I read or skimmed the comments and generally agree. You construct you physical (sans mathematical) wall logically collating known underpinnings. Concise. Accurate. Easy to watch. Wot not to like…! Consider, if you will, another such piece with more of the recent and historic known underpinnings from Planks hv relation between mass and energy and the latest on exchange times etc sheding light (pun) on the exchange between photons and nuclear/ electronic particles.
Great parenting! Please try your best to encourage your kids to understand and enjoy Linear Algebra, which will be very important for lasers, you got a future engineer 👍
Hello Sir, I am Laser Instructor in Beauty School and last part of your video is what I tell students to write down so they understand how lasers work. They don’t need anything more to remember. Thank you! You make it easy to understand!
Finally someone start to explain first and then Mathematically, this is how I liked and learn in my engineering time, today a lot of Academic start with Mathematics first,but can’t used without understanding why I need this Math and what I like to calculate, in this way makes more sense and the trick is done. Good Job, definitely I subscribe
So you got the stimulated part wrong. The meta stable atoms are pumped, not stimulated. The stimulation part refers to the quantum stuff you skipped. When the atom decays to the ground state, there is some amplitude to do that, call it A. That amplitude is to emit a photon in any direction, but thanks to the Pauli exclusion principle (for photons), if there is alread a photon there, the amplitude becomes 2A. If there a N photons already in that state, it becomes (N+1)A. So, you slap the mirrors on, and the aligned photons quickly take over so that all emitted photons are aligned. So stimulated emission refers to the fact that the photon emission is stimulated by the photons already present, and since the emitted photon is the same as the ones in the laser, that laser state is amplified. Note it’s not just a consecutive doubling as you described (that sounds more like a chain reaction), it a multiplication …so if the laser has 1,000,000,013 photons in it, a pumped atom has an amplitude on A to emit a photon in any direction and phase, while the amplitude to be in phase and aligned is 1,000,000,014A, So it’s going to join the laser photons.
We truly live in a wonder age. As a kid I would have to look this up on paper now I just click a button and it's there for me. Technology really is grand.
I loved your explanation, thanks. I have been working in the auto industry for a long time. I would like to read books in English with more content about laser, YAG and Laser Diodes for example. Professor, could you recommend good books. Thank you very much!!
Quick question I bought a laser pointer online you've probably seen it it's a big silver metal laser it's really strong lately I just noticed that it's not as right as it once was or when I turned the focus ring it doesn't seem to get as small as it used to be there for making it brighter it tends to want to be a lot larger now is that a problem with the laser or something inside or is it just possibly the lens I was going to open it up to look inside but there is no way to get all the way inside completely without breaking something as it's a solid metal frame it looks like the laser itself is threaded and I did a lot of twisting and turning but nothing has really helped it yet could it have possibly died it's not that old and there's no scratches or any damage to the actual lens that I can see under the microscope thank you for your time
Unfortunately, I don’t think I can help you. It does sound like you have a diode type laser which works a little bit differently to the one I described in the video. If your laser pointer is faulty, maybe contact the manufacturer
Great video, thanks! I have a question: in the cavity how can we select the appropriate integer n to get the frequency we want? I think we will get a lot of forms of standing waves in the reflection process. 👀
It barely does, it’s effectively entirely dominated by the transition you’re lasing on, the length of the cavity makes (incredibly) fine modifications to that frequency
Also doesn't help that none of these videos I've seen so far explaining how lasers work reveal what element is being used as a conduit for the laser beam.
8:50, why does the electron stay longer in this metastate after falling from a higher unstable state, vs. being excited immediately up to that higher state?
Usually a spin flip suppresses the amplitude to decay. See “selection rules”…at least that is what they called for nuclear decays. It’s the same thing that makes stuff flow in the dark.
