Spectral broadening of femtosecond lasers based on the interaction of multiple broadening methods under dispersion equilibrium

Broadband lasers have extensive applications in many fields such as spectroscopy, photochemistry, medicine, and biology, so they have obtained significant attention, particularly for their enormous potential in broadband imaging, pollution monitoring, and semiconductor material processing. This paper presents a 1-micron femtosecond laser with a broadened spectrum, achieved by integrating both intracavity and extracavity spectral broadening methods. Initially, a 1-micron single-mode fiber is introduced into the laser cavity to reduce the total dispersion. Subsequently, the collimated output laser is directed onto a negative dispersion grating. After being reflected by the dual grating system, the laser is measured, all while maintaining a stable mode-locked state. To address spectral distortion caused by the loss in non-target gain intervals, dual filtering is employed to retain only the 1064 nm gain interval. Through the balance between these two negative dispersions, the laser’s spectral width is expanded by approximately six times from its original 5 nm to 30 nm. During the experiments, the laser demonstrated remarkable stability and compared to using only intracavity single-mode fiber expansion or extracavity grating expansion, this approach offers superior results and greater potential. It aids in the precise measurement of pollutants and plays a crucial role in enhancing the resolution of broadband imaging.