What are you trying to do, it won't hold that diameter over distance, that's why there is a built in expander in every dpss green I have ever seen.
If you take the double concave/GRIN lens and the final focus lens out, then you will see the beam straight out of the crystal is less than needle thin, it's like 3 hairs thick, but it will diverge over distance faster.
If you find a tiny beam that carries please let us know, I would like to see it because the emitter, in this case pump and crystal set will have to be sub micro with an expander set up after that. The crystal out may be 2 hairs thick or 1 hair thick.
The original 532's were set to infinity with a 1.5 - 2.0 mm beam at the aperture, but match lighters wanted it concentrated to, well light matches so the final focus lens was changed, you can't even get a good infinity focus, so I use my own lens and expand them even wider and to a very nice point in the clouds.
The size of the exiting beam from the crystal is the part we can't change, you could have a 1mm beam at the aperture, but far field will not be as tight, in fact even the ones that look like they come to a point far away are really a much bigger spot, it just looks small because of our perception, just like streetlights look a lot bigger sitting on the ground by your feet than up on a wire, imagine how big that green dot really is...it's many feet wide in the clouds but looks like a pin point.
Now they could employ and align a lot of complicated telescopic optics, but they slowly rob power and 1mm or 2 out has never been a big selling point, just match lighting at the expense of a moon size spot.
I like the infinity focus myself.
In short you can change your final focus lens and have a sub mm beam, but your far field spot will be bigger.
This is with just the final focus lens removed and my own larger and longer focal length lens in the sliding tube, this simple setup allows me to get a pinpoint looking far field dot. The output is smaller than it looks, I should have set a penny down under it, now without the double concave inside that is right now expanding the beam out of the crystal the beam is hair thin, but diverges faster. My set up makes a 2.5 - 3.5 mm beam out of the end of my slider, but the spot will paint the bottoms of clouds quite well. Yes the paste is mounting type and has solidified, but I know I should clean it up.
