Research Topics

Since one of the major expertise of Prof. Tsing-Hua Her is in the laser ablation and micromachining of 3D bulk materials, during 2018-2022, we extended from that field to investigate the strong-field physics of 2D materials, such as the most popular 2D material: graphene and a variety of transition metal dichalcogenides TMDs (MoS2, WS2, MoSe2, and WSe2). This work is an international multi-cooperation project. 2D TMD samples were supplied by Prof. Wen-Hao Chang (National Yang Ming Chao Tung University, NYCU, in Taiwan), while parts of 800-nm laser-ablation experiments with variable pulse durations were proceeded by Prof. Chih-Wei Lou (NYCU). We discovered that several mechanisms play the important roles in the optical dielectric breakdown of 2D materials. Firstly, instead of complicated wave propagation in 3D materials (accompanied with the effects listed above) that is required nonlinear Schrödinger equation for description, the field in 2D materials becomes quasi-static because of strong etalon effect. Several our experimental results regarding this issue have been published in “AIP Advances” (AIP Adv. 12, 015217 (2022)) and “Scientific Reports” (Sci. Rep. 12, 1-9 (2022)). Secondly, many nonlinear optical processes, such as multiphoton and tunneling ionization, plasma heating, and the subsequent avalanche ionization in 2D materials change significantly from their counterparts in 3D cases. It is because of the change of dimensionality (3D→2D) and the significant exciton effect under strong quantum confinement. Therefore, several necessary modifications on the existed theoretical models for 3D materials are required. Prof. Her and I have completed parts of preliminary works and we will devoted to comparing the theoretical predictions and experimental results in the following several years.