Optical parametric oscillator

Okay kiddo, so have you seen a rainbow before? It's really pretty right? The colors you see in a rainbow are made from light. Each color has a different wavelength, and when they all come together, they make a pretty rainbow.

Now, imagine that we have a special kind of crystal that can take a beam of light and split it into two separate beams with different wavelengths. This is sort of like splitting the rainbow into two separate rainbows with different colors.

But wait, there's more! This crystal can also take those two separate beams and combine them back together to make a new beam of light. This new beam of light has a different wavelength than the original beam, which means it has a different color!

This new beam of light is called an "optical parametric oscillator." It's like taking two colors and mixing them together to make a brand new color. Cool, right? This is how scientists and engineers can create laser beams of different colors for different purposes.