Study On Ultra-short Optical Pulse Generation

Ultra-short pulse source, which is one of the key techniques in high-speed optical communication system, has become the hotspot in the current research. And with the development of high-power fiber laser and amplifier, the ultra-short pulse generation technology is of great importance now. The presented dissertation focuses on the generation of ultra-short pulse and optical pulse compression techniques in fiber by theoretical analysis and experiments, and the main contents are as follows:1. SESAM passively mode-locking techniques1) Numerical simulation on passively mode-lock fiber lasers with SESAM is carried out by using the nonlinear Schrodinger equation (NLSE). The evolvement processes of the mode-locked pulse shape with different gain and dispersion are presented in the simulation.2) Based on an SESAM mode-locked fiber ring laser, steady mode-locking pulses at 97.7MHz repetition rate with central wavelength of 1567.6nm are obtained when the pump power is 30mW.2. Nonlinear polarization rotation passively mode-locked fiber laser1) Operation principle of a nonlinear polarization rotation passively mode-locked fiber laser is investigated theoretically by solving temporal mode-locking equation.2) Stable, self-starting mode-locked pulse train at 14.49MHz repetition rate with central wavelength of 1563.3nm, pulse-width of 330.5fs and spectral width of 14.4nm is obtained when the pump power is as small as 23mW. The influence of coupling ratio on mode-locked pulse is experimentally investigated too.3) The ultra-long cavity passively mode-locking laser is obtained with 420m HNLF. And the single pulse energy has achieved 12nJ when the repetition rate is 444kHz, the pulse quality gets better, and the pulse frequency spectrum is smoother.4) An S-band passively mode-locking fiber laser based on the W-type EDF is obtained with repetition rate at 12.5MHz and central wavelength of 1525nm.5) High erbium-doped fiber and high nonlinear fiber (HNLF) are used to get dual-wavelength and trial-wavelength mode-locking states.3. Optical pulse compression techniques based on SOA 1) The chirp imposed by the semiconductor optical amplifier (SOA) on the optical pulse propagating in it has been analyzed using the classical partition model. Moreover, the basic principle for optical pulse compression using SOA is also analyzed.2) Simulations prove that the new optical pulse compression based on the SOA is feasible. Under the different pump power and injection current condition, an optical pulse with pulse-width of 25ps can be compressed into about 3ps by an SOA and a piece of standard single-mode fiber with resonable length, and the compression factor achieves 8.3.