Unique Dispersion Relation for Plasmonic Photodetectors with Submicron Grating

We proposed a plasmonic photodetector with a submicron grating pitch for accurate and robust near-infrared reconstructive spectroscopy. Miniaturized spectrometers have been intensively studied, and one promising candidate is the use of wavelength-specific plasmonic photodetector, which presents a correspondence between the detectable wavelength and the angle of incidence under measurements. However, the method fails to accurately reconstruct the spectrum because multiple wavelengths to be detected correspond to one angle. We, therefore, propose a plasmonic photodetector that has a one-to-one correspondence by shrinking the grating pitch to submicron, which was ~3 µm in previous reports. We compared reconstructed spectra with those with conventional photodetectors in the near-infrared range from 1150 to 1500 nm and confirmed the effectiveness of this method.