Advanced Photonics for On-Chip Sensing: Design, Optimization, and Implementation in Integrated Sensor Devices

Student’s name: Meklit Tilahun Home Institution: Washington and Lee University NNCI Site: MRC @ UT Austin REU Principal Investigator: Dr. Ray Chen – Department of Electrical and Computer Engineering, University of Texas Austin REU Mentor: Sourabh Jain – Department of Electrical and Computer Engineering, University of Texas Austin Abstract: In pursuing better-performing devices, the scientific community creates innovative device ideas around The Figure of Merit (FOM). Traditional water quality testing methods perform less efficiently among the FOM values because they require larger sample sizes, greater laboratory analysis, less mobile equipment, and higher energy consumption. Pursuits for water quality testing have emerged to address practicality. Therefore, photonic crystal sensors’ sensitivity and specificity capabilities provide greater long-term experimental potential in water quality testing than traditional laboratory methods. In this study, we fabricated a Si3N4 photonic crystal slab utilizing a rectangular air-hole array on a fused SiO2 substrate. Crystal dimensions such as the radius and lattice constant were optimized using the commercially available computational tool “Lumerical FDTD.” The fabrication process involves advanced electron beam lithography followed by plasma etching techniques to create a periodic nanostructure that boosts light-matter interactions and should thus enhance Raman scattering for the molecular identification of metals such as lead (Pb²⁺) and mercury (Hg²⁺). The future extension of this project will include the assembly of nanocapsules with silver nanoparticles onto the photonic crystal to provide a constant enhancement of its SERS effect, making the sensors more sensitive beyond hotspot proximities.