Modeling of Near-field Optical Contrast and Spectra

Описание: Alexander Govyadinov - attocube Systems AG
key learning objectives:

Understanding the Theory and Models Behind s-SNOM: Sasha delved into various theoretical models used to understand and interpret s-SNOM data. He explained the Point Dipole Model (PDM) and its limitations, particularly in capturing the correct tip-sample distance dependence. He also introduced the Finite Dipole Model (FDM), which more accurately represents the tip-sample interaction by considering a larger effective dipole size. Sasha emphasized that while these models provide a basis for understanding the interaction, they have their specific applications and limitations. For instance, FDM works well for non-resonant materials but may not be effective for materials with strong phonon or plasmon resonances.

Importance of Reference and Normalization in s-SNOM Data Interpretation: Sasha highlighted the crucial role of referencing and normalization in interpreting s-SNOM data. Since s-SNOM does not provide absolute measurements, it's essential to reference the near-field response to a known standard. He discussed the complex normalization process, where the amplitude and phase signals are normalized to a reference measurement. This step is vital for meaningful comparison and interpretation of s-SNOM data, particularly in material characterization.

Practical Approaches and Challenges in s-SNOM Data Analysis: The talk also covered practical aspects and challenges in processing and analyzing s-SNOM data. Sasha discussed the demodulation of s-SNOM signals and how various models can be computationally intensive or straightforward, depending on the approach. He also touched upon the intricacies of indirect illumination in s-SNOM and how it can affect data interpretation. This part of the talk underscored the need for careful experimental setup and post-processing to ensure accurate s-SNOM measurements.

Overall, the talk provided a comprehensive understanding of the theoretical background, practical challenges, and nuances in analyzing and interpreting s-SNOM data, essential for researchers and practitioners in the field of near-field microscopy.

This video was recorded with the financial support of the Teaming for Excellence program (European Union Horizon 2020; GA 857543) during the Near-field Optical Nanoscopy Summer School (Donostia- San Sebastian; 6-9 June 2023) organized by neaspec/attocube AG, CIC nanoGUNE BRTA and the ENSEMBLE3 Centre of Excellence.