Plasmonic photodetector with submicron grating for reconstructive spectroscopy of low-intensity broadband light

Abstract

Reconstructive spectroscopy, a spectroscopic method that derives the spectrum of incident light using photodetection elements with various dispersion characteristics, is emerging as a promising approach for constructing compact spectroscopic devices. The generally adopted approach of simultaneously irradiating spatially distributed multiple elements is not suitable for weak light because the elements divide the total incident power spatially. Temporarily tilting a single-eyed diffraction grating photodetector that couples the light with the surface plasmon resonance can utilize the whole incident optical power, which is advantageous when only weak light is available. However, to perform robust spectroscopy, a carefully designed dispersion relation of surface plasmon resonance is required. In this study, we propose a suitable grating structure for reconstructive spectroscopy of low-intensity broadband near-infrared light. Using an optimal sub-micron pitch of 0.95 µm grating, the reconstruction of the light from a halogen lamp light with an intensity density as small as around 10µW/nm is presented in the 1200–1400 nm wavelength range. The reconstructive spectroscopy with the plasmonic photodetector also allows for the identification of materials such as glass, cycloolefin polymer, and acrylic resin within this wavelength band. The potential for integration with microelectromechanical systems technology opens up possibilities for a compact near-infrared spectroscopic device that is compatible with a variety of light sources, offering applications in various scientific fields.