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[Virtual Presenter] Today, we will be discussing lasers, their working, pumping schemes, and types. We will also be looking into how a laser works, the pumping requirements in order to initiate laser action, and why some lasers can only be operated in a pulsed mode. We will be exploring the various aspects of lasers in order to gain a deeper understanding..

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[Audio] By the end of today's session, you should be able grasp and explain the mechanisms of lasing action, the requirements for overcoming the population inversion threshold, the implications of both Nd Yag and CO2 lasers, and the concept of 3 and 4 level pumping schemes. With this information, you should be fully prepared to take the next steps with laser-related applications and technologies..

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[Audio] The process of laser action is intricate, but fascinating. Spontaneous emission of photons provides an initial push to trigger stimulated emissions. These emissions are reflected back by the end mirrors of a resonator structure. When the amount of gain within the resonator equals the amount of loss, stable laser emission is achieved. Photons travel axially throughout the medium in the resonator, stimulating more photons in the process. The reflection of photons in the same axial direction amplifies the energy while photons travelling in different angles eventually die down. To maintain constant laser emission, a minimum population inversion must be established. All these components cooperate to produce the powerful laser phenomenon..

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[Audio] The slide under discussion is quite intricate, with the title only giving an indication of the laser related content. It outlines the physics and maths of laser operation, particularly touching on the need for a threshold population inversion. It explains that the stimulated emission intensity is determined by the gain and absorption coefficients in the laser medium, with the threshold population inversion having to be met to ensure the laser runs efficiently. The slide provides equations to exemplify how this works..

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[Audio] We discussed different types of lasers and how they work, looking at the requirements for laser action and why some lasers can only be operated in pulsed mode. Investigating how, for sustained oscillations, intensity after one round trip must equal the initial intensity, we looked into the formula involving the cavity round-trip losses, the cavity gain, and the minimum population inversion required to start oscillations, or the threshold population inversion..

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6 AI&DS PH 1001 T Lec # 34 13.12.23 Dr Prita Nair Pumping & laser levels 3 level and 4 level laser systems Upper laser level – Metastable higher energy level where population inversion is created Lower laser level – Energy level to which the excited atoms de-excite through stimulated emission To create N2 > NI we need to pump up more than N0 /2 and maintain it. (Remember, N0 is a large number) Difficult to maintain practically. Hence not that efficient, only pulsed operation possible. Eg : Ruby laser – spiked output 3 level systems Lower laser level = ground level Upper laser level N1 =N0 N2 Pumping level Fast non- radiative decay.

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[Audio] We discussed various working and pumping schemes and types of lasers, focusing on how a laser works and what the pumping requirements for achieving laser action are. We went on to explain why some lasers can only be operated in pulsed mode due to the depletion of the lower laser level, and the advantages of four level systems for easier maintenance of inversion for continuous-wave or CW operation. Lastly, we discussed the possibility of two-level laser systems..

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[Audio] Today's lecture discussed the various types of lasers and their characteristics. We looked at lasers based on the active medium, which include gas lasers such as He-Ne, CO2 and Ar+, and solid-state lasers such as Ruby, Nd-Yag and Alexandrite. We also discussed semiconductor lasers such as GaAs and GaAl As, and liquid lasers such as dye lasers. We looked at lasers based on wavelength, such as visible, infrared and UV, as well as by their pumping mechanism, or how they work. We discussed the three-level and four-level pumping schemes, and the different classes of laser output based on power and temporal output. Finally, we explored the safety requirements set for laser output with the 10J/cm2 threshold..

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[Audio] The laser system is a complex mechanism made up of multiple components. Today's lecture has discussed what these components are and the required steps to construct a laser system. We looked at the pumping mechanism, active medium, and resonator, all of which work together to create the population inversion needed for laser action. We also discussed the importance of understanding the material of the active medium and the optimal conditions for the resonator in order to achieve powerful laser beam amplification. Finally, we touched on the role of the mirrors, which ensures the laser light is reflected back into the active medium..

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[Audio] Today we discussed various types of lasers and how they work. We started by looking at Nd YAG lasers. This particular type of laser has a 4 level pumping scheme, with both optical and semiconductor diode pumping. This laser has a solid-state active medium of Nd3+ in yttrium aluminium garnet. It has a wavelength of 1.064μm, and can be operated both in continuous wave and pulsed mode with T>1 MW. It is used for applications such as welding, drilling, cutting, eye surgery and second harmonic generation. We then discussed the energy level diagram of Nd3+, and how to construct and work this particular laser. Through this discussion, we learnt how a laser works, the pumping requirements for laser action and why some lasers have to be operated in pulsed mode..

