Department of Physics, Unit Catalogue 2011/12
|Level:||Honours (FHEQ level 6)|
|Supplementary Assessment:||Mandatory extra work (where allowed by programme regulations)|
|Requisites:||Before taking this unit you must (take PH20013 or take PH20060) and (take PH20014 or take PH20061) and take PH20020|
The aim of this unit is to outline the main physical principles underlying the generation and manipulation of laser radiation.
After taking this unit the student should be able to:
* design simple resonant cavities and analyse their main features;
* describe and analyse the interactions between light and matter that lead to spontaneous emission and lasing in 3- and 4-level systems;
* treat cw, mode-locked and Q-switched laser operation and describe the resulting temporal, spectral and power characteristics;
* outline the effects of group velocity dispersion and self-phase modulation on short pulses;
* compare the properties of different laser classes and assess their suitability for applications;
* analyse the propagation of Gaussian beams.
Numeracy T/F A, Problem Solving T/F A.
Optical beams and resonators (5 hours): Gaussian beams; Rayleigh length, beam waist, phase front curvature. Q-factor, parallel mirror resonator, three-dimensional resonators. Resonators with curved mirrors; stability criterion. Mode density in resonators. Losses in resonators.
Emission and absorption of radiation (2 hours): Spontaneous emission; lineshape and broadening mechanisms. Stimulated emission. Einstein relations. Absorption and amplification. Gain saturation. Complex susceptibility of laser medium.
The Fabry-Perot laser (3 hours): Amplitude and phase conditions for oscillation, population inversion at threshold, frequency of oscillation, cavity lifetime and Q-factor. Three- and four-level lasers. Critical fluorescence power. Output power in lasers above threshold.
Types of gain medium (5 hours): Examples of specific 3- and 4-level lasers and pumping mechanisms: gas, solid state, semiconductor and fibre lasers.
Pulsed lasers (7 hours): Q-switching. Mode-locking; time-bandwidth product for pulses, active and passive mode-locking. Examples of mode-locked lasers. Dispersion; group velocity dispersion, Gaussian pulse spreading caused by GVD, dispersion of optical fibres, frequency chirp. Autocorrelation. Frequency conversion; second-harmonic generation, phase-matching.
PH30032 is Optional on the following programmes:Programmes in Natural Sciences