Made in PSCS, I'm not sure if it can be used in other programs.
Hopefully someone will find this helpful. I don't think I've seen one like this, so I'm sorry if anyone has already posted one. :)
Step o1
Make a canvas of your size choice. I'm using 400x400. Fill with black.
Step o2
Take a soft round brush, choose white as your color, and the size you want your light to be. Mine is 5px. Make a new layer and brush the line where you want it to be.
Step o3
Select Blending Options and set your setting to this, or play around until you find something you like.
Step o4
Then press CTRL+J to duplicate your "light" and position it where you want.
This is my final product
Umm?
And one I made on a picture.( I know it sucks I didn't know what to do with it :P)