Abstract
Analysis of trends in the development of silicon photonics shows the high efficiency regarding the creation of optical sensors. The concept of bimodal sensors, which suggests moving away from the usual paradigm based only on single-mode waveguides and using the inter-mode interaction of guided optical waves in a two-mode optical waveguide, is developed in the present paper. In this case, the interaction occurs in the presence of an asymmetric periodic perturbation of the refractive index above the waveguide surface. Such a system has unique dispersion properties that lead to the implementation of collinear Bragg diffraction with the mode number transformation, in which there is an extremely high dependence of the Bragg wavelength on the change in the refractive index of the environment. This is called the “effect of dispersion-enhanced sensitivity”. In this paper, it is shown by numerical calculation methods that the effect can be used to create optical sensors with the homogeneous sensitivity higher than 3000 nm/RIU, which is many times better than that of sensors in single-mode waveguide structures.
Highlights
Sensors 2021, 21, 5492. https://Silicon photonics [1,2,3,4,5,6] are promising technologies with huge potential for the mass production of modern optical elements and functional systems based upon them
Over the past 10 years, 20% of all publications on sensors have been based on silicon photonics technologies, and 20% of publications on silicon photonics are devoted to optical sensors [13]
The main factors influencing the scale of optical sensor application include the sensitivity (S), intrinsic limit of detection, and manufacturability
Summary
Silicon photonics [1,2,3,4,5,6] are promising technologies with huge potential for the mass production of modern optical elements and functional systems based upon them. In recent studies [36,37], to increase the sensitivity of optical sensors, it has been proposed to use the anomalous blocking effect, which is observed in a silicon waveguide that is tunneled with a segment periodic structure of a relatively large period (about 1.4 μm). This segment diffraction grating exhibits the properties of a leaky waveguide, the effective refractive index of which strongly depends on the refractive index of the surrounding medium. Zehnder interferometers [38], as well as Bragg grating-based structures [39,40,41]
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