Objective The femtosecond optical frequency comb (FOFC) comprises a series of ultrashort laser pulses with the same temporal separation in the time domain and discrete, equidistant, and stable phaserelated frequency components in the frequency domain. The FOFC can accurately measure the absolute frequency of an atomic clock and serve as a natural timefrequency reference. Currently, the most stable and compact light source is the modelocked erbiumdoped fiber laser with a central wavelength of 1.55 μm, typically employing highly nonlinear fibers to broaden the spectrum across the entire transparent range of silica fiber (350-2400 nm). However, the output power of the erbiumdoped fiber FOFC is generally in the range of a few hundred milliwatts. Therefore, increasing the output power of the FOFC remains a crucial challenge. The midinfrared FOFC holds significant application value in nextgeneration spectroscopy, as it can be used to detect gases such as carbon dioxide and ammonia and extend the FOFC wavelength to the molecular fingerprint spectrum range (3 -20 μm) through nonlinear crystals. This spectrum range is vital for chemical composition analysis, making the development of highpower midinfrared FOFCs a pressing need.Methods This system comprises an erbiumdoped fiber FOFC, a supercontinuum converter, a doublecladding thuliumdoped fiber amplifier system, and a transmission diffraction grating pulse compressor. Initially, the erbiumdoped fiber FOFC utilizes a
