Construction of a solid-state pulsed laser with Q-switching and intracavity frequency doubling

For my undergraduate senior seminar project, I built a diode-pumped Nd:YVO₄ pulsed laser (pictured). The goal of the project was to convert the continuous-wave laser into a passively Q-switched pulsed laser by placing a saturable absorber (Cr:YAG) crystal in the cavity.

Funny story: I was overly cautious not to increase the electric current driving the laser diode to a point that exceeded the ability of its thermoelectric temperature controller to maintain a steady output power for the pump. This meant that the pump power was too low for there to be sufficient intensity of the 1064‑nm laser beam within the cavity to saturate the Cr:YAG crystal and trigger passive Q-switching. I found out the following year—during my first year of graduate studies—that the student who picked up where I left off simply turned up the power and observed the expected pulses. Honestly, I’m still kicking myself. 🤦‍♂️

Ultimately, I realized the pulsed operation via active Q-switching instead, using a mechanical chopper wheel, which was much less satisfying. The shortest pulse width measured was 477 ± 32 ns.