## 2 Microchip Laser
### Design of Fixed Cavity  
In the second setup, the optomechanics used for mounting and positioning the laser cavity components were reviewed. As such, the assembly of the fixed optical cavity used a setup similar to the one shown in Figure 1. To hold the glass components, aluminum and Polyethylene Terephthalate Glycol (PETG) material (3D printed parts) clamps were designed and manufactured. The set of new aluminum and 3D printed parts (shown in Figure 3) substituted the previous aluminum holders (shown in Figure 1). The gluing of the optical components to a common substrate allowed for easier integration with the pumping system of the microchip laser. The active medium used had a thickness of 1 mm. An assembly table was designed for this purpose, and a procedure was drawn. The resulting cavity was characterized.  
The glue used to secure the glass components to the aluminum substrate needed to be heated to 66 \({}^{\circ}\)C. For this reason, a system to hold and heat up the aluminum substrate was designed and manufactured, as shown in Figure 3. In Figure 3a, the heating system for the substrate is presented, and in Figure 3b, the clamp for the glass components is detailed. The heating system for the substrate assembled in the optomechanics is shown in Figure 3c.  
Three attempts at the gluing of the cavity were necessary to reach success, the main limitation being the shrinkage of the glue during the curing process. The first attempt consisted of the gluing of the active medium, followed by the gluing of both the output coupler and Q-switch simultaneously. The second gluing is shown in Figure 4.  
The first attempt was not successful because the laser emission disappeared during the second gluing. The output coupler and Q-switch were removed from the substrate for a second attempt. For the second attempt, the procedure was modified to separate the gluing of the Q-switch and the output coupler. Instead of being conducted simultaneously, the output coupler was glued first, followed by the gluing of the Q-switch. During the gluing of the Q-switch, the emission disappeared, and the process was stopped. During the removal of the Q-switch from the substrate, the active medium came loose.  
Figure 3: CAD designs of (**a**) the heating system for the substrate, (**b**) the clamps for the glass components, and (**c**) the heating system assembled on its optomechanics.  
For the third attempt, the active medium was glued first. This process is shown in Figure 5a. After the gluing of the active medium, laser emission was observed. Without gluing the Q-switch, the emission obtained from this cavity was not stable. After several attempts at aligning the Q-switch to obtain pulsed laser emission, the third attempt was considered successful in assembling a fixed optical cavity with continuous wave (CW) emission, shown in Figure 5b.  
The pulse shape for each cavity emission was observed (see Figure 6), and the energy and peak power of the pulses are presented in Section 2.3. The dependency of the output optical power with the pumping power was measured (see Figure 7).  
Figure 4: Gluing of the output coupler and the saturable absorber on the first attempt for the second implementation.  
Figure 5: (**a**) The gluing of the active medium on the third attempt for the second implementation and (**b**) the resulting fixed optical cavity.  
Figure 6: Shape of the pulse observed on the oscilloscope. The x-axis is time, with the time division being (**a**) 10 ns, (**b**) 20 ms, and (**c**) 5 ms. The y-axis is voltage.