Optical modulators and biochemical sensors based on low-symmetric nanophotonic structures with interferometric configurations

Low-symmetric photonic crystals (PCs) have a high level of tunability in terms of their iso-frequency contours or refractive indices via angular orientations as well as spatial variations of unit cell elements. This phenomenon brings along emerging extraordinary dispersion properties dependent to rotation and position of unit cells. In this study, we show that the electromagnetic waves propagating inside the low-symmetric waveguides can be exposed to phase delays by tuning the angular orientations of unit elements. In this way, low-symmetric PC waveguides based Mach-Zehnder Interferometers (MZIs) exhibiting controllable phase properties are designed. The investigated all-dielectric tunable interferometric systems are numerically analyzed in both frequency and time domains. Furthermore, by exploiting spectral sensitivity of proposed MZIs, conceptual demonstration of gas sensor systems is performed. The designed optical gas sensors have minimum selectivity of 200 nm/RIU even in the case of refractive index variation on the order of 10-4 RIU in analytes. Having these advantages, proposed interferometric configurations based on low-symmetric periodic structures may offer a significant alternative for photonic applications that require controllable output power or sensing of gaseous substances.