The team focused on germano-silicate resonators, employing an inductively coupled plasma chemical vapor deposition (ICP-PECVD) technique to deposit the upper silica cladding at a relatively low temperature of 250 °C. This process used a deuterated silane precursor combined with oxygen plasma, which allowed precise control over film thickness and composition. Notably, the researchers implemented a rapid thermal annealing step at 1,000 °C for 20 minutes following every 500 nm of cladding deposited. This annealing served a dual purpose: it mitigated stress-induced optical losses and repaired damage caused by direct plasma exposure during deposition.

The effectiveness of this approach was confirmed by depositing a 6-micron thick upper cladding, which fully encapsulated the resonator’s coupling gap, thereby significantly shielding the device from environmental contaminants. This protective encapsulation contributed to maintaining ultrahigh Q values—up to 160 million over several months. Although this represented some reduction from the pristine, unclad Q of approximately 250 million, the results affirmed that partial recovery and long-term stability were attainable through the annealing treatment. The observed trade-offs align well with previous findings in ultralow-loss (ULL) silicon nitride, suggesting that further refinement in deposition methods or precursor materials might eliminate this Q degradation entirely.

To analyze the Brillouin gain spectrum, the researchers utilized a highly sensitive dual-intensity-modulation pump-probe technique. The test devices had upper claddings made of 1.5 mol% P₂O₅-doped silica deposited via plasma-enhanced chemical vapor deposition (PECVD). This slightly phosphorus-doped glass demonstrated excellent ability to produce thick, stress-free films critical for confining both optical and acoustic modes effectively. Post-fabrication characterization revealed waveguide propagation losses below 0.5 dB/m and facet coupling losses around 1.4 dB, underscoring the exceptional optical quality achieved.

In their experimental setup, counterpropagating pump and probe lasers operating near 1560 nm were used. The pump laser was intensity-modulated at 10 MHz, while the probe was modulated slightly off-frequency at 10.075 MHz. A lock-in amplifier measured the probe transmission signal referencing a 75 kHz beatnote originating from the modulation difference. Scanning the probe over a 20 GHz detuning range from red to blue relative to the fixed pump frequency allowed precise acquisition of the stimulated Brillouin scattering (SBS) gain spectrum.

Complementing experimental work, numerical simulations based on finite element methods were employed to calculate the optical and acoustic fields. Material parameters derived from prior studies formed the basis of their models, including indices of refraction, material densities, Poisson ratios, Young’s moduli, Brillouin linewidths, and photoelastic coefficients for the core, upper cladding, and bottom cladding layers. This multi-parameter simulation framework facilitated a holistic understanding of the interaction between optical and acoustic waves within the device structure.

To investigate thermorefractive noise (TRN), the study also employed sophisticated COMSOL Multiphysics simulations using a fluctuation-dissipation theorem-based model. Simulations compared Ge-silica waveguides with both thin and thick silicon nitride (SiN) structures, each modeled as 3 mm diameter microresonators with specific rectangular waveguide cross sections. These simulations incorporated detailed material thermal properties such as thermo-optic coefficients, thermal conductivities, specific heat capacities, and densities, all calibrated to an ambient temperature of 300 K. The Ge-silica waveguides featured air cladding, while the SiN devices were silica-clad, reflecting realistic fabrication conditions.

The combination of meticulous material engineering, thermal processing, and rigorous experimental verification offers a promising route toward integrated photonic devices with loss figures rivalling those of bulk optical fibers. Such advancements are critical in enabling the next generation of on-chip lasers, modulators, and frequency combs, which rely heavily on ultralow-loss resonators to achieve unprecedented performance in communications, sensing, and quantum technologies.

However, challenges remain. The slight but persistent reduction in Q factor upon cladding deposition indicates that further innovation in deposition chemistry or approaches may be necessary. Alternatives such as low-pressure chemical vapor deposition or novel precursors like tetraethoxysilane PECVD may hold the key to minimizing plasma-induced damage and residual stress. The researchers highlight these potential pathways, underscoring that the current work lays a solid foundation for ongoing optimization.

This study heralds a significant milestone for photonic integration, demonstrating that fibre-like loss performance across a broad spectral range is achievable, connecting violet to near-infrared wavelengths seamlessly. Such capability opens new horizons for compact, high-performance photonic chips, integrating functionalities once thought to require bulky and fragile fiber setups.

In summary, by innovating on cladding deposition methods and leveraging advanced characterization and modeling, the researchers have resolved longstanding challenges in photonic device losses. Their results promise transformative impacts across telecommunications, precision metrology, and quantum information science, where low-loss photonics are essential cornerstones. Future efforts will doubtless extend and refine these techniques, pushing photonic integration toward new frontiers in performance and scalability.

Subject of Research: Photonic integrated circuits, ultralow-loss waveguide resonators, and deposition techniques for high-quality silica cladding.

Article Title: Towards fibre-like loss for photonic integration from violet to near-infrared.

