Experimental Research On High Average Power,Low Noise Yb Doped Femtosecond Fiber Laser

Mode-locked rare-earth-doped fiber laser can be used for the generation of femtosecond laser pulses. It has a number of advantages such as small size, low cost, high stability, high beam quality, maintenance-free and so on. It has find many applications in research, industrial, military and medical field. With the invention of double-cladding fibers and photonic crystal fibers, fiber amplifiers are able to endow the high power laser system with these advantages and enable an age of rapid development in recent years.The thesis focuses on the femtosecond ytterbium doped fiber laser and the amplifier of optical frequency comb(OFC). The detailed work in this thesis includes: 1. The principles and applications of OFC were introduced. The high power OFC system and the experiment concerning the low-noise OFC were summarized. 2. The theory concerning the low-noise OFC was introduced. Then the mode-locking principle and devices for dispersion compensation were expounded. A fiber laser was built using the nonlinear polarization evolution(NPE) method, which produced a 63 fs laser pulse at 250 MHz pulse repetition rate. It has an average power of 270 m W and an optical spectral bandwidth of 45 nm. 3. A double cladding fiber amplifier was built using the nonlinear chirped pulse amplification(NCPA) technique. When the seed laser power was 270 m W and the pump power of amplifier was 7 W, it produced a 93 fs pulse with a 2.3 W average power and a spectral bandwidth of 33 nm. The relation between the pre-chirp quantity and FWHM optical spectral bandwidth of pulse after amplified was also studied. 4. To achieve a higher average output power, a photonic crystal fiber amplifier was built using the nonlinear amplification technology. It produced a 66 fs pulse with a 23 W average power and a spectral bandwidth of 28 nm when the pump power of amplifier was at 60 W. The relationship between the pulse width and the pump power was studied. The reason why the center frequency of the optical spectrum varies during the amplification process was discussed.