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1. Fabry-Perot Bragg grating nanoresonator with ultrahigh intrinsic Q based on low-loss silicon nitride

   https://doi.org/10.1364/OE.499930  

   Zhang, Yang; Veilleux, Sylvain; Dagenais, Mario (January 2023, Optics Express)

   Photonic integrated circuits based on ultralow loss silicon nitride waveguides have shown significant promise for realizing high-performance optical systems in a compact and scalable form factor. For the first time, we have developed a Fabry-Perot Bragg grating nanoresonator based on silicon nitride on silicon dioxide platform with an ultra-high intrinsic quality factor of 19.3 million. By combining the introduction of tapered grating between cavity and periodic Bragg grating, increasing the width of cavity to multi-mode region and optimized annealing strategy for Si₃N₄film, the propagation loss is reduced to around 0.014 dB/cm. Fabry-Perot Bragg grating nanoresonator can be easily implemented in a simple straight waveguide occupying a minimal amount of space. Therefore, it is a key component to build a high performance photonic integrated circuit for many applications. 

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2. Ultra-low-loss photonic integrated chips on an 8-inch anomalous-dispersion Si ₃ N ₄ -SiO ₂ -Si wafer

   https://doi.org/10.1364/OL.573741  

   Liu, Shuai; Puckett, Matthew W; Wu, Jianfeng; Hariri, Abdulkarim; Zhang, Yuheng; Al-Hallak, Abdur-Raheem; Yusuf, Ruhi; Zhang, Zheshen (January 2025, Optics Letters)

   We report the fabrication of 8-inch crack-free, dispersion-engineered Si₃N₄-SiO₂-Si wafers fully compatible with industrial foundry silicon photonics fabrication lines. By combining these wafers with a developed amorphous silicon (a-Si) hardmask etching technique, we achieve ultra-low-loss Si₃N₄photonic integrated circuits (PICs) with intrinsic quality factors exceeding 22×10⁶using standard ultraviolet stepper photolithography, corresponding to a low propagation loss of 1.54 dB/m. We demonstrate the generation of a soliton frequency comb on these high-quality Si₃N₄PICs, corroborating the designed anomalous dispersion. These results establish the feasibility of mass-manufacturing high-performance, dispersion-engineered Si₃N₄PICs using standard foundry-grade processes, opening new pathways for applications in optical communications, nonlinear optics, and quantum optics. 

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3. Automated assembly of hybrid-integrated, chip-scale laser systems

   https://doi.org/10.1364/OE.558968  

   Levaur, Taylor; Zhao, Xiaolei; Sweatt, Lance; Ghimire, Mohan; Zhu, Lin (January 2025, Optics Express)

   Hybrid photonic integration provides a platform to design and implement novel functionalities unavailable to active or passive material systems alone. We present an automated alignment and assembly process for hybrid-integrated laser systems, comprising silicon nitride (Si₃N₄) photonic integrated circuits (PICs) edge-coupled to gallium arsenide (GaAs) gain chips (GCs). We design and optimize spot size converters (SSCs) to increase the alignment tolerances between the PICs and GCs. Our automated assembly process has achieved experimental coupling losses of 2.7 dB between the PICs and GCs, closely matching the simulated values. Packaged hybrid lasers, when coupled to a lensed fiber, exhibit slope efficiencies of ∼ 97 mW/A. These results show the feasibility of scaling the production and widespread application of these hybrid laser systems by automating their assembly, which should drive down packaging costs and accelerate research. 

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4. Over 100 million Q silicon nitride Fabry–Perot Bragg nanoresonators enabled by advanced tapered gratings

   https://doi.org/10.1364/OL.578449  

   Zhang, Yang; Heidari_Khouzani, Masoud; Yu, ChengDao; Veilleux, Sylvain; Dagenais, Mario (January 2025, Optics Letters)

   We report new, to the best of our knowledge, advances in Fabry–Perot Bragg grating nanoresonators on low-loss silicon nitride (Si₃N₄). Building on a previous demonstration of an intrinsic quality factor Q_inof 19.3 million with 1.4 dB/m propagation loss, we now achieve Q_inup to 121 million on a 100-nm Si₃N₄platform with an ultralow propagation loss of 0.19 dB/m. Even on a 300-nm Si₃N₄platform, Q_inof 58 million is obtained with 0.45 dB/m loss. Crucially, an advanced tapered grating design is introduced to minimize mode mismatch between the waveguide and Bragg mirror. These improvements pave the way for compact ultrahigh-Q photonic integrated resonators for applications in nonlinear optics and precision photonics. 

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5. Ultra-low loss quantum photonic circuits integrated with single quantum emitters

   https://doi.org/10.1038/s41467-022-35332-z  

   Chanana, Ashish; Larocque, Hugo; Moreira, Renan; Carolan, Jacques; Guha, Biswarup; Melo, Emerson G.; Anant, Vikas; Song, Jindong; Englund, Dirk; Blumenthal, Daniel J.; et al (December 2022, Nature Communications)

   Abstract The scaling of many photonic quantum information processing systems is ultimately limited by the flux of quantum light throughout an integrated photonic circuit. Source brightness and waveguide loss set basic limits on the on-chip photon flux. While substantial progress has been made, separately, towards ultra-low loss chip-scale photonic circuits and high brightness single-photon sources, integration of these technologies has remained elusive. Here, we report the integration of a quantum emitter single-photon source with a wafer-scale, ultra-low loss silicon nitride photonic circuit. We demonstrate triggered and pure single-photon emission into a Si₃N₄photonic circuit with ≈ 1 dB/m propagation loss at a wavelength of ≈ 930 nm. We also observe resonance fluorescence in the strong drive regime, showing promise towards coherent control of quantum emitters. These results are a step forward towards scaled chip-integrated photonic quantum information systems in which storing, time-demultiplexing or buffering of deterministically generated single-photons is critical. 

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