Abstract

The LANCET project tackles one of the outstanding challenges for the construction of the Einstein Telescope, the future European gravitational-wave detector: reducing light absorption in the mirrors, which will have to operate at cryogenic temperatures. The Einstein Telescope (ET) will enable us to observe the Universe with unprecedented sensitivity. To achieve this, however, it is necessary to develop extremely advanced components, including multi-coated mirrors capable of maintaining high performance even at very low temperatures.

Amorphous silicon (a-Si) and amorphous silicon nitride (a-SiN) are among the most promising candidates for the construction of the ET’s cryogenic mirrors. However, their optical absorption has so far proved too high for the ET’s extremely stringent requirements. The LANCET project proposes new strategies to reduce this absorption in both materials, with the aim of making them genuinely suitable for use in the ET’s cryogenic mirrors.

To achieve this, LANCET will combine advanced thin-film fabrication techniques with post-deposition treatments. In both cases, in-situ diagnostic techniques will enable the monitoring of changes in the relevant parameters throughout the process. This will make it possible to identify the most effective conditions for reducing optical absorption, bringing it down to levels compatible with those required by the ET design.

By reducing the optical absorption of a-Si and a-SiN to levels never before achieved, the LANCET project will contribute not only to the construction of the Einstein Telescope’s cryogenic mirrors, but also to opening up new applications for these materials in other fields of photonics and optoelectronics. Materials characterised by extremely high transparency are, in fact, required, for example, in integrated photonic circuits, photothermal microscopy and multilayer mirrors for high-power lasers.