Contrast-enhanced phase-resolved second harmonic generation microscopy

• Published in: Optics letters Vol. 49; no. 8; p. 2117
• Main Authors: Wang, Zhanshan, Hong, Canyu, Sun, Zeyuan, Wu, Shuang, Liang, Bokai, Duan, Xidong, Liu, Wei-Tao, Wu, Shiwei
• Format: Journal Article
• Language: English
• Published: United States 15.04.2024
• ISSN: 1539-4794
• DOI: 10.1364/OL.520814

The characterization of inverted structures (crystallographic, ferroelectric, or magnetic domains) is crucial in the development and application of novel multi-state devices. However, determining these inverted structures needs a sensitive probe capable of revealing their phase correlation. Here a contrast-enhanced phase-resolved second harmonic generation (SHG) microscopy is presented, which utilizes a phase-tunable Soleil-Babinet compensator and the interference between the SHG fields from the inverted structures and a homogeneous reference. By this means, such inverted structures are correlated through the π-phase difference of SHG, and the phase difference is ultimately converted into the intensity contrast. As a demonstration, we have applied this microscopy in two scenarios to determine the inverted crystallographic domains in two-dimensional van der Waals material MoS . Our method is particularly suitable for applying in vacuum and cryogenic environments while providing optical diffraction-limited resolution and arbitrarily adjustable contrast. Without loss of generality, this contrast-enhanced phase-resolved SHG microscopy can also be used to resolve other non-centrosymmetric inverted structures, e.g. ferroelectric, magnetic, or multiferroic phases.