Continuing the discussion from Staff still closing threads too early:
I believe this would operate as you propose - but it has some drawbacks.
- The lens is more expensive than the window.
- I believe the “lens 2” you show is a more expensive optic than the existing one.
- If the optics are not perfectly matched, the beam is diverges.
- Even if the optics are perfectly matched, the beam is still slightly diverging, because of quantum mechanical effects.
- (most importantly) if the beam reflects in the current design, it diverges so that the power density drops quickly. In the proposed design, if the beam reflects, it’s extremely destructive.