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Short‐Wave Infrared Chip‐Spectrometer by Using Laser Direct‐Writing Grayscale Lithography

Short‐wave infrared (SWIR) information is critical for material analysis, imaging sensing, and other fields. To acquire SWIR spectrum with compact devices, strategies for reconstructive microspectrometer have emerged, such as photonic crystal and quantum dot filter. However, the current SWIR microspectrometer needs many filters with insufficient resolution. In this work, the authors develop a SWIR chip‐spectrometer based on Fabry–Perot microcavities array which can be fabricated by using fast and low‐cost UV laser direct‐writing grayscale lithography. The ultra‐compact chip‐spectrometer can work in a very wide range from 900 to 1700 nm with only 20 detector pixels and a reconstruction algorithm. The spectral resolution achieves 2 nm by 50 pixels set and 5 nm by 20 pixels set at SWIR range, which is 3 times higher, with 3.9 times less units number, than for recently reported SWIR quantum dot spectrometers. To the best of our knowledge, this is a minimum high‐resolution SWIR InGaAs detector based chip‐spectrometer which can work in the whole SWIR band with only 20 detector pixels. It has great potential for applications in smart‐phone or other miniature portable spectrometers.