It can be as simple as a rectangle shape layer, scale one end, then add a blur to it. If necessary you could rasterize the shape before blurring, just make sure it is on its own layer first. When your satisfied, duplicate and scale for how ever many beams you need.
Instead of bluring the object, you could blur a layer mask. In fact, that may be better,
Fill the layer with white
add a path on the layer mask with the brush tool, then blur the mask.
Play with each and see which one works better for you and which is easier, they may not be necessarily the same thing.