The Cavity
The quality factor Q of the cavity, as well as the time duration of the measurement, determines the achievable frequency resolution of a ring to a large extent. The quality factor depends largely on the reflection properties of the mirrors. For high quality rings, reflectivities larger than 99.999% (R = 1-10 ppm) are indispensable. At this time, the main limitation of mirrors is the extinction coefficient of the evaporated high-index material TiO2. The size and shape of the cavity as well as the presence of interfaces also influence the quality factor.
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