(SEM-III) THEORY EXAMINATION 2017-18 LASER SYSTEMS AND APPLICATIONS

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.