Previously the pump laser has been drifting in and out of multimode. Today I came in and found it constantly running multimode (an obvious symptom being low green production out of the SHG). So I put the current half way between where the multimode starts and clamp current (and set the temperature to keep PSL and pump beat note at 158 MHz beat note at zero MHz offset on the TTFSS temp servo). The multimode was monitored with the SHG GR PD (Thorlabs) while scanning the SHG cavity. Below is a few data point regarding this particular shitty laser.
| Current (A) | Temperature (deg C) | |
| Before (constantly running multimode) | 2.134 | 29.69 |
| Now (no more multimode) | 2.193 | 29.65 |
| Multimode starts (approaching from clamp) | 2.137 | 29.68 |
| Clamp | 2.250 | 29.59 |
| Mode hop (beat note disappeared) | 2.050 | 29.75 |
These numbers were read of the controller box LCD screen. The current readback on the medm screen aren't the same.
Keeping the temperature the same I tweaked the current to figure out MHz/A calibration
| Current (A) | Beat note (MHz) |
| 2.193 | 164.2 |
| 2.136 | 30.2 |
| 2.250 | 308.2 |
| 2.222 | 235.2 |
This set of data yields 2.5MHz/mA (+- 0.1MHz).
Then I keep the current the same, and tweaked the temperature
| Temperature (C) | Beat note (MHz) |
| 29.65 | 164.8 |
| 29.63 | 89.1 |
| 29.62 | 48.2 |
| 29.69 | 290.8 |
| 29.72 | 361.1 |
This yields 34.21MHz/0.01degC (+-6.6MHz)
If I calculated things correctly here this means we are +70 MHz away from multimode at the moment. The temperature would only have to drift .02 deg C to go back to multimode. Could there be a region beyond mode hop that works?
There should be more mode hop free regions at lower currents (so you can get away from the max current).