Flat sheet 780nm laser diode

For some measurement techniques, I have to produce a sheeted (rectangular) laser beam in dimensions of the range of 20/30mmx1mm or 2mm. (max 0.5-3mW)

I searched on the internet already for some weeks find such low-cost laser diodes of compact systems, but without luck.

I hope someone can help me to find a laser diode that can give me this result.

Thanks in advance.

Is this needed for some photosensor or night vision? 780nm won't be visible.

scratch this idea said:

I have no idea where you can find such a low powered 780nm diode-- however this is what you want to make the effect you're looking for.

Click to expand...

Oh wait those dimensions... you want a multimode diode at those... Scratch the ebay suggestion. I do not think there are any multimode diodes at such a low power

Thanks for answer,

In fact, it's for a photosensor/phototransistor. I want to sense small particles and calculate the time the particle enters/exits the beam and measure the size of the particles. So it has to have relative fixed dimensions.

Some more information: I want making something like this:
Laser precipitation monitor (Distrometer)