Dear Sir, I really need your help. How can I find out if a laser could do any damage to the eyes with a skin tightening procedure. My dermatologist did not use glasses for safety, he said a laser does not scatter, but then I later I found out, that some practicioners do use eye protection. I kept my eyes closed of course but I am concerned if some light could go in the eyes within the little gap which sometimes maybe left I had at the second day a lightly blurry view, but maybe that happened only because of the streching the upper eyelids. I did a treatment not to much but on one side minimal under the eye and my upper eyelids wit a fraktional co2 Laser. Could you please tell me in which scope energy can disapear from the laser shuts? Can Laser really not scatter? Thank you!
He said already, so they have time to meet a laser photon and join the party. Otherwise the lifetime is the same order as the emission time, and nothing special happens
Perhaps next time you could make two videos... a 5 minute video giving the facts; and an 8 minute video of how you like to verbally retrace your own linguistic tracks.
Working on a video about lasers and trying to understand how they work, after watching this I can confidently say I know how lasers work... Mostly haha
Yes it does Anthony Yeh at Quora has a good answer www.quora.com/Is-the-light-from-lasers-reduced-by-the-inverse-square-law-as-distance-grows-similar-to-other-light-sources
Bose Einstein statistics. Yeah, the meta stable state doesn’t absorb that ambient photon, rather the presence of the ambient photon stimulates the emission of an identical photon. The other name for it is stimulated emission.
Based on your explanation it seems unnecessary to have that highest energy state since electrons immediately drop to that middle state. What’s the purpose of that top state? Why not just move electrons to the middle state directly from the ground state?
@@DarthExecutorno, that’s not right. The ambient photons (not just one, but billions) increase the probability of emitting an identical photon (in frequency, phase, and polarization). That’s why it’s called stimulated emission.
It does go to ground state eventually. The lifetime of this transition 2 →1 is much longer than the lifetime of the 3 → 2 radiationless transition. also not all transitions between electron states are equally probable.
Hi! Before anyone thinks that an atom multiplicates light, for these people who did not listen at the start i tell, that the atom collects up photons to emit them in a uniform way, at the same time, just like a pulse. Naturally you can not make an atom to collect up more photons, because it starts to leak rather quickly. However you can give your atom more coloured photons, and overshoot its photon capacity, in order to gain more photon collection time. Due to this extended time, you can increase the probability of stronger photon pulses. At least this is what the video said to me. I wonder, if i was wrong.
I kept trying to listen to you; but you kept talking over what you were trying to say. Two words forward, one word back. You sprinkled a scientific explanation with hymning and hawing.
How does this now deplete an atom to nothing? With all these amplifications I am not understanding how all of this energy can be taken out without the mass being reduced overall
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I looked up a lot of videos for lasers, and this is the cleanest and clearest of them so far. Great video! Covers the basics concisely!
I read or skimmed the comments and generally agree. You construct you physical (sans mathematical) wall logically collating known underpinnings. Concise. Accurate. Easy to watch. Wot not to like…!
Consider, if you will, another such piece with more of the recent and historic known underpinnings from Planks hv relation between mass and energy and the latest on exchange times etc sheding light (pun) on the exchange between photons and nuclear/ electronic particles.
My 4yr old son asked me, “why is a laser called a laser?” I said, “let’s find out!” and here we are! Thank you for your video! We really enjoyed it! ❤
I’d be interested to hear how you relayed that explanation to your son!
Great parenting! Please try your best to encourage your kids to understand and enjoy Linear Algebra, which will be very important for lasers, you got a future engineer 👍
I also have the same question HOW and just HOW is a 4 year old able to understand why LASER is called LASER
Lol same
A laser by any other name is just as coherent, is it not?
Hello Sir, I am Laser Instructor in Beauty School and last part of your video is what I tell students to write down so they understand how lasers work. They don’t need anything more to remember. Thank you! You make it easy to understand!
Finally someone start to explain first and then Mathematically, this is how I liked and learn in my engineering time, today a lot of Academic start with Mathematics first,but can’t used without understanding why I need this Math and what I like to calculate, in this way makes more sense and the trick is done. Good Job, definitely I subscribe
Thanks for the feedback.
