Rise times and fall times

[DZ]

Ok, not as fancy as the graphs above, and this doesn't show the same thing, but it does show the maxy as being alot more stable. Red on bottom, green laser on top.

[mixedgas]

Ok, not as fancy as the graphs above, and this doesn't show the same thing, but it does show the maxy as being alot more stable. Red on bottom, green laser on top.

The spike half way back on the green looks like a self Q-switch.

Steve

[fuzcub]

Time for more pix.
Now I've lashed up a quick version of the Pangolin colour correction circuit:
http://www.pangolin.com/resguide03d.htm
- just the offset/gain control makes a tremendous difference to the turn on time.

Before:



After:



Pulse - with offset and delays:



1 second ramp up, with offset and delay:



10 second ramp up , with offset and delay:




The big red diodes are quite quirky in their modulation charicteristics - if you look closely ( but safely) at their output close up ( especially the narrow divergence lasever red, 6mmx6mm beam at source) It starts off as a big red LED untill the threshold point , when a thin red line of laser action starts in the middle of the beam, that then spreads out untill it fills the whole beam.
I think as this lasing edge passes over the 'light' and 'dark' areas of the diode's surface it makes lumps in the linearity readings . Especially if the light/dark area starts ocsillating.
Ah, the joys of multmode diodes.

I'm using a tektronix TDS2024B scope , and capturing data using Openchoice Desktop. Capturing images direct from the scope is a bit nasty - 320x240 .

I couldn't find a good low frequency signal generator, so I rolled my own with a PIC + USB serial adaptor.
However, it would seen that a USB sound card DAC would be ideal for this type of thing , if someone with the required programming experience were to apply themselves to the task.....

Barney.