The Mechanisms Of The Third-Order Nonlinear Optical Absorption Of 2D Materials

As a graphene-like material,various types of two-dimensional materials have excellent nonlinear absorption characteristics such as fast recovery time,large modulation depth,tunable saturation light intensity,wide spectral response range,and strong nonlinear polarization,which have great potential in optical modulator fabrication.In addition,on the one hand,the traditional saturable absorber for laser Q-switching and mode-locking both of which generate laser pulses has reached the performance bottleneck.On the other hand,the main component of the optical neural network that can surpass the performance of the traditional electronic computing architecture--nonlinear activators are in the ascendant.Above all,the development of new optical modulators has far-reaching implications.At present,the most three concerned two-dimensional materials in the field of nonlinear optics are perovskites,transition metal chalcogenides and topological insulators.However,they are very different from the traditional bulk materials in carrier dynamics and band structure,and each of the three types of materials has its own characteristics.The nonlinear absorption theory based on traditional bulk materials needs to be improved,and the detection methods urgently needs to be optimized.The subject is based on the problems of the three types of materials which are urgely to be solved in the field of nonlinear absorption research.The self-designed micro P-scan system is used to carry out related work.The results are as follows: 1.A micro P-scan system for the characterization of nonlinear absorption and refractionof micron-sized two-dimensional materials is constructed.2.The specific influence mechanism of material thickness on the nonlinear opticalproperties of perovskite structural material CsPbBr3 is revealed.3.The laser pulse width affects the physical nature of the nonlinear absorptionproperties of the transition metal chalcogenide MoS2 is studied.4.The effect of the massless Dirac electrons on the nonlinear absorption of the secondsurface state of the topological insulator Bi2Se3 is analyzed.The above work provides theoretical support for the development of new generation optical modulators based on the third-order nonlinear optical absorption effect of two-dimensional materials.