Peparation Of The Grating Structure In Polymer Optical Fiber By Femtosecond Laser

Polymer optical fiber has many advantages as a new type of optical fiber. It islight and soft, has good toughness, good durability, high-bandwidth, high sensitivity,and others, It has a good prospect. The fiber grating is a kind of periodic refractiveindex modulation structure in the optical fiber. It can be used as a important photonicdevices for sensing and communication function. Polymer optical fiber gratingstructure on the field of communications and sensing are of great value andsignificance. The traditional preparation of gratings by UV laser technology, inducerefractive index modification to inscribe fiber grating. The effect and stability is notvery good. It dependent on the fiber photosensitivity, and has many other limitations.The grating preparation method combined with the femtosecond laser technology hasmany advantages than UV laser. It breaks through the limit of the fiber photosensitivity.The refractive index modification has been greatly improved. It also can shorten theexposure time needed by the production of devices.We have done a lot of work about it, studied the characteristics of femtosecondlaser, the principle of femtosecond laser induce refractive index modification in thematerial. We have tested the feasible method and conditions of the grating structurepreparation in polymer optical fiber. We do some polymer fiber end processing toachieve a simple butting with silica fiber. And we attempt some corrosion method onsome kinds of polymer fiber to make the diameter size of them changed. We researchthe phase mask method with femtosecond laser. Induce a good and uniform gratingstructure by two ways, as fixed-point exposure and scanning exposure. It can achieve ahigh refractive index modification, legible. It is a Bragg grating structure with a periodof1.665μm. The time of exposure acts on the width of the grating structure by fixed-point exposure. Different laser energy induces different width of the gratingstructure in x-axis direction by scanning exposure. Also we research on theexperimental conditions and the effect of the direct writing method with femtosecondlaser. Achieve a line effect of5-60μm by the way that polymer optical fiber is inair,and a point effect of1μm that in oil. That different diameter size of polymeroptical fiber needs different energy conditions. Research the width of the line effect bydifferent laser energy and laser repetition rate. Attempt to fabricate Bragg gratingstructures by the point effect and long-period grating structure by the line effect. Wecarry on the optical test and spectral detection about polymer optical fiber gratingstructure, but the experimental results is not very satisfactory. Specific analysis thepossible causes that unable to accurately identify the corresponding resonance peaks ofthe grating structure in the spectrum.That the polymer fiber grating structure can be obtained in our research work, inthe study of polymer fiber grating preparation by femtosecond laser, is a quiteexcellent result. And we also have more attempts of method and effect to the polymerfiber grating structure preparation. The work of us expands the way for polymeroptical fiber grating preparation.