Thermostable refractive index sensors based on whispering gallery modes in a microsphere coated with poly(methyl methacrylate)

Nai Lin; Lan Jiang; Sumei Wang; Hai Xiao; Yongfeng Lu; Hailung Tsai

doi:10.1364/AO.50.000992

Thermostable refractive index sensors based on whispering gallery modes in a microsphere coated with poly(methyl methacrylate)

Appl Opt. 2011 Mar 1;50(7):992-8. doi: 10.1364/AO.50.000992.

Authors

Nai Lin¹, Lan Jiang, Sumei Wang, Hai Xiao, Yongfeng Lu, Hailung Tsai

Affiliation

¹ Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.

PMID: 21364722
DOI: 10.1364/AO.50.000992

Abstract

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.