How To Optics

Lasing in an Open Cavity Laser

Once you get a hang of it, getting an open cavity laser to lase only takes a few minutes, but it can also seem impossible to do without the proper guidance. Most of the mirrors being used are labeled with a front sticker, this side of the mirror should be placed towards the laser, as its surface is the one we want to reflect off of. You will then want to align the height of the center of the mirror to the height of the center of the white light coming out of the laser, while it doesn't have to be exact, it is much easier to achieve lasing with this setup. Once this is complete, move the mirror ~2 inches away from the tip of the Brewster Window, and align the center of the mirror to the center of the beam horizontally.

This next part takes a little bit of finesse and practice. What you want to do is adjust the vertical angle of the mirror in steps while rotating the entire mirror mount with your hand. The trick is to try and keep the mirror as centered on the beam as possible. The laser will be close to lasing when the beam is centered on the mirror and the back reflected mirror is centered on the Brewster Window.

Mirror Walking

Place the first iris in front of the second mirror. . Now you will learn to mirror-walk the beam so that it goes directly through the center of both irises.

To mirror-walk a laser beam, you must utilize the vertical and horizontal adjustment knobs on the two silvered mirrors to guide the beam. Before beginning, make sure that the mirrors are roughly aligned by physically turning them in their mounts. Next, close the first iris, and open the second. Adjust the H/V knobs on the first mirror such that beam goes through the closed iris. Similarly to Step 1, observe the laser dot on the wall while wearing goggles (to reduce laser dispersion effects) and adjust the knobs until the dot reaches a maximum intensity. Next, open Iris 1 and close Iris 2. Adjust the H/V knobs on such that the beam goes through the closed, making a maximum brightness dot on the wall behind it. Next close Iris 1, and open Iris 2, repeat. Continue this back-and-forth process until satisfied. You will not be satisfied until the beam goes through both irises when they're closed and makes a maximum brightness dot on the wall.