Sequential Atmospheric Pressure Plasma-Assisted Laser Ablation of Photovoltaic Cover Glass for Improved Contour Accuracy

Abstract

Abstract:In this paper, we present sequential atmospheric pressure plasma-assisted laser ablation of photovoltaic cover glass. First, glass samples were plasma pre-treated using a hydrogenous plasma process gas in order to accomplish a modification of the near-surface glass network by a chemical reduction and the implantation of hydrogen. As a result, the transmission at a wavelength of 355 nm was reduced by approximately 2% after plasma treatment duration of 60 min. Further, the surface polarity was increased by approximately 78%, indicating an increase of the near-surface index of refraction. Subsequently to the plasma pre-treatment, the samples were laser ablated applying the above-mentioned laser wavelength of a Nd:YAG nanosecond laser. Compared to untreated samples, a significant decrease of the form error by 45% without any mentionable change in the ablation rate was obtained in the case of pre-treated samples. For comparison, the results and findings are discussed with respect to previous work, where the presented plasma-assisted ablation procedure was applied to optical glasses.

Plasma-Induced Generation of Optically Active Defects in Glasses

“…In the present case, the maximum surface temperature of the treated glass surface was approximately 38°C as ascertained via infrared camera measurements [7]. Experiments were performed on different optical and technical glasses [10,11], but mainly on fused silica as reported in more detail elsewhere [12,13]. The process gas used was forming gas 90/10, i.e.…”

Impact of the plasma power on plasma-induced increase in absorption of fused silica

“…Thus, the amount of atomic hydrogen is decreased whereas the amount of ionised hydrogen is increased. Consequently, the concentration of the actually needed species for hydrogen-induced chemical reduction, the electrically neutral hydrogen atom (Gerhard et al 2014), is reduced and the treatment effi ciency decreases. Second, increasing the discharge voltage and plasma power, respectively, leads to an increase in the electric fi eld strength E within the plasma volume.…”

Plasma-Enhanced Laser Materials Processing

“…Due to the plasma-induced increase in UV absorption, 4th-harmonic Nd:YAG lasers instead of excimer lasers can be applied for machining fused silica [39]. Even though the highest efficiency of the plasma pretreatment is found in the case of fused silica as substrate material, this approach can also be successfully applied to optical glasses [40] or technical glasses such as photovoltaic cover glasses [41]. However, due to the significantly denser network of multi-component glasses, the implantation of hydrogen and the formation…”