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Sample Exam Paper

MPY301Sample Examination Paper — II

Course: Laser Physics (MPY301)Programme: M.Sc. Physics (Electronics Specialization) — Semester III
Time: 3 HoursMaximum Marks: 70

General Instructions:

  1. All questions in Section A are compulsory.
  2. Attempt any two parts from each question in Section B.
  3. Attempt any two questions in full from Section C.
  4. Support your answers with neat diagrams where necessary.

Section A — Short Answer (Compulsory)

  1. What is meant by temporal and spatial coherence of a laser beam? (2 marks)
  2. List any three types of gas lasers. (2 marks)
  3. What is an excimer molecule? Give one application of excimer lasers. (2 marks)
  4. Define attenuation and dispersion in the context of optical fibre communication. (2 marks)
  5. What is stimulated Raman emission? (2 marks)
  6. State two medical applications of lasers. (2 marks)
  7. What is laser annealing used for in semiconductor processing? (2 marks)

Section B — Attempt any two parts of each

  1. Explain the role of the optical cavity/resonator in a laser and how it determines the output beam's coherence properties. (5 marks)
  2. Describe the construction and working principle of a semiconductor (diode) laser. (5 marks)
  3. Explain the working of the Ruby laser with an energy level diagram, and state why it is a pulsed laser. (5 marks)
  4. Discuss the different types of optical fibres (step-index, graded-index, single-mode, multimode) and their relative merits. (5 marks)
  5. Explain the principle of laser fusion (inertial confinement fusion). (5 marks)

Section C — Attempt any two questions in full

  1. Explain in detail the fundamentals of laser action, covering spontaneous emission, stimulated emission, Einstein's coefficients and the requirement of population inversion, with reference to a specific laser system of your choice. (10 marks)
  2. Compare and contrast atomic, molecular, excimer, liquid, solid-state, semiconductor and fibre lasers in terms of gain medium, pumping mechanism, typical wavelength and principal applications. (10 marks)
  3. Discuss the use of lasers in scientific spectroscopy, covering saturation spectroscopy, non-linear spectroscopy and time-domain spectroscopy, explaining the advantage each offers over conventional spectroscopic methods. (10 marks)
  4. Explain the physical basis of holography in detail, including the mathematical description of interference between object and reference beams, and discuss at least two modern applications. (10 marks)
  5. Describe LIDAR technology and laser-based industrial processing (drilling, cutting, welding, hardening), explaining the underlying physics that makes lasers uniquely suited to each application. (10 marks)