Vol.:(0123456789) Optical and Quantum Electronics ( 2020) 52:19 https://doi.org/10.1007/s11082-019-2140-1 1 3 Design of photonic crystal microring resonator based all‑optical refractive‑index sensor for analyzing diferent milk constituents Uttara Biswas 1  · Jayanta Kumar Rakshit 1  · Gaurav Kumar Bharti 1 Received: 26 September 2019 / Accepted: 2 December 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Milk has almost all essential nutrients which is required for human nutrition. Controlling the quality of milk and milk-based products is imperative for the safety of consumers. In the present paper, an ultra-compact and an ultra-fast photonic crystal based microring reso- nator is proposed for refractive index sensing applications which can be used for determin- ing the diferent constituents of milk. The sensitivity of the proposed structure is 1 nm/% of water content and 0.42 nm/% of fat content in the milk. The high value of Q-factor is obtained which is around 16,857 by using the fnite diference time domain simulation method. The shift in the resonant wavelength of the output light at the through port of the structure is observed for the diferent milk samples. Keywords FDTD simulation · Microring resonator · Photonic crystal · PWE method · Refractive-index sensor 1 Introduction Photonic crystals are being used adequately for diferent sensing purposes because of its unique optical behavior. Research interest in photonic based light-matter interactions and higher sensitivity of photonic crystal (PhC) sensors are dominating in the recent years. The broad range of constitutional specifcations of a PhC gives the fexibleness to control the properties of the device based on PhCs (Robinson and Nakkeeran 2013; Sreenivasulu et al. 2018; Hussein et al. 2018; Zhang et al. 2015). A PhC was frst proposed by Yablonovitch (1987). This concept is proved to be stepping stone in the feld of optics and photonics based sensors. In past few years, safety of food as well as other issues related to food adul- teration are becoming important, and also provide opportunities for research and develop- ment in feld of real-time sensing technology. PhC plays a vital role in sensing due to its various advantages like the fexibility in miniaturization as well as the bandgap properties. The PhC prohibits the propagation of * Jayanta Kumar Rakshit jayantarakshit.eie@nita.ac.in 1 Department of Electronics and Instrumentation Engineering, National Institute of Technology Agartala, Agartala, Tripura 799046, India