The aim of the course is to describe the principles of lasers and laser action. The course covers interactions of atoms and molecules with light (absorption, emission and dispersion) and includes concepts such as Doppler, collision, and natural lifetime broadening, population inversion, and optical pumping. The principles of laser resonators and laser action (gain, threshold, power) are discussed. The course will treat some common types of laser in more detail, including continuous-wave (cw) and pulsed, gas and solid-state lasers and at the end, some laser applications will be discussed.

**Learning Outcomes:** At the end of this course, students should be able to:

- Explain the operational principles and construction of lasers
- Describe optical components that can be used to tailor the properties of the laser
- Distinguish between the different optical cavities/resonators.
- Describe the conditions of producing a laser beam.
- Describe how pulsed laser beams can be obtained from a laser cavity.
- Understand the laser applications in daily life.

**Contents**

- Introduction to Lasers
- Properties of laser beam
- Electromagnetic waves and photons
- Energy levels, Transition and spectral lines, The metastable level
- Spontaneous and Stimulated emission, Stimulated Absorption
- Line shape function
- Black-Body Radiation
- Relation between Einstein
*A*and*B*Coefficients - Conditions for large stimulated emissions
- Gain coefficient and threshold Gain coefficient
- Line-broadening mechanism
- Population inversion
- The three and four-level system
- Rate equations
- Optical resonators
- Conditions for steady state oscillation in a two mirror Resonator
- Cavity resonance frequencies
- Longitudinal and Transverse modes in a cavity
- Pumping Process, Pulsed vs Continuous emission
- Threshold condition and output power
- Optimum output coupling
- Laser tuning
- Oscillation and pulsations in lasers
- Q-Switching and mode-locking methods
- Phase velocity and Group Velocity
- Dispersion and Pulse Width
- Non-linear crystals
- Solid state lasers: Ruby Laser, Nd:YAG and Nd:Glass lasers
- Semiconductor lasers: Homojunction lasers, Double Hetrostructure lasers
- Gass Lasers: Helium Neon laser, CO2 laser, Nitrogen laser and Excimer laser
- Free-Electro and X-ray lasers
- Laser Applications.

**Recommended Books**

- Laser Fundamentals by W. T. Silfvast, Cambridge University press, (2003).
- Understanding lasers b y J. Hecht, Howard W. Sams & Company, USA (1988).
- Lasers by P. W. Milonni and J. Eberly, Wiley, New York. (2010).
- An Introduction to Lasers by M. N. Avadhanulu, S. Chand & company (2001).

*Suggested Books*

- Principles of lasers by O. Svelto, Plenum press new York & London (1992).
- Lasers by A.E. SiegmanUniversity, Science Books Mill Valley, C. A. (1986).
- Laser Theory by H. Haken, Springer, Berlin (2003).
- Lasers, Principles and Applications by J. Wilson and J. F. B. Hawkes, Prentice Hall, New York, (1988).
- Lasers and Electro-Optics: Fundamental and Engineering by Christopher C. Davis, Cambridge University press, (1996).

**ASSESSMENT CRITERIA**

- Sessional: 20 (Presentation / Assignment 10, Attendance 05, Quiz 05)
- Mid-Term Exam: 30
- Final-Term Exam: 50

**Time of Class Meeting**

Monday to Wednesday ** **9:30 am to 10:30 am

**Key Dates **

Commencement of Classes January 13, 2020

Mid Term Examination March 16 to March 23, 2020

Final Term Examination May 11-15, 2020

Declaration of Result May 22, 2020