Correlation of UV damage threshold with post-annealing in CVD-grown SiO₂ overlayers on etched fused silica substrates

Abstract

Chemical vapor deposition (CVD) has been used for the production of fused silica optics in high power laser applications. However, relatively little is known about the ultraviolet (UV) laser damage threshold of CVD films and how they relate to intrinsic defects produced during deposition. We present a study relating structural and electronic defects in CVD films to the 355 nm pulsed laser damage threshold as a function of post-deposition annealing temperature (T HT ). Plasma-enhanced CVD, based on SiH 4 /N 2 O under oxygen-rich conditions, was used to deposit 1.5, 3.1 and 6.4 m thick films on etched SiO 2 substrates. Rapid annealing was performed using a scanned CO 2 laser beam up to T HT~2 100 K. The films were then characterized using X-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL). A gradual transition in the damage threshold of annealed films was observed at T HT up to 1600 K, correlating with a decrease in NB silanol and broadband PL emission. An additional sharp transition in damage threshold also occurs at ~1850 K indicating substrate annealing. Based on our results, a mechanism for damage-related defect annealing is proposed, and the potential of using high-T HT CVD SiO 2 to mitigate optical damage is also discussed.

Influence of Thermal Annealing on Mechanical and Optical Property of SiO2 Film Produced by ALD

“…The structure of the ALD SiO 2 film was the same as that of the fused silica substrate, both of which contained a stretching vibration mode and a stretching vibration mode of Si-O. In Figure 2a, the measurement of 980 cm −1 is attributed to Si-O asymmetric stretching vibration (Vs), 784 cm −1 to Si-O bending vibration (Vb) [30,31], and 950 cm −1 and 3300 cm −1 to Si-OH vibration [32,33]. It can be seen in Figure 2b that the asymmetric stretching vibration peak position was related to the film thickness and that the vibration peak position gradually increased with the increase in film thickness.…”

Localized planarization of optical damage using laser-based chemical vapor deposition

“…7 To assess the damage threshold of our L-CVD material, a 36-site sample was produced which could be 351 nm, 5-ns pulse laser damage tested in our Optical Sciences Laser damage test facility. 8 The results are displayed in Table 1, along with data for laser-grown damage sites (~150 m in diameter) and data from our previous study.…”

Optical and Laser-Induced Damage Characterization of Porous Structural Silicon Oxide Film with Hexagonal Period by Nanoimprint Lithography

“…The smooth surface of the optical element helps to improve its LIDT [11]. In the past, various preparation methods, such as e-beam evaporation [12], plasma-enhanced chemical vapor deposition [13][14][15], atomic layer deposition [16,17], and the sol-gel method [18], were used to fabricate laser films, but these methods are not suitable for the preparation of large-area nanostructured surfaces with high-precision patterns. Laser surface treatment can be used to process some functional surfaces, but large-area nanoscale patterning is difficult to fabricate.…”