Slow-Light Enhanced Liquid and Gas Sensing Using 2-D Photonic Crystal Line Waveguides—A Review

Abstract

Photonic Crystals (PhCs) are periodically structured dielectric materials that have attracted significant research interest in the last two decades for their ability to slow down group velocity of a propagating pulse envelope with promising sensing applications. This review paper discusses the properties of two-dimensional (2D) PhCs including the slow-light phenomenon, band-gap generation and application of these properties for gas and liquid sensing. Waveguide generation by introducing defects with light guiding and confinement is discussed. Additionally, for 2D PhC line waveguides, a comprehensive review on slow-light principle and phenomenon of slow-light enhanced sensing for gases and liquids is discussed. One-dimensional (1D) and three-dimensional (3D) PhCs are also reviewed for band-gap generation and defects in PhCs along with present fabrication challenges and future trends. Our study highlights an increase in the detection capabilities of PhC based sensors paving way for high sensitivity detectors with applications in ubiquitous monitoring of gases and liquids.

On-chip two-dimensional material-based waveguide-integrated photodetectors

“…2(e). 102,103 In the PhC waveguide, light propagation is constrained by the forbidden band structure, resulting in a high-quality factor for its dominant mode. This allows light to be transmitted over long distances in the waveguide with minimal attenuation.…”

“…The slow-light effect means that in PhCs, their periodic structure will lead to the interference and scattering of light propagation, thus reducing the propagation speed of light in the medium, that is, the group velocity of light is slower than that in free space. 103,104 This extended interaction time between photons and 2DMs enhances the optoelectronic conversion efficiency, ensuring a superior performance. In addition, special cavities can also be formed in PhC waveguides, resembling resonant cavities, which also contribute to enhancing the light absorption.…”

Design of classification-based photonic crystal sensor for chemical substance detection

“…By scrutinizing the dispersion curves of defect modes, obtained through the intentional creation of defects in the photonic crystal structure, the behavior of light in the photonic crystal, including critical optical properties such as group velocity and group velocity dispersion, can be determined [8]. In particular, the reduction of the group velocity of light as it passes through the crystal enhances matter-field interaction, paving the way for the design of high-sensitivity sensors in photonic crystal sensor designs [9][10][11][12]. With these sensors, more precise measurements can be made even in conditions of minimal substance concentration or quantity.…”