| Different from traditional fiber,photonic crystal fiber possesses some excellent characteristics,such as high birefringence,high nonlinearity,chromatic dispersion controllable and endlessly single mode transmission,and it has unparalleled advantages in optical signal transmission and optical sensing.With the development of the application filed on photonic crystal fiber,the design,analysis and application of new type photonic crystal fiber become one of the hot research fields in recent years.The precise numerical calculation methods are adopted to calculate the optical properties of the new type photonic crystal fiber,and the application of the new type photonic crystal fiber is also studied systematically.The main research results are as follows:(1)A polarization splitter based on a new type of dual-core photonic crystal fiber(DC-PCF)is proposed.The effects of geometrical parameters of the DC-PCF on performances of the polarization splitter are investigated by finite element method(FEM).The numerical results demonstrate that the polarization splitter possesses ultra-short length of 119.1 ?m and high extinction ratio of 118.7 dB at the wavelength of 1.55?m.Moreover,an extinction ratio greater than 20 dB is achieved over a broad bandwidth of 249 nm,i.e.,from 1417 nm to 1666 nm,covering the S,C and L communication bands.It has a potential application in promoting the large capacity and the integration development of the optical communication system.(2)Through filling the liquid crystal into the air holes of a dual-core holey fiber with a simple structure,the transmission mechanism of the fiber is changed from total internal reflection to photonic bandgap(PBG),and a polarization splitter based on the liquid crystal-filled dual-core PBG holey fiber is investigated.The results demonstrate that,by setting appropriate geometrical parameters,the polarization splitter possesses a short length of 890.5?m,and its wide bandwidth of ~150 nm almost covers all the S,C,and L communication bands.Besides,it has an excellent electro-interference resistance property and certain sensitivity to temperature.(3)An asymmetrical dual-core photonic crystal fiber(DC-PCF),which possesses all circular air holes,is proposed.By setting appropriate geometrical parameters,the wavelength-selective coupling property is realized,and a compact optical filter with a short length of 1.83 mm based on the DC-PCF is designed.The spectral transmission characteristics of the filter are investigated by the beam propagation method.The results demonstrate that the optical filter possesses a bandwidth of 58 nm and small sidelobes.The proposed optical filter could be used in the integrated optical systems.(4)By using an As2Se3 based photonic crystal fiber(PCF)with a normal flat dispersion profiles,a flattened and broadband mid-infrared super-continuum generation is investigated.The transmission of an ultra-short pulse in the PCF is numerically simulated by solving the generalized nonlinear Schr?dinger equation under various parameters.The results demonstrate that,by launching a pulse with a width of 50 fs and a peak power of 4.25 kW at 4375 nm into the 6 mm-long PCF,a flat and broadband super-continuum at 3dB level is successfully generated.The super-continuum covers the wavelengths from 3866 nm to 5958 nm(about 2092nm)which is the largest flat bandwidth reported in such a short fiber,to the best of our knowledge.It has a potential application in the fields of material structure detection,biomedicine,food quality control and environment monitoring,etc. |
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