Laser excitation of transversal and longitudinal polar modes in lithium niobate and tantalate crystals

Vladimir S. Gorelik; Nikolay V. Sidorov; Pavel P. Sverbil; Alexander I. Vodchits

doi:10.1117/12.2268158

14 December 2016 Laser excitation of transversal and longitudinal polar modes in lithium niobate and tantalate crystals

Vladimir S. Gorelik, Nikolay V. Sidorov, Pavel P. Sverbil, Alexander I. Vodchits

Proceedings Volume 10176, Asia-Pacific Conference on Fundamental Problems of Opto- and Microelectronics; 101761H (2016) https://doi.org/10.1117/12.2268158
Event: Asia-Pacific Conference on Fundamental Problems of Opto- and Microelectronics, 2016, Khabarovsk, Russia

Abstract

The excitation of longitudinal and transversal electromagnetic waves in lithium niobate and tantalate crystals is of interest for establish the conditions of coherent longitudinal and transversal waves generation in media and in vacuum. In this paper the results of laser excitation of transversal and longitudinal polar modes in these crystals are presented. We have measured spontaneous Raman spectra of lithium niobate and tantalate crystals in 0° (forward), 90°, and 180° (backward) scattering geometries. We have observed Raman peaks, related to fundamental transversal and longitudinal A₁(Z) and E((X,Y) polar optical modes. In addition, there were pseudoscalar symmetry A₂ peaks, forbidden by selection rules in Raman spectra for point group C_3v. This was explained by reducing of the point group from C_3v to C₃ due to the presence of impurities in real crystals. Besides, the acoustic biphonon at low frequency has been observed. High intensity of spontaneous A₁(Z)LO and A₁(Z)TO Raman satellites gives the opportunity for generation of coherent longitudinal and transversal terahertz waves in lithium niobate and tantalate crystals with the help of Stimulated Raman Scattering under using high-power laser pumping. The presence of pseudoscalar and biphonons mode in low frequency region results in the strong interaction with fundamental soft mode and sharp central peak near the phase transition.

Citation Download Citation

Vladimir S. Gorelik, Nikolay V. Sidorov, Pavel P. Sverbil, and Alexander I. Vodchits "Laser excitation of transversal and longitudinal polar modes in lithium niobate and tantalate crystals", Proc. SPIE 10176, Asia-Pacific Conference on Fundamental Problems of Opto- and Microelectronics, 101761H (14 December 2016); https://doi.org/10.1117/12.2268158

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