The collaborative work of professor Wang Ping and professor Lei Ye from Huazhong University of Science and Technology, China, and assistant professor Wei Bao from electrical and computer engineering at UNL, published online their breakthrough results inOptica(IF: 9.778, flagship journal of OSA). This research work demonstrated a far-field label-free super-resolution transient absorption microscopy imaging technology (STAN). It realizes far-field high-resolution imaging of two-dimensional materials and down to 50 nm, a thousand time smaller than human hairs, providing important tools for super-resolution optical imaging and characterization of emerging materials.
Nano imaging or characterization is one of the main directions for the development of advanced materials. Although great progress has been made in electron microscopy and atomic force microscopy, the requirements for sample preparation and imaging conditions are high. Although the direct far-field optical microscope is easy to operate and has superior time and spectral resolution, the inherent optical resolution limit limits its use. Therefore, the tools currently used to characterize nanomaterials still rely heavily on SEM, TEM and AFM.
The super-resolution transient absorption microscopy (STAN for short) proposed by the team is based on the saturated absorption effect, which achieves an ultra-high spatial resolution comparable to that of a near-field optical microscope. By introducing short-wavelength vortex light as saturated light, the transient absorption transition driven by near-infrared (NIR) photons at the periphery of the focus is effectively suppressed, and the effective focal spot volume is reduced, making the transient absorption microscope based on near-infrared laser a breakthrough Diffraction limit resolution. The team used the system to actually image a single nanoparticle of graphene and found that the image resolution increased with the increase of the saturated optical power, and finally achieved a horizontal resolution of 36 nm.
Fig. 1. Schematic of saturated transient absorption nanoscopy (STAN).a, Principle of STAN system；b, Energy diagrams；c, Real experimental schematic diagram of the STAN setup.
Fig. 2. Super-resolution imaging of graphene nano-grains (a-e) and monolayer graphene (f-h).
Fig. 3.Ping’s Lab in Huazhong University of Science and technology.
The Doc. Yali Bi, Chi Yang and Lei Tong are the first authors with same contribution. Prof. Wang Ping, Prof. Ye Lei, and Prof. Bao Wei are the corresponding authors. This work is in cooperation withProfessor Yi Wang from Huazhong University of Science and Technology, China.The Wuhan National Laboratory for Optoelectronics of Huazhong University of science and technology is the first unit.
The research work has been strongly supported by the the National Natural Science Foundation of China (61675075, 61704061, 61974050); National Key Research and Development Program of China (2016YFA0201403); Science Fund for Creative Research Groups of China (61421064); Innovation Fund of the Wuhan National Laboratory for Optoelectronics; University of Nebraska-Lincoln Startup Fund.
Article links
Y. Bi, C. Yang, L. Tong, H. Li, B. Yu, S. Yan, G. Yang, M. Deng, Y. Wang, W. Bao, L. Ye, and P. Wang, "Far-field transient absorption nanoscopy with sub-50  nm optical super-resolution," Optica 7, 1402-1407 (2020).
https://www.osapublishing.org/optica/abstract.cfm?uri=optica-7-10-1402
