Compact, High‐resolution Inverse‐Designed On‐Chip Spectrometer Based on Tailored Disorder Modes

Abstract Integrated optical sensors have garnered much interest for lab‐on‐chip applications such as chemical and biological sensing and detection. Among various ways for detection schemes, spectral analysis performed by a spectrometer has shown great promise. Typically, such spectrometry is carried out in a relatively large device, owing to the fact that spectral resolution is often dictated by large optical path length. Here, a high‐resolution compact spectrometer utilizing random scattering events in a disordered medium is demonstrated. The spectrometer is inverse designed by objective‐first method and fabricated using two‐photon polymerization technique. The compact spectrometer consists of a disordered photonic structure and an inversed‐designed mode decomposer. A spectral resolution of 0.25 nm with a bandwidth of 30 nm in the near‐infrared regime is realized from a spectrometer occupying a relatively small footprint of 30 × 12.8 µm 2 . The proposed platform has a great potential to be used as a versatile lightweight and compact spectrometer for various applications including on‐chip spectrometer and sensing.