So you got the stimulated part wrong. The meta stable atoms are pumped, not stimulated. The stimulation part refers to the quantum stuff you skipped.
When the atom decays to the ground state, there is some amplitude to do that, call it A.
That amplitude is to emit a photon in any direction, but thanks to the Pauli exclusion principle (for photons), if there is alread a photon there, the amplitude becomes 2A.
If there a N photons already in that state, it becomes (N+1)A.
So, you slap the mirrors on, and the aligned photons quickly take over so that all emitted photons are aligned.
So stimulated emission refers to the fact that the photon emission is stimulated by the photons already present, and since the emitted photon is the same as the ones in the laser, that laser state is amplified.
Note it’s not just a consecutive doubling as you described (that sounds more like a chain reaction), it a multiplication …so if the laser has 1,000,000,013 photons in it, a pumped atom has an amplitude on A to emit a photon in any direction and phase, while the amplitude to be in phase and aligned is 1,000,000,014A,
So it’s going to join the laser photons.
We truly live in a wonder age. As a kid I would have to look this up on paper now I just click a button and it's there for me. Technology really is grand.
I have watched several laser videos and this is the only one where it actually clicked in my brain. Thank you.
Glad it helped.
very true life saving
sir, make more videos like this with animation ,
it is very very helpful for us ,
we appreciate your efforts,
Thank you very much sir
Glad it helped
Thats so great,i cant imagine how laser works in my theory class but now,its so cool..thank u sir
very thorough and informed and informative explanation of this common question. Thank you.
Thankyou for the feedback.
Great job on this one! Very clear!
This is the best video I have watched by far to explain what Laser is to me, it helps me a lot, thanks for making this video.
amazing explanation! its a delight to watch your videos!
Very helpful Paul!! Many many thanks!!! Definitely I understand laser more now!!
Great job, Paul. Clear explanations are your forte.
Thanks George!
Brilliant presentation. Thank you sir! 👍👍👍
Excellent video, well done. I will be using it with my physics classes from now on.
Awesome explanation!
Great Explanation, few of my doubts got cleared.
Amazing explanation. Thank you sir !
Great video explaining the creation of a laser beam! Super simple but still very in depth and easy to understand!
Thanks
Preparing for my Modern Physics exam, this one really helps! Thanks a lot! More power to your chanel.
You are good at explaining,thank you
beautifully explained....wanaa watch more like this..
fantastic video! helped me out
Very, very helpful! Thanks!!
Great video, thanks. 👍
Great explanation!
super informative .. thanks a lot
Thank god. Someone who can explain something
AMAZING! Photons bless you sir. THANKS
Well put and very easy to follow and understand
Thank you for this interesting video. I also want to thank you for not using any distracting background music. Nice!
very good explanation!
very helpful. Thank you sir
Great video, thank you Paul.
Very welcome
Oh my.. this is a wonderful way to explain lasers, Thanks a lot.. I finally get the whole population inversion and stimulation
Amazingly explained..was looking for such basics since a week❤
Glad it was helpful!
GREAT EXPLANATION :))))))))))))))
Thank you for this video, helped alot.
Amazing explanation!
Thanks
Frickin great Video. I am an engineer in a completely different field and just curious. Loved the explanation
Great information
sir wonderful explaination
Good stuf, thank you!
Amazing. New subscriber
Nice explanation
great!!!
Amazing
good illustrations thanks so much.
You’re welcome
Nice video.
Thanks for simplest explanation
You’re welcome
Loved how you showed photon multiplication as if it was neutron fission with uranium :D
Thanks 🤓
Not lying I thought of that too lmao
I used to study that stuff
But it's been a while lol
But that was the only part that was inaccurate, though still good enough for ppl who don’t need quantum.
Thank you sir! helped me a lot, have university finals next week.
dunning Kruger always finds me. thanks for reminding me im stupid. there's so much to learn.
thank youu 🙌
Excellent
Very nice !
