This study proposes a thermostable refractive index (RI) sensor consisting of a silica microsphere coated with a poly(methyl methacrylate) (PMMA) layer. The first-order and second-order whispering gallery modes (WGMs) of both TE and TM polarizations are considered theoretically. The layer thickness is carefully optimized to eliminate the thermal drift and enhance the RI sensitivity and detection limit. In various WGMs, at the thermostable thickness of the PMMA layer, the first-order TM mode corresponds to the highest sensitivity and the smallest detection limit. The theoretical predictions provide guidelines for the design and fabrication of thermostable RI sensors.
© 2011 Optical Society of America
Lasers and Laser Optics
Original Manuscript: December 3, 2010
Manuscript Accepted: December 29, 2010
Published: February 23, 2011
Vol. 6, Iss. 4 Virtual Journal for Biomedical Optics
Nai Lin, Lan Jiang, Sumei Wang, Hai Xiao, Yongfeng Lu, and Hailung Tsai, "Thermostable refractive index sensors based on whispering gallery modes in a microsphere coated with poly(methyl methacrylate)," Appl. Opt. 50, 992-998 (2011)