Experimental determination of intracavity losses of monolithic Fabry-Perot cavities made of Pr3+:Y2SiO5.

We propose an experimental method with which all the following quantities can be determined separately: the intracavity loss and individual cavity-mirror transmittances of a monolithic Fabry-Perot cavity and furthermore the coupling efficiency between the cavity mode and the incident light. It is notable that the modified version of this method can also be applied to whispering-gallery-mode cavities. Using this method, we measured the intracavity losses of monolithic Fabry-Perot cavities made of Pr3+:Y2SiO5 at room temperature. The knowledge of the intracavity losses is very important for applications of such cavities, e.g., to quantum information technologies. It turns out that fairly high losses (about 0.1%) exist even for a sample with extremely low dopant concentration (2×10(-5) at. %). The experimental results also indicate that the loss may be mainly due to the bulk loss of Y2SiO5 crystal. The bulk loss is estimated to be 7×10(-4) cm(-1) (0.003 dB/cm) or lower.