MPhys Physics with Theoretical Physics

Lasers are now commonplace in the world we live in – being used for many applications ranging from games machines and printers to ultra-high-resolution spectroscopy.  It is estimated that there are now more lasers in circulation than there are people on the planet.  Lasers are one of the devices used to produce photonic systems, where light is used for measurement/sensing, communications, data transfer/storage and displays. They are also key to the rapid development of quantum technologies.  

This unit provides a grounding in the theory behind the operation of lasers, during which the propagation of Gaussian beams, optical resonators, the interaction of radiation with atomic systems and transient effects are covered.  It also looks at the properties of the light produced, including coherence and the statistical nature of light.

On a practical level, specific lasers are discussed, along with methods of detection and modulation.  A number of photonic applications (not necessarily involving lasers), such as communications and displays will also be covered.  

The unit aims to provide a grounding in understanding the operation of lasers and providing an introduction into the wider area of photonics.   

ILO 1

Know the properties and propagation of rays and Gaussian beams through lenses, between mirrors and through optical waveguides, linking this to optical resonators.

ILO 2

Know the interactions of light with atomic systems, including spontaneous and stimulated emission, and develop an understanding of gain and its saturation, the oscillation conditions, mode structure and transient effects key to Q-switching.  

ILO 3

Know the properties of laser radiation, including broadening mechanisms, coherence and the statistical nature of light.

ILO 4

Know details of specific laser systems, detection methods and modulation techniques and then understand a selection of photonic systems used, for example, in communications and for displays.  

1. Intro and mathematical formalism 
   Representation of an EM wave and complex notation
   
    
2. Propagation of rays and beams 
   Lens waveguide
   Rays between mirrors
   Wave equation and Gaussian beams
   ABCD law
   Higher order Gaussian beams
   
   
    
3. Propagation of beams in fibres 
   Waves in cylindrical coordinates
   Step-index waveguide
   Graded index fibres
   Attenuation in silica fibres
   
   
    
4. Optical resonators 
   Fabry-Perot etalon
   Resonators with spherical mirrors
   Stability criteria
   Resonance frequencies
   Losses in resonators
   
   
    
5. Interaction of radiation and atomic systems 
   Spontaneous transitions and broadening mechanisms
   Induced transitions
   Absorption and amplification
   Electron oscillator model and susceptibility
   Gain saturation
   
   
    
6. Laser oscillation 
   Fabry-Perot laser
   Oscillation frequency
   3 and 4-level lasers
   Power and optimum output coupling
   Multi-mode operation
   Transient effects – relaxation oscillations Q-switching and mode locking
   
   
    
7. Statistic optics and coherence 
   Random light
   Interference of partially coherent light
    
8. Specific laser systems Nd:YAG
   Fibre lasers
   Semiconductor laser
   DPSS lasers
   
   
    
9. Detection of optical radiation 
   Photomultiplier
   Photodiode
   Noise in detectors
   
   
    
10. Modulation 
    Electro-optics (including liquid crystals)
    Acousto-optic
    
    
     
11. Applications 
    Fibre-optic communications Displays

Two one hour, live in-person lectures per week where the core material with examples will be delivered.  The recordings of these lectures will be on the course online page.  The lectures are accompanied by detailed notes and for some of the material explanatory videos that the students are expected to assimilate before the lecture.  This is augmented weekly by problems.  

Feedback & exercises will be available through examples presented during the lectures together with answers available via Blackboard, and through working through the solution of selected examples in the lectures.

Lasers and Electro-optics: C. C. Davis

Lasers: P. W. Milloni, J. H. Eberly.

Introduction to Optical Electronics: A. Yariv

Fundamentals of Photonics: B. E. A. Saleh, M. C. Teich

Optoelectronics: An Introduction: J. Wilson, J. F. B. Hawkes