Study Of Supercontinuum In Tellurite Glass Photonic Crystal Fiber

When a short pulse transmits in a nonlinear medium,frequency spectrum will be broaden because of the dispersion and nonlinear effects in the nonlinear medium.The phenomenon is called Supercontinuum?SC?.Supercontinuum that generated in the Photonic crystal fiber combine the attributes of good coherence,high power and wide spectrum,which make them widely apply in the fields of spectroscopy,optical coherence tomography and military.Tellurite glass has many excellent properties,such as high thermal stability,wide transparency in the infrared region,high nonlinear coefficient and good fiber-forming ability,so it is widely used as the material of Photonic crystal fiber generated supercontinuum.In this paper,a new kind of tellurite glass with the composition of70TeO₂-22ZnO-3Al₂O₃-5La₂O₃?mol%?was fabricated by high temperature melting method.The preparation process and process of melting glass were studied.The transmittance in the mid-infrared wavelength and the dependence of the refractive index with the wavelength of 70TeO₂-22ZnO-3Al₂O₃-5La₂O₃?mol%?were measured.The differential scanning calorimeter?DSC?was studied.The results show that the glass has good glass-formed ability,high refractive index,and high transmittance,which is one of the ideal materials for photonic crystal fiber.The finite element method was analyzed in detail,three different structures of photonic crystal fibers are designed.The effective refractive index,dispersion characteristic,effective mode field and nonlinearity of TZAL photonic crystal fiber are studied.The results show that these characteristics are related to the structure parameters of photonic crystal fiber.By reasonably designing and adjusting the structure parameters of the photonic crystal fiber,a kind of photonic crystal fiber could be obtained which is suitable for supercontinuum generation.From the Maxwell equations,the nonlinear Schrodinger equation for the supercontinuum in photonic crystal fiber was deduced,and several kinds of photonic crystal fibers with different structural parameters are designed.The transmission characteristics of the hyperbolic secant pulse in photonic crystal fiber are simulated by Matlab.The structural characteristics of the photonic crystal fiber,the length of the fiber,the type and arrangement of the air hole in the cladding,the peak power and the pulse width on the supercontinuum are studied.In addition,the innermost cladding of the photonic crystal fiber filled with the liquid oil or the silicate glass also affect supercontinuum.The results show that the reasonable parameters of the photonic crystal fiber,the length of the fiber and the parameters?peak power,pulse width?of the pump light source can obtain a wide and flat supercontinuum.The photonic crystal fiber of 150?m outside diameter and 25?m core diameter was drawn by using the prefabricated rod with special structure.The supercontinuum of the photonic crystal fiber was studied by femtosecond laser pulses.