Cuvette Holder Upgrade

The previous cuvette suffered from astigmatism which reduced the amount of ligth processed by the spectrometer. The new cuvette holder improves on this and allow 4 to 4.5 more signal to reach the spectrometer which yield better spectra for diluted compounds.

The new cuvette is shown below and requires new 3D parts to be printed. I strongly advice to use SLS printing technology and not FDM technology for these parts. The files can be downloaded here.

The cuvette holder already foresee an interlock mechanism for the laser but it is not used now so don’t pay attention to it. The cuvette holder also implements a beam dump slot to prevent unwanted reflections to enter back into the setup.

Once you received the parts, you will need to make several small modifications using some of your workshop tools:

  • Use a large 10.0 mm drill bit to bring the vial hole to the correct dimension. Do the same for the 4 rods holes using a 6.0 mm drill bit;
  • Pass a 2.7 mm drill bit in the the five small holes and tap them to M3;
  • Pass a 3.2 mm drill bit into the two larger holes holding the optics and tap them to M4;
  • Tap the four remaining bottom holes to M4 helicoils;
  • Pass a 2.9 mm drill bit into the cuvette holder folding holes and then a H7 bore;
  • Put the cuvette cap in place and insert a 3×50 DIN7 m6 pin to create the cap folding mechanism (you’ll need to use a vise and gentle force).

Once you have applied all the fixes to the printed parts and flushed them with air to remove dust, you can insert the cylindrical lens and the spherical lens according to the following illustration:

The cylindrical lens can be inserted from below and may require a gentle push to fit in place. Do not force as it may break the lens. Once in place, secure the lenses using M4 set screws with nylon tip.

You can now fix the new cuvette holder on the breadboard through the 6 mm cage rods and secure it with 4 M3x10 set screws. Alignment is performed using Rhodamine as done previously.

The BOM is given here-below and increase the price of the spectrometer by an additionnal 67.70€.