• Українська
  • English
ISSN 2415-3400 (Online)
ISSN 1028-821X (Print)

Focusing of inhomogeneous polarized modes of a laser waveguide dielectric resonator

heading: 
MICROWAVE AND TERAHERTZ TECHNOLOGY
Degtyarev, AV, Dubinin, MM, Maslov, VA, Senyuta, VS
Organization: 

 

V.N. Karazin Kharkiv National University
4, Svobody Sq., 61022, Kharkiv, Ukraine
E-mail: a.v.degtyarev@karazin.ua
https://doi.org/10.15407/rej2020.02.054
Language: russian
Abstract: 

 

 

Subject and Purpose. In this paper, spatial power characteristics of laser beams with inhomogeneous spatial polarization are theoretically investigated depending on whether they have moderate or sharp focusing. The spotlight of the numerical simulation of laser beam focusing in the terahertz range is on the laser waveguide dielectric resonator modes coincident with waveguide eigenmodes. Symmetric and asymmetric modes with both spatially inhomogeneous azimuthal and radial polarizations and homogeneous linear polarization of the field are considered.

Methods and Methodology. The study of the electric field components of laser radiation beams in their free space propagation employs Rayleigh-Sommerfeld integrals in nonparaxial approximation. The focusing lens action on the laser radiation is considered using the amplitude-phase correction function. The total intensity distributions of the resonator modes and their particular field components in the lens focal area are examined.

Results. Wave beams with inhomogeneous spatial polarization of radiation are needed for meeting important fundamental and applied problems concerning terahertz electromagnetic wave interaction with matter and including diagnostics of material surface, thin films and biological objects, design and development of terahertz systems of information transmission and processing, terahertz communication systems, achievement of subwave resolution in terahertz tomography, etc. The literature on pulsed radiation beam focusing in the terahertz region is available, which cannot be said about continuous radiation beam focusing, data on the subject being practically absent. In the present work, physical features of moderate and sharp focusing of laser beams have been theoretically studied in the case of their excitation by modes of the resonator with a circular dielectric waveguide with different spatial polarizations of the field. The obtained results give a more in-depth view of the focusing features of terahertz laser beams.

Conclusions. Physical features have been established for spatial power characteristics of radiation beams with different spatial polarizations of the field in the case of the excitation by modes of the laser cavity upon a circular dielectric waveguide in the terahertz range and with the regimes of moderate and sharp beam focusing in the free space considered. 
Keywords: dielectric resonator, focusing, modes, polarization, terahertz laser

Manuscript submitted 17.10.2019
PACS: 52.35.Mw, 73.20.Mf, 74.72.-h
Radiofiz. elektron. 2020, 25(2): 54-63
Full text (PDF)

References: 
  1. 1. Xiaoqiang, Z., Ruishan, C., Anting, W., 2018. Focusing proper-ties of cylindrical vector vortex beams. Opt. Commun., 414, pp. 10-15. DOI: https://doi.org/10.1016/j.optcom.2017.12.076.
     
    2. Fu, J., Yu, X., Wang, Y., Chen, P., 2018. Generation of pure longitudinal magnetization needle with tunable longitudinal depth by focusing azimuthally polarized beams. Appl. Phys. B, 124(1), 11(4 pp.). DOI: https://doi.org/10.1007/s00340-017-6886-5.
     
    3. Kozawa, Y., Sato, S., 2007. Sharper focal spot formed by higher-order radially polarized laser beams. JOSA A, 24(6), pp. 1793-1798. DOI: https://doi.org/10.1364/JOSAA.24.001793.
     
    4. Zhan, Q., Leger, J., 2002. Focus shaping using cylindrical vector beams. Opt. Express, 10(7), pp. 324-331. DOI: https://doi.org/10.1364/OE.10.000324.
     
    5. Sundaram, C.M., Prabakaran, K., Anbarasan, P.M., Rajesh, K.B., Musthafa, A.M., Aroulmoji, V., 2018. Tight focusing properties of phase modulated transversely polarized sinh Gaussian beam. Opt. Quantum Electron., 49(1), 11 pp. DOI: https://doi.org/10.1007/s11082-016-0857-7.
     
    6. Winnerl, S., Hubrich, R., Mittendorff, M., Schneider, H., Helm, M., 2012. Universal phase relation between longitudinal and transverse fields observed in focused terahertz beams. New J. Phys., 14(10), pp. 103049. DOI: https://doi.org/10.1088/1367-2630/14/10/103049.
     
    7. Minami, Y., Kurihara, T., Yamaguchi, K., Nakajima, M., 2013. Longitudinal terahertz wave generation from an air plasma filament induced by a femtosecond laser. Appl. Phys. Lett., 102(15), pp. 151106. DOI: https://doi.org/10.1063/1.4802482.
     
    8. Waselikowski, K.J., Fischer, C., Wallauer, J., Walther, M., 2013. Optimal plasmonic focusing on a metal disc under radially polarized terahertz illumination. New J. Phys., 15(7), pp. 075005. DOI: https://doi.org/10.1088/1367-2630/15/7/075005.
     
    9. Kaltenecker Z., König-Otto J.C., Mittendorff M., Winnerl S., Schneider H., Helm M., Walther M., 2016. Gouy phase shift of a tightly focused, radially polarized beam. Optica, 3(1), pp. 35-41. DOI: https://doi.org/10.1364/OPTICA.3.000035.
     
    10. Gurin, O.V., Degtyarev, A.V., Maslov, V.A., 2015. Propagation and focusing of modes of dielectric resonators of terahertz range lasers. Telecommunications and Radio Engineering, 74(7), pp. 629-640. DOI: https://doi.org/10.1615/TelecomRadEng.v74.i7.60.
     
    11. Gurin, O.V., Degtyarev, A.V., Maslov, V.A. Senyuta, V.S., Svich, V.S., Topkov, A.N., 2014. Propagation and focusing of modes of the dielectric resonator of terahertz laser. In: 2014 Int. Conf. «Laser Optics». St. Petersburg, Russia, 30 June - 4 July 2014. DOI: https://doi.org/10.1109/LO.2014.6886325.
     
    12. Vlasenko, S.A., Degtyarev, A.V., Dubinin, M.M., Maslov, V.A., 2019. Spatial and power characteristics of focused modes of the metal cavity of a terahertz laser. Telecommunications and Radio Engineering, 78(5), pp. 373-383. DOI: https://doi.org/10.1615/TelecomRadEng.v78.i5.10.
     
    13. Henningsen, J., Hammerich, M., Olafsson, A., 1990. Mode structure of hollow dielectric waveguide lasers. Appl. Phys., 51(4), pp. 271-284. DOI: https://doi.org/10.1007/BF00325048