(ed.). Gravitational waves (IOP, 2001)(422s).

The physics of interferometers 29 Figure 3.1. Five steps to a gravitational-wave interferometer. (a) The simple Michelson.Notice that there are two return beams: one goes toward the photodetector and the othertoward the laser. (b) Delay line: a Michelson with multiple bounces in each arm to enhancethe signal. (c) Power recycling. The extra mirror recycles the light that goes towards thelaser, which would otherwise be wasted. (d) Signal recycling. The mirror in front of thephotodetector recycles only the signal sidebands, provided that in the absence of a signalno light goes to the photodetector. (e) Fabry–Perot interferometer. The delay lines areconverted to cavities with partially silvered interior mirrors.same response as a longer interferometer, the extra bounces introduce noise fromthe mirrors, as discussed below. There is, therefore, a big advantage to long-arminterferometers.