Download AKTU B-Tech 3rd Sem 2017-2018 ROE033 Laser Systems And Applications Question Paper

SECTION A

1. Attempt all questions in brief: 2 x 7 = 14
   1. What do you mean by Polarization of X-ray?
   2. What is tunnel effect?
   3. Why spontaneous emission of radiation is incoherent?
   4. What is the function of optical cavities in a laser?
   5. What do you mean by population inversion?

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   6. What are characteristic properties of the argon ion laser?
   7. Can we get a hologram with ordinary light?

SECTION B

2. Attempt any three of the following: 3 X 7 = 21
   1. What do you mean by a black body? Explain the features of the black body spectrum.
   2. What are pumping techniques? Discuss different types of pumping techniques in different types of laser.

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   3. What is a Q-switched laser? Discuss various methods.
   4. With a necessary diagram, explain the construction and working of the Nd:YAG laser.
   5. Explain laser welding and its advantages over conventional welding techniques.
   6. Briefly explain how lasers are useful in drilling and cutting?

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SECTION C

3. Attempt any one part of the following: 1X7=7
   1. Explain Bohr's theory of the hydrogen atom. If an electron transits from the third orbit to the first orbit, find the wavelength of the electron in the hydrogen atom.
   2. Solve the Schrodinger wave equation to find the Eigen value and Eigen function for a particle in an infinite potential well.

4. Attempt any one part of the following: 1X7=7
   1. What are the important features of stimulated emission of radiation?
   2. Discuss essential conditions for producing a laser beam. Find the population ratio between two energy states in a Ruby laser producing a laser light of wavelength 7000Å at 330K.

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   3. What do you know about the threshold condition for laser oscillation? Find an expression for the threshold condition for lasing.

5. Attempt any one part of the following: 1X7=7
   1. What are the main components of a laser? Discuss each component in detail.
   2. With the help of a suitable diagram, describe three-level laser actions. If the population ratio of two states is 3x10-40 in a He-Ne laser, it produces light of wavelength 6328Å. Find the temperature of the energy states.

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6. Attempt any one part of the following: 1X7=7
   1. What are molecular gas lasers? Describe the construction, working, and application of a carbon dioxide laser.
   2. Explain the working of a semiconductor laser. Differentiate between Homojunction and Heterojunction lasers.

7. Attempt any one part of the following: 1X7=7
   1. What is LIDAR? Discuss its components and their role. How are atmospheric pollutants measured using LIDAR?
   2. Discuss how lasers can be used in FirstRanker.com optical communication.

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Physical Constants

• Rest mass of electron mo = 9.1 x 10-31 kg
• Rest mass of Proton mp = 1.67 x 10-27 kg
• Speed of light C = 3 x 108 m/s

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• Planck Constant h = 6.63 x 10-34 J-s
• Charge on electron e = 1.6 x 10-19 C
• Boltzmann Constant k = 1.38 x 10-23 J K-1