About this previous year paper
This document contains the complete B.Tech (Semester III) Theory Examination 2017–18 question paper for the subject Laser Systems and Applications (ROE-033). The exam spans two printed pages, carries 70 marks, and evaluates a student’s understanding of laser physics, quantum mechanics, laser construction, pumping techniques, and modern applications of lasers in engineering and technology.
Section A – Short Conceptual Questions (14 Marks)
Section A consists of seven short questions that test foundational knowledge of laser physics and quantum principles. Students must define or explain:
Polarization of X-rays
Tunnel effect
Why spontaneous emission is incoherent
The role of optical cavities in a laser
Meaning of population inversion
Characteristics of argon-ion lasers
Whether holograms can be made using ordinary light
This section checks basic understanding of essential laser phenomena and optical principles.
Section B – Descriptive & Analytical Questions (21 Marks)
In this section, students must attempt any three out of five questions related to laser construction, pumping techniques, and industrial applications:
Definition and properties of a black body, and features of black-body spectrum
Different laser pumping techniques across various types of lasers
Meaning of a Q-switched laser, and explanation of Q-switching methods
Construction and working of the Nd:YAG laser, supported by diagrams
Laser welding, its advantages over conventional welding, and use of lasers in cutting and drilling
These questions assess a deeper understanding of how lasers operate, how they are excited, and how they are applied in real engineering tasks.
Section C – Long Questions (35 Marks Total)
Section C contains five main questions, each with two advanced subparts. Students must attempt one part from each question, covering quantum theory, laser mechanisms, molecular and semiconductor lasers, and laser-based measurement systems.
1. Quantum Theory & Schrödinger Equation
Bohr theory of hydrogen atom and calculation of emitted wavelength during electron transition
Solving the Schrödinger wave equation for a particle in an infinite potential well
2. Stimulated Emission & Lasing Conditions
Features of stimulated emission and conditions for laser generation; population ratio calculation for a Ruby laser
Derivation of threshold condition for laser oscillation
3. Laser Components & Three-Level Laser
Main components of a laser system, with detailed descriptions
Operation of a three-level laser, population ratio calculations for He–Ne laser
4. Gas Lasers & Semiconductor Lasers
Construction, working, and applications of CO₂ laser (a key molecular gas laser)
Working principle of semiconductor lasers, and comparison between homojunction and heterojunction lasers
5. LIDAR & Optical Communication
Definition and components of LIDAR, and its use in atmospheric pollution measurement
Use of lasers in optical communication, including principles and advantages
These questions assess mathematical reasoning, conceptual depth, practical laser applications, and strong understanding of quantum and optical physics.
Summary
This Laser Systems and Applications (ROE-033) exam paper thoroughly evaluates:
Basics of laser physics
Quantum mechanics and emission processes
Pumping techniques and laser construction
Different types of lasers (Nd:YAG, CO₂, semiconductor, argon-ion)
Industrial uses (welding, drilling, cutting)
Lasing conditions and optical cavity behavior
Application of LIDAR and laser communication systems
It is a complete academic resource for students studying lasers in engineering, physics, and applied sciences.