Direct CO_2 laser-based generation of holographic structures on the surface of glass

Abstract

A customized CO(2) laser micromachining system was used for the generation of phase holographic structures directly on the surface of fused silica (HPFS(®)7980 Corning) and Borofloat(®)33 (Schott AG) glass. This process used pulses of duration 10µs and nominal wavelength 10.59µm. The pulse energy delivered to the glass workpiece was controlled by an acousto-optic modulator. The laser-generated structures were optically smooth and crack free. We demonstrated their use as diffractive optical elements (DOEs), which could be exploited as anti-counterfeiting markings embedded into valuable glass-made components and products.

Hybrid laser precision engineering of transparent hard materials: challenges, solutions and applications

“…In the laser-induced front side etching (LIFE), the laser beam is directly focused onto the front side of the transparent substrates, which avoids the issues of absorption and interference from the substrate material [156][157][158] . With the aim of increasing laser energy absorption, a thin absorber layer is deposited on the front surface, such as chromium 159,160 , aluminum 161 , silver 160 , titanium 160 , and silicon monoxide layer 156 .…”

Potential of CO2-laser processing of quartz for fast prototyping of microfluidic reactors and templates for 3D cell assembly over large scale

“…Additionally, it allows high geometrical freedom, high lateral and vertical resolution, fast laser processing of the material without contacting it, the formation of patterns (including channels) with different depth and width, processing of thicker materials in a reasonable time scale (less than 24 ​h), large substrate area processing, mass production of custom-designed features with precise alignment and length-scale from μm to nm and laser engraving in ambient air (no controlled environment needed) [ 20 , 24 ]. Glass micromachining can be accomplished based on a wide range of wavelengths (ultraviolet to infrared) and pulse width (micro-to femtosecond) [ [26] , [27] , [28] , [29] , [30] ]. The primary requirement to be fulfilled for successful laser ablation-induced machining is strong absorption of the material to be processed at the laser operating wavelength, with micrometer-scale absorption depth in the material.…”

“…Ultrafast picosecond laser was demonstrated as a valuable tool for direct cutting, drilling and micro-machining of glass as well as for glass-to-glass bonding without adhesive layers [ 31 ]. Despite excimer ultra-short (i.e., pulse width in the femtosecond to picosecond range) lasers provide high-precision material processing with crack- and almost debris-free surfaces and high precision profiles with respect to nanosecond or longer laser pulses [ [32] , [33] , [34] ], the related highly expensive instrumentation favored spreading use of economic (relatively simple equipment and low capital investment) microsecond-pulsed carbon dioxide (CO 2 ) laser sources operating at wavelengths strongly absorbed by glasses [ 28 , 30 , 35 ]. Hence, although limited to the realization of micro-sized structures (since heat dissipation in the surrounding material during the photo-thermal process influences the spatial resolution), nowadays CO 2 laser–based ablation/micro-machining represents a serial method to engrave patterns on glass materials (such as quartz, borofloat and pyrex) [ 35 ] that have found applications in solar cells to enhance light trapping efficiency [ 36 ].…”

Optimized single-shot laser ablation of concave mirror templates on optical fibers

“…In the last decade CO 2 laser ablation has become a mature technique for the processing of optical glasses, uniquely suited to fabricating micrometer-scale structures with sub-nanometer surface roughness [1,2]. A wide range of shapes can be produced using this technique, including microspheres [3], microlenses [4,5], microtoroids [6], gratings [1], holographic structures [7] and concave mirror templates [8,9]. In particular, such concave mirror templates can be realized on the tip of optical fibers [8], and can be used to define tunable open-access Fabry-Perot microcavities with high finesse [10,11].…”