CC BY
4The 30th International Conference on Advanced Laser Technologies
ALT'23
LM-P-11
Double depolarizer for controllable laser writing surface relief gratings in chalcogenide glasses
A. Porfirev1, S. Khonina1, N. Ivliev1, D. Porfirev1
1-Image Processing Systems Institute ofRAS—Branch of the FSRC "Crystallography and Photonics " RAS, Samara,
Russia
porfirev. [email protected]
It is well known that in the interferometric approach widely used for recording of surface relief gratings (SRGs) the interference of two laser beams creates light filed with periodically changed intensity distribution. The polarization distribution of the generated light field is also periodical. For example, in the case of right-handed and left-handed circular polarizations of the interfering laser beams, the polarization vector of the formed light field continuously rotates from 0 to 180 degrees. However, a Gaussian or uniform laser beam with such a non-uniform polarization distribution can be shaped without any interferometric setup. The so-called depolarizers, patterned microretarder arrays can be used for transformation of the polarization distribution of a linearly polarized Gaussian laser beam and allow one to generate complex vector beams. In our recent work [1], we showed a possibility of fabrication of SRGs in chalcogenide glasses (CGs) thin films using the structured laser radiation formed with a liquid crystal polymer (LCP) depolarizer transforming uniform linear polarization distribution into space variant polarization distribution. The photoionization process underlying the processing of such materials strongly depends on the local polarizations of the transversal and the longitudinal laser electric field components [2]. The photo-induced mass transport, a lateral redistribution of amorphous material under illumination by the near-bandgap light, is one of the fundamental physical phenomena used for laser patterning of CGs [3].
In this work, we propose to use two depolarizers to control the period of the polarization modulation of the transformed light field. The angle of the fast axis of each depolarizer is increased by 2 degree and the retardation has a periodic variation between 250 nm and 300 nm across each consecutive 25 ^m strip [4]. The period is controlled by turning the axis of one depolarizer relative to the axis of the other. This allowed us to change the period of the fabricated SRGs in the range from 1 to 3 ^m (see Fig. 1). This work was financially supported by Russian Science Foundation (grant No. 22-79-10007).
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Figure 1. Examples of SRGs fabricated with the help of two depolarizer with different orientations of thier axes. The atomic force microscopy images and the cross-sections of the fabricated reliefs for period
of 1 (a) and 3 (b) ^m are shown.
[1] A.P. Porfirev, S. N. Khonina, N.A. Ivliev, D.P. Porfirev, Laser processing of chalcogenide glasses using laser fields with a spatially varying polarization distribution, submitted to Optics and Laser Technology (2023).
[2] J. Watzel, J. Berakdar, Spatiotemporal delay in photoionization by polarization-structured laser fields, Phys. Rev. A, vol. 103, pp. 063107 (2021).
[3] E. Achimova, A. Stronski, V. Abaskin, A. Meshalkin, A. Paiuk, A. Prisacar, P. Oleksenko, G. Triduh, Direct surface relief formation on As2S3-Se nanomultilayers in dependence on polarization states of recording beams, Opt. Mater., vol. 47, 566-572 (2015).
[4] https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=8043
