Substrate Cleaning Processes and Their Influence on the Laser Resistance of Anti-Reflective Coatings

Substrate cleaning prior to coating has a strong influence on the performance of the optical component. Exemplary, none or inadequate cleaning reduces the resistance against laser irradiation drastically. Especially in laser components coated with anti-reflective layers, the interface between substrate and coating is one of the most limiting factors. This study investigates different precision cleaning processes and their influence on the laser resistance of ion-beam sputtered anti-reflective coatings. Therefore, a SiO2/Ta2O5 multilayer anti-reflective coating for a wavelength of 1064 nm and a normal angle of incidence was deposited onto high-quality fused silica substrates. Prior to deposition, the substrates were cleaned with various cleaning processes using different solutions and ultrasonic frequencies. To characterize the cleaned surface quality, the surfaces were analyzed with respect to root-mean-square (RMS) roughness and particle density. Laser damage was measured using a 1064 nm ns-pulsed laser test bench. It was found that an alcoholic pre-clean is recommendable to prevent laser damage caused by organic films remaining from the polishing process. The applied ultrasonic frequencies strongly influenced the particle density down to the sub-micrometer range and in consequence, the laser-induced damage threshold (LIDT). Ultrasonic cleaning at excessive power levels can reduce laser resistance.

Couple formation and spawning between two female Discus Fish (Symphysodon aequifasciatus - Cichlidae) in captivity

ABSTRACT In an experiment performed to characterize the reproductive behavior of the discus fish in captivity, couple formation with two females was observed. The observations were carried out in captivity, based on ad libitum methodology. Adult individuals were allowed to naturally form couples. The couple formation was considered when individuals performed the substrate cleaning behavior. Fifteen couples were selected. The eggs of three couples did not initiate embryonic development and became infeasible within three days after spawning. We found that these spawnings belonged to all-female couples. The sex of the individuals in same-sex couples was confirmed through subsequent couple formation and spawning of fertile eggs with known males. Eggs were deposited by one or both females in the same-sex couples. Double spawnings were larger and differentially colored. The motivations that lead individuals of the same sex to form couples in this species are still unknown.