Actively Tunable Spectral Filter for Compact Hyperspectral Camera Using Angle-Sensitive Plasmonic Structures

Abstract

Hyperspectral imaging provides enhanced classification and identification of veiled features for diverse biomedical applications such as label-free cancer detection or non-invasive vascular disease diagnostics. However, hyperspectral cameras still have technical limitations in miniaturization due to the inherently complex and bulky configurations of conventional tunable filters. Herein, a compact hyperspectral camera using an active plasmonic tunable filter (APTF) with electrothermally driven spectral modulation for feature-augmented imaging is reported. APTF consists of angle-sensitive plasmonic structures (APS) over an electrothermal MEMS (Microelectromechanical systems) actuator, fabricated by combining nanoimprint lithography, and MEMS fabrication ona 6-inch wafer. APS have a complementary configuration of Au nanohole and nanodisk arrays supported on asilicon nitride membrane. APTF shows a large angular motion at operational voltages of 5-9 V-DC for continuous spectral modulation between 820 and 1000 nm (45 nm/V). The compact hyperspectral camera was fully packaged with a linear polarizer, APTF and amonochromatic camera, exhibiting asize of 16 mm (phi) x 9.5 mm (h). Feature-augmented images of subcutaneous vein and a fresh fruit have been successfully demonstrated after the hyperspectral reconstruction and spectral feature extraction. This functional camera provides a new compact platform for point-of-care or in vivo hyperspectral imaging in biomedicalapplications.