Design and prototyping of a multi-segment grating for broadband and miniaturized spectrometer

Abstract

Compact and broadband spectrometers are used for diagnosis of cancers to distinguish healthy and tumorous tissues at point-of-care locations and remote clinical centers. In this paper, we present a design of a broadband and compact spectrometer based on a three-segment grating which is able to operate from 300 nm to 1700 nm. The spectrometer has a resolution of 6 nm in the ultraviolet-visible-near infrared (UV-VIS-NIR) spectral range and 10 nm in the short wave infrared (SWIR) range. A minimum signal-to-noise ratio (SNR) of 650 in the VIS range and 9300 in the NIR- SWIR range is achieved. Afterwards, the designed three-segment grating was fabricated in-house with ultra-precision diamond tooling followed by replication in poly-methyl-methacrylate (PMMA). The replicated three-segment grating was then experimentally characterized. The experimental results show that the three-segment grating significantly improves the acquired signal level of the spectrometer in the NIR-SWIR spectral region by at least a factor of 2 compared to a corresponding single segment Richardson grating. This result opens a new way of realizing compact and broadband spectrometers which could be integrated with portable devices.