Research On Dispersion Properties And Ultrashort Laser Pulses Propagating In Microstructure Fibers

The research achievements of photonic crystal fibers (PCFs) during several years are particularly surveyed in this paper. A fast vector method by which simulating PCFs dispersion has been established. The flattened chromatic dispersion and compensating properties of PCFs are simulated and analyzed. For the first time to our knowledge, it is put forward that generalized nonlinear Schrodinger equation (GNSE) can be resolved by the adaptive split-step Fourier method (ASSFM) in this paper. It is simulated and analyzed that laser pulses with different parameters transmit in PCFs when varying their dispersion by ASSFM. The fabrication of microstructure fibers and integrated microstructure fibers in our group is reported. We have done the experiments of femtosecond laser pulses propagating in these fibers and given the explanation to the phenomenon. First, basing on scalar approximation the dispersion properties of PCF's with lower air filling fraction are investigated and analyzed by an effective index approach in this paper. Second, a fast vector method by which simulating PCFs Dispersion is put forward in this paper. The correctness and reliability of the fast vector method can be validated by comparing with the results obtained from biorthonormal-basis method, plane-wave method and experiment results. Rationality and necessity of synthetic material dispersion have been validated by comparing the results from different methods. For high accuracy at larger air-filling fraction or lower normalized wave-number A/λ it is necessary that the vector method is used to simulate the dispersion of PCFs. Under the same precision the CPU time about plane-wave method is 12~14 times of vector method. The fast vector method can be used to simulate PCFs dispersion in real time. Third, the dispersions of fundamental mode in PCFs are computed with the fast vector method in this paper. It is found that the dispersion property of PCF's can be modulated effectively by changing the pitch and the air hole size in PCF's cladding. We can design PCF's with closing to zero and flattened chromatic dispersion in wavelength division multiplexing waveband of optical communication. We can design PCF's not only with closing to zero and flattened chromatic dispersion but also with two zero-dispersion wavelengths at the wavebands of all visible and near-infrared. It is found that the dispersion, dispersion slope, and Kappa parameter of PCFs can be designed neatly by changing the air hole size and the pitch in PCFs cladding. Basing on the compensated fiber dispersion parameters we can design the PCFs with optimized combination of the dispersion, dispersion slope, and Kappa parameters. Forth, for the first time to our knowledge, it is put forward that GNSE can be resolved by the adaptive split-step Fourier method basing on split-step Fourier method in this paper. It is found that ASSFM must be used to resolve GNSE for precision when the frequency shift corresponding to soliton peak value is remarkable and PCFs' parameters change along with frequency remarkably. The precision of numerical simulation by ASSFM is higher than SSFM in the process of laser pulses propagating in the PCFs. Fifth, It is simulated and analyzed that laser pulses with different parameters transmit in PCFs' different dispersion regions by ASSFM. It is found that the influence of initial durations, peak powers and frequency chirping on laser pulses evolution is different in PCFs' different dispersion regions. If we want to obtain optimization supercontinuum when laser pulses transmitting in PCFs, we not only choose the PCF with optimum parameter but also choose optimum pulses. Supercontinuum generation in photonic crystal fibers is a systems engineering of multiple parameters optimum combination. Sixth, the fabrication of microstructure fibers and integrated microstructure fibers is reported. We have done the experiments of femtosecond laser pulses propagating in these fibers and observed supercontinuum phenomenon. It is found from experiments that not only PCFs with periodic...