Coatingless, tunable finesse interferometer for gravitational wave detection

Future generation gravitational wave interferometric detectors will require a strong reduction of thermal noise, and will be limited by quantum fluctuations of laser light, namely, shot noise and radiation pressure noise. One of the factors which currently constrain the thermal noise performances of this kind of instruments is the dissipation introduced by the optical coating of the mirrors. In a recent article Braginsky and Vyatchanin proposed to reduce the contribution of thermoelastic noise in the coating building an optical cavity with corner reflectors instead of spherical mirrors. In this work we study a solution which, avoiding completely any kind of coating, allows for injection and extraction of light. We discuss the proposed optical scheme, evaluating the expected thermal noise performances.