The free running frequency noise of the spare Mephisto 2000NE laser (S/N 7974) was measured.
The laser was locked to a reference cavity using an SR560 with a 0.3 Hz low pass filter
at a gain of 5. The PZT coefficient was measured to be ~1.35 MHz/V.
Following on from a remark Daniel made about excess noise, I repeated the measurement of the free running frequency noise of the NPRO out to 250 kHz and 1 MHz (fn2.png and fn1.png respectively). Just beyond 100 kHz we can see that the noise rises again contrary to the expectation where it continues falling off.