After a brief review of microcomb physics, new device designs based on the powerful ultra-low-loss (ULL) silicon nitride platform are described. These microcombs bypass the inherent normal dispersion of ULL nitride and mode lock by pulse-pair formation [1]. In addition to multi-color operation, their unusual physics enables dynamic dispersion control to optimize device operation and even program function [2]. Generation of record low phase noise microwaves is described using these systems [3]. [1] Z. Yuan, at al, `Soliton pulse pairs at multiple colours in normal dispersion microresonators', Nature Photonics 17, 977–983 (2023) [2] Q-X Ji, et al, `Multi-modality integrated microresonators using the Moire speedup effect’, Science, March (2024) [3] I. Kudelin, et al, `Photonic chip-based low noise microwave oscillator', to appear in Nature

Integrated Bragg filters are fundamental building blocks for a wide range of cutting-edge applications, such as quantum optics, biosensing, optical signal processing, programmable photonics, datacom and telecom. Cladding-modulated Bragg gratings have proven to be a versatile topology for implementing filters with complex spectral responses in silicon photonics, as they provide a simple way to synthetize the wide dynamic range of coupling coefficients typically required in these designs. In this work we will present our recent advances in the design of high-performance cladding-modulated integrated Bragg gratings on two different technological platforms, Silicon-on-Insulator and Silicon Nitride.

The emergence of data-intensive applications pertaining 5G technologies and AI has highlighted the need of low power energy efficient integrated photonic devices. Hybrid and heterogeneous integration schemes have provided a means of incorporating various materials with traditional integrated platforms to create new functionalities to address the challenges of current technologies but often require complex and strict fabrication processes. In this work, we introduce a robust monolithic fabrication scheme that allows the seamless integration of silicon nitride devices with thick silicon and multiple-quantum-well (MQW) stacks. Using this approach, we have demonstrated quantum-confined Stark effect (QCSE) modulators butt-coupled to SiN waveguides operating in the O-band.