Physics

Dr.Shuren Hu
Global Foundaries, NY, USA

Abstract :

Engineering light-matter interaction at the nanoscale has the promise to enable technological advances in a wide range of technological applications, including biomolecular sensing, communication, quantum optics, displays, optomechanics, and optical trapping. In this talk, I will talk about enhanced light-matter interaction through simulation, design, fabrication, and characterization of dielectric nanophotonic resonators. Based on an analysis of Maxwell’s equations, three key parameters that govern light-matter interaction are highlighted: (i) change in refractive index, (ii) modal overlap, (iii) and optical field strength. Enhancement of light-matter interaction through these avenues is studied with a particular focus on practical applications. First, a new method to increase the refractive index change in optical biosensors is presented, which overcomes the challenge of having a limited number of bioreceptor binding sites on label-free nanophotonic biosensors. It is shown that an in-situ synthesis technique for attaching bioreceptors to silicon photonic sensors produces at least 5 times higher bioreceptor surface density than traditional approaches, leading to amplified sensing signals, due to larger refractive index changes, and faster sensor response times. Next, a suspended TM microring resonator biosensor is demonstrated with improved light-matter interaction through increased modal overlap. Suspending the resonator allows biomolecules to access the underside of the resonator and also delocalizes the optical resonance mode; these effects lead to a 3-fold increase in bulk detection sensitivity and the label-free detection of Herceptin, a breast cancer therapeutic, at a clinically relevant 100 nM concentration. Finally, increased light-matter interaction through enhanced optical field strength is achieved using a de novo design method that strategically modifies the unit cell of photonic crystals. Through both finite-difference time-domain simulations and experiments, a high quality factor (Q ~ 10⁶) bowtie-shaped silicon photonic crystal resonator with deep subwavelength mode volume (V_m ~ 10^-3(l/n_si)³) is demonstrated. This Q/V_m metric is the largest reported to date.