Superresolution THz solid immersion microscopy

Abstract

Terahertz technologies are increasingly used in areas ranging from medical diagnostics and non‑destructive testing to 6G communications. Yet their broader adoption in imaging and spectroscopy remains constrained by the Abbe diffraction limit, which hinders observation of subwavelength features. Solid‑immersion microscopy overcomes this by focusing the THz beam close to the surface of a high‑refractive‑index lens. Earlier SI microscopes relied on continuous‑wave sources and thus lacked spectroscopic capability. In this work, we introduce a pulsed THz solid immersion microscope that integrates a high‑numerical‑aperture SI lens with photoconductive antennas for both broadband pulse generation and detection. This combination unites the super‑resolving power of SI optics with the comprehensive data provided by pulsed THz imaging. We quantitatively evaluated the spatial resolution in the time and frequency domains using a test object with a sharp metal‑air interface. The spectral‑phase imaging delivered the best performance, achieving resolution between 0.047λ and 0.156λ. The microscope's practical utility was demonstrated on test media and biological specimens. Moreover, it successfully discriminated various condensed materials and liquids—including crystalline quartz, TPX, HDPE, PG, glycerol, and water—by analysing experimental transfer functions extracted from reflected pulse waveforms. This confirms the method’s high sensitivity to local optical properties and underscores its potential for applications in biophotonics and materials science.

Speaker

Demyan Rybnikov
Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia;
Russia

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