Blackened Optical Slit Plate: 20 μm Case Study
What We Cut
These are stainless slit plates for optical light-blocking. We laser-cut the slits first, then blacken the surface to kill reflections. The final slit width is 20 μm, held to ±3 μm after the blackening step. That last part is what makes this job tricky—the oxide layer changes the dimension.
The Problem
Blackened surfaces do not conduct heat. Standard laser cutting dumps enough energy into the surrounding oxide to blister the edge. On a 20 μm slit, a 2 μm peel-back is a 10% error. We also learned early that if we cut exactly 20 μm, the blackening shrinkage closes the slit to 17–18 μm. The plate is scrap.
How We Fixed It
We cut on a femtosecond UV line. Pulse width is under 300 fs, so the material vaporizes before heat spreads into the blackened layer. We cut the slit at 23–24 μm to feed the oxide growth. After blackening, every lot gets sampled under an optical measuring scope. The slit settles at 20 μm ±3 μm, edges stay intact, and the surface reflectance drops to instrument noise.
Numbers That Matter
Optical grade
Across the full plate
No stray light
Product Gallery
Blackened Slit Plate Sample
Related Manufacturing Capability
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