freedom for light and is widely leveraged in free space and fiber optics. Finally, we use our operator-based framework to develop a novel class of invariants for topology stemming from a system's crystalline symmetries, which allows for the prediction of robust localized states for creating waveguides and cavities. Using this framework, we show that non-trivial topology, and associated boundary-localized chiral resonances, can manifest in photonic crystals with broken time-reversal symmetry that lack a complete band gap, a result which may have implications for new topological laser designs. Here, we develop a theoretical framework for assessing a photonic structure's topology directly from its effective Hamiltonian and position operators, as expressed in real space, and without the need to calculate the system's Bloch eigenstates or band structure. However, current band theoretic approaches to understanding topology in photonic systems yield fundamental limitations on the classes of structures that can be studied. Recently, the study of topological structures in photonics has garnered significant interest, as these systems can realize robust, non-reciprocal chiral edge states and cavity-like confined states that have applications in both linear and non-linear devices. Optical isolators and circulators, enabling future low-cost, large-scale Non-reciprocal optical resonator may serve as a fundamental buildingīlock in a variety of ultracompact silicon photonic devices including Significantly smaller than a conventional integrated optical isolator onĪ single crystal garnet substrate. Our device has a small footprint that is 290 µm in length, Telecommunication wavelength in a homogeneous external magnetic field. Transmission with an isolation ratio up to 19.5 dB near the 1,550 nm Silicon-on-insulator substrate, we demonstrate unidirectional optical Using a non-reciprocal optical resonator on an Here, we report the first monolithically integrated magneto-optical Wafer bonding, and because of the large footprint of isolator designs. Platforms has been challenging because of material incompatibilitiesīetween semiconductors and magneto-optical materials that necessitate However, the integration of such devices on semiconductor Non-reciprocal photonic devices, including optical isolators andĬirculators, are indispensible components in optical communication
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