Active plasmonic tunable filter for hyperspectral imaging using angle-sensitive nanostructures

Abstract

Hyperspectral imaging provides enhanced classification and identification of veiled features in diverse biomedical applications such as label-free cancer detection or non-invasive diagnosis of vascular disease. However, hyperspectral cameras still have technical limitations in miniaturization due to the inherently bulky and complex configurations of conventional tunable filters. Here, we report an active plasmonic tunable filter (APTF) with electrothermally driven spectral modulation for hyperspectral imaging. APTF features angle-sensitive plasmonic structures (APS) over an electrothermal MEMS actuator, fabricated by nanoimprint lithography and subsequent MEMS fabrication at a 6-inch wafer level. APS have a complementary configuration of Au nanohole and nanodisk arrays supported on a silicon nitride thin membrane. APTF shows large angular motion at low operational voltages of 4 - 9 V for continuous and linear spectral modulation between 772 nm and 998 nm (45 nm/V). The compact hyperspectral camera was fully packaged with a linear polarizer, APTF, and a compact monochrome camera, exhibiting a module size of 16 mm (ϕ) × 9.5 mm (h). Augmented subcutaneous vein imaging has been successfully demonstrated after the hyperspectral reconstruction and spectral feature extraction. This work opens up a new direction for a compact hyperspectral camera and expands the scope of HSI to point-of-care or in-vivo imaging, based on high compactness and portability.