Highly efficient relief diffraction gratings inscribed in a chalcogenide bulk glass by a femtosecond laser

Abstract

Direct laser writing has been already demonstrated for the fabrication of under surface "buried" 3D mid-IR waveguides in chalcogenide glasses by employing a large photo-induced refractive index change in the features formed in the path of the focused beam from a short pulse laser. In this paper, we report on direct laser writing of relief diffraction gratings with periods of 6, 14 and 24 μm into the surface of Ge 15 Ga 3 Sb 12 S 70 chalcogenide glass by using a 800 nm Ti:saphire femtosecond pulse laser. The first order diffraction efficiency of the fabricated gratings was over 60 % at 650 nm. We have also fabricated a "composite" grating composed of three relief diffraction gratings inscribed in the same position, but with a mutual tilt. Composite grating provided complex multidirectional diffraction of the light in the accordance with geometrical arrangement and grating period of all the gratings inscribed. The fabrication was implemented on a computer controlled stage employing surface-to-beam alignment, laser power and raster pattern control. Pulse energies of 1.5, 3.0 and 4.5 μJ were used, resulting in channel widths of around 4, 5 and 6 μm, respectively, and depths up to 1.7 μm. We propose practical applications including surface relief diffraction micro-gratings at the ends of multimode chalcogenide optical waveguides or on the surfaces of bare core optical fibers used for chemical sensing.

Infrared microlenses and gratings of chalcogenide: confined self-organization in solution processed thin liquid films

“…[5][6][7] Although hot embossing or laser inscribing of these microstructures are well established techniques for bulk ChG in order to demonstrate the feasibility of these methods, patterning of thin lms has received more interest recently since typical required heights of these structures is only a few micrometers. [7][8][9][10][11] Earlier, these thin ChG lms were created with thermal evaporation mostly, but now solution processed ChG lms are beginning to show signicant advantages on lms deposited thermally. 1,2,[12][13][14][15][16][17][18][19][20][21][22] It has been shown that various amine solvents dissolve ChG via nucleophilic substitution of sulphide or selenide units with amine groups and may prove to be ideal for creating thin lms and structures for photonic, electronic or imaging application.…”