I redid the PZT Phase Modulation measurement out to 5 MHz for both the Innolight and the Lightwave. The previous measurement stopped at 2MHz, and we wanted to see if there were any sweet spots above 2MHz. I also reduced the sweep bandwidth and increased the source amplitude at high frequency to reduce the noise (the Lighwave measurement, especially, was noise dominated above 1MHz). I also plotted the ratio of PM/AM in rad/RIN, since this is the ultimate criterion on which we want to make a determination.
It looks like there is nothing extremely useful above 2MHz for either laser. There are several candidates for the lightwave at about 140 kHz and again at about 1.4 MHz. The most compelling peak, however, is in the innolight at 216 kHz, where the peak is about 2.3e5 rad/RIN.
Below about 30kHz, the loop suppresses the measurement, so one should focus on the region above there. |