Solaris doesn't work the best with the 4K, none of the VCSELS do , I'd say VCSEL are excellent for rear add ons, due to the poor IR transmission of the optics and multiple lenses.
The solaris beam is too tight for the Alpex 4K FOV, I'd say the little Zulus VCSEL IR gives a cleaner image than most other vcsels I've tried...
LED gives a cracking image, at most peoples shooting ranges...on the Alpex, etc <200yds ..
At night go and take a ShootNC target and place it 40yds away, look through with a VCSEL and you will notice the image has very small tiny artefacts in it, also there is a sort of reflection back that actually loses detail on some smooth surfaces... The small inner rings will not be visible on the target. For a quick example look through a Pard DS35 you will not see the target inner rings clearly...
Swap to an LED illuminator and the target will be crystal clear, the image silky smooth and no artefacts at all... you will also vividly see the smaller inner rings of the target and shot impact with more definition..
This image difference is noticeable in the field also , the LED retains a very smooth detailed image, but the VCSEL although having more intensity and further throw obviously from being laser based , has nowhere near as clean an image, diffused on non diffused makes no difference.
Thats why for C50, Alpex A50T, Alpex A50E , you don't need anything more under <200yds, they cost less than <£50 , the image on close range rats and rabbits and flood ability is unreal, pin sharp. They work much better also on the likes of an NV008S (transform them) and IMO the Zulus looks great with these also..
All of the footage I upload of rats and rabbits is using a 50mm LED 95% of the time.