He-Ne Laser
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- เผยแพร่เมื่อ 15 เม.ย. 2021
- A helium-neon laser takes advantage of the similarity in energy between an excited state of He gas and a different state for Ne gas. The He is pumped into the excited state, and the lasing transition occurs in the Ne, emitting red light of 633 nm.
- วิทยาศาสตร์และเทคโนโลยี
wish you healthiness in ramadan month🥰🥰🥰
Ramadan Mubarak to you as well
Greetings, I've got a question which is bugging me a bit.
A He-Ne-Laser is supposed to emit monochromatic light. But wouldn't the spontanious emission from E2,Ne to E1,Ne also produce a photon which in turn would change the color emitted? Thanks in advance
You're right, there are usually transitions between many different states, producing photons with many different wavelengths. That's where the optical cavity comes in: it is designed to amplify only photons with the desired resonant frequency / wavelength. Others will undergo destructive interference.
Excellent video presentation. Question--what about the conservation of angular momentum in collisional transfer of energy from Helium to Neon? Also this means that the electron in the 2p^5 orbital has the same spin as the electron in the 5s level in the Neon excited state?
The two-atom system will conserve its total angular momentum when two atoms collide, but that just applies a constraint on the post-collision velocities.
And there is no requirement that the spin states be matched for the two colliding atoms
miss you! will be there more lectures?
There will. I'm taking a short break right now, but will prepare some more soon, in preparation for the fall semester.
Why include the He at all? It seems we could just directly "pump" the Ne. As a guess, is it because He has fewer energy levels between the ground state and the desired energy level, so heating will produce more molecules in the desired energy level? Thank you
Yes, you're absolutely right. The He energy levels are more sparse. The pumping isn't done with light (which would allow careful targeting of a specific upper state) but by collisions with hot electrons (that populate a broad range of excited states). One of the few He states happens to line up well with the lasing transition in Ne. But a pure Ne laser would be less efficient because the denser energy ladder means a bunch of non-lasing excited states would be populated.
@@PhysicalChemistry Makes sense. Thank you!
I think this will make an avalanche condition in laser system, he atom can control the situation
Do you write backwards?
.sdrawkcab gnitirw ta taerg m'I ,seY
Just kidding. I write normally, and the computer reverses the image digitally. More info: th-cam.com/video/YmvJVkyJbLc/w-d-xo.html