How to prepare a tapered nanofiber to be mounted on the scattering / transmission optical characterization setup.

Disclaimer

This document was written in February 2022. Its aim is to work as a step-by-step guide for the preparation of the nanofibers to be measured in the setup for transmission and scattering measurements in its February 2022 form.

Fiber Preparation

1. Take the fiber mounted on the C-shaped metal holder from the storage box.
2. Place the holder on the Lab Jack placed inside the pulling system hood.
3. On the pulling system, run the pulling procedure you used to pull the VERY SAME FIBER you want to mount. I.e., for 360 nm diameter optimized to work at a wavelength of 780 nm fibers used for the NanoBright project, run the following profile: D:/Tirage/HP780/07_Dec_2020_10h27-PUTM-rw180-Lw3-L00.43.txt. This will ensure that the clamps of the pulling stage are at the right distance for the next steps.
4. Approach the pulling stage with the fiber, manually and carefully moving the Lab Jack block. At the end of this step, the fiber should approximately match the grooves of the two clamps.
5. When approximately in the right position, change the fiber height to precisely match the grooves, close these latter and fix the Lab Jack at the optical table.
6. Take a small vial and fill it with acetone. Then, close the vial with a piece of Parafilm and cut a small opening, in order to insert the fiber later. Acetone can soften the external jacket of most of the silica fibers, making its removal easier.
7. Insert the fiber into the hole cut into the Parafilm and submerge one end into the acetone. Wait for ~20 minutes for the jacket to be softened.
8. Remove the jacket using the fiber stripping tool. Before doing this, with the help of a ruler, measure ~4.5 cm from the edge of the sample holder towards the end of the fiber and remove the remaining jacket starting from there, as this length will be important for the next steps.
   This is one of the most high-risk steps of the entire procedure, before doing this on an important sample, try it on a ''dummy'' sample.
9. Repeat steps 7 and 8 for the other side of the fiber.
10. Open the two clamps that block the fiber.
    Attention! There is the possibility that the clamps could be sticked to the fiber, thus their opening could potentially break the fiber. To avoid this, use the tweezers to block the fiber in its position without touching it and just exert a slight pressure on it while carefully opening the clamps.
11. Without removing the holder from the Lab Jack, approach it with the fiber cleaver.
12. Measure the actual distance from the edge of the holder to the edge of the jacket. If you properly estimated the length in step 8, it should be around 4.5 - 4.8 cm. Write down the two lengths at the highest precision you can.
13. Calculate the length you need to reach 6.06 cm. This latter is the exact length from the side of the holder to the lateral walls of the box.
14. On the fiber cleaver, there is a scale. When placing the fiber to match the grooves of the cleaver, align the jacket edge with the tick that matches the length you calculated in the previous step. Please take in mind that you will have only one occasion to cut the fiber at the right length, hence do this step as precisely as you can.
15. Clamp the fiber inside the fiber cleaver.
16. Cut the fiber. The cleaver requires only a slight pressure to cut the fiber, hence try to familiarize with the pressure you should exert before the actual cut, also without any fiber.
17. Oper the clamp, move the fiber up by means of the Lab Jack, move apart the cleaver. After using the fiber cleaver, remove the small fiber piece that will remain inside it and dispose it into the red boxes under the hood.
18. Pick the box in which the fiber has to be mounted. If not already done, remove the lid and unscrew the screws that are fixing the lateral parts of the box. Do this operation under the hood, to avoid contamination of the box by dust. If the box is contaminated by dust, wipe it with IPA (Isopropyl Alcohol) and optical paper.There are also two screws that fix the central block on the base of the box, slightly unscrew these, as this will allow to perfect the position of the fiber inside the box.
19. Place the sample in the central block of the box, by matching the groove shaped like the sample holder. If the holder can move inside the grooves, fix it with a small clamp (there are four threaded holes on the central block).
20. Before mounting again the lateral box walls, wipe the ends of the fiber with IPA and optical paper, as it will remove electrostatics charges on the fiber, favoring the insertion of this latter inside the connectors.
21. Mount the lateral wall of the box, paying a lot of attention to insert the fiber end in the connector while not bending it or forcing it against the connector wall.
    This is one of the most high-risk steps of the entire procedure, before doing this on an important sample, try it on a ''dummy'' sample.
22. Screw-in the four screws in the threaded holes to fix the wall of the box in its position.
23. Repeat steps 20-22 for the other fiber end.
24. Close the box lid.
25. Screw-in the FC connectors on both sides of the box.
26. Profit.

Unmounting the box and the samples from a previous measurement

Most of the times, the procedure described in the previous section will be followed after having measured a previous sample. In this section the steps to follow to move the box from the measurement setup and to unmount the sample from the box will be described.

1. Mark the position of the box with the lateral clamps that you will find on the optical table. Although the best position of the sample will change for each fiber, this step can ensure a rough positioning of it around the good spot.
2. Store the position of the micrometric screw mounted on the principal post. Also in this case, doing this could help in finding the right focus for the new sample.
3. Move the same micrometric screw all the way up, carefully unscrew the objective lens.
   IMPORTANT!! The objective lens is mounted on a 3-axis micromanipulator. Try to move ONLY the axis that moves the fiber parallel to its axis, the other ones must be moved ONLY if an evident misalignment occurs. If one moves the other axes, the alignment of the entire scattering detection branch will be lost and it is very hard to align it again.
4. Unscrew the FC connectors from the input and transmission side of the fiber. ATTENTION Do not unscrew the connectors directly linked to the box, but the ones connecting the small patch cables to further optical fibers.
5. Move the box under the pulling system hood.
6. Unscrew the other two FC connectors from both sides of the box.
7. Remove the box lid.
8. Unscrew the four screws that fix the lateral wall of the box.
9. Remove the lateral wall very carefully, as the fiber is not fixed to the connectors and the wrong movement can break the fiber very easily.
   This is one of the most high-risk steps of the entire procedure, before doing this on an important sample, try it on a ''dummy'' sample.
10. Repeat steps 8 and 9 for the other fiber side.
11. Unmount the fiber from the box and store it in the storage box.
12. At this point, the box will be empty and the procedure described in section Fiber preparation can be followed.