The invention relates to an intermediate 
infrared femtosecond mode-locked 
laser which comprises a collimating mirror, a focusing mirror, an input spherical surface mirror, a 
laser medium and a spherical surface high-reflection mirror which are sequentially arranged along a direction of a pumping 
light beam outputted by a 
laser diode, wherein lasers in a five-mirror 
laser resonance cavity formed by the input spherical surface mirror, the spherical surface high-reflection mirror, the spherical surface high-reflection focusing mirror, an output 
coupling mirror and a 
graphene mode-locking element is reflected onto the high-reflection focusing mirror through the input spherical surface mirror, is focused on the 
graphene mode-locking element, returns back along the original path by sequentially passing through the spherical surface high-reflection focusing mirror, the input spherical surface mirror, a laser 
crystal and the spherical surface high-reflection mirror, is deflected and reflected to a 
dispersion compensation prism pair by the spherical surface high-reflection mirror, and is output from the output 
coupling mirror through a slit. According to the intermediate 
infrared femtosecond mode-locked laser, 
graphene growing by adopting a CVD (
Chemical Vapor Deposition) method is transferred to a laser 
wavelength high-reflection mirror, and is protected by using 
inert gas, and thus stable mode-locked laser pulse output is realized in an intermediate 
infrared band. The intermediate infrared 
femtosecond mode-locked laser has the advantages of being simple in regulation, low in manufacture cost, and easy to realize single layer (little non-saturated loss).