In-situ high-precision surface topographic and Raman mapping by divided-aperture differential confocal Raman microscopy

Highlights: • High-precision surface topographic imaging and Raman mapping data simultaneously in-situ. • The axial focusing ability to 2 nm, which is more than two orders of magnitude higher than that of conventional CRM. • Capable of real-time refocusing to correct the defocus, enabling the minimum excitation spot on the sample. • Suppress background noise interference, Owing to the symmetrical design of the illumination optical path and the collection optical path. Confocal Raman microscopy (CRM) is extensively employed in several fields owing to providing molecular fingerprint information without destroying and labelling samples. Most materials are heterogeneous; therefore, it is important to not only identify the chemical composition of samples, but also acquire high-precision surface topographic information. However, conventional CRM cannot accurately obtain the surface topographies of samples, which restricts the further application. We propose divided-aperture differential confocal Raman microscopy (DADCRM), which combines divided-aperture differential confocal microscopy with CRM. We use the reflected light to achieve accurate focus tracking, which is combined with Raman scattering to perform high-precision surface topographic imaging and Raman mapping simultaneously. The axial focusing ability of the proposed DADCRM system is estimated at 2 nm, which provides inherent anti-drift capability. The abilities of DADCRM to suppress background noise interference and improve stability are also demonstrated. We present in-situ Raman mapping and high-precision surface topographic imaging using DADCRM. These results provide new perspectives for both conventional CRM and CRM-based imaging in various fields.