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Abstract Total internal reflection (TIR) governs the guiding mechanisms of almost all dielectric waveguides and therefore constrains most of the light in the material with the highest refractive index. The few options available to access the properties of lower-index materials include designs that are either lossy, periodic, exhibit limited optical bandwidth or are restricted to subwavelength modal volumes. Here, we propose and demonstrate a guiding mechanism that leverages symmetry in multilayer dielectric waveguides as well as evanescent fields to strongly confine light in low-index materials. The proposed waveguide structures exhibit unusual light properties, such as uniform field distribution with a non-Gaussian spatial profile and scale invariance of the optical mode. This guiding mechanism is general and can be further extended to various optical structures, employed for different polarizations, and in different spectral regions. Therefore, our results can have huge implications for integrated photonics and related technologies. 

Abstract Low propagation loss in high confinement waveguides is critical for chip‐based nonlinear photonics applications. Sophisticated fabrication processes which yield sub‐nm roughness are generally needed to reduce scattering points at the waveguide interfaces to achieve ultralow propagation loss. Here, ultralow propagation loss is shown by shaping the mode using a highly multimode structure to reduce its overlap with the waveguide interfaces, thus relaxing the fabrication processing requirements. Microresonators with intrinsic quality factors (Q) of 31.8 ± 4.4 million are experimentally demonstrated. Although the microresonators support ten transverse modes only the fundamental mode is excited and no higher order modes are observed when using nonlinear adiabatic bends. A record‐low threshold pump power of 73 µW for parametric oscillation is measured and a broadband, almost octave spanning single‐soliton frequency comb without any signatures of higher order modes in the spectrum spanning from 1097 to 2040 nm (126 THz) is generated in the multimode microresonator. This work provides a design method that can be applied to different material platforms to achieve and use ultrahigh‐Qmultimode microresonators. 

We propose multipartite Bragg-scattering to perform all-to-all transformation among N frequency modes, realizing a bosonic N-level system. We demonstrate the N = 3 case illustrating a pathway towards scalability for frequency-domain optical quantum information systems. 

We demonstrate two-photon interference of three frequency modes via three-pump Bragg-scattering four-wave mixing in analogy to a three-level system. Correlated photon input pairs display distinct behavior from that of coherent-state input fields. 

We apply the homomorphism between the Schrödinger and Helmholtz-Maxwell wave equations to experimentally demonstrate an integrated photonic analogue of the zero-curvature eigenfunctions predicted in quantum mechanics. 

We demonstrate the loading of very short optical pulses into a high-Q cavity with linewidth much narrower than the pulse frequency envelope. We show that loading into the cavity is significantly enhanced if the pulse is combined with a cw-field, thus altering the pulse frequency profile to better match the cavity profile. 

We show the ability to control the degree of mode coupling in high quality factor silicon nitride (Si3N4) microresonators by controlling the atomic nature of the resonators interface. 

Using silicon-nitride microresonators with integrated Moiré-Bragg gratings to suppress parasitic nonlinear processes, we demonstrate on-chip frequency conversion to a single idler tone with a record-high 71% efficiency using Bragg scattering four-wave-mixing. 

We propose and analyze a room-temperature photon-number-resolving detection scheme based on cascaded sum-frequency generation. We measure an effective |n2| of 6×10−12 cm2/W in lithium niobate, which is 600x larger than the intrinsic value. 

We perform classical unitary conversion between three frequencies mediated by Bragg-scattering four-wave mixing with three pump fields. In the quantum regime, such a scheme can be scaled to realize N-frequency-bin W-states and boson sampling.