摘要： Modulation instability is responsible for the symmetry breaking of homogeneous spatio-temporal states or wave envelopes and the formation of stable patterns in a variety of physical media. Recently, by using this phenomenon in laser physics, remarkable developments have been made based on the use of the effect of self-phase modulation in Mamyshev oscillator [1-3]. The oscillator is designed using a spectral filter and a gain to compensate for filtering losses. By mismatching spectral filter offsets, entire cavity works as an element with the power-dependent transmission, suppressing the continuous wave lasing and favouring the formation of ultrashort pulses. Recently application of semiconductor optical amplifiers (SOA) as a gain media in fibre lasers as a gain medium has drawn a new wave of research attention due to their potential applications in telecommunications, all-optical square-wave clocks, range finding, and optical sensing. In this work, we developed a Mamyshev oscillator based on SOA operating in square pulses and high harmonic generation at 1550 nm.