On-Chip Measurement of Photoluminescence with High Sensitivity Monolithic Spectrometer

Monolithic spectrometer is exceptionally attractive to enable compact, low-cost spectroscopy for portable sensing and lab-on-a-chip functionality. Unfortunately, simple down-scaling of the microspectrometer size to the chip-scale severely weakens light-matter interactions and degrades the sensor performance to unacceptable level. Unlike other state-of-the-art miniature spectral splitting filters or photonic structures, bandgap-graded nanowire strongly enhances the light-matter interaction, which is a highly demanded yet unfulfilled feature for high-precision on-chip sensing. Here, on-chip measurement of photoluminescence by a monolithic spectrometer made of a single composition-graded CdSxSe1-x nanowire is reported. The nanowire is engineered to a waveguide-mode-operated, dispersive photodiode array. It works as a monolithic spectrometer chip with strong light-matter interaction and superior noise figure. On-chip measurement of single-point photoluminescence signals with 10(13) Jones room-temperature detectivity and 5 nm spectral resolution is illustrated. This demonstration of a compact, low-cost, and high-performance miniature spectrometer marks a major step towards on-chip spectroscopy for fine resolution and sensitive detection.