Ultra-sensitive MDM plasmonic sensor for refractive index, CO2 concentration, biomolecule, and temperature detection

Abstract

This paper presents a metal-dielectric-metal configuration based plasmonic refractive index sensor for applications like gas, biomolecule and temperature detection. The device consists of a rectangular ring resonator coupled to a straight waveguide. Initially the device has shown its application as a simple refractive index sensor, where the device can sense refractive indexes in the range from 1.0 to 1.1 with the maximum sensitivity of 2400 nm/refractive index unit (RIU). This device is used as a gas sensor for detecting the concentration of CO₂, for that Polyhexamethylene biguanide (PHMB) is added to the rectangular ring resonator and then by changing the refractive index of PHMB layer via adsorbing CO₂ molecules, the change in the concentration of CO₂ gas is detected. A sensitivity of 46.51 p.m./parts per million (ppm) is theoretically obtained for the different concentrations of CO₂ from 0 ppm to 524 ppm. Then the device is simulated to sense various biomolecules, where detection of colorless biomaterial, anemia, creatinine and prostate cancer is performed. In the detection of anemia, the sensitivity of 3333nm/RIU is predicted. Additionally, for colorless biomolecules, static sensitivity of 2000 nm/RIU, for creatinine maximum sensitivity of 1500nm/RIU and maximum sensitivity of 2259.8 nm/RIU is predicted for prostate. Besides, this device is also used as a temperature sensor by using the Polydimethylsiloxane (PDMS) as the dielectric material, whose refractive index changes from 1.3861 to 1.4041 for different temperatures ranging between 80 °C and 20 °C. For the temperature detection, the sensitivity of 2 nm/°C is predicted.