Thin film materials with large optical nonlinearity and ultrafast response are required as the promising candidates for future integrated photonics applications like all-optical neural network. Recently, the two dimensional layered transition metal dichalcogenides (TMDs) and black phosphorus (BP) have attracted much attention due to their unique electronic, optical, mechanical, chemical and thermal properties. We investigated the optical nonlinearity of mono- and few-layer WS2, MoS2 and PtSe2 using the Z-scan technique with femtosecond pulses. The monolayer WS2 exhibited giant optical nonlinearities. The mechanism of the optical nonlinearity was discussed in detail. We have obtained the ground-state absorption (GSA) and excited-state absorption (ESA) cross section of BP nanosheets. It is clear that the ESA/GSA ratio of BP is the smallest. The superior saturable absorption performance of BP over MoS2 and graphene can be well explained from this perspective. We also demonstrated that the nonlinear optical technique, in conjunction with ultrafast carrier dynamics measurement, was able to quantitatively determine the transition point from semiconductor to semimetal in the layered PtSe2. The results fundamentally support 2D materials to be used in optical devices, such as fiber laser mode-locking, Q-switching, all-optical switches, etc.
张赛锋，上海光学精密机械研究所副研究员。2002—2006年，上海大学物理系本科；2007—2012年，复旦大学物理系博士研究生；2012—2014年，上海光机所助理研究员；2014年至今，上海光机所副研究员，中科院青年创新促进会会员。在ACS Nano, Nature Communications, Physics Review Letters, Laser&Photonics Reviews, Nanoscale等期刊发表SCI论文30余篇，2篇入选“ESI高引论文”，被Phys. Rev. Lett., Nano Lett., Phys. Rev. B等期刊正面他引800余次，申请发明专利5项。主要研究二维层状材料的光学非线性效应、超快动力学过程，低维半导体中激子等准粒子的光谱特征、光电特性及器件应用。