OPTICAL PHYSICS

Science, 365, 1017 (2019)

Optical spectrometers have been playing significant roles in our life since Sir Isaac Newton demonstrated in 1666. Up to now, they still majorly rely on the dispersion of light by prisms or gratings in free space. For in-situ measurements, it was a wide dream to miniaturize these spectrometers while keeping their resolution and spectral range.

Recently, researchers from the Cambridge Graphene Centre at the University of Cambridge have reported an ultra-compact optical spectrometer with a size down to nanoscale. They use a bandgap graded semiconductor nanowire as the active material and fabricate a series of parallel photodetectors along its length. The bandgap gradient enables the photodetectors to selectively detect the wavelengths. A target spectrum is computationally reconstructed by cross-referencing the measured set of photocurrents and response functions of each of these photodetectors. Therefore, the light dispersion and detection are conducted simultaneously in a single nanowire. Despite the simplicity in design, this nanowire spectrometer is capable of accurate monochromatic and broadband light reconstruction. This further enables macro and micro spectral imaging. This work not only opens new opportunities in in-situ spectroscopy, but also provides a new conceptual platform for rich light-matter interactions based on compound materials and semiconductors.

Baicheng Yao (University of Electronic Science and Technology of China, Chengdu, China)

doi: 10.1088/1674-4926/40/10/100201