Abstract-Saturated absorption of different layered Bi2Se3 films in the resonance zone [Invited]

Jun Zhang, Tian Jiang, Tong Zhou, Hao Ouyang, Chenxi Zhang, Zheng Xin, Zhenyu Wang, and Xiang’ai Cheng

http://65.202.222.105/prj/abstract.cfm?uri=prj-6-10-C8

Here, we used the micro P-scan method to investigate the saturated absorption (SA) of different layered Bi2Se3${\mathrm{Bi}}_2{\mathrm{Se}}_3$ continuous films. Through resonance excitation, first, we studied the influence of the second surface state (SS) on SA. The second SS resonance excitation (∼2.07  eV$\sim 2.07\mathrm{eV}$) resulted in a free carrier cross section that was 4 orders of magnitude larger than usual. At the same time, we found that the fast relaxation process of the massless Dirac electrons is much shorter than that of electrons in bulk states. Moreover, the second SS excitation resonance reduced the saturation intensity. Second, we studied the effect of the thickness on the SA properties of materials. The results showed that the saturation intensity was positively correlated to the thickness, the same as the modulation depth, and the thicker the Bi2Se3${\mathrm{Bi}}_2{\mathrm{Se}}_3$ film was, the less the second SS would influence it. This work demonstrated that by using Bi2Se3${\mathrm{Bi}}_2{\mathrm{Se}}_3$ as a saturable absorber through changing the thickness or excitation wavelength, a controllable SA could be achieved.

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