High power femtosecond semiconductor laser based on saw-toothed taper mode-locked laser and amplifier was demonstrated with compressed amplified spontaneous emission (ASE). The external-cavity mode-locked taper laser generated the clean optical pulses without any sub-pulse components. A semiconductor optical amplifier (SOA) with tilted taper waveguide and saw-toothed edge reduced evidently the ASE background. The saw-tooth microstructures were optimized and it was found that the saw-tooth of right-right angled triangle showed the best effect. The ratio of the maximum intensity to background radiation was increased by 21.9% and the power was increased by 30.5% due to the saw-tooth microstructure in the SOA. The pulse duration of 495 fs and a peak power over 1.5 kW with repetition rate of 579 MHz were realized after a double-pass grating compressor.