Researchers have developed a hybrid silicon photonic and computational spectrometer that achieves picometer-scale reconstructed resolution across a broad bandwidth, offering a new way around the usual trade-off between resolution, bandwidth, and footprint. The design occupies less than 0.002 mm² and shifts part of the performance burden from photonic hardware to computational reconstruction.
Chip-scale spectrometers have improved steadily, but broad bandwidth, high resolution, and compact footprint remain difficult to combine. Computational methods can relax some of those constraints, though often at the cost of numerical stability or device simplicity.
To get around those limits, the Southeast University team built the system around two thermally tunable trapezoidal subwavelength grating microring resonators arranged as a Vernier filter. Each 10 µm ring was dispersion-engineered to maintain a more uniform response across a wide spectral range. By synchronously tuning the resonances, the device generated a sequence of measurements that could be reconstructed in software, allowing it to operate with a single detection channel rather than a large detector array.
The reconstruction workflow was tailored to two different measurement tasks. For narrow spectral features, the researchers used an L-BFGS-based peak deconvolution routine to recover closely spaced peaks. For gas-phase absorption spectra, they used a lookup-table-based algorithm designed for densely overlapped lines. Both were implemented on an Nvidia Jetson platform, giving the system an edge-computing loop rather than relying on offline post-processing.
In testing, the device achieved picometer-scale reconstructed resolution across the full bandwidth. It then applied that performance to a dense hydrogen cyanide spectrum, resolving 49 absorption lines with closer agreement to a tunable-diode-laser reference than a commercial optical spectrum analyzer. This suggests the platform’s real strength lies not just in headline resolution, but in recovering analytically useful spectra from a highly compact single-channel system.
The authors suggest that the same co-design strategy could be extended further through lower-loss photonic platforms, broader array architectures, and faster tuning schemes, offering a route toward compact, high-resolution spectrometers for portable sensing and lab-on-a-chip analysis.
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