[Torrey, Daniel]

We set up a Michelson Interferometer using a Flexure Mirror Mount and a standard tip-tilt mirror mount as end mirrors to test if there was a resonance that produced the noise source around 520 Hz that is observed in the output filter cavity. The beamsplitter was a 50:50 non-polarizing plate, and the readout was done by a Thorlabs PDA50B2 amplified photodetector. The alignment was such that the contrast from hitting the table was above 80%. On the frequency trace, there was no discernable increase in noise around 520 Hz (see photos). I also played sinusoids at 520 Hz and did not observe any increase in the noise. This indicates this noise is not inherent to all flexure mounts. Perhaps some flexure mounts are manufactuered or mounted sufficiently differently as to produce a 520 Hz noise source. The large peaks appear to be 60 Hz noise and its overtones.