Research On Characteristic Of Special Fiber Gratings And The Application In Fiber Laser Technology

Fiber gratings,as a kind of optical passive component,have multiple functions and a wide range of applications.With the rapid development of optical fiber laser,fiber sensor and fiber communication,there have been higher requirements for the fiber gratings in terms of special structure and function,extended data range,higher performance,more fiber types and extreme environment adaptability.As key devices for the relative applications,new fiber gratings are of great scientific significance and urgent demand.Focusing on this research area,in this thesis,the fabrication,property and application of the 45 degree tilted fiber grating,excessively tilted fiber grating and high temperature resistant fiber grating are systematically studied.The main results and innovations of this thesis are as follows:1.Fabrication technology of special fiber graings is explored,a mask-scanning fabrication system is built,and various spectial fiber gratings are written including 45 degree tiled fiber gratings,excessively tilted fiber gratings,type Ia high temperature resistant fiber gratings,small-period long period fiber gratings,long period fiber gratings written in few-mode fiber,etc.Besides,a dual-beam-interference-scanning fabrication system is designed and fabrication of special wavebands fiber gratings is realized accordingly.2.The polarization principle and property of 45 degree tiled fiber gratings is studied in theory.Based on the property,an all fiber polarization interference comb-like filter with free spectral range of 0.164 nm is developed.For the first time,all-fiber multiwavelength laser based on the new filter is introduced with flat and uniform multiwavelength spectrum.The laser has 82 peaks within 3 dB bandwidth and signal-to-noise ratio(SNR)of 33 dB.Besides,the mechanism of dual-wavelength fiber laser is studied.By employing a 45 degree tiled fiber grating with polarization extinction ratio of 33 dB,a single-polarization all-fiber dual-wavelength mode-locked laser is realized.The dual-wavelength laser centered at 1033 nm and 1053 nm with 3 dB bandwidth of 10 nm has 27 dB degree of polarization.3.The mode coupling property of excessively tilted fiber gratings is theoretically researched,the series-dual-wavelength spectrum is analysised and experimentally verified.The excessively tilted fiber gratings are originally introduced into saturable absorber based on the coupling property.In the experiment,the transmited light can interact with nanoparticles by ferroferric-oxide nanoparticles deposited excessively tilted fiber grating,a saturable absorber with excellent performace is made and applied in a mode locked fiber laser.The laser can operate at stable mode-locking state with SNR of 67 dB.4.Fiber gratings with high temperature resisitance are fabricated in Yb-doped fibers and Er-doped fibers respectively.At 500°C,the grating still has a high reflectivity of over 99%.These high temperature resistant fiber gratings written in gain fibers can contribute to fiber lasers with ultra-short cavity and single longitudinal mode.Based on a pair of high temperature resistant Yb-doped fiber gratings,a distributed Bragg reflector(DBR)laser at 1 ?m waveband is obtained in the experiment.The laser with linewidth of 16 pm has a total cavity length of 10 mm and can operates well at 450°C with over 50 dB SNR.This laser is of great significance for the high-precision long-distance fiber sensing working in high temperature environment.