Objective To build a low repetition rate femtosecond fiber laser with its pulse width narrower than 200 fs and pulse energy bigger than 50 nJ and realize making blasting holes on pig cornea by optical expanding and focusing femtosecond laser. Methods Experimental study. Introducing very long polarization maintaining fiber into the ring cavity， the mode-locking fiber laser under the similariton amplifier scheme was used to be the oscillator. The signal laser was amplified and compressed by propagating it through the construction of pre-chirp， amplifier and de-chirp to realize outputting high quality pulse train. The high power fiber laser was expanded by the lens group. The expanded laser beam was focused into the pig cornea by the plane objective with different numerical aperture （NA） to realize making high quality blasting holes. Results This laser facility realized outputing a very stable 19.1 MHz， 109 fs， 1.4 W， 73.2 nJ mode-locking fiber laser. After five fold expansion， the laser beam was focused into the pig cornea by the NA=0.2 plane objective to get blasting holes whose aperture were 45~75 µm. Focusing the laser beam into the pig cornea by the NA=0.5 plane objective， the aperture of the blasting holes were about 30 µm. Conclusion Introducing very long Polarization Maintaining fiber into the similariton amplifier ring cavity can improve stability effectively. The construction of pre-chirp， amplifier and de-chirp can use the nonlinear affects to depress the third order dispersion to realize high quality amplify and compression. After expanded by lens group， using higher NA plane objective to focus the expanded laser beam into the cornea can realize making higher quality blasting holes.
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