• Kohoutek, T.
• Ohishi, Y.
• Orava, A.
• Mastumoto, M.
• Hughes, Mark A.
• Misumi, T.
• Kawashima, H.
• Suzuki, T.

Abstract

We inscribed relief diffraction gratings with periods of 6, 14, and 24 μm into the surface of Ge15Ga3Sb12S70 bulkglass by the material’s ablation using a femtosecond λ � 800 nm Ti:sapphire pulsed laser. The laser writing wasdone with sample implemented on a computer-controlled stage employing surface-to-beam alignment, laserpower, and raster pattern control. Pulse energies of 1.5, 3.0, and 4.5 μJ were focused on spot diameter of1.5 μm, resulting in channel widths, measured on the surface, of around 4, 5, and 6 μm and depths up to1.7 μm. The first-order diffraction efficiency of the fabricated gratings was up to 10% at λ � 650 nm. We have alsofabricated a “composite” grating combining the three relief diffraction gratings inscribed in the same position, butwith a mutual tilt. The composite grating provides complex multidirectional diffraction of the light in accordancewith geometrical arrangement and grating period of all the gratings inscribed. We propose practical applications offemtosecond pulsed-laser surface patterning, for example, surface-relief diffraction microgratings integrated at theends of multimode mid-IR chalcogenide optical waveguides or on the surfaces of bare core chalcogenide glassoptical fibers used for chemical sensing.

Topics

• surface
• glass
• glass
• composite