Anneal-free ultra-low loss silicon nitride integrated photonics.

Heterogeneous and monolithic integration of the versatile low-loss silicon nitride platform with low-temperature materials such as silicon electronics and photonics, III-V compound semiconductors, lithium niobate, organics, and glasses has been inhibited by the need for high-temperature annealing as well as the need for different process flows for thin and thick waveguides. New techniques are needed to maintain the state-of-the-art losses, nonlinear properties, and CMOS-compatible processes while enabling this next generation of 3D silicon nitride integration. We report a significant advance in silicon nitride integrated photonics, demonstrating the lowest losses to date for an anneal-free process at a maximum temperature 250 °C, with the same deuterated silane based fabrication flow, for nitride and oxide, for an order of magnitude range in nitride thickness without requiring stress mitigation or polishing. We report record low anneal-free losses for both nitride core and oxide cladding, enabling 1.77 dB m-1 loss and 14.9 million Q for 80 nm nitride core waveguides, more than half an order magnitude lower loss than previously reported sub 300 °C process. For 800 nm-thick nitride, we achieve as good as 8.66 dB m-1 loss and 4.03 million Q, the highest reported Q for a low temperature processed resonator with equivalent device area, with a median of loss and Q of 13.9 dB m-1 and 2.59 million each respectively. We demonstrate laser stabilization with over 4 orders of magnitude frequency noise reduction using a thin nitride reference cavity, and using a thick nitride micro-resonator we demonstrate OPO, over two octave supercontinuum generation, and four-wave mixing and parametric gain with the lowest reported optical parametric oscillation threshold per unit resonator length. These results represent a significant step towards a uniform ultra-low loss silicon nitride homogeneous and heterogeneous platform for both thin and thick waveguides capable of linear and nonlinear photonic circuits and integration with low-temperature materials and processes.

Engaging a community to focus on upper limb function in people with multiple sclerosis: the ThinkHand campaign case study.

BACKGROUND: Solving complex research challenges requires innovative thinking and alternative approaches to traditional methods. One such example is the problem of arm and hand, or upper limb function in multiple sclerosis (MS), a neurological condition affecting approximately 2.9 million people worldwide and more than 150,000 in the United Kingdom. Historically, clinical trials and research have focused on mobility and walking ability. This excludes a large number of patients who are wheelchair users, limiting their quality of life and restricting access to possibly helpful medications. To address this issue, the ThinkHand campaign was launched in 2016, aiming to raise awareness about the importance of upper limb function in MS and develop alternative ways to measure, record, and account for hand and arm function changes. MAIN BODY: The campaign utilised innovative strategies at scientific conferences and online surveys to engage people affected by MS, healthcare professionals, charities, and researchers in discussing the importance of preserving upper limb function. Through co-design and interdisciplinary collaboration, the campaign developed new tools like the low-cost cardboard version of the Nine-Hole Peg Test, facilitating remote monitoring of hand function. Additionally, the campaign co-created the "Under & Over" rehabilitation tool, allowing individuals with advanced MS to participate in a remote rehabilitation program.The impact of the ThinkHand campaign has been significant, helping to shift the focus of both academic and industry-supported trials, including the O'HAND and ChariotMS trials, both using upper limb function as their primary end point. The campaign's patient-centred approach highlighted the importance of recognising patients' perspectives in research and challenged established assumptions and practices. It demonstrated the effectiveness of interdisciplinary collaboration, systems thinking, and co-creation with stakeholders in tackling complex problems. CONCLUSION: The ThinkHand campaign provides valuable insights for health research practices. By involving patients at all stages, researchers can gain a deeper understanding of the impact of disease on their lives, identify gaps and focus research on their needs. Experimentation and iteration can lead to innovative solutions, and openness to unconventional methods can drive widespread change. The ThinkHand campaign exemplifies the potential of patient-centred approaches to address complex research challenges and revolutionise the field of MS research and management. Embracing such approaches will contribute to more inclusive and impactful research in the future.

