In this paper, we investigate the mode sensitivity (S mode) of subwavelength grating slot (SWGS) waveguides. S mode is an important parameter in various waveguide-based photonic circuits such as sensors, modulators, and thermally-controlled devices. It is a measure of the sensitivity of the waveguide effective index towards the refractive index perturbations in the cladding medium. The SWGS waveguide exhibits high mode sensitivity, as it combines sensitivity enhancement features of both slot and subwavelength grating waveguides. Finite-difference time-domain simulations are performed for the analysis, design, and optimization of the hybrid structure. The SWGS waveguide is incorporated into a Mach-Zehnder interferometer and fabricated on a silicon-on-insulator platform for the experimental estimation of S mode. The measured S mode value of 79% is consistent with the theoretical prediction of 83%.

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The need for a high optical spectrum throughput, high conductivity, and controlled energy levels of transparent conductive oxide used in solar cells stresses the development of novel materials that help reduce the existing dependency on indium-based oxides. ZnO is a promising material in this context, and in this work, we demonstrate how Hf doping of ZnO films allows engineering both electrical and optical properties to fit the requirements of different solar cell architectures and materials. We focus on the lightly doped domain where Hf substitution is believed to be the key for band gap tunability without negatively affecting the carrier transport behavior. We provide experimental analysis of controlled changes in the optical and electrical properties, including work function, and a detailed analysis of the structural behavior resulting from the deposition at elevated temperature. We finally present first-principles density functional theory simulations to elucidate the mechanisms responsible for the obtained electronic and electrical properties that predict a modification in the band structure of ZnO when Hf is substituted and/or embedded in the ZnO matrix as HfO2 phases.

The outstanding performance and facile processability turn two-dimensional materials (2DMs) into the most sought-after class of semiconductors for optoelectronics applications. Yet, significant progress has been made toward the hybrid integration of these materials on silicon photonics (SiPh) platforms for a wide range of mid-infrared (MIR) applications. However, realizing 2D materials with a strong optical response in the NIR-MIR and excellent air stability is still a long-term goal. Here, we report a waveguide integrated photodetector based on a novel 2D GeP. This material uniquely combines narrow and wide tunable bandgap energies (0.51–1.68 eV), offering a broadband operation from visible to MIR spectral range. In a significant advantage over graphene devices, hybrid Si/GeP waveguide photodetectors work under bias with a low dark current of few nano-amps and demonstrate excellent stability and reproducibility. Additionally, 65 nm thick GeP devices integrated on silicon waveguides exhibit a remarkable photoresponsivity of 0.54 A/W and attain high external quantum efficiency of ∼ 51.3% under 1310 nm light and at room temperature. Furthermore, a measured absorption coefficient of 1.54 ± 0.3 dB/µm at 1310 nm suggests the potential of 2D GeP as an alternative infrared material with broad optical tunability and dynamic stability suitable for advanced optoelectronic integration.