Article References:
Chen, HJ., Colburn, K., Liu, P. et al. Towards fibre-like loss for photonic integration from violet to near-infrared. Nature 649, 338–344 (2026). https://doi.org/10.1038/s41586-025-09889-w

DOI: 08 January 2026

Keywords: ultralow-loss resonators, photonic integration, silica cladding, ICP-PECVD, thermal annealing, Brillouin scattering, thermorefractive noise, waveguide propagation loss, phosphorus-doped silica, COMSOL Multiphysics simulations

The study highlights that energy storage materials are pivotal in the transition to renewable energy sources and improving the efficiency of electronic devices. With the global shift towards sustainable energy solutions coupled with the advancement of technologies in electronics and electric vehicles, the demand for efficient energy storage systems has surged. Researchers have thus directed their endeavors towards identifying and optimizing materials that can meet these rigorous demands, and polyetherimide stands out due to its commercial viability and inherent properties.

Rapid thermal annealing is a process involving the quick heating and subsequent cooling of materials to enhance their characteristics. This technique has long been utilized in semiconductor manufacturing but is now being repurposed for material sciences, particularly for polymers like PEI. By inducing rapid thermal cycles, the molecular structure of PEI can be altered, resulting in changes to its physical and electrical properties. The significance of this method lies in its ability to fine-tune the polymer’s structure without degrading its core attributes.

In their research, Ou et al. demonstrated that applying rapid thermal annealing to pure polyetherimide films markedly improved their energy storage capabilities. The team meticulously crafted samples of PEI and subjected them to a series of rapid thermal annealing processes, monitoring the ensuing effects on their structural and electrical properties. The results were striking; not only did the energy density improve significantly, but the dielectric properties also exhibited noticeable enhancements, suggesting a strong correlation between thermal treatment and material performance.

One of the remarkable findings was the increase in the dielectric constant of the annealed PEI films. A higher dielectric constant translates to more effective energy storage, which is crucial for applications in capacitors and high-performance batteries. The study reports that the dielectric breakdown strength of these films remained intact, ensuring that the enhanced properties did not compromise the material’s stability. This balance is vital for practical applications where energy density must be maximized without risking failure during operation.

Further investigation into the microstructural changes revealed that rapid thermal annealing induced an arrangement of molecular chains within the polymer that facilitated improved dipole alignment. This structural refinement likely contributes to the enhanced dielectric behavior observed in the processed films. Understanding these molecular behaviors is essential as it paves the way for future innovations in polymers designed for energy applications.

In their conclusion, the authors stress the implications of their findings on both the material science community and industry applications. The ability to utilize rapid thermal annealing not only positions polyetherimide films as formidable contenders in energy storage technologies but also shows promise for scalability in production. Integrating such advanced materials into existing manufacturing processes can bridge the gap between theoretical research and practical deployment.

The versatility of polyetherimide, combined with the strategic application of rapid thermal annealing, opens up a myriad of potential applications. From lightweight, high-efficiency capacitors to components in electric vehicles, the implications reach far into the future of energy solutions. As industries work towards meeting the increasing global energy demands sustainably, innovations like those presented by Ou et al. could lead to groundbreaking improvements in how energy is stored and managed.

Moreover, the ongoing exploration into polymer-based energy storage solutions continues to highlight the important role of material engineering in scientific advancement. As researchers seek to refine these materials further, it is essential to highlight collaborations across disciplines — from chemistry and material science to engineering and manufacturing — to spearhead this evolution in energy technology.

This study not only demonstrates the promising capabilities of pure polyetherimide films but also calls for further research to explore the limits of rapid thermal annealing and its effects on various polymer matrices. Future work could investigate the interactions of different additives or coatings during the annealing process, potentially unlocking even greater enhancements in energy storage properties.

As the landscape of energy storage continues to evolve, the methodologies employed to refine materials will undoubtedly play a pivotal role in determining the success of new technologies. As highlighted in Ou et al.’s research, the combination of innovative techniques and proven materials may very well be the key to ushering in the next generation of energy storage solutions that the world so desperately needs.

This scientific exploration not only advocates for a renewed focus on existing materials but serves as a reminder that the potential for breakthroughs in energy storage lies in both innovation and refinement. As more researchers delve into the intersections of polymers and advanced processing techniques, the future of energy storage promises to be as dynamic as the materials themselves.

Subject of Research: Enhanced energy storage properties of pure polyetherimide films via rapid thermal annealing.

Article Title: Enhanced energy storage properties of pure polyetherimide films via rapid thermal annealing.

Article References: Ou, J., Chen, H., He, G. et al. Enhanced energy storage properties of pure polyetherimide films via rapid thermal annealing. Ionics (2025). https://doi.org/10.1007/s11581-025-06653-y

Image Credits: AI Generated

DOI: https://doi.org/10.1007/s11581-025-06653-y

Keywords: polyetherimide, rapid thermal annealing, energy storage, dielectric properties, thermoplastic, high-performance materials.