For a simple ruby laser to work it needs a ruby rod that has a fully silvered mirror on one side and a partially silvered mirror on the other, it also needs two flashlamps, one on either side, just like in the image.
The Ruby laser is the most simple example of a solid state laser
Other types of laser
There are many types of laser such as, gas lasers which use chemical reactions as power, different chemicals are the lasing mediums.
Also there are gas lasers that use different gases as lasing mediums.
back to LASER