| Since it was proposed,photonic crystal fibers have attracted much attention in the fields of optics,communication,material detection and so on.With the deepening of related research,the focus and difficulty of research has shifted from solid-core photonic crystal fiber to hollow-core photonic crystal fiber.Previous studies on hollow-core photonic crystal fiber mainly focus on the study of hollow-core photonic crystal fiber with multilayer air holes in the cladding.In this paper,Based on the transmission mechanism between multilayer air holes hollow-core photonic crystal fiber and single layer air hole hollow-core photonic crystal fiber,the principle of eliminating surface mode and the transmission mechanism of single layer air hole hollow-core photonic crystal fiber were studied.In view of the simplification of hollow-core photonic crystal fiber structure,preparation and expansion of hollow-core photonic crystal fiber wavelength conversion,the core innovations and corresponding research results of this paper are as follows:1.To study light-guiding mechanism of hollow bandgap photonic crystal fiber,kagome-latticed fiber and hollow core antiresonant photonic crystal fiber,we analyzed the structure characteristics of these three kinds of hollow fibers and the controversial issues about the light guide mechanisms in the existing literature.Differences and connections have been found in some parts of the three hollow core photonic crystal fibers,such as the shape of the core,the thickness of the core-wall,the gap-holes between the cladding air holes and the number of layers of the air holes in the cladding,then the influence of different structural parameters on the transmission cha-racteristics of optical fiber is also studied by using the finite element method.Finally a conclusion was found that the transmission characteristics of the three fibers can be explained by using the theory of‘‘antiresonant reflective waveguide”.The common character of the three is that the wall thickness of the fiber core is the key factor that determines the transmission wavelength and bandwidth of the fiber.2.In order to study the four wave mixing effect and wavelength conversion in a hollow core gap photonic crystal fiber filled with argon,we conducted an experiment using a femtosecond laser with the pulse width of 120 fs,a repetition rate of 76 MHz,tunable central wavelength from 760 nm to 980 nm.It is observed that both sides of the pump generated new spectra at some special wavelength,which can exactly satisfy the phase matching conditions of four wave mixing.Combined experimental results with theoretical analysis,we find that the experimental phenomenon is mainly caused by four wave mixing,but some other nonlinear phase effects such as self-phase modulation,stimulated Raman scattering and soliton effect have also occurred in this nonlinear process.3.We present a new suspended core photonic crystal fiber,which has the advantages of simple structure,wide bandwidth,dispersion compensation,low loss and high nonlinear coefficient.The suspended core fiber can be transmitted at the wavelength of 0.7?m-2?m for single mode,the dispersion can reach-500 ps/nm/km at 1550 nm,and the nonlinear coefficient is always greater than 50 w-1km-1.The most interesting characteristic of air-hole guide light is studied.We analyzed the change rule of energy share in air holes for different wavelengths,then the distinctive propagation mechanism is analyzed by evanescent wave coupling.The transmission parameters show many anomalous rules when the power ratio in air holes is greater than 15%.In addition,a modified structure is proposed for reducing the loss and increase the energy in holes,and the technique of stacking method for drawing the suspended core optical fiber is discussed. |
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