(SEM-III) THEORY EXAMINATION 2018-19 LASER SYSTEMS AND APPLICATIONS

The uploaded file is a B.Tech (Semester III) Theory Examination 2018–2019 question paper for the subject LASER SYSTEMS AND APPLICATIONS, with Subject Code ROE033.
The document contains 2 printed pages, carries 70 marks, and has a duration of 3 hours.

This examination paper tests the fundamental and applied understanding of laser physics, laser types, laser-tissue interaction, optical coherence, holography, medical applications of lasers, and construction of advanced laser devices.

PAGE 1 — STRUCTURE & CONTENT

Page 1 contains the exam title, general instructions, and SECTION A.

SECTION A — Short Questions (2 × 7 = 14 Marks)

Students must answer all seven short conceptual questions. These questions focus on basic definitions and numerical understanding in laser physics.

Topics include:

Fermi–Dirac Distribution Function

Understanding electron distribution in energy states.

Temporal Coherence

How consistent a wave remains over time; essential for laser operation.

Duty Cycle Calculation

A numerical question involving:

Laser diode emitting 150,000 pulses per second

Pulse duration 30 ns

Ruby Laser Dye

Basic knowledge of ruby laser medium.

Laser Beam Divergence

Factors affecting beam spread.

Population Inversion

Core requirement for laser action.

Spontaneous vs Stimulated Emission

Fundamental difference between natural radiation and induced emission.

These questions evaluate a student’s foundational grasp of laser physics principles.

PAGE 2 — APPLICATION-BASED & EXPLANATORY QUESTIONS

Page 2 contains SECTION C, which includes long, diagram-oriented, explanatory questions worth 7 marks each.

QUESTION 6 — Laser Construction & Working (7 Marks)

Students must attempt any one part:

(a) Dye Laser Working with Schematic Diagram

Construction of dye laser

Principle of operation

Tuning mechanisms (e.g., grating, prism tuning)

Importance of organic dyes as active medium

(b) Excimer Laser Construction & Applications

Working principle of excimer lasers (XeCl, KrF, etc.)

Energy transition between excited dimers

Applications in:

Microelectronics                                 LASIK eye surgery

Material processing                            Lithography

This section tests understanding of complex laser systems used in modern industries.

QUESTION 7 — Medical Applications & Holography (7 Marks)

Students must attempt one of the following:

(a) Lasers in Medicine

Explains:

How lasers are useful in Ophthalmology and General Surgery

Applications like:                         Retinal photocoagulation

LASIK                                           Laser angioplasty

Tissue ablation & cutting            Benefits of precision, minimal bleeding, sterilization capability

(b) Principle of Holography

Students must describe:

Basic principle of holography                   Construction of a hologram

Reconstruction using reference beam      Use of coherent laser light

Real vs virtual image formation

This section tests advanced conceptual clarity on how lasers interact with human tissue and how coherent light can create 3D holographic images.