Design, Fabrication And Applications Of Graphene Based Mode-locking Fiber Devices

Graphene was discovered in 2004 and since then it has attracted wide attention due to its superior performance in various aspects, and a serious of achievements has been made. Because of the the high transparency, high electron mobility, strong nonlinear Kerr effect and saturable absorption characteristics of graphene, it has wide applications in the optoelectronic field, such as touch-screen, high speed photo-detectors, optical polarizer and mode-lock fiber laser, etc. Also, the excellent properties of the graphene make it suitable for the fabrication of wide bandwidth, high data rate and high responsibility optoelectronic devices.In all the applications, graphene based mode-locked fiber laser is among the attractive ones. Graphene has a strong saturable absorption property and a fast recovery time, which can be used in fiber lasers as the saturable absorber to realize mode-locking and generate ultra-short pulses. The key issues in the fabrication of graphene based saturable absorber are trying to increase the interaction between graphene and the light field, and also, to find the simple, effective method to transfer the graphene samples onto the fiber.In order to enhance the interaction between graphene and light field, and increase the saturable absorption property and modulation depth of the SA, we propose to transfer CVD monolayer graphene onto a moderate-polished D-shape. However, the residual PMMA would increase the scattering and absorption of the light, which realizes a high IL of the SA. As a result, a graphene based SA is obtained with a modulation depth of ~2.5% and an insertion loss of 12 dB.To overcome the PMMA caused absorption and scattering problem and further decrease the loss and optimize the polarizing properties of the SA, we coat the CVD monolayer graphene with 100-nm gold layer to decrease the IL, increase the polarizing property and protect the graphene sample as well. Besides, we modified the fiber polishing process to achieve more stable polished fiber with flatness. We achieve polarized saturable absorber with 5dB IL and 14% modulation depth. 303 fs, 12 nJ and 263 fs and 13.65 nJ soliton pulses are obtained by using the two kinds of graphene saturable absorber as mode-locker in the fiber laser. Further more, we manage the dispersion in the cavity and obtain 105 fs and 7.4nJ ulstra-short pulse. And then we fabricate a fiber laser product using the gold-coated graphene saturable absorber. The stability of the laser product has also been tested.Utilising the multifunctional SA, 51 nm noise-like pulse is generated in a common fiber laser. To demonstrat the potential application in optical sensing and other fields, 1000 nm supercontinuum spectrum is achieved by launching the noise-like pulse into HNLF. Besides we also do some work on graphene SAM. And find that the increasing the modulation depth is the difficulty.