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[Audio] We are discussing diode-pumped Nd-YAG and diode-pumped frequency-doubled Nd-YAG lasers which are capable of generating extremely high powers of up to hundreds of watts. These lasers rely on semiconductor diode lasers for pumping, allowing for an effective optical energy transfer. We have examined the requirements for laser action and why certain lasers can only be operated in pulsed mode..

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[Audio] Lecture discussed different kinds of lasers, including the carbon dioxide laser, and the essential role the pumping mechanism plays for laser action to happen. The carbon dioxide laser is special as it needs the right mix of CO2 gas, nitrogen, and helium to produce lasing effect. It also has a wavelength of 9.6 micrometers and 10.6 micrometers in both continuous wave and pulsed modes. According to the lecture, the pumping scheme of the carbon dioxide laser involves resonant transfer to a metastable state, which is a vibrational level. This vibrational energy level is important for the carbon dioxide laser to work..

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[Audio] Molecular transitions can be complicated. Each electronic level can be divided in to vibrational sub-levels, and each vibrational level further divides into rotational levels. As seen in the diagram, the (0,0,0) level symbolizes the electronic energy level and m, n, and q symbols represent the different vibrational energy levels, associated with each energy level hv. In the case of the CO2 molecule, these vibrational levels include symmetric, bending, and asymmetric modes. This complexity of energy levels has an important role in molecular transitions..

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[Audio] At the lecture, we looked into how CO2 and N2 lasers are constructed and operated. We examined the water jacket and NaCl window for cooling as well as the excitation and de-excitation process of CO2 molecules through electric discharge. We explored how the excited N2 atoms transfer energy through collisions to the CO2 molecule, enabling the molecule to vibrate in the asymmetric mode, a metastable upper laser level. We discussed how this process of spontaneous and stimulated emission leads to the symmetric and bending modes of vibration. To cap it off, we looked at how a small diameter of the tube and the high thermal capacity of helium help to maintain the population inversion..

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[Audio] I'd like to delve into the world of artificial intelligence and data science. We'll be examining how combining these two technologies is allowing for smarter and more effective machine learning. We'll look at the concept of deep learning, its properties that make it so powerful, and the technology that powers it. We will also explore how data science and AI can be used together to create solutions that offer users smarter and more personalized experiences. Finally, we'll discuss the ways these two disciplines can be leveraged to make our lives more efficient..

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[Audio] We discussed the various applications of lasers in this lecture. TEA lasers are used in many industries to generate GW of peak power at 20 pulses per second whilst requiring low power. Additionally, the wavelength of the CO2 laser has the lowest atmospheric absorption and the OH ion absorption, making it suitable for a range of applications..

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[Audio] In today's lecture, we discussed the different types of lasers, such as Nd Yag and CO2. We also discussed how these lasers work, the pumping requirements for proper laser action, and why some lasers can only be operated in the pulsed mode. We concluded with a summary of the lecture topics." Today's lecture presented the technical aspects of two types of lasers - Nd Yag and CO2. We discussed how Nd Yag is a four level solid state laser that can be pumped optically via the 0.73 and 0.8 micron lines and that it is capable of both CW and pulsed operation with an output of 1.064 microns. We also discussed how CO2 is a gas laser, with laser transitions between the vibrational levels of the CO2 molecule, and that N2 gas is used to excite CO2 via resonant energy transfer, and He gas is used to depopulate lower levels, with an operating wavelength of 9.6 and 10.6 microns. We concluded with a summary of the topics of the lecture..

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[Audio] We are discussing the He-Ne laser with a four-level pumping scheme containing helium and neon in a ratio of 10:1. Its output characteristics are a wavelength of 633nm and power generally measured in milliwatts in a continuous wave. The He-Ne laser has many applications such as holograms, interferometry, and aligning. It is pumped by an electric discharge, which causes accelerating electrons to excite helium atoms followed by a resonant energy transfer to neon atoms. To further the process, high temperature Brewster angle windows and collisions with the tube are also needed..

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19 AI&DS PH 1001 T Lec # 34 13.12.23 Dr Prita Nair Dr. Ali Javan & associates, Bell Labs.

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[Audio] I have discussed the various elements of a Ruby Laser, such as its active medium, pumping scheme, and output characteristics. We have looked at the Ruby Laser's various applications, construction, and how it works. Additionally, we have considered the advantages of the Ruby Laser's pulsed mode output. I hope that this has been an informative and interesting session..