Description
MAD: Substrates
In Lyon, we are investigating the potential of using sapphire mirrors for the Einstein Telescope Low-Frequency (ET-LF) detector. Compared to silicon, sapphire offers several advantages in cryogenic environments. These include superior thermal conductivity, higher density and optical transparency across the visible and the near infrared spectrum. Although KAGRA currently uses sapphire test...
The Float-Zone (FZ) method is the only industrially established technique for producing large silicon crystals of ultrahigh purity. The resulting low absorption at 1550 nm makes FZ silicon a strong candidate for cryogenic mirror substrates in next-generation gravitational wave detectors such as the Einstein Telescope (ET). Absorption levels below 10 ppm/cm have been measured in crystals grown...
The Einstein Telescope (ET) is a future 3rd generation gravitational wave observatory in Europe and crystalline silicon is under investigation to be used for mirrors. For the semi-transparent ET interferometer mirrors, large Si crystals [1] with ultrahigh purity are needed to minimize thermal noise (low laser light absorption and mechanical loss).
The defect structure and purity of the volume...
The NeoGrowth method, originally developed for high-efficiency photovoltaics, is a crucible-free crystal growth technique with promising potential for producing cryogenic mirror substrates for next-generation gravitational wave detectors such as the Einstein Telescope (ET). Crystal diameters of 450 mm—within the required range for ET—have already been demonstrated. The method enables oxygen...
The use of composite silicon substrates — assembled from multiple bonded components — offers a practical path to realising large test masses for the Einstein Telescope Low-Frequency (ET-LF) interferometer, while relaxing constraints on boule diameter and availability. However, these designs introduce bond lines across the optical aperture, which are expected to exhibit excess absorption and...
Due to a very low mechanical loss, resulting in low thermal noise, crystalline silicon is a very interesting mirror-substrate material for future cryogenic gravitational-wave detectors.
To maintain the low detector operation temperature, low optical absorption of the mirrors is required. This requirement includes all components of the mirrors, i.e. the mirror substrates as well as the...
