| Microstructured fibers have received intense attention due to the unique optical properties and flexible design.Along with the development of the fiber design fabrication technology,various novel fiber structures and materials have been proposed,which greatly promoted the development of fiber-based components.Supported by National Nature Science Foundation Program and oriented to the requirement of optical fiber components with high performance,this dissertation focuses on the theoretical and experimental investigations on broadband dual-core micro structure fiber,dual hollow-core microstructure fiber and high nonlinear fiber.Based on this,ultra-broadband polarization splitter,polarization-insensitive coupler,high-nonlinear fibers and its application in supercontinuum generation are studied.The main achievements of the dissertation are listed as below:1.A dual-core microstructured fiber is designed and fabricated.And a dual-core fiber-based sensor is fabricated by using 15cm long dual-core microstructured fiber.Simultaneous measurement of curvature,strain and temperature can be achieved by monitoring the wavelength shifts of selected valleys in the transmission spectrum.The maximal sensitivities to curvature,strain and temperature are 10.89 nm/m-1,1.24 pm/?? and 73.9 pm/?,respectively.Compared with the traditional dual-core fiber,the dual core microstructured fiber-based sensor has higher sensitivity and better linearity.2.A polarization-insensitive ultra-broadband microstructured fiber with two elliptical fluorine-doped cores is proposed.Based on the proposed fiber,a polarization-insensitive 50:50 coupler is achieved.Its coupling ratio stabilizes at 50%±1%in the wavelength range from 1.255 ?m to 1.725 ?m.And the coupling ratio difference between two polarizations is lower than 0.2%.The mode field area of each core is around 70 ?m,which makes the splice loss caused by mode field area mismatch with single mode fiber lower than 0.02 dB.In addition,the fabrication of elliptical solid core is easier than elliptical air holes.3.A dual-core microstructured fiber with simple structure is proposed.Two fluorine-doped cores are introduced to eliminate its sensitivity to wavelength.In addition,two large air holes are introduced to adjust the coupling between the two cores.The proposed fiber has high compatibility with single mode fibers due to low splicing loss of 0.02 dB.And all of the air holes are circular holes,which makes it easy to fabricate.Numerical results demonstrate that an ultra-broadband splitter with 320 nm bandwidth with an extinction ratio lower than-20 dB can be achieved.And the extinction ratio is as low as-38 dB at the wavelength of 1.55?m.4.A polarization splitter based on dual hollow-core anti-resonant fiber is proposed and numerically investigated for the first time.Two elliptical tubes are introduced to separate the core into two symmetrical cores.And nested tubes are introduced to achieve low confinement loss and good single mode performance.The proposed polarization splitter has a broad bandwidth of 310 nm covering the wavelength range from 1.41 ?m to 1.72 ?m with an extinction ratio as low as-20 dB.And the loss ratio of higher order mode to fundamental mode is larger than 100,which means the proposed splitter also possesses good single mode performance.Moreover,a modified dual hollow-core anti-resonant fiber structure is proposed to further improve the bandwidth to 355 nm.5.An As2Se3-based photonic quasi-crystal fiber with high nonlinearity and birefringence is proposed.Due to the introduction of the large air holes in the cladding,the birefringence reaches up to the order of 10-2,and a nonlinear coefficient up to 2079 W-1km-1 can be achieved at the wavelength of 2 ?m.By using a 15 mm long proposed fiber,polarized supercontinuum can be obtained.The spectral width for x-polarization and y-polarizations covers from 1 ?m to 10.2 ?m and 1 ?m to 12.5 ?m,respectively.The polarization state can be well maintained when the incident angle of the input pulse changes within ±20. |
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