What's the difference between red, green and blue laser?

Question

I see that the red is the cheapest, green costs a bit more and blue is expensive. So what's the difference?

Answer 1

You ask about the color or about the device?

About the color, the only differs in their frequency. Red is a  frequency lower than Green and Green lower that Blue. Approx 390 THz Red; 540 THz Green and 700 THz Blue (Tera Hertz)

About the device: They all are semiconductors diodes from LED types, (Light emitted diode), working as LASER, (highly inverted electrons population); you need higher energy than common LED to get the LASER. And made by different materials, depending on the quantum level gap in order to get the right wave length for light.

Wave length is related to frequency and speed of light. Approx. 750 nm Red; 550 nm Green; 350 nm Blue (nano meter)

The emission wave length (or frequency) depends on the quantum difference between electron 'orbits' on the diode 'junction'. When the electron fall from the upper level to the lower level, a photon is emitted. The wave length of the photon depends on the quantum level difference.

In order to 'produce the quantum level difference' you need to choose different materials to build the diode junction.

Red LASER are easy to build and they are produced in big quantities that lower their price.

Green LASER area little more difficult ro build, so, they cost a little more.

Blue LASER was searched for many years, finally they get the proper mix to build the 'blue junction'. Is harder to build, and there is not enoguht production yet, so, the cost is higher.

Furthermore, every year the diode are build with more 'power', that is another challenge in order to build the proper junction with enough current capacity. Current must flow through the junction in order to 'elevate' the electrons level.