4" 4% Transmission Flat, Uncoated

The 1/20 wave flatness on this 4" optic made aligning my interferometer a breeze. The uncoated surface gives me exactly the 4% reflection I needed for my reference beam.

Finally got around to checking this 4" flat against my Newport mirror, and the 1/20 wave PV figure is spot-on. The uncoated side gives a clean 4% reflection that's perfect for my alignment setup without any ghosting issues.

Checked the flatness with my interferometer and it read right at 1/20 wave PV, exactly as specified. The uncoated surface gives that clean 4% reflectance for my setup, and the back coating holds up well without any visible haze.