Lossy Mode Resonance Based Fiber Optic Sensors

In the past couple of years, lossy mode resonance (LMR) phenomena has attracted the attention of researchers with its promising benefits in the field of fiber optic sensing. LMR based sensors have become a useful tool in sensing applications ranging from physical sensing to biosensing in a short span of time. In addition to sensing, LMR phenomena can also be utilized as wavelength filters for communication purposes. LMR based sensors are able to work independently of the specific polarization of light for sensing operations. Also, unlike evanescent wave and surface plasmon resonance (SPR) based sensors, the sensitivity of these LMR sensors does not get affected by the geometrical parameters of fiber and primarily depends on the thickness of thin film material. Till date, various geometries of fiber probes such as straight, D-shaped, tapered etc., have been explored. Bending and tapering of multimode fiber based LMR sensors improve the detection accuracy without affecting their sensitivity. However, in single mode fiber based LMR sensors the side polishing and tapering of fibers improve both the detection accuracy and sensitivity. Another method to improve the sensitivity is by using two LMR supporting thin film layers of higher refractive index instead of one. This chapter describes the theory and developments made in the field of LMR based fiber optic sensors for various sensing applications. Finally, future scope of the LMR sensing technology and possible research in this emerging area are suggested.