The beamdump

Before my summer vacation I ordered 100 razor blades, and here they all are bolted together to create closest thing to a dark body that I care to construct:razors2

The razor blades were wrapped individually, and the discarded wrappings is the big mess in the background.

It’s not 100% black, the reflection of the laser is still visible:


but it’s still a lot better than the next best thing; a piece of black anodized aluminium:


The razors are placed in a 3D-printed structure, where a clever combination of geometry and absorbing filters takes good care of any excess photons.¹ And here it is:


The filters are the cheapest red colour correction filters I could find, and while they exhibit an optical density >3 at 532 nm, they are quite unusable.


The reddish dot next to the razors is fluorescence inside the red filter. It will likely cause severe interference with the Raman signal.

I will exchange them with Hoya B-390 or Schott BG12 bandpass filters, whichever I stumble upon first.

OpenSCAD file for the beamdump

¹ A simple, high-performance Thomson-scattering diagnostic for high-temperature plasma research
D J Den Hartog and M Cekic 1994 Meas. Sci. Technol. 5 1115


3 thoughts on “The beamdump

  1. LonC says:

    Have you stacked the razor blades directly on top of each other?
    The graphic from your previous post ( suggested a space between the blades.

    I think a thin sheet of black dyed paper between the blades could reduce the reflection of your laser even further. But the black edge of the paper shouldn’t align with the edges of the razor blades. The razor blades should build something like a “fence” (again see the linked graphic) so that the light can get in between the blades and the light intensity can degrease over multiple reflections.

    Nice project!


  2. Hi LonC
    Yes the razor blades are stacked directly on top of each other. I have no idea if a razor-paper-razor stack would work as well. If you try it out I would love to hear.


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