Research On Fabry-perot Cavity Based On Microfiber Bragg Gratings Imprinted By UV Irradiation

As a multi-beam interference structure，a FP cavity plays an important role in fabrication ofoptical lasers, filters, sensors, and etc. It’s extensively studied to minimize optical devices bycombination of modern fiber geometries and conventional optical theory. With development offiber-optic technology, a variety of fiber-based devices have emerged. Recently, opticalmicrofibers have attracted many research interests due to their particular characteristics..This paper presents a kind of FP cavity that is UV imprinted in optical microfibers. Similarto the traditional structures, the FP cavity has a smaller volume, strong evanescent field, goodspectral characteristics, and high sensitivity to environs. Compared with the reportedcounterparts, our fabricated FP cavity can have a simple manufacturing process, low cost, highextinction ratio in the interference spectrum. and so on. Such a structure is of miniaturization andintegration of modern optics devices. It is promising for future applications in optical lasing,filtering, sensing, and etc.This paper begins with discussion of the work principles and numerical methods forinscribing fiber Bragg grating (FBG)by use of a UV exposure. With combination of a FBG and amicrofiber, we analyze the difference between two types of microfiber-based FBG (mFBG)bymeans of analysis of its waveguide structures and mode field distribution, numerical simulationwith a finite element method, and experiments. With the discussion results by theoreticalanalysis and simulation, we design the plan for realization of microfiber FP cavity.Subsequently, this paper describes the manufacture of m FBGs and the mFBG-based FPcavity. We discuss the spectral characteristics of the FP cavity, especially the dispersionphenomenon of the spectrum, and demonstrate the spectral responses of the structure to externalrefractive index, temperature, and strain, respectively. We also find the polarization-dependenttransmission for the FP with a relatively small microfiber size. We demonstrate the origin of thepolarization-dependent characteristics.Finally, we investigate the spectrum of a tapered mFBG. Such kind of mFBG can haveadvantages of small size, wide forbidden band, and temperature-independent high sensitivity totensile. By writing a FP cavity with two chirped gratings，we can obtain a comb-like filter with abroad band.