Ultraviolet-Visible-Enhanced Fiber Supercontinuum Source

Supercontinuum(SC)generation has attracted a great deal of scientific attention over the past few decades due to its characteristics of good spatial coherence,high brightness and broad bandwidth.SC,especially in the visible spectral range,possesses great po-tentials of application in plenty of fields,including optical frequency combs,optical coherence tomography,frequency metrology,hyper spectral microscopy and so on.Photonic crystal fibers(PCF)have been proved to be the excellent media for SC gen-eration because of the design flexibilities in their dispersion and nonlinearity,since the first observation of visible SC generation in PCF in 1999.In this thesis,we investigate the visible SC generation for enhancing the blue edge theoretically and experimentally.The main innovative achievements of this dissertation are presented as follows:1.The generalized nonlinear Schrodinger equations(GNLSE)are described in de-tail.And the nonlinear processes that are involved in the SC generation are introduced.The physical mechanisms of SC generation in optical fibers pumped by ultrashort pulses and long pulses are reviewed.Then the temporal and spectral evolutions of the input pulses are simulated based on GNLSE by MATLAB and the influences of differ-ent pulse parameters and fiber length on the SC generation pumped by long pulses are analyzed.2.An ultraviolet-visible-enhanced SC generation,which is pumped by a nonlinear polarization rotation(NPR)mode-locked Yb-doped fiber laser,is obtained in a uniform PCF with no post-processing.An extremely broad spectrum spanning from 380 nm to 2400 nm with the total average output power of 3.3 W is obtained.Over 35%of the output power is located in the 380-700 nm band.3.An ultraviolet-visible-enhanced SC generation is demonstrated by launching 1064 nm semiconductor saturable absorber mirror(SESAM)mode-locked laser pulses with high peak power into a PCF which is the same as that described above.A total output average power of 2 W with the spectrum range from 350 nm to 2400 nm is obtained.4.The high peak power picosecond laser pulses at 1064 nm based on dispersive wave are adopted as the pump to generate a visible-enhanced SC in a PCF which is the same as that described above.The total average output power can reach 1.5 W and the corresponding spectrum is from 400 nm to 2400 nm.