3. What is population inversion? 4. Mention the important characteristics of laser. 5. How four level laser is more efficient than the three level laser? 6. What is a resonant cavity? 7. What role does an optical resonant cavity play in a laser? 8. What are the host materials for solid lasers? 9. Mention the different techniques involved in lasers. 10. Define atmospheric effect. 11. How will you measure the distance using laser? 12. What is the basic principle behind the holography? 13. Mention the medical applications of lasers. Understand 1. Write the conditions needed for laser action. 2. What is meant by pumping of atoms? 3. How optical excitation occurs in three level lasers? 4. What is the principle of laser action? 5. Compare the activator and host materials for solid lasers. 6. Distinguish between Czochralski and Kyropoulous techniques. 7. How will you determine the velocity of laser source? 20. The remaining 10 marks will be calculated based on assignments. Accordingly internal assessment will be calculated for 50 marks.
Department of Electrical and Electronics Engineering, Bannari Amman Inst. of Tech. | Regulation 2011 357 8. List the applications of laser in welding and cutting. 9. Why laser is called as non-material knife? 1. The first line of the principal series of sodium is the D line at 580 nm. This corresponds to a transition from the first excited state (3p) to the ground state (3s). What is the energy in electron volts of the first excited state? 2. What is the ratio of the stimulated emission and spontaneous emission at a temperature of 250oC for the sodium D line? 3. Calculate the threshold condition for the ruby laser in which the appropriate parameters are as follows: ν o =4.3x 10 14 Hz; Δν o =1.5x10 11 Hz; n o = 1.76; τ sp = 4.3x10-3 s; τ photon =6x10-9s. 4. A He-Ne laser emits light at a wavelength of 632.8 nm and has an output power of 2.3mW. How many photons are emitted in each minute by this laser when operating? 5. Calculate the wavelength of emission from a GaAs semiconductor laser whose band gap energy is 1.44 eV. Analyze 1. Why laser beam should be monochromatic? 2. How the population inversion happening in lasers? 3. Write the reaction for excimer laser action. 4. Which method is used to achieve population inversion in a dye laser?
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