Surface microstructures of silica glass by laser-induced backside wet etching

Abstract

Surface micro-structuring of silica glass plates was performed by using laser-induced backside wet etching (LIBWE) upon irradiation with a single-mode laser beam from a diode-pumped solidstate UV laser at 266 nm. We have succeeded in a well-defined micro-pattern formation without debris and microcrack formations around the etched area on the basis of galvanometer-based point scanning system with the laser beam. The behavior of liquid ablation (explosive vaporization) was monitored by impulse pressure detection with a fast-response piezoelectric pressure gauge. LIBWE method is suitable for rapid prototyping and rapid manufacturing of surface microstructuing of silica glass as mask-less exposure system in a conventional atmospheric environment.Keywords: laser ablation, explosive vaporization of liquid, diode-pumped solid state UV laser, single mode laser beam, silica glass, surface micro-structuring IntroductionLaser-induced micro-structuring of various materials has served as an important technique in surface fabrication for optics and optoelectronic devices [1]. In particular, significant attention has been given towards the microstructuring of silica glass in spite of the difficulty involved, since silica is a commonly used material. The use of pulsed lasers can involve several approaches, such as conventional UV laser ablation [2], vacuum UV laser processing [3,4], pulsed-laser-generated x-ray [5], plasmaassisted UV ablation [6,7], and femtosecond laser micromachining [2,8]. We have demonstrated a novel one-step method, laser-induced backside wet etching (LIBWE), for micro-fabrication on a silica glass plate, involving irradiation with nanosecond-pulsed UV lasers . The LIBWE method is based on the deposition of laser energy onto a thin layer at the glass-liquid interface during the explosive vaporization (ablation) of a liquid substance. Assuming negligible UV absorption by the silica glass, the incident laser beam passes through the glass plate resulting in the excitation of the dye solution. When the dye solution close to the interface becomes ablated using laser irradiation with sufficient fluence, etching on a surface layer of the silica glass is achieved. The depth of the etch increases linearly with the number of laser shots. Typical etch rates of the material were 0.1-40 nm pulse -1 , depending on irradiation conditions such as laser wavelength, laser fluence, and dye concentrations.Micro-fabrications of various transparent materials, such as silica glass [9,[12][13][14][15][16][18][19][20][21][22][23][24][25][26][27]29,30,34,35], quartz [10,25,28,[31][32][33], glasses (Pyrex, etc.)

Surface Roughness Analysis of Microchannels Featuring Microfluidic Devices Fabricated by Three Different Materials and Methods

“…LIBWE is a technique that indirectly processes transparent materials by heating a liquid absorbent located on the rear side using a laser. Nevertheless, despite its promise, LIBWE still faces practical challenges when applied to a range of glass applications, primarily due to issues like crack formation and imprecise final geometry, and it is also limited to transparent materials [15][16][17].…”