I measured the RF transimpedance of the POX photodiode by measuring the optical transfer function with the AM laser and by measuring the shot noise with a light bulb. The plots of these measurements are at http://lhocds.ligo-wa.caltech.edu:8000/40m/Electronics/POX.

I measured the noise of the photodiode at 11 MHz for different light intensities using an Agilent 4395a. The noise of a 50 ohm resistor as measured by this spectrum analyzer is 10.6 nV/rtHz. I fit this noise data to the shot noise formula to find the RF transimpedance at 11 MHz to be (2.42 ± 0.08) kΩ. The RF transimpedance at 11 MHz as measured by the transfer function is 6.4 kΩ.