True enough, but the issue is where it ends up as heat. If the partially reflective mirror reflects some of the beam and passes the rest through, which is how I understand beam splitters to work, the pass-through part of the beam needs to be caught by a non-reflective surface to convert the beam to heat safely.
Just went on the assumption it wasn’t any kind of beam splitter, just ‘partially’ reflective. If it isn’t reflected it must be absorbing it. Anytime there is something in the beam path you loose power.
Good luck with this…
You need a small amount of air to ensure debris doesn’t collect on the lens…
Found what I am looking for but it’s not cheap. AKA “Beam Attenuator”:
surprise 
How about this: Electric motor with black steel disk with holes in it that interrupts the beam at highish frequency. If I have a tube black on the inside on the input side, it would stop any potential reflections. The spinning disk cools itself.
The disk could be more of a star shape rather than holes so depending on how far it is across the beam, the more it blocks it. What do you think?
Agreed, but not knowing how much air pressure he is using I thought it would be a simple test.
I had a K-40 in the beginning then I upgraded the controller board to a Cohesion3d. with the new upgrade I was able to do exactly what you are asking to do. the trick was that I had the old power controller board in the system. When i had lightburne as low as it would go I then lowered the old digital controler. I was able to print text at .4 mm I had to use a eye loop to read it and it was clear and readable.
This would reflect to a “beam dump”- a piece of black anodized (not painted) aluminum. That should not have a further reflection.
For continuous use, it would need to be a fan-cooled heatsink in back, or even water cooled.
I know this thread is a few months old and I haven’t been on in a while. I have a K40 but recently added a 5w and 10w diode laser from xTool (the D1). If you want very fine text, and you can afford $600 for a base model, the D1 diode is the way to go. Works great with Lightburn and you get the additional working area and open frame, easy to use. I now have 3 devices. K40, extended bed xTool 10w (24x48") and the standard with a 5w head that is interchangeable with the 10w. Very fine text and pinpoint focus can be achieved.
Play with your PWM frequency. At lower PWM freq you should be able to go to a lower % of power since each ON time pulse width will increase and should give the laser a long enough time to respond with output.