My first N2 laser was built in 2002, it consists of a custom cavity manufactured from acrylic and (aka Plexiglas) by the owner of a local plastics shop. I provided him with the specifications and he cut, milled and machined the pieces which I needed. There are probably some design changes I would make if I were to recreate this laser today, but overall it was effective for a first ‘from scratch’ laser project.
The cavity consists of two half pieces with a wide channel cut down the center of them. I mounted my brass electrodes between these two halves and then drilled through the cavity and the electrodes, then used 5 bolts and nuts on each side to clamp the entire assembly close. I drilled the holes on the top to install the two nipples used for the gas feed, and vacuum draw lines. The ends are Plexiglas plates with holes in the center, which microscope glass slide covers where adhered to to create the windows.
The whole assembly was sealed and held together using clear silicone sealant which was allowed to cure for some time. The picture below is a bottom/side and top/side view.
In the photo below you can see an overall view of the nitrogen laser. The copper plates are the top plates of the capacitor, they are glued to a Mylar film sheet which is underneath them. Just below that sheet of Mylar is another sheet of copper which covers the full width and is the bottom plate of the capacitor. The white cylindrical component is a pressurized spark gap I built from scratch. The pressure line from the nitrogen tank regulator (not ocnnected in this photo) feeds into the spark gap, and then an exhaust line runs from the spark gap to a needle valve which feeds the laser cavity near the top of the photo. The vacuum line is connected to the front of the laser tube. Bridging across the top of the laser cavity and attached with duct tape is the charging inductor and you can see the red high voltage lead taped to the surface of the capacitor on the left hand side.
Seen below is a closer shot of the spark gap I built. It’s not a very complex design and ran at a pressure of 40PSI. The bolt on the top is adjustable up and down to adjust the spacing of the internal spark gap. Seals for the adjustable bolt were made from washers I cut out of inner tube tire rubber and those worked pretty well with minimal leakage. Building the spark gap in this manner, enclosed and pressurized, greatly reduced the operational noise of this laser. If you watch videos of home built nitrogen lasers running with open spark gaps, I’m sure you can appreciate the noise levels they generate.
I experimented with several different materials for use as a dielectric before I found one I could lase on without blowing a hole through it. When I moved to a bigger high voltage transformer the dielectric which was working for me previously, also had a hole blown in it. I quit working on this laser when I could not find an immediate source for a better dielectric material. In the photos below you can see a couple of the holes I blew through some trial dielectrics. The first is black polyethylene plastic, the type used in contractor type garbage bags. The second picture is of another material I tried, however the name escaped me at the time of the original documentation of this project.
While I was able to get this laser to work, I was not ever able to achieve what I would call a stable output. Being a first prototype based on limited information I believed I did pretty well, and I believe if I pursue this project again I have gathered enough information to be much more successful. I was able to create a lasing output from the end of the laser to excite various fluorescent dyes, however I never tried it with actual laser dyes in a dye cell.
I did try to use the laser with some R6G solution I had, however the R6G was mixed for use in a dye jet laser, and not a dye cell and I believe it was too concentrated of a mix to illuminate properly through and through. I have preserved some of that solution for future nitrogen projects. Here are some of the final photos I took before I decommissioned this project due to frustration with dielectric materials.