The design of the laser source is described at Laser4DIY Micro Chip Laser. Here we focus on assembling the laser source

Micro Chip Laser Block

The Micro Chip Laser block is our pulsed IR laser source and integrates several functionalities into one assembly:

• Mounting points for the needed optical components, namely laser diode, GRIN lens and laser crystal (including passive Q switch and vapour-deposited mirrors)
• Heat spreader for laser diode and laser crystal
• integrated peltier element for thermoelectric cooling
• water cooling block (hot side of peltier element)
• mounting bracket to be used on the Laser4DIY base plate or standard optical bread boards

Apart from the optical components, it consists of several parts, most of them are machined, either from copper (Cu), aluminum (Al) or acrylic (PMMA). These need to be mounted in the following order (bottom-to-top):

• baseplate (Al)
• plexi spacer (PMMA)
• cooler (Al)
• Peltier element 20W, 15V
• MC-heatspreader (Cu)
• MC-bracket-A (Cu)
• MC-bracket-B (Cu)
• MC-lensbar (Al)

Additionally, the following is also needed

• an thermistor (connected to the TEC controller for reading the temperature)
• 2 tube fittings (for connecting the water cooling)

The STEP files for the machined parts can be found on github: https://github.com/Laser4DIY/LaserSource
Details on the other parts can be found in the BOM below.

For now, we only assembly the cooling stack. The optical components are added later, when the electrical and cooling setup is working.

Assemble the pieces in the order as listed above. Do not add optical components yet. The stacked parts are hold together by 4 M3 screws. MC-bracket-A and -B are hold by 2 M4 screws. Just screw them in loosely now, we will have to add the crystal later.

Setting Up Optical Components

For setting up the optical components, we have chosen to use a custom bread board made from 8mm thick aluminum:

It features a grid of holes with M6 threads that allow the use of standard fixtures for optical components. The micro chip laser block is designed to be placed directly on the bread board as well, the height of the optical axis matches the one of standard components.

There is a 1 inch wide hole in the board, which can take up a beam expander mechanic and a lens. There the laser beam is mirrored downwards and focused onto the PCB lying on the table below.

The bread board is laser cut, you can find the dxf for it in the github repository: https://github.com/Laser4DIY/Laser4DIY_Enclosure/tree/main/lasercut/8mm_aluminum

Now we start setting up the components for the laser source:

• Use the annotated images and the BOM to see where the parts go to
• Start with the large components, the micro chip laser block is the first you should add
• If possible, use the same position for the components. Use the same hole for screwing them down (count the holes in the grid). We will do a fine adjustment later, but now we have to make sure everything fits on the base plate.
• The images show the copper block for the optical amplifier. This is an optional piece, that is not covered yet by this assembly guide. Simply leave it out. The water cooling just uses two tubes to the microchip laser, nothing more.
• Make sure the cables and cooling tubes are not blocking the path of the laser beam.