Self-similar Pulse Compression And Supercontinuum Generation In Noval Photonic Crystal Fiber

Ultrashort pulses have a lot of important applications in supercontinuum generation,frequency comb generation,biological imaging.Currently,the usual methods of pulse compression have specific disadvantages:long nonlinear media are always required in adiabatic soliton compression which is not realistic for integrated applications.The quality of compressed pulse is usually not very good after higher-order soliton compression so that many applications will be limited.Comparatively,self-similar pulse compression can obtain compressed pulse with high quality and a short medium.Supercontinuum with highly coherence has a lot of applications in frequency comb generation,light source,measurement etc.Pulse propagation in nonlinear media with all-normal dispersion can effectively reduce soliton effect and increase coherence.Single-polarization supercontinuum is attracting reseachers'attention now.High birefringence photonic crystal fiber(PCF)with different dispersion charateristics in two polarization directions is an effective medium for single-polarization supercontinuum generation.Therefore,we can obtain supercontinuum with different characteristics in different polarization directions.Self-similar pulse compression and supercontinuum generation in noval PCF is researched in this paper.The corresponding research contents and results are arranged as follows:1.A tellurite tapered PCF which satisfied the self-similar conditions has been designed.And the propagation dynamics with 1-ps pulse in the fiber have been researched.Simulation results show that 1-ps pulse can be compressed to 62.16 fs at wavelength 2.5 ?m with compression factor of 16.09 and compression quality of 83.16%is get.Futhermore,we have analyzed that higher-order dispersion and loss are the most important factors influencing the compression factor and compression quality,respectively.2.A tellurite PCF has been designed.And the pulses of 1 ps and 62.16 fs before and after compression into the PCF are pumped in order to analyse the differences of their coherence.As a result,we find that narrower pulse can improve the coherence a lot.3.A tellurite PCF with an all-normal dispersion has been designed.And the relationship of different pumping wavelength,different pulse width,different peak power with supercontinuum generation have been analyzed.Simulation results show that when pumping in longer wavelength with narrower pulse and higher peak power is benifical for wider supercotinuum.4.A polarization-maintaining PCF with CS2-core has been designed.The relationship of different fiber structure parameters with dispersion and nonlinear coefficient has been analyzed.Finally,the fiber structure with all-normal dispersion in x-polarization direction and two zero dispersion points in y-polarization direction is chosen.The influence of different fiber lengths,different pumping pulse widths,different peak powers on supercontinuum has been analyzed.Simulation results show that when a pulse with width of 80 fs and pumping peak power of 1 kW into a 4.5 cm fiber is pumped,the supercontinuum range of x polarization direction(1.36-2.24 ?m)and y polarization(1.13-2.71 ?m)at-30 dB is obtained respectively.Self-similar pulse compression and supercontinuum generation in the thesis can not only enrich the theories and methods of pulse compression,but also provide solutions for large bandwidth,highly coherence and single-polarization supercontinuum generation.Our researches will develop important applications in optical frequency comb generation,optical precision measurement and bio-optics.