Semiconductor THz microsensors based on ultrahigh-contrast T-shape patterned interferometers

Abstract

A plasmonic interferometer consisting of a T-shape patterned semiconductor is investigated in THz regime. The microslit couples incident THz radiation into unidirectional SPPs waves, which are reflected by bilateral sidewalls and interfere with directly transmitted THz wave. The phase/amplitude of interfering SPPs waves can be effectively engineered by structural tuning, offering a flexible and efficient control over the shape of interference pattern. Spectral fringes with large amplitude and high contrast have been demonstrated and permit figure-of-merit for intensity detection (wavelength sensitivity) up to 15255%RIU−1 (160 μm/RIU). The results could be promising for developing ultrasensitive biosensors and on-chip platforms.

Bragg-Mirror-Assisted High-Contrast Plasmonic Interferometers: Concept and Potential in Terahertz Sensing

“…Hence, the parameters of the microslit (i.e., D and H ) can be approximately designed to maximize the intensities of two interfering SPPs waves in the spectral range of interest. In order to maximize the excitation efficiency of SPPs waves, the physical parameters of the slit were chosen as D = 60 μm and H = 300 μm [ 28 ]. Figure 4 b,c shows the simulated electric field distributions at positions of interference peak ( λ = 300 μm) and valley ( λ = 316 μm) with a separation length of L = 2000 μm, respectively.…”

“…On the basis of the above discussions, we note that the proposed interferometric sensor could be either operated based on the spectral shift monitoring or the intensity interrogation at several wavelengths, or in other words, it possesses a distinguished spectroscopic capability in practical applications to maintain high sensing performance over a wide wavelength range. Particularly, by comparing the performance with that for the T-shape patterned Interferometers reported in [ 28 ], the FoM is moderately enhanced by a factor of 1.2. However, the shortcomings of utilizing the T-shape pattern were also very distinct.…”

“…The periodic structure-based biosensors can easily realize the on-chip integration, however, they suffer from their narrow-band resonant linewidths, or in other words, their sensitivities decrease significantly when the response spectra are away from the resonant wavelengths [26]. To address this spectroscopic issue, we recently proposed and studied several semiconductor-based interferometers based on the waveguide-coupled and slit-groove patterned structures [27,28]. However, it is still believed that finding new realizable schemes to further enhance the interferometric intensities and spectral contrast remains highly desired.…”