The Influence of Defects on the Absorption of Terahertz Radiation in a CdSiP 2 Single Crystal
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IR, AND TERAHERTZ OPTICS
The Influence of Defects on the Absorption of Terahertz Radiation in a CdSiP2 Single Crystal V. S. Nozdrina,*, S. V. Chuchupala,b, G. A. Komandina, V. N. Kurlovc, O. E. Porodinkova, I. E. Spektora, G. M. Katybaa, c, d, P. G. Schunemanne, and K. T. Zawilskie a
Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow, 119991 Russia b Physical Faculty, Lomonosov Moscow State University, Moscow, 119991 Russia c Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia d Bauman Moscow State Technical University, Moscow, 105005 Russia e BAESystems, Inc., MER15-1813, P.O. Box 868, Nashua, NH03061-0868, United States *е-mail: [email protected] Received December 20, 2019; revised January 22, 2020; accepted February 28, 2020
Abstract—The transmission and reflection spectra of a CdSiP2 single crystal are measured in the temperature interval from 80 to 300 K using the terahertz (THz) pulsed and infrared Fourier spectroscopy methods. A significant influence of postgrowth defects on the absorption in the THz frequency range is revealed. This absorption is found to depend weakly on temperature compared to that observed previously for other chalcopyrite crystal with substantially lower concentration of defects. Upon cooling, intrinsic absorption mechanisms are minimized, and the contribution of defects to absorption is separated. Keywords: terahertz radiation generation, nonlinear optical crystals, extrinsic absorption DOI: 10.1134/S0030400X20070164
INTRODUCTION Single crystals of chalcopyrites possess high nonlinear optical coefficients [1–3], which, along with their good optical, mechanical, and temperature characteristics, determine their widespread use as optical parametric oscillators in the infrared (IR) range. Their characteristics and parameters have been described in [4–8]. These crystals also have good prospects for operating as terahertz (THz) radiation generators [9]. In view of the fact that the generated radiation propagates directly in the crystal, the operation efficiency of these converters substantially depends on the absorption, which, among other things, is determined by the presence of defects. A number of studies [10–13] have been devoted to studying their effect on the absorption of IR radiation by these compounds. In contrast to the visible and IR ranges, for the THz frequency range, this question is poorly studied. The reason for this is the complex superposition of various mechanisms by which the absorption in this range is formed. In the THz frequency range, absorption is formed by both intrinsic and extrinsic mechanisms, and extrinsic absorption is determined mainly by crystal defects and can be minimized by improving the technology of crystal growth. Previously, it has been shown [14] that postgrowth processing of crystals, for example, their electron irradiation, may significantly reduce losses in
the pump range, without causing additional absorption bands to appear in the THz generation range. Commonly, investi
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