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Laser Fabrication


The first and most critical part of fabricating the OpenQuantum apparatus is building the precision laser that enables atomic cooling. For more background on why this is necessary, please read our article that describes the mechanics of laser cooling.

Our laser is capable of achieving sub-10MHz linewidth, which is necessary and sufficient for cooling Rb-87 atoms.



Bill of Materials


To fabricate the laser, you will need access to a soldering iron, hex drivers, 12mm M4 and M6 bolts, superglue or epoxy, and an FDM 3D printer. Optional but recommended is a gauge block and some form of mechanical indicator to ensure alignment. The total bill of materials comes out to roughly $300, with plenty of spare parts.

- Sharp GH0782RA2C 200mW 780nm LD                 ($46 for five)
- Aspheric collimation lens                                           ($10 each)
- Laser mount holder                                                      ($12 for four)
- Copper laser mount                                                      ($12 each)
- Thermoelectric (Peltier) cooler                                  ($12 for two)
- 10K NTC thermistor                                                       ($9 for 5)
- Heatsink                                                                           ($12 for two)
- Piezo actuator                                                                ($65 each)
- 100TPI screw & bushing                                             ($12 for one set)
- 1800grooves/mm holographic grating                   ($97 each)
- Steel compression spring                                           ($8 for five)
- M3 heat-set inserts                                                      ($20 for a kit)


3D Printing

All of the files required for the laser can be downloaded using the following links:

- Base 
- Cover
- Flexure
- Piezo/Screw Coupler




Assembly

To assemble the laser module:

  1. Place the diode inside the spring and then clamp it tightly in the copper mount
  2. Use a single drop of glue to secure the thermistor inside the copper mount, as close to the diode as possible to get the most responsive temperature measurement
  3. Place the copper mount inside the aluminum holder block and bolt it shut very tightly
  4. Attach the Peltier cooler to the bottom of the aluminum holder with one of the included thermal adhesive pads
  5. Attach the copper heatsink to the other side of the Peltier cooler with the other thermal adhesive pad
  6. Using a soldering iron, insert two M6 heat-set threaded inserts into the base
  7. Bolt the aluminum holder tightly into the base with two M6 bolts. It is recommended to use an indicator and a gauge block to ensure that the copper mount is as parallel as possible to the laser base
  8. Using a soldering iron, inserts four M4 heat-set threaded inserts into the base
  9. Bolt down the flexure with four M4 bolts. Again, it is very helpful to use an indicator to ensure parallelism to the base
  10. Place a compression spring between the base and flexure to preload it
  11. Epoxy or glue the 100TPI bushing into the base
  12. Place the piezo actuator into the pocket on the opposite side of the flexure
  13. Tighten the 100TPI screw into the bushing until it makes contact with the piezo
  14. Place the grating into the slot on the flexure
  15. Insert four more M4 heat-set threaded inserts into the walls of the base
  16. Bolt down the cover to seal the laser with four M4 bolts


Operation


To operate the laser, three precision controllers are needed:

1. Laser current controller (0-250mA, <100uA RMS noise)
2. Thermoelectric cooler controller (stability to 0.005° C)
3. Piezoelectric actuator controller (0-50V, <10mV RMS noise)

We are working on publishing documentation for these controllers.