Laser science questions (beginner)

[pobri19]

Hi guys, I'm reading up on lasers and what they are/how they work to get a better understanding of what I'm going to be diving into. Is my understanding right? Feel free to correct whatever I'm saying incorrectly or raise significant points By the way keep in mind this is coming from someone with zero physics background, so I wouldn't be surprised if I'm way off.

Electrical current is 'pumped' through the diode to raise the energy level of the atoms (excite them) so they emit photons, these photons then hit the excited atoms, these excited atoms will then release another photon of the same wavelength in the same direction and so on, until a lot of photons are released in the same direction producing the laser beam.

However, if my understanding is correct, what I want to know is, how is it ensured the the beam is going in the right direction? I.e straight out the end of the laser (opposed to it bouncing off in a different direction from the diode).

And how are these photons reflected in the diode as to produce a stronger beam (I read that partially reflective mirrors (output couplers) are used in some setups to bounce the protons back and fourth through the medium to increase the size of the beam by exciting more atoms with the protons).

Are they not reflected in the diode? Is it a single stream of protons that aren't replicated inside the diode like a mirror setup would do?

Thanks!

 

[Fonduman]

a basic model (but probably doesnt happen in solid state diodes) is a tube with a mirror at one end and the other end has a semi reflective sheet (so some can pass through as the laser beam) so theres a degree of the light that keeps passing between the mirrors to help stimulate further emission. i believe (but not certain) that this is how the first ruby laser worked.

the lense focuses the light coming out of the diode: its not all going the same direction until its focused.

 

[ossumguywill]

Yep-the photons bounce back and forth between a mirror and semi-reflective sheet. And if you look at the output of a laser diode, it's not focused. The reason a gas laser has a tight beam and a diode has a divergent beam is because of the length of the lasing cavity compared to the width. A diode has a short and fat cavity while a gas laser has a skinny and long cavity.