Performance analysis of different slot waveguide structures for evanescent field based gas sensor applications

Abstract

Slot waveguide has emerged as a potential candidate for the design of evanescent field absorption based photonic gas sensors, optical quantum information applications, etc. In this paper, three different slot waveguide structures, i.e., conventional slot, partial-strip-loaded slot, and full-strip-loaded slot waveguides have been explored to analyze their sensing performance for the methane gas. As the methane gas has the peak absorption at around 3.31 µm, therefore, this has been considered as the operating wavelength for the analysis. In anticipation of improvement in evanescent field ratio in slot region and hence, the sensing capabilities of the gas sensor, the slot waveguide structures have been designed by depositing the germanium layer over the calcium fluoride in different manners. To realize the significant evanescent field and sensitivity along with relatively low propagation loss, the suitable dimension of the slot waveguide structures has been chosen very judiciously. Several waveguide parameters, such as evanescent field ratio, propagation loss, and sensitivity have been chosen for the analysis and comparison of slot waveguide structures, by varying the arm-width and thickness of germanium layer. Simulation results have demonstrated that the full-striploaded slot waveguide has the superior performance in terms of higher evanescent field and higher sensitivity, which is followed by the partial-strip-loaded slot waveguide, even for the fixed target value of propagation loss. Moreover, the current analysis may be extended for the design of suitable photodetector that can further enhance the performance of the gas sensor.

Dielectric Waveguide-Based Sensors with Enhanced Evanescent Field: Unveiling the Dynamic Interaction with the Ambient Medium for Biosensing and Gas-Sensing Applications—A Review

“…The slot WG has emerged as a promising candidate for designing evanescent field absorption-based photonic gas sensors. In [84], three different slot WG structures-conventional slot, partial-strip-loaded slot, and full-strip-loaded slot-are discussed with the aim of analyzing their sensing performance with methane gas as shown in Figure 6a-c. To enhance the EFR in the slot region and consequently improve the gas sensor's capabilities, these slot WG structures are designed by depositing the germanium layer over calcium fluoride in various ways.…”

Silicon-on-sapphire slot waveguide based evanescent field absorption sensor for detection of trace gases in mid IR

“…The EFR in the conventional strip waveguides can be increased to as high as 55% by tailoring the waveguide design parameters, however, the waveguides at such high EFR become weakly guiding and leaky [28]. In this regard, a slot waveguide offers an attractive feature as the EFR in a slot waveguide can be obtained as high as 50% while simultaneously maintaining a low effective mode area and single mode operation by tuning the waveguide structure parameters [32][33][34][35]. The widely used CMOS-compatible silicon-on-silicon dioxide platform cannot be used for the midinfrared (IR) region, as it has higher waveguide losses that occur due to the high material losses of SiO 2 [27,28].…”

Tunable Fabry-Pérot interferometer integrated in a silicon waveguide of an on-chip optical platform for long infrared wavelengths

“…Modular approaches with the integration of components like waveguides, bends and couplers on one single chip are reported [5,6]. The evanescent field of waveguides in the mid and long infrared wavelength range is used for spectral analyses of gases [7][8][9]. In general, spectrometers can be distinguished according to their wavelength selecting principle in grating based diffraction spectrometers (e.g.…”