Enhanced temperature sensing based on birefringence induced Vernier effect in a symmetrical metal-cladding waveguide

Abstract

A temperature sensor with high sensitivity based on the birefringence induced Vernier effect in a symmetrical metal-cladding waveguide (SMCW) structure is theoretically proposed. Due to the guiding layer of SMCW is extended to a sub-millimeter scale, the excited ultra-high order modes is highly sensitive to the variation of thermally modulated refractive index (RI) and the obtained comb-like resonance reflectivity spectrum shifts accordingly as changing the ambient temperature. There is a little difference between the RI of the ordinary light and the extraordinary light of the filled nematic liquid crystal (LC), the resulted slight different free spectral range of two orthogonal polarizations makes their superposition of reflectivity spectrum metamorphose into a period envelope with multiple sub-peaks. The dips in the fitting upper envelope possesses a much enhanced temperature dependent spectrum shift which can be measured by a low-cost integrated-type micro-spectrometer. Such a sensor has no reference resonant cavity and its sensing range can be easily controlled by filling with different kinds of LC.

KEYWORDS:

• Temperature sensor
• high sensitivity
• birefringence
• vernier effect
• symmetrical metal-cladding waveguide

Disclosure statements

The authors declare no conflicts of interest.

Additional information

Funding

The Open Fund by State Key Laboratory of Advanced Optical Communication Systems and Networks. [grant number 2017GZKF18], the National Natural Science Foundation of China [grant numbers 61765008, 11764020, 11804133, 51567011], the Fundamental Research Funds for the Central Universities of China [grant number 2017B14914], the Postdoctoral Science Foundation of China [grant number 2016M601586], and the Science and Technology Project of Changzhou [grant number CJ20180048], Scientific Research Fund of Jiangxi Provincial Education Department [grant numbers GJJ150313, GJJ160273, GJJ170184].