Photonic Bragg waveguide platform for multichannel resonant sensing applications in the THz range

Abstract

In this paper, we study a photonic Bragg waveguide sensor for resonant sensing applications in the THz range. In order to enhance the resolution and detectivity of the sensor, we modify the relatively broad transmission spectrum of the Bragg waveguide with spectrally narrow transmission dips by creating a geometrical defect in Bragg reflector and causing anti-crossing phenomenon between the core-guided mode and defect mode. The spectral position of the resonant dip is highly sensitive to the thickness variation in the vicinity of the waveguide core. By designing and manufacturing a Bragg waveguide which includes several sections with different defect layer thicknesses, we can interrogate more than one sample simultaneously and thereby realize multichannel resonant sensing by directly tracking the independent resonant dips. Furthermore, we demonstrate the waveguide platform for online monitoring of the thickness variation of lactose powders, which is captured on the waveguide core via a centrifugal force using a home-built rotating setup. Additionally, we also demonstrate the waveguide for fingerprint detection of powder analytes, which further enriches the sensing scenario of the sensing platform. Finally, we discuss the advantages and the spectral tailoring flexibility of the THz Bragg waveguides sensors for future implementations.

Full-Vectorial Fiber Mode Solver Based on a Discrete Hankel Transform

“…Indeed, compensation via an increase in spatial mesh points, i.e., Fourier-Bessel coefficients, might be a viable counter-strategy but will increase the computational time. Similar problems will certainly arise for thin but pronounced refractive index wells and dips for example in Bragg fibers [29] (or other Bragg-type waveguides [30]) or quantum well waveguides [31]. With respect to such designs, another disadvantage of the DHT-based solving approach is the inflexible meshing because the sampling is determined by the zeros of the corresponding Bessel function and cannot be chosen freely.…”

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“…Additionally, electromagnetic wave propagation within waveguides offers a better signal-to-noise ratio. Over the past few years, sensing platforms have used several kinds of metal and dielectric waveguides such as single wire waveguide, 28 microstrip line, 29 coplanar waveguide, 30,31 Goubau line waveguide, 32 photonic Bragg waveguide, 33 photonic crystal, 34 PMMA grating waveguide tube, 35 and so on. The boosting of wide-band terahertz absorption spectroscopy of trace-amount analytes is based on the local effects of the metal and dielectric waveguides on electromagnetic fields.…”

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