[Laser] Digikey IR Laser.

[Andrew T. Flowers, K0SM]

David,

I have a couple of those wired up in my expanders and running into a 
10mm lens.  I don't have any way to measure output power right now, so 
I'm keeping current a bit below I(op) to be safe.  I'm not really 
concerned with linearity in my system, but I can tell you that the 
active current region for these devices is something like 50-150ma, so 
you have alot of room to play.  They don't even come with a feedback PD, 
so it's just assumed that you set it and forget it.  I'd like to try 
some troposcatter stuff once I get back to Nebraska this month (clear 
sky, one farmlight every mile or so) and it would be since to have some 
measurement of power output-I don't expect it to be the same at -10C as 
it is in my apartment :-) If anyone knows how to get a rough power 
measurement with out spending big $$$ I'd like to hear it.

I built my expander out of a few sections of PVC and utilized the 5-10cm 
adapter/lens/housing unit that is also on digikey's site.  That seems to 
be enough to keep it cool--mind you I'm running it at  a little below 
I(op) at 50% duty cycle, but it doesn't really get warm.  Anyway, this 
all results in a well collimated "rectangle" of light about 7-8cm long. 
 I used my computer's quickcam to do some alignement--I know it's not 
optimal, but it's good enough until I can borrow a decent camcorder or 
something witha zoom feature.

 I have a schematic of the expander and other laser stuff on my webpage:

http://mail.rochester.edu/~af006m/laser.html

Andy K0SM/2

G0MRF@aol.com wrote:

>Hi group.
>
>A few months ago someone mentioned the 120mW IR laser available from digikey 
>at $20 (ish)
>
>I was going to order one, but wondered if anyone in the group has used one of 
>these devices and has any practical tips.
>
>e.g.
>What's the supply current to output power response like?
>
>Is the standard brass housing large enough to dissipate the heat from a 120mW 
>diode or should I be looking at mounting it in a large heatsink?
>
>It's the first time I'll have used IR.  Does anyone know if a typical digital 
>camera LCD for monitoring my attempts to focus the optics.
>
>Finally, I realise that 120mW is dangerous..........I plan to use a 50mm dia 
>lens with a short focal length to produce a beam that's somewhere between 30 
>and 50mm dia. Hopefully this will be a safe level of 'power density'.  If the 
>diode has a divergence of 30 degrees, then a convex lens of about 25mm focal 
>length should do the job.
>Now to find the best material for the wavelength......
>
>Thanks.
>
>If it all works I'll write up the results on my laser pages.
>
>
>David    G0MRF              <A HREF="www.g0mrf.freeserve.co.uk">www.g0mrf.freeserve.co.uk</A>
>
>
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