Stimulated Emission Explained

[@krishnasphysics]

Sir,i understood your explanation of conservation of energy,but what about conservation of momentum,before interaction E/C,after2E/c,is it violation of conservation of momentum?Pls reply sir

[@anishsaraf4613]

Great video! Just had a small doubt, why does stimulated emission occur, what’s the reason behind the electron transitioning to a lower energy when an external photon is incident on it?

[@idektega4271]

It’s funny how we are both looking for the same answer Just saw your comment on another video asking the same question

[@azb77]

same question, watched the video to get the answer, found the question in the comments instead lol

[@b048peyyettipavankartikpra4]

I think its beacuse of a fact that for an electron to jump into another Energy level it takes a very specific amount of energy which is definitely higher than what is incident on it in this instance.

[@srijanisallyouneed]

Im not expert in this, but to my account : Energy levels are higher in amount to above ( as En = n^2π^2h_cut^2 / 8ml^2) So, lower level = lower energy states As, some sort of hw or E falls on the lower level , it gets too high energy to remain in the lower state and gets transitioned to higher one🙏🏻

[@luciferinjustice2632]

It had to do with resonance phenomenon and electron photon scattering.

[@adityarawat5659]

if photons carry energy, shouldn't the electron be forced to higher excited states? What makes it drop even lower? why an electron chooses to drop rather than raise to higher levels upon photon absorption "It's just like I passed an heatwave through water but it froze" Plz explain

[@JordanEdmundsEECS]

Yeah, it’s better to think of it more like “add heat -> something intermediate happens that causes generation of more heat” than the heat itself just getting dissipated (absorbed), because here it is not. This is a very weird feature and to really understand it you need to understand time-dependent perturbation theory.

[@adityarawat5659]

@@JordanEdmundsEECS so I guess I will just accept it without any further argument. It is what it is. Thanks for replying tho.

[@physicswithsirmuneer8975]

good sir but i had a question if there are four electrons in the excited state can it possible that all can absorb single photon or there must be four photons necessary to absorb the electron?

[@salanove]

Hi Jordan, thanks for the video again. Just a simple question... In photon absorption it's easy to see that the energy coming from the photon is absorbed as a gain in "potential energy" of the electron which has been promoted to a higher energy state i.e. Ei=hv-->Ef=(E2-E1). Ei=Ef--> hv=(E2-E1). Now, how is energy conserved in stimulated emission? I mean if we have Ei=hv and Ef=hv+(E1-E2)---> hv=hv+(E1-E2)...?

[@JordanEdmundsEECS]

Great question! The incoming photon’s energy isn’t affected, but the potential energy of the electron in the conduction band is converted into photon energy. The total energy is the same (2*hf), it’s just half of it is converted from potential to kinetic.

[@zustzu9013]

Very nice video,❤️ I am from india, i like your video ❤️

[@hekk_tech5975]

is there not a level 3? i cannot understand why the excited electrons dont go further to, lets say to level 3 or just out of its orbit? why should they go down again where more resistance (if i shall put it this way) happens?

[@JordanEdmundsEECS]

Great question. There might be a level above, here we are assuming there is not, and we are treating the two energy levels in isolation. We could add more energy levels, but the basic idea of what’s going on is the same. Also, because of quantum mechanics weirdness, it turns out that the probability of getting stimulated emission is exactly the same as absorption (if the electron it were in the lower level rather than the upper one).

[@saketpanigrahi]

@@JordanEdmundsEECS if probability of absorption and emission are same than why dont we get two wavelength coming out.

[@TriPham-xd9wk]

After we synchronize all body cells we could slowly stimulated it to higher vibration to emit particle and a few weeks the Corps left nothing or freeze it into statue

[@4pharaoh]

Great Video thanks: Question though - @3:15 you mention phase or mode locked- what is the mechanism that allows this? How can absorption and emissions occur instantaneously? shouldn't their be a prorogation delay along the lenght of the laser that would throw the light out of phase?

[@ARCSTREAMS]

funny how he gave your comment a like but did not answer it, i dont get that

[@jbragg33]

Hi, at 3:55 when you say "we cannot have the same energy for electrons in state 1, but if we have E_1 being a very degenerated energy level, each of the associated states have the same energy, right ? Say we have E_1 the energy, and states |1>, |2>, |3> associated to that same energy, and each state has 2 electrons (with opposite spins according to the Pauli exclusion principle), we could have 6 electrons with the same energy level right ? Albeit not the same "state", because the eigenstates of the energy are degenerated.4:03

[@cachecacheboris]

@2:29 the magnitude is not the same, you have factor 2, hence "stimulated"

[@TriPham-xd9wk]

This technology could recycle waste in vast scale to reclaim material in original matter and energy extraction in landfill a clean way

[@goodexams3064]

@2:19 why? how? ( other than lifetime explanation)

[@SaurabhShukla_22]

so can anybody tell me "why does stimulated emission happen in first place". Note: Please don't answer "what is stimulated emission", i know that, answer (if you can) "why". other ways of asking this question is : what exactly is the incoming photon doing to the excited electron, what is this "Stimulation". The reason I ask this is: it is non intuitive that you give something energy and it comes down; now if you are going to argue that it came down due to population inversion or because it was in (unstable) excited state, then it anyway had to come down (via spontaneous emission). then what is the role of incoming photon, and why the outgoing photons (2 of them) in stimulated emission have same phase and direction?

[@goodexams3064]

@4:28 why?

[@ZangpoJigme]

wrong explanation