Thank you very much!
I loved your explanation, thanks. I have been working in the auto industry for a long time. I would like to read books in English with more content about laser, YAG and Laser Diodes for example. Professor, could you recommend good books. Thank you very much!!
Google explains it all without hassling the TH-cam author, do the work.
I've been loading a rust server and forgot to mute the background music while watching this video and it sounded FIRE
Thank you.
Best video
thank you !
Welcome!
Wow, lasers are how we exploit quantum properties of light. Amazing.
Quick question I bought a laser pointer online you've probably seen it it's a big silver metal laser it's really strong lately I just noticed that it's not as right as it once was or when I turned the focus ring it doesn't seem to get as small as it used to be there for making it brighter it tends to want to be a lot larger now is that a problem with the laser or something inside or is it just possibly the lens I was going to open it up to look inside but there is no way to get all the way inside completely without breaking something as it's a solid metal frame it looks like the laser itself is threaded and I did a lot of twisting and turning but nothing has really helped it yet could it have possibly died it's not that old and there's no scratches or any damage to the actual lens that I can see under the microscope thank you for your time
Unfortunately, I don’t think I can help you. It does sound like you have a diode type laser which works a little bit differently to the one I described in the video. If your laser pointer is faulty, maybe contact the manufacturer
Great video, thanks! I have a question: in the cavity how can we select the appropriate integer n to get the frequency we want? I think we will get a lot of forms of standing waves in the reflection process. 👀
That’s why you tune lasers.
Hi ! Thank you so much ❤️
But I didn't get the resonance part :(
(The part where you where talking about length of the tube)
is there energy loss when the atom kicks out the electron that is the same as the one it absorbed?
You are absolutely the best !
THE BEST !
Thanks !
A PhD student here, thank you sir. It's very interesting to know the length of the tube is what determines the frequency.
It barely does, it’s effectively entirely dominated by the transition you’re lasing on, the length of the cavity makes (incredibly) fine modifications to that frequency
@@mjgd7624does the laser care if it has 10,000 nodes or 10,002 nodes..I don’t think so.
Guess I should keep this bookmarked, I've got a relative that's going to start year 11 physics next year and they want help with study :)
Where are they studying?
@@PhysicsHigh NSW
Perfect. I teach in NSW so I have playlists specific to NSW curriculum and lots of HSC practice.
@@PhysicsHigh I know, my physics teacher back in 2018 introduced me to the channel because it went through the syllabus content and it helped a lot.
I’m glad it helped. Thanks for the feedback.
The way he is explaining amplification makes it sound like you are getting free photons out of nowhere.
Also doesn't help that none of these videos I've seen so far explaining how lasers work reveal what element is being used as a conduit for the laser beam.
@@LJdaentertainerwell that depends on the laser. Styropyro has a beautiful ruby 💎 rod that he uses.
The photon has to already be there in order to stimulate the emission of an identical photon. That’s where the mirrors help.
wonderful explanation despite funny pronunciations to mine americanized wernicke's area.
All I want to know How the battery supplies the enregy where is negative n positive...on what leg of the switch does positive get solders to...
It depends if you're right handed or left handed
Does atom in excited state emit any photon when it comes down to metastable state?
8:50,
why does the electron stay longer in this metastate after falling from a higher unstable state, vs. being excited immediately up to that higher state?
Usually a spin flip suppresses the amplitude to decay. See “selection rules”…at least that is what they called for nuclear decays. It’s the same thing that makes stuff flow in the dark.
Dear Sir, I really need your help. How can I find out if a laser could do any damage to the eyes with a skin tightening procedure. My dermatologist did not use glasses for safety, he said a laser does not scatter, but then I later I found out, that some practicioners do use eye protection. I kept my eyes closed of course but I am concerned if some light could go in the eyes within the little gap which sometimes maybe left I had at the second day a lightly blurry view, but maybe that happened only because of the streching the upper eyelids. I did a treatment not to much but on one side minimal under the eye and my upper eyelids wit a fraktional co2 Laser. Could you please tell me in which scope energy can disapear from the laser shuts? Can Laser really not scatter? Thank you!
