Rutile solid immersion lens for high-resolution THz microscopy
Authors:
Vladislav A. Zhelnov 1, Nikita V. Chernomyrdin 1, Vladimir N. Kurlov 2, Kirill I. Zaytsev 1
1 – Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia;
2 – Institute of Solid State Physics of the Russian Academy of Sciences, Chernogolovka, Russia
Abstract
Terahertz (THz) solid immersion (SI) microscopy is a new approach, migrated from visible and IR range, which allows to overcome the Abbe diffraction limit and significantly increase resolution. The SI effect allows to reduce dimensions of light beam when it is focused at a small distance behind a material with a high refractive index. Optionally, this approach provides high throughput compared to other near-field imaging techniques since there are no subwavelength apertures or probes in the optical path. The combination of these advantages opens up wide possibilities for application in various fields, including biomedical diagnostics and non-destructive testing of materials. The refractive index of the lens is the main limiting factor in SI microscopy, with optically denser lenses exhibiting higher resolution. Therefore, for the first time we used rutile crystal (TiO2) as a lens material, which, according to our data, is characterized by the highest refractive index of ~10 in the THz region. Our experimental setup used a continuous wave impact ionization avalanche transit-time diode-emitter at the 0.2 THz frequency (the λ = 1.5 mm wavelength) and a Golay detector. According to numerical and experimental estimates, the spatial resolution of a rutile microscope is 0.06–0.11λ. This is the highest normalized resolution achieved in solid immersion imaging systems.
Speaker
Vladislav A. Zhelnov
Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia
Russian Federation
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