Passive synchronous ultrashort pulse fiber laser based on dual wavelength cross absorption modulation theory

In this work, we propose a theory of ultrafast dual wavelength pulsed laser modulation. The modulation effect of modulated light on signal light is studied based on a four- level cross absorption modulation system with the principle of in band relaxation and inter band Pauli incompatibility in single-layer graphene. The study find that the signal saturation absorption decreases with the increase of modulation intensity; In addition, modulation light and signal light also affect each other's transmittance. The model of dual wavelength synchronous laser based on modulation theory can obtain stable output. Under the guidance of this model, we have built passively Q-switched synchronous erbium-doped and ytterbium doped fiber lasers. With the increase of pump power, the repetition rate of synchronous pulses changes from 24.50 kHz to 39.90 kHz. The laser has potential applications in Raman scattering spectroscopy, multicolor pump detection spectroscopy and nonlinear frequency conversion.