Absorption is a key parameter for optical materials and coatings in an increasing number of applications. Following the need for absorption measurements, a variety of different techniques have been established in the past 2 decades. Although all of them are very sensitive - allowing to measure down to the ppm absorption level – the absolute calibration remains a main challenge. For the first time to the best of our knowledge, we present data of a Round-Robin absorption test with a total of 11 participants using 5 different measurement techniques, including scientific institutes as well as companies. The subject of the test is the measurement of two highly reflective (HR) coatings (Bühler Alzenau GmbH) with different expected absorption levels at a wavelength around 1064nm. Besides a look on the overall absorption data scattering, the goals are comparing data obtained by identical test equipment at different locations as well as the influence of sample cleaning procedures. Additional CRD, total scattering, and residual transmission measurements provide information on the expected absorption data.
The production of clean energy is nowadays a very important and critical topic and Laser Fusion is one of the possibilities to achieve this goal. In order to improve the efficiency of this technology, one of the problematics is the increase in laser energy in the optical systems, and therefore the need for optical coatings able to sustain higher fluence. In this study, the contribution of the substrate surface quality on the optical performance and Laser Induced Damage Threshold (LIDT) will be investigated. Mirror coatings for a wavelength of 532nm will be coated using an Ion Beam Sputtering System on different types of glass substrates and the optical properties like scattering, absorption and Laser Damage will be presented and discussed.
Ion Beam Sputtering systems are well established as state-of-the-art deposition tools for the coating of high quality optical thin films with high density and low losses. These coatings are used for many laser applications, with an ever-increasing demand for higher sustained fluence. Ion Beam Sputtering (IBS) is a known technique to provide such high optical quality thin films. Indeed, it allows to achieve high density layers with low absorption and scattering. In this work, various coatings were developed using Bühler IBS technology. Then, total losses were measured using Cavity Ring Down, absorption using Laser Induced Deflection or Laser thermography, and Total Integrated Scatter using dedicated scatterometers. A correlation between the effect of the chosen deposition method and parameters and the measurement performances were made with the aim of a better understanding of the level and the origin of losses in the coatings. Finally, highly reflecting mirror coatings for 1064 nm wavelength were fabricated with different designs and deposition parameters. The results of the different measurements of absorption, scattering and total losses using different equipment are presented and discussed.
In many laser applications, there is a higher and higher demand for more efficient coatings with reduced losses, in terms of absorption and scattering as those are contributing factors to diverse laser damage regimes. Ion Beam Sputtering (IBS) is a known technique to provide such high optical quality thin films. Indeed, it allows to achieve high density layers with low absorption and scattering. In this work, various coatings were developed using Bühler IBS technology. Then, total losses were measured using Cavity Ring Down, absorption using Laser Induced Deflection or Laser thermography, and Total Integrated Scatter using dedicated scatterometers. A correlation between the effect of the chosen deposition method and parameters and the measurement performances were made with the aim of a better understanding of the level and the origin of losses in the coatings. Finally, highly reflecting mirror coatings for 1064 nm wavelength were fabricated with different designs and deposition parameters. The results of the different measurements of absorption, scattering and total losses using different equipment are presented and discussed.
Completing our suite of deposition equipment, we are developing a new Ion Beam Sputtering (IBS) System with different substrate configurations: the High Throughput version (HT) and the High Precision version (HP). The HT version enables the coating of 4 planets of up to 350mm diameter substrates, whereas the HP version allows coating of substrates up to 600mm diameter in a single planet configuration. The IBS system is configured with a Bühler proprietary Optical Monitoring System for layer termination, a large 22cm RF sputtering source, and a LION plasma source for assist. In this presentation the optical performance of this IBS coatings, including LIDT, absorption, total loss and residual coating stress, will be discussed and compared to the other available deposition techniques, such as Plasma Assisted Reactive Magnetron Sputtering, and Plasma Ion Assisted deposition (PIAD). Preliminary results of a 1064nm mirror show less than 5ppm absorption, reflectivity’s of 99.997%, and no visible damage in CW LIDT testing up to 10MW/cm2. Pulsed laser damage testing is in process and will be reported. These results will be compared to the coatings being done using PARMS and Evaporation.
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