CC BY
9*
ALT'23
The 30th International Conference on Advanced Laser Technologies
LM-I-10
Properties of a terahertz holographic axicon fabricated by laser
ablation of a black diamond
M. Komlenok1, V. Pavelyev2' 3, B. Knyazev, A. Bolshakov1, V. Konov1
1- Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilova St., Moscow, 119991, Russian Federation 2- Samara National Research University, 34 Moskovskoye Shosse, Samara, 443086, Russian Federation 3- IPSIRAS - Branch of the FSRC "Crystallography and Photonics " RAS, 151 Molodogvardeyskaya St., Samara,
443001, Russian Federation [email protected]
The use of high-power sources of terahertz radiation requires durable and highly efficient optics. Silicon diffractive optical elements have a low coefficient of thermal conductivity and high reflective losses (51%) in comparison with diamond elements. However, large plates of optical grade polycrystalline diamond are expensive for the fabrication of terahertz optics and, moreover, are difficult in direct precise processing, even if laser technologies are used for these purposes. In the case of using high-performance IR lasers, a breakdown occurs in the bulk of the diamond [1]. Here, we propose to use the so-called "black" diamond to create optical elements operating in the terahertz range. It is distinguished by transparency in the far infrared range and the presence of developed boundaries between crystallites, which should prevent self-focusing of laser radiation in the bulk. Usually this material is used as a heat sink, and also has a cheap production cost due to fast synthesis. In this work, we report on the fabrication of holographic axicon for powerful THz radiation by structuring of the surface of "black" diamond with the disk Yb:YAG laser (Dausinger + Giesen GmbH, X = 1030 nm, t = 1 ps, f = 200 kHz), which provides high productivity of ablation to create a maximum relief depth of about 100 |im on a plate with a diameter of 20 mm. Under the optimized irradiation condition, the necessary relief with piecewise continuous profile (fig. 1) was formed by the moving of the laser beam over the diamond surface by a galvanic XY scanner. The results of the testing of the fabricated axicon on the Novosibirsk free electron laser at a wavelength of 141 p,m showed good agreement between experimental and calculated optical properties. The experimental and calculated cross sections of Bessel beam at the distance of 120 mm from the axicon are shown in fig. 2a and c, respectively. The perfect beam, which is formed in the focal plane when Bessel beam is focused by a lens, demonstrates a homogeneous narrow ring (fig. 2b) according to the numerical calculation (fig. 2d). The obtained result demonstrates the high potential of the proposed approach for production of high-efficient complex optical elements based on the "black" diamond to control the powerful THz radiation.
Fig. 1. Optical image of the fabricated diamond axicon.
Fig.2. Intensity distribution for Bessel beam: (a) experiment, (c) calculation. Perfect vortex beams: (b) experiment, (d) calculation.
[1] T.V. Kononenko, P.A. Pivovarov, A.A. Khomich, R.A. Khmelnitskii, and V.I. Konov, Effect of absorbing coating on ablation of diamond by IR
laser pulses. Quantum Electronics vol. 48 (3), pp. 244-250, (2018).
