Ultra-compact ferrofluid infiltrated magnetic field sensor utilizing microring resonator in silicon-on-insulator platform

In this paper, we aim to propose a compact high Q-factor magnetic field sensor which is CMOS compatible. Hence, we have proposed a novel micro-ring resonator (MRR) design using a silicon-on-insulator (SOI) platform where a magnetic ferrofluid is filled in the slot cavity. First, we initiated the design of slotted MRR for maximal light confinement by tuning the dimensions of rail widths, height, and slot width. After optimization, the rail width of 250 nm and the slot width of 100 nm with a height of 220 nm are reported to have a maximal confinement factor, forming the base design of the proposed magnetic field sensor. The application of an external magnetic field to the slotted MRR device with a ring radius of $50\mu m$ resulted in a considerable change in the effective index, leading to significant variations in phase and transmission characteristics. A sensitivity of 5.399 pm/Oe is observed through consecutive dips in the transmission characteristics for the proposed model. To design an efficient magnetic sensor, the qualitative analysis, namely the quality factor (Q-factor) and extinction ratio (ER) are optimized by using rail widths and slot width. The reported results infer that the dimension of rail widths of 250 nm and slot width of 125 nm offer a high Q-factor of approximately 6.5 $\times$ 10⁴ with an ER of 37 dB. The results pave the way for further advancements in integrated photonics and magnetic field manipulation.