Any laser more than 20-30 mW dangerous for eye !
And more than 60-70 mW even for skin .
So in all case you must work very carefully, no any reflective objects on working table etc. It is serious ! I know number of peoples that lost their eye thanks to accidental reflection.
As far as I know - to buy 2-3 lasers will not a problem,
nobody not buy at once 1000 witout sample testing !
If you need not more than 150-200 mW of power @0.8 range
real price will be 30-150 $ mostly depend of packaging.
Unpackaged sandwich (only laser between 2 copper heatsinks) = 30-50$
but you'll need active cooling, I meen termoelectrical cooling with appropriate thermal capacity ( Melcor for example, approx. 20-30 buks) and some electronics for driving of course. As a rule uncollimated laser
light is unusable, beam profile for diode laser is cone with 3-5 degree
@ top, and try to calculate what your reciever will get after 200-300m !
A few nanowatts (if not pico-!). So for real working open space communication line you'll need 2 telescopes (collimators) for laser and for reciever with max. achievable aperture... and lenses with 15-20 sm
diameter will be, I think, most expensive part of project.
Also you will need narrowband optical filter for your reciever
to avoid sunlight that have enough power @0.8 mkm, it's price 10-15$
but it hard to get, becouse most of filters is customize devices so
as a rule it is not "on shelf" product.
I not meen that such project is unreal, I try to show you possible buttlenecks! :roll: