All-optical Tuning of Microsphere Whispering Gallery Mode Resonance Wavelength to Lock to the DFB Laser Wavelength for Using in CH4 Detection

Abstract

Methane is a flammable and explosive gas, which is the main component of mashgas and natural gas.Methane monitoring plays an important role in coal mine safety and natural gas.The high-Q whispering gallery mode (WGM) of optical microcavity has a long photon lifetime, which greatly prolongs the effective optical path between light and surroundings,and has the potential to be made into miniaturized and highly sensitive gas sensor device.In order to realize the high Q microcavity WGM enhancement light absorption methane gas sensor,the key technology is to lock the resonant frequency of the microsphere cavity to the DFB laser frequency.In order to ensure the intrinsic safety of the CH4 sensor, the resonance wavelength of the all-optically tuning microsphere cavity was studied, so that it was locked to the wavelength of the CH4 absorption peak of 1653.72nm. The resonant wavelength of the microsphere was tuned by injecting light along the fiber handle of the microsphere, and the refractive index of the microsphere was changed by absorbing light and converting heat with the coating of the sphere crown.