2 research outputs found
Reduction of coating thermal noise by using an etalon
Reduction of coating thermal noise is a key issue in precise measurements
with an optical interferometer. A good example of such a measurement device is
a gravitational-wave detector, where each mirror is coated by a few tens of
quarter-wavelength dielectric layers to achieve high reflectivity while the
thermal-noise level increases with the number of layers. One way to realize the
reduction of coating thermal noise, recently proposed by Khalili, is the
mechanical separation of the first few layers from the rest so that a major
part of the fluctuations contributes only little to the phase shift of the
reflected light. Using an etalon, a Fabry-Perot optical resonator of a
monolithic cavity, with a few coating layers on the front and significantly
more on the back surface is a way to realize such a system without too much
complexity, and in this paper we perform a thermal-noise analysis of an etalon
using the Fluctuation-dissipation theorem with probes on both sides of a
finite-size cylindrical mirror.Comment: 12 pages, 7 figure
Reducing Thermal Noise in Future Gravitational Wave Detectors by employing Khalili Etalons
Reduction of thermal noise in dielectric mirror coatings is a key issue for
the sensitivity improvement in second and third generation interferometric
gravitational wave detectors. Replacing an end mirror of the interferometer by
an anti-resonant cavity (a so-called Khalili cavity) has been proposed to
realize the reduction of the overall thermal noise level. In this article we
show that the use of a Khalili etalon, which requires less hardware than a
Khalili cavity, yields still a significant reduction of thermal noise. We
identify the optimum distribution of coating layers on the front and rear
surfaces of the etalon and compare the total noise budget with a conventional
mirror. In addition we briefly discuss advantages and disadvantages of the
Khalili etalon compared with the Khalili cavity in terms of technical aspects,
such as interferometric length control and thermal lensing.Comment: 13 pages, 9 figure