I’m sorry but laser eye surgery is not my expertise. I suggest seeing another ophthalmologist for second opinion
thank you, have a nice Christmas time@@PhysicsHigh
12:09, May I ask what exactly the 'n' means? Can someone describe it in other words?
It’s the number of wavelengths in the cavity
WoW
Why do we need metastable state in lasing action?
Please give me answer
He said already, so they have time to meet a laser photon and join the party. Otherwise the lifetime is the same order as the emission time, and nothing special happens
Perhaps next time you could make two videos... a 5 minute video giving the facts; and an 8 minute video of how you like to verbally retrace your own linguistic tracks.
Working on a video about lasers and trying to understand how they work, after watching this I can confidently say I know how lasers work... Mostly haha
I have a question I have never been able to find an answer. Since the laser light is collimated does it obey the inverse square law?
Yes it does
Anthony Yeh at Quora has a good answer
www.quora.com/Is-the-light-from-lasers-reduced-by-the-inverse-square-law-as-distance-grows-similar-to-other-light-sources
Dr Evil probably watched this 100 times.
☺️ thanks
Welcome!
شكرًا على الشرح الرائع، طلاب السادس اين انتم.
good explanation my teacher but we -arab- need to translate your videos for people who can't understand the english plz and thanks to you
I like his T shirts.
4:53 can you name the phenomena please? thanks for the video!
Bose Einstein statistics. Yeah, the meta stable state doesn’t absorb that ambient photon, rather the presence of the ambient photon stimulates the emission of an identical photon. The other name for it is stimulated emission.
Based on your explanation it seems unnecessary to have that highest energy state since electrons immediately drop to that middle state. What’s the purpose of that top state? Why not just move electrons to the middle state directly from the ground state?
Why does the 1st photon increase the electrons energy level, but then the next photon makes it drop down again?
it doesn't, they are both absorbed and then released. when they're released it drops.
@@DarthExecutorno, that’s not right. The ambient photons (not just one, but billions) increase the probability of emitting an identical photon (in frequency, phase, and polarization). That’s why it’s called stimulated emission.
using this to make a laser gun for my assignment for English class
why does an excited electron go to the metastate instead of the ground state?
It does go to ground state eventually. The lifetime of this transition 2 →1 is much longer than the lifetime of the 3 → 2 radiationless transition.
also not all transitions between electron states are equally probable.
I am studying this for the first time so i might be wrong, do check the answer somewhere as well! :)
@@abhisheknandannclose enough
Hi! Before anyone thinks that an atom multiplicates light, for these people who did not listen at the start i tell, that the atom collects up photons to emit them in a uniform way, at the same time, just like a pulse. Naturally you can not make an atom to collect up more photons, because it starts to leak rather quickly. However you can give your atom more coloured photons, and overshoot its photon capacity, in order to gain more photon collection time. Due to this extended time, you can increase the probability of stronger photon pulses.
At least this is what the video said to me. I wonder, if i was wrong.
yeah 2 photons came in at different times and were reemitted at the same time, although he mistakenly thought one came in and two came out
Sir I thaught. The electron will leave the atom after taking the second photon
I kept trying to listen to you; but you kept talking over what you were trying to say. Two words forward, one word back. You sprinkled a scientific explanation with hymning and hawing.
That 299792458 m/s isn’t the law. It’s the definition. Of length, when combined with cesium 133.
True but it doesn’t sound as nice on a tshirt 😉
4:04 why is that?
How does this now deplete an atom to nothing? With all these amplifications I am not understanding how all of this energy can be taken out without the mass being reduced overall
Bro, this is atomic physics, not nuclear physics
I dont understand how laser cutting devices work . How do photons cut something?
Maybe you title should read: How to be as confused as I am about lasers.