Research On Large Mode Area Dispersion Shifted Fiber For Fiber Laser

Fiber lasers play an important role in the manufacturing industry,military and biomedical fields due to their high beam quality,small volume,high efficiency,and fast heat dissipation.It is still the challenges that high beam quality at high power and the generation of ultrashort or ultrafast pulses at 1.064?m.The large mode area single mode fibers and the dispersion-managed fibers are introduced to solve the nonlinear effects and negative dispersion at 1.064?m.Increasing the mode area is considered to be the most effective way to solve the nonlinear effects of power boosting of high-power fiber lasers.Many types of large mode area fibers have been proposed.However,most of the large mode area fibers focus on the single mode operation and ignore the dispersion characteristics.This has led to ultrafast fiber lasers requiring external dispersion compensation fibers,which breaks the integrity of the system and eliminate the advantage of the all-fiber design.This dissertation proposes a modified leaky multi-trench fiber(MTF)with rod-arrays which can achieve large mode area single mode operation and manage chromatic dispersion.This fiber is composed of low refractive-index leaky multi-trench,high refractive-index rod-arrays and a cladding.The rod-arrays consists of germanium-doped rod and arrange along the x-axis direction in the leak path of the trench,the trench is fluorine doped,and the cladding substrate is silicon dioxide.The germanium-doped rods and multi-trenches can be formed by Modified chemical vapor deposition(MCVD).The leaky multi-trench can be fabricated by carving grooves in Multi-trench fibers and inserting rods into these grooves.The high-order modes can be removed efficiently by leaky multi-trench.Moreover,the chromatic dispersion can be managed by controlling the rod-arrays.The effects of the structure parameters have been studied in detail by using the full vector finite element method(FEM).Through optimizing the parameters,the fiber can shift the zero chromatic dispersion wavelength to 1.064?m and reach 1051?m~2 mode area at 30 cm bending radius with effective single mode operation.The modified MTFs can be further applied to high power fiber lasers and amplifiers.