The Effect of Short Pulses of Terahertz Radiation on the Destruction of Thin Lead Films
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MOPHYSICAL PROPERTIES OF MATERIALS
The Effect of Short Pulses of Terahertz Radiation on the Destruction of Thin Lead Films A. V. Ovchinnikova, *, O. V. Chefonova, and M. B. Agranata a
Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia *e-mail: [email protected] Received February 25, 2020; revised March 10, 2020; accepted March 31, 2020
Abstract—The obtainment of new experimental data on the deformation, modification, and destruction of thin lead films under the influence of sub-picosecond pulses of terahertz radiation at an electric-field strength of up to 23 MV/cm is considered. DOI: 10.1134/S0018151X20040112
INTRODUCTION A new direction has arisen in fundamental and applied research due to the appearance of one- and two-period pulses of the terahertz (THz) emission spectrum with an electric field amplitude of the order of 107–108 V/cm [1–4]: nonlinear processes induced by THz fields in the surface layers of metals and semiconductors and the force action (deformation, modification, and destruction) on thin metal films [5–14]. A THz pulse with a duration of half the period of an electromagnetic wave (fractions of a picosecond) essentially simulates the nonresonant action of a quasi-constant electric field with high intensity on the object, which cannot be created with other methods. This paper presents the results of experimental studies of the occurrence of high-speed deformation, modification, and destruction of thin lead films under the influence of ultrashort pulses of the far infrared THz spectrum of radiation. EXPERIMENTAL FACILITY An experimental stand consisting of a femtosecond chrome-forsterite laser system, a THz-pulse generator, and a diagnostic system for laser and THz radiation was developed and created for the study. The THz-radiation pulses were generated via optical rectification of femtosecond laser pulses in nonlinear organic crystals OH1 [4, 15] and DSTMS [16]. The THz crystals were pumped with a chromium-forsterite femtosecond laser system, which made it possible to obtain radiation at a wavelength of 1240 nm with a pulse duration of 80 fs and an energy of up to 90 mJ. Radiation with a wavelength of 1240 nm is optimal for the generation of THz pulses with a high conversion efficiency (up to 3%) and a Gaussian spatial distribution of the intensity profile.
The output energy of the pulses of THz radiation was measured with a calibrated Golay cell (GC-1D Tydex). A THz crystal with a working diameter of 8 mm made it possible to obtain THz radiation energy of up to 120 μJ. The energy density of the pump energy was adjusted on the surface of the THz crystal and, therefore, the energy of the pulse was controlled by changing the energy of the laser pulse with a polarizing attenuator consisting of a half-wave plate and a Glan prism. The electric field of the THz pulse was measured via the electro-optical detection technique with a 100-μm thick electro-optical GaP (110) crystal mounted on an optical contact on a GaP (100) substrate with a thickness of 2 mm. The
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