What, exactly, is a laser?

What, exactly, is a laser?

How is it possible that the same technology that is used to cut diamonds is popular for its ability to remove hair permanently, or even that this same technology can measure the distance to the moon?

That’s the ‘magic’ of a laser: its many and diverse characteristics – including the ability to generate light and heat energy, as well as its rapid speed and coherence or frequency stability, and the spectrum of colours available – means that the light amplifying qualities of lasers can be applied to solve a wide variety of problems.