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3The 30th International Conference on Advanced Laser Technologies N-I-23
ALT'23
Terahertz surface plasmon refractometry of conducting surfaces and thin dielectric layers on the Novosibirsk free-electron laser
V. V. Gerasimov12, V. D. Kukotenko1, O. E. Kameshkov12, A. G. Lemzyakov1, V. P. Nazmov1, A. I. Ivanov3, I. A. Azarov3, I. Sh. Khasanov4, A. K. Nikitin4
1-Budker Institute of Nuclear Physics of SB RAS, 11, Lavrentiev prospect, 630090, Novosibirsk, Russia
2- Department of Physics, Novosibirsk State University, 630090 Novosibirsk, Russia 3- Rzhanov Institute of Semiconductor Physics SB RAS, 13 Lavrentiev Aven., Novosibirsk 630090, Russia 4- Scientific and Technological Centre of Unique Instrum. of RAS, 15, Butlerova str., 117342, Moscow, Russia
Plasmon refractometry has found wide application in optical sensor devices in the visible range due to such features of surface plasmons (SPs) at these frequencies as short propagation length (which meets the requirement for miniaturization of sensors) and concentration of the SP field in the metal surface vicinity, that results in high sensitivity of SP devices to changes in optical characteristics of the sensor layer on the metal surface [1].
In the THz range, where the SPs propagation length on metals extends to tens of centimeters [2], plasmon refractometry based on plasmon interferometry [3] can be effectively used to control quality of the metal surface as well as to determine the effective permittivity of metal coatings used in plasmonic THz integrated circuits [4]. Besides, THz SP interferometers can be employed for investigations of thin dielectric films on metal surfaces, and for various sensor applications. The complementary experimental method that makes it possible to determine the effective permittivity of a conducting surface is the study of the attenuation of the evanescent field of the SPs over the conductor [5].
If semiconductors with a plasma frequency lying in the THz frequency range are used as the substrate on which the SPs propagate, then it is possible to implement the refractometry of semiconductor surfaces and dielectric (or weakly conductive) films deposited on them using the surface plasmon resonance (SPR) method [6]. If a dielectric film has an inhomogeneous relief on the semiconductor surface, then by taking images of the reflected radiation using a focal plane array under SPR conditions, it is possible to determine the inhomogeneous regions of the film. This method in the literature is called surface plasmon microscopy [7].
All the above methods of plasmon refractometry were tested on the THz radiation of the Novosibirsk free electron laser, which generates monochromatic linearly polarized coherent radiation, tunable in the wavelength range of 50 - 400 ^m. Many of these methods have been implemented for the first time and will be presented in the talk.
The work was done at the shared research center SSTRC on the basis of the Novosibirsk FEL at BINP SB RAS.
[1] Y. Gao, Z. Xin, Q. Gan, X. Cheng, and F. Bartoli, Plasmonic interferometers for label-free multiplexed sensing, Opt. Express., vol. 21, no 5, pp. 5859-5871 (2013).
[2] Vasily V. Gerasimov, Boris A. Knyazev, Alexey G. Lemzyakov, Alexey K. Nikitin, and Guerman N. Zhizhin. Growth of terahertz surface plasmon propagation length due to thin-layer dielectric coating, Journal of Optical Society of America B. V. 33, Is. 11, P. 2196-2203 (2016).
[3] V. V. Gerasimov, A. K. Nikitin, and A. G. Lemzyakov, Planar Michelson interferometer using terahertz surface plasmons, Instruments and Experimental Techniques, N. 3, pp. 67-79 (2023).
[4] S. Pandey, B. Gupta, A. Chanana, A. Nahata, Non-Drude like behaviour of metals in the terahertz spectral range ,Advances in Physics, vol. 1, no 2, pp. 176-193 (2016).
[5] V. D. Kukotenko, V. V. Gerasimov, Approaches to studying the evanescent field of surface plasmons using THz radiation from the Novosibirsk free electron laser, Abstract book of the 5-th International Conference TERAHERTZ AND MICROWAVE RADIATION: GENERATION, DETECTION AND APPLICATIONS, 27 February — 2 March 2023, Moscow, Russia, p. 115.
[6] I. Sh. Khasanov, V. V. Gerasimov, O. E. Kameshkov, A. K. Nikitin, Observation of surface plasmon resonance in monochromatic terahertz radiation on indium antimonide, Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques, to be published (2023).
[7] V. V. Gerasimov, O. E. Kameshkov, A. K. Nikitin, I. Sh. Khasanov, First experimental demonstration of the wide-field amplitude surface plasmon microscopy in the terahertz range, Photonics, to be published (2023).
