Out of alignment?

I have read that gas lasers can become out of alignment. This is something new to me, as I haven't heard of it before. How can you tell if one is? How is it fixed?

Also, can other types of lasers, especially diodes, be out of alignment as well?

Gas Lasers like HeNe must have mirrors mounted to each end
of the tube to direct 100% of the beam at the rear back to the
front to a ~99% reflective mirror that again reflects the beam
back to the rear mirror. When the power of the internal plasma
gets high enough it will exit at the ~99% reflective mirror.

These mirrors are mechanically adjustable and can come out
of alignment if mechanically disturbed.

The reflecting "mirrors" on a Laser Diode are not mechanically
adjustable as far as I know..


Jerry

You can contact us at any time on our Website: J.BAUER Electronics

Gas lasers have mirrors that are physically adjustable, as do many other types of lasers. They're not always easily adjustable, as in the case of the majority of HeNe tubes, but even these can be adjusted by using a jig designed for the purpose.

Unless the reflective surfaces of the mirrors in any laser system are perfectly aligned, the output will drop off and in extreme cases disappear altogether. With most larger gas laser systems the mirrors are both adjustable and replaceable, and they require regular alignments in order to maintain peak output.

The process of aligning gas lasers involves a laser power meter (preferably analog instead of digital since it's easier to read power peaks with a needle on a meter than with a digital number display) and a tool to adjust the angle of the mirrors. One begins making tiny adjustments to one of the mirrors while watching output. As the adjustment is made, the power will either rise or fall. Once this mirror has been adjusted to peak power, the other is adjusted the same way. Once that hits a peak, it's back to the other mirror, and so it goes, back and forth until the absolute highest power output is reached. This process is called "walking" the mirrors.

With diodes, the mirrors consist of the front and rear facets of a tiny piece of crystal, so they cannot be adjusted nor can they go out of alignment. They can, however, be blown completely apart by overvoltage/overcurrent.

I see. Can you tell just by looking if it's out of alignment though? Sorry if this seems like a dumb question...

Sometimes the beam shape and power level are indicators, so yes a trained eye might often be able to tell just by looking.