Effect of conventional fused silica preparation and deposition techniques on surface roughness, scattering and laser damage resistance Simona Liukaitytė 1 , Gintarė Batavičiūtė 1 , Egidijus Pupka 1 , Mindaugas Ščiuka 1 , Irena Kraujalienė 2 , Dainius Tumosa 2 , Alfridas Skrebutėnas 3 , Kęstutis Juškevičius 4 , Tomas Tolenis 4 , Simonas Kičas 4 , Ramutis Drazdys 4 , Rytis Buzelis 4 and Andrius Melninkaitis 1* 1 Laser Research Center, Vilnius University, Saulėtekio al. 10, 10223 Vilnius, Lithuania 2 UAB "Optolita", Mokslininkų g. 11, 08412 Vilnius, Lithuania 3 UAB "Optida", Savanorių pr. 231, 02300 Vilnius, Lithuania 4 State Research Institute for Physical Sciences and Technology, Savanorių pr. 231, 02300 Vilnius, Lithuania * Corresponding author: andrius.melninkaitis@ff.vu.lt ABSTRACT Despite the growing improvement in optical polishing and deposition technologies optical resistance of the laser components used for high-power UV applications remains insufficient in many cases. In this study influence of different fused silica substrate preparation, post treatment processing and deposition techniques are examined in terms of surface roughness, optical scattering and laser damage performance. The conventional techniques of polishing, etching, and finally surface cleaning of substrates have been investigated. Further, a part of samples were also coated with SiO 2 monolayer by Ion Beam Sputtering (IBS) technique. Surface quality was characterized prior to and after the treatment and deposition processes by the means of total integrated scattering (TIS) and atomic force microscopy (AFM). The experimental results of surface roughness measurements exhibited a good correlation between AFM and TIS methods. Further optical resistance was characterized with 10 ns duration pulses for 355 nm wavelength laser radiation performing 1-on-1 sample exposure test with high resolution micro-focusing approach. A dominating damage precursor ensembles produced during manufacturing processes were identified and directly compared. Finally, the conclusions about the quality influencing factors of investigated processes were drawn. Keywords: laser damage threshold, total integrated scattering, polishing, cleaning, etching, coating, ion-beam sputtering. 1. INTRODUCTION Great interest in high power UV laser applications challenges quality standards of nowadays optical components. Requirements for surface roughness and optical resistance are constantly increasing. For example, scattering losses of mirrors used in laser gyros must be less than 1 ppm (one part-per-million) [1]. In this sense Laser-Induced Damage Threshold (LIDT) and optical scattering have become important limiting factors to overcome. Both parameters could be interrelated [2], [3], [4] and highly depend on manufacturing processes such as polishing, cleaning, etching and coating. Polishing is essential procedure in order to treat any optical surfaces to high quality product. Basically it is chemo- mechanical phenomenon that generates various digs, scratches and other optical damage precursors. Due to the nature of polishing an amorphous or microcrystalline structure so called Beilby layer is formed. Such refractive index matching layer, covers the element and makes the surface quite smooth. Oxygen vacancies, abrasive particles as well as water vapor or hydrocarbons available from the external environment are mixed within Beilby layer [5]. So most defects generated in the polishing processes (that is supposed to be eliminated in finishing stages) remain hidden [6], covered or trapped [7] in optical component surface or thin sub-surface layers beneath it. Laser light interaction with surface or sub- surface defects is reported to result in multiple reflections or increased absorption. Both of these processes might be related with laser induced damage occurrence. After polishing, optical components must be cleaned precisely to avoid scattering losses and absorption due to remaining contamination [8], [9] and also for better adhesion. Standard cleaning is performed using ethanol and polymer film stripping. Thus, various different cleaners have been tested in order to Laser-Induced Damage in Optical Materials: 2012, edited by Gregory J. Exarhos, Vitaly E. Gruzdev, Joseph A. Menapace, Detlev Ristau, M J Soileau, Proc. of SPIE Vol. 8530 853027 · © 2012 SPIE · CCC code: 0277-786/12/$18 · doi: 10.1117/12.977244 Proc. of SPIE Vol. 8530 853027-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 12/12/2012 Terms of Use: http://spiedl.org/terms