The Features Of Cross Absorption Modulation Of Graphene And Its Application In Synchronization Of Laser

The progress of ultrafast science and technology has pushed the resolution of time to subfemtosecond and attosecond region. Meanwhile, the progress in ultrashort pulse technology make it easier to fabricate femtosecond lasers. However, in many field of scientific research, not only the ultrashort laser pulses, but also the multicolor laser pulses of precise synchronization are needed, such as ultafast laser spectroscopy, multicolor pump probe research, the coherent anti stokes raman scattering microscope, the generation of mid-infarared based on nonlinear frequency conversion, terahertz source generation and so on. Fabrication of synchronized mode-locked fiber laser, which has low time-jitter and long length of mismatch, has been a hot issu studied by scientists. Here, we have fabricated an all optical modulator made of graphene and micro-nanofiber based on the cross absorption modulation of graphene. And we have done some experiments related to laser pulses of synchronization by this modulator. The main reserch contents are illustrated as follows:1. Based on the zero band gap of graphene, we have successfully fabricated a broadband all optical modulator, which was made of micro-nanofiber covered by graphene. According to the result of research, we found that graphene not only has saturable absorption properties, but also has cross absorption modulation. That is to say, the transmission of signal light through graphene varies with its power, and it will vary with the power of different wavelength modulation light. We have used continuous waves modulation light and rectangle pulses modulation light to study the modulation property of graphene, we have successfully test the time response ability and modulation depth of the all optical modulator made by ourselves.2. We have designed a actively Q-switched ytterbium-doped fiber laser by the all-optical graphene modulator, which has injection cavity structure. The output laser of a passively Q-switched erbium-doped fiber laser served as the modulation light.We have realized the synchronization of 1550 nm and 1060 nm Q-switched pulsessuccessfully. The repetition rate of 1060 nm pulses can be modulated by 1550 nm laser pulses from 30.32 kHzto 101.29 kHz. Besides, we have fabricate a common cavity structure erbium-doped and ytterbium-doped dual wavelength synchronized Q-switched fiber laser.3. We fabricated an all normal dispersion ytterbium-doped and a negative dispersion erbium-doped mode-locked fiber laser based on saturable absorption of graphene. The two fiber lasers output dissipative soliton and soliton laser pulses respectively. Because of the zero band gap of graphene, it has broadband saturable absorption property. We have fabricated a sharing cavity structure to share a common graphene and realize 1550 nm and 1060 nm mode-locked pulses at the same time,which is essential to the realization of synchronized mode-locked laser pulses.4. In order to measure the timing-jitter of the synchronized mode-locked laser pluses, we constituted a cross-correlation device corresponding to 1550 nm and 1060 nm laser pulses. And we analysised the theory of the cross-correlation technique to measure the timing-jitter, which provided scientific basis to test the result of synchronization.