Solving complex research challenges requires creative thinking and new ways of doing things. One such challenge is understanding the problems with arm and hand function in multiple sclerosis (MS), a neurological condition that affects more than 150,000 in the United Kingdom. In the past, research focused mainly on walking ability, leaving out many people who use wheelchairs.To tackle this issue, we created the ThinkHand campaign in 2016. Its goal was to raise awareness about the importance of hand and arm function for people with MS (pwMS) and find better ways to measure changes in these functions such that they can become outcomes in clinical trials. This could provide a pathway to better treatments for pwMS who cannot walk.The campaign used various methods, including surveys, social media posts, exhibitions and music to involve pwMS, healthcare professionals, charities, and researchers in discussions about the issues. Working together, they created tools to support pwMS, particularly those at an advanced stage of the disease (pwAMS), to take part in research and measure their hand and arm function. Through our collaborative approach focusing on patients' perspectives, the campaign challenged old ideas and deeply embedded practices. It showed that collaboration between different areas of expertise involving pwMS at all stages of research can help solve complex problems. This campaign teaches us valuable lessons for health research. When researchers listen to patients and try new things, they can better understand how a disease affects people's lives and develop better solutions.In conclusion, we show how embracing a patient-centred approach can address complex research challenges and improve how we study and manage MS and other conditions in the future.

Integrated optical frequency division for microwave and mmWave generation.

The generation of ultra-low-noise microwave and mmWave in miniaturized, chip-based platforms can transform communication, radar and sensing systems1-3. Optical frequency division that leverages optical references and optical frequency combs has emerged as a powerful technique to generate microwaves with superior spectral purity than any other approaches4-7. Here we demonstrate a miniaturized optical frequency division system that can potentially transfer the approach to a complementary metal-oxide-semiconductor-compatible integrated photonic platform. Phase stability is provided by a large mode volume, planar-waveguide-based optical reference coil cavity8,9 and is divided down from optical to mmWave frequency by using soliton microcombs generated in a waveguide-coupled microresonator10-12. Besides achieving record-low phase noise for integrated photonic mmWave oscillators, these devices can be heterogeneously integrated with semiconductor lasers, amplifiers and photodiodes, holding the potential of large-volume, low-cost manufacturing for fundamental and mass-market applications13.

Integrated photonic molecule Brillouin laser with a high-power sub-100-mHz fundamental linewidth.

Photonic integrated lasers with an ultra-low fundamental linewidth and a high output power are important for precision atomic and quantum applications, high-capacity communications, and fiber sensing, yet wafer-scale solutions have remained elusive. Here we report an integrated stimulated Brillouin laser (SBL), based on a photonic molecule coupled resonator design, that achieves a sub-100-mHz fundamental linewidth with greater than 10-mW output power in the C band, fabricated on a 200-mm silicon nitride (Si3N4) CMOS-foundry compatible wafer-scale platform. The photonic molecule design is used to suppress the second-order Stokes (S2) emission, allowing the primary lasing mode to increase with the pump power without phase noise feedback from higher Stokes orders. The nested waveguide resonators have a 184 million intrinsic and 92 million loaded Q, over an order of magnitude improvement over prior photonic molecules, enabling precision resonance splitting of 198 MHz at the S2 frequency. We demonstrate S2-suppressed single-mode SBL with a minimum fundamental linewidth of 71±18 mHz, corresponding to a 23±6-mHz2/Hz white-frequency-noise floor, over an order of magnitude lower than prior integrated SBLs, with an ∼11-mW output power and 2.3-mW threshold power. The frequency noise reaches the resonator-intrinsic thermo-refractive noise from 2-kHz to 1-MHz offset. The laser phase noise reaches -155 dBc/Hz at 10-MHz offset. The performance of this chip-scale SBL shows promise not only to improve the reliability and reduce size and cost but also to enable new precision experiments that require the high-speed manipulation, control, and interrogation of atoms and qubits. Realization in the silicon nitride ultra-low loss platform is adaptable to a wide range of wavelengths from the visible to infrared and enables integration with other components for systems-on-chip solutions for a wide range of precision scientific and engineering applications including quantum sensing, gravitometers, atom interferometers, precision metrology, optical atomic clocks, and ultra-low noise microwave generation.