  This paper reviews some of the key enabling technologies for advanced and
future laser interferometer gravitational wave detectors, which must combine
test masses with the lowest possible optical and acoustic losses, with high
stability lasers and various techniques for suppressing noise. Sect. 1 of this
paper presents a review of the acoustic properties of test masses. Sect. 2
reviews the technology of the amorphous dielectric coatings which are currently
universally used for the mirrors in advanced laser interferometers, but for
which lower acoustic loss would be very advantageous. In sect. 3 a new
generation of crystalline optical coatings that offer a substantial reduction
in thermal noise is reviewed. The optical properties of test masses are
reviewed in sect. 4, with special focus on the properties of silicon, an
important candidate material for future detectors. Sect. 5 of this paper
presents the very low noise, high stability laser technology that underpins all
advanced and next generation laser interferometers.
