Some tips in laser path debugging

Some tips in laser path debugging
First of all, safety is the most important, all the items that may occur specular reflection, including various lenses, frames, pillars, wrenches and jewelry and other items, to prevent their reflection of laser; When dimming the light path, cover the optical device in front of the paper first, and then move it to the appropriate position of the light path; When disassembling optical devices, it is best to block the light path first. Goggles are useless in the dimming path, and they add a layer of insurance to themselves when doing experiments to collect data.
1. Multiple stops, including those fixed on the optical path and those that can be moved at will. In optical experiments, the role of the diaphragm is self-evident, because two points determine a line, and two stops can accurately determine a light path. For the stops fixed on the path, they can help you quickly check and restore the path, even if you accidentally touch which mirror, as long as you can adjust the path to the center of the two stops, you can save a lot of unnecessary trouble. In the experiment, you can also set one to two fixed height but not fixed diaphragm, in the adjustment of the light path, you can move them casually, to test whether the light is on the same level, of course, pay attention to the use of safety.
2. Regarding the adjustment of the level of the light path, in order to facilitate the construction and correction of the light path, keep all the light at the same level or several different levels. In order to adjust a beam of light in any direction and Angle to a desired height and direction, at least two mirrors are required to adjust, so let me talk about a local optical path consisting of two mirrors + two stops: M1→M2→D1→D2. First, adjust the two stops D1 and D2 to the desired height and position to determine the position of the optical path; Then adjust M1 or M2 so that the light spot falls in the center of D1; At this time, observe the position of the light spot on D2, if the light spot is left, then adjust M1, so that the light spot continues to move to the left for a distance (the specific distance is related to the distance between these devices, and you can feel it after proficiency); At this time, the light spot on D1 is also tilted to the left, adjust M2 so that the light spot is again in the center of D1, continue to observe the light spot on D2, repeat these steps, the light spot is tilted up or down. This method can be used to quickly determine the position of the optical path, or to quickly restore the previous experimental conditions.
3. Use the combination of round mirror seat + buckle, which is much easier to use than the horseshoe shaped mirror seat, and it is very convenient to rotate around and before.
4. Adjustment of lens. The lens must not only ensure that the position of the left and right in the optical path is accurate, but also ensure that the laser is concentric with the optical axis. When the laser intensity is weak, can not obviously ionize the air, you can first do not add the lens, adjust the light path, pay attention to the position of the lens behind the placement of at least a diaphragm, and then place the lens, only adjust the lens to make the light through the lens behind the center of the diaphragm, it should be noted that at this time, the optical axis of the lens is not necessarily coaxial with the laser, In this case, the very weak laser light reflected from the lens can be used to roughly adjust the direction of its optical axis. When the laser is strong enough to ionize air (especially the lens and lens combination with a positive focal length), you can first reduce the laser energy to adjust the position of the lens, and then strengthen the energy, through the radiation shape of the plasma generated by laser ionization to determine the optical axis direction, the above method of fixing the optical axis will not be particularly accurate, but the deviation will not be very large.
5. Flexible use of displacement table. The displacement table is generally used to adjust the time delay, focus position, etc., using its high precision characteristics, flexible use, will make your experiment a lot easier.
6. For infrared lasers, use infrared observers to observe weak spots and be better for your eyes.
7. Use half wave plate + polarizer to adjust the laser power. This combination will be much easier to adjust the power than the reflective attenuator.
8. Adjust the straight line (with two stops to set the straight line, two mirrors to adjust the near and far field);
9. Adjust the lens (or beam expansion and contraction, etc.), for occasions requiring precision adjustment, it is best to add a displacement table under the lens, generally adding two stops on the optical path first, after the lens focus. Ensure that the light path is collimated, and then put in the lens, adjust the transverse and longitudinal position of the lens to ensure that through the diaphragm, and then use the lens reflection (generally very weak) to adjust the left and right of the lens and pitch through the diaphragm (the diaphragm is in front of the lens), until the lens front and rear diaphragm are in the center, generally considered to be well adjusted. It’s also a good idea to use plasma filaments to visualize them, a little more precise, and someone upstairs mentioned it.
10. Adjust the delay line, the core idea is to ensure that the space position of the outgoing light does not change within the full stroke. Best with hollow reflectors (incident and outgoing light naturally parallel)