Helium Neon Laser

Laser is very important technological device these days.There is a use of laser in almost every field of science and technology. It also gives it's application in medicines also.
This presentation shows how it works and what is the mechanism behind this laser phenomenon. Here it is explained from atom theory to application.
Very good explanation with photographs.

1. He – Ne Laser Let’s explore it! He lium – Ne on L aser A mplification by S timulated E mission of R adiation

2. Contents About Helium About Neon About Helium Neon LASER Construction of He-Ne LASER Working of He-Ne LASER Advantages of He-Ne LASER Disadvantages of He-Ne LASER Applications of He-Ne LASER References

3. Helium Symbol: He Atomic mass: 4.002602 u Atomic number: 2 Electron configuration: 1s² WHY HELIUM IS USED IN LASER? The direct excitation of Neon gas is inefficient, but the direct excitation of He gas atoms is very efficient. Also, An excited state of the He atom has an energy level which is very similar to the energy of an excited state of the Neon atom. REMEMBER Helium gas does not participate in the lasing process, but increases the excitation efficiency

4. Neon Symbol: Ne Atomic mass: 20.1797 u Atomic number: 10 Electron configuration: [He] 2s²2p⁶ WHY NEON IS USED IN LASER? Neon is used in laser to produce light as It is capable to produce light when it gets energy from Excitation of Helium.

5. Helium Neon Laser Helium Neon Laser consists of 90% Helium and 10% Neon atom inside it. It has pressure of about 1 torr inside of a small electrical discharge. This Laser light gives light of 632.8 nm. It gives emission light in continuous beam of laser. This is due to population inversion.

6. Construction of He-Ne Laser The construction of laser consist of three essential components : High Voltage Power Source Gain Medium ( Mixture of He & Ne) Resonating Cavity

7. Construction of He-Ne LASER

8. High Voltage Power Supply To produce Laser beam, Population Inversion is essential. Population Inversion is process of achieving more electrons in higher energy states as compared to lower energy states. As it is quite unstable condition, we need to supply high enough energy from source. This can be achieved by these high voltage power supply.

9. Gain Medium This is just a mixture of 90% He gas and 10% of Ne gas. Partial pressure of He is 1 mbar and that of Ne is 0.1 mbar. As He is in more proportion we would have to first excite the low energy states of Helium atoms. In He-Ne Lasers , neon atoms are active centers (atom which produces light). Thus, we try to excite Ne atoms by exciting helium atoms.

10. Resonating Cavity This cavity is a glass tube with two mirrors placed opposite to each other. One mirror is partially silvered and other one is fully silvered. This is called Resonating Cavity because the small portion of produced light oscillated between these two mirrors. While oscillating this beam get strengthen up and finally after getting enough strength the ray comes out from one side.

11. Working of He-Ne LASER

12. Working of He – Ne Laser As power switches on , a high voltage is applied across gas mixture. ( 10kV approx. ) This high voltage DC produces energetic electrons that travel through gas mixer. Thus, electrons accelerated between anode and cathode through the gas mixture. Due to these Helium atoms get excited. Lower state electrons of Helium atoms gain enough energy and jumps into the excited states or metastable states.

13. Working of He – Ne Laser Metastable state electrons of the helium atoms cannot return to ground state by spontaneous emission. Thus ,They can return to ground state by transferring energy to the lower energy state of electrons of neon atoms. The lower energy state electrons of neon atoms gain enough energy and jumps into higher energy states or metastable states.

14. When millions of electrons of neon excited to the metastable states, we would achieve population inversion state. After this state ,electrons of neon atoms will fall into next state with lower energy which is called spontaneous emission. Thus photons are emitted by this transition. These photons oscillates back and fourth between two mirrors until it stimulates other excited electrons of the neon atoms and cause them to emit light. Finally Optical Gain is Achieved. Working of He – Ne Laser

15. This process of photon emission is called stimulated emission of radiation. Working of He – Ne Laser The light or photons emitted stimulated emission will escape through the partially reflecting mirror or output coupler to produce laser light.

16. Advantages of He-Ne Laser Operates without damages at high temperature. Highly Stable Economic (cheaper) Light emission in visible region.

17. Disadvantages of He-Ne Laser Low Efficiency Low gain These lasers are limited to low power tasks.

18. Application of He – Ne Laser These Lasers are used to demonstrate optics experiment in laboratories. These laser is also most commonly used in holography. Pointing beams Barcode Scanners

19. Application of He – Ne Laser Particle counting and Particle sorting Tool alignment Non-contact measuring and monitoring

20. References https://www.quora.com/Why-is-helium-gas-used-in-the-helium-neon-laser-system https://en.wikipedia.org/ https://www.physics-and-radio-electronics.com/physics/laser/heliumneonlaser.html https://www.sciencephoto.com/media/92698/view/double-slit-diffraction

21. Focus like a laser, not a flashlight --Michael Jordan Thank You