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arXiv · 1412.3627

Mapping the Optical Absorption of a Substrate-Transferred Crystalline AlGaAs Coating at 1.5um

Jessica Steinlechner·Iain W Martin·Angus Bell·Garrett Cole·Jim Hough·Steven Penn·Sheila Rowan·Sebastian Steinlechner
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Abstract

The sensitivity of 2nd and 3rd generations of interferometric gravitational wave detectors will be limited by thermal noise of the test-mass mirrors and highly reflective coatings. Recently developed crystalline coatings show a promising thermal noise reduction compared to presently used amorphous coatings. However, stringent requirements apply to the optical properties of the coatings as well. We have mapped the optical absorption of a crystalline AlGaAs coating which is optimized for high reflectivity for a wavelength of 1064nm. The absorption was measured at 1550nm where the coating stack transmits approximately 70% of the laser light. The measured absorption was lower than (30.2 +/- 11.1)ppm which is equivalent to (3.6 +/- 1.3)ppm for a coating stack that is highly reflective at 1530nm. While this is a very promising low absorption result for alternative low--loss coating materials, further work will be necessary to reach the requirements of <1ppm for future gravitational wave detectors.

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Jessica Steinlechner, Iain W Martin, Angus Bell, Garrett Cole, Jim Hough, Steven Penn, Sheila Rowan, Sebastian Steinlechner. 2014-12-11. Mapping the Optical Absorption of a Substrate-Transferred Crystalline AlGaAs Coating at 1.5um. https://doi.org/10.1088/0264-9381%2F32%2F10%2F105008

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