[Briana, Torrey]

We have been attempting to fit some 1550 ringdown measurements to a decaying exponential unsuccessfully. Part of the problem is using the wrong equation. Attached is a derivation for the proper equation to fit the decaying voltage on a PD due to a cavity ringdown measurement. Note that this is an example for the two fields being detected on the PD in reflection but the same should hold true for in tranmission. The main difference will be Ar > > At. Once these are properly fit the, extracting the tau, A_r and A_c will allow for some interesting parameters like, finesse and the product of the transmissivities of the two individual input/output couplers.

An example of the effect in the difference in amplitudes. Note how the overall amplitude of the fluctuations relative to the whole decay is much bigger when the fields are even, as expected.