on/off cycle limit for VCSELs, 100's MHz possible?

[DopeYtt]

Assuming a suitable drive circuit,

Is it physically possible to pulse VCSELs or other diodes to microWatt power at an on/off "pulse" rate of for instance 500 MegaHertz or faster?

Will I encounter problems of quantum tunnelling?

 

[Wolfman29]

I think you should be able to... purpose-built laser diode drivers can usually do >1Gbps, so I'd think >1GHz is possible.

 

[DopeYtt]

Excuse me, but I must also introduce three caveats:

1. the VCSELs are in the visible spectrum

2. they are regular production units and not created for telecommunications (high performance)

3. the VCSELs' on state must have an exact output intensity which can be any one of at least 256 discrete levels in a range from 1 to 16 microWatts.

 

[Wolfman29]

But I would suppose that regular laser diodes (not VCSELs) should be able to do this, no?

 

[SKeeZ]

i don't think so, VC SELs are specialized for this and i think this application requires more precision than would be possible by a laser diode (keeping fluctuation within 1/16 of a microwatt or less and modulating it over 256 level with 1-16 microwatts is incredibly precise). i think using a VCSEL is a better plan of attack. I also don't know if there are production units easily available for the application. (correct me if im wrong or if i have no idea what im talking about)

 

[DopeYtt]

I would agree that VCSELs are best.

The difficulty for me lies in the fact that of the 40 to 50 suppliers I have contacted, they do not seem to understand issues like:

thermal expansion and contraction

output power as a function of current and temperature induced resistance

average and peak power

uniformity of production unit characteristics

light emittance (if any) below lasing threshold

modulation across the lasing threshold instead of only above it


and so on...

 

[SKeeZ]

In my opinion, there is virtually no way to keep modulation that specific with a diode. and to calibrate a diode & driver pair to the accuracy necessary for this application would be very expensive.