Photonics

Photonics is a specialty in which light is the central focus, whether in its wave or corpuscular form. Photonic solutions are essential in an immense number of fields, such as ultra-high-speed telecommunications, medicine, aeronautics, lighting, the environment (observation, processing), defense (night vision, guidance), metrology, etc. As part of the EEA bachelor's degree and this module, which is both practical (TP) and theoretical (CM/TD), we'll cover the basics of electromagnetism, such as the propagation equation of an electromagnetic wave, the properties of these waves, and their behavior at interfaces. This will be followed by the study of key phenomena in wave photonics in particular, such as diffraction and interference, enabling us to understand how light can be used for spectroscopic analysis, to measure deformations, to encode information for ultra-high-speed communications, to store information, and so on.

The aims of this module are firstly to be able to describe electromagnetic waves and how they behave, by manipulating Maxwell's equations and the usual differential operators.

In a second phase, the aim is to understand diffraction and interference phenomena, so as to acquire the knowledge needed to implement interferometers in common photonics applications such as spectroscopy, communications and strain measurements.

knowledge of waves (acoustic, microwave or other).

Recommended prerequisites: knowledge of geometrical optics.

1. I. Electromagnetic waves (CM7.5h - TD 3h)
2.  Reminders
3. Vector operators
4. Basic electrostatic/magnetostatic relationships, fields and sources
5. Harmonic plane wave model
6. Maxwell's equations
7. Historical review
8. Description of Maxwell's equations
9. Linking EMs to static relations
10. Expression of harmonic EM
11. Electromagnetic field propagation
12. Electromagnetic field structure
13. Propagation in vacuum, propagation equation
14. (Potential propagation)
15. In LHI environments
16. Interface relationships
17. Polarization
18. Notion of light polarization
19. Law of Malus
20. Reflection/transmission at interface
21. (Fresnel formulas)
22. Electromagnetic energy
23. Energy carried by an electromagnetic wave
24. Poynting vector
25. Mean value of the Poynting vector and applications

1. II. Interference & Diffraction (CM7.5h - TD3h)
2. Introduction: Interference & Diffraction (1h30)

            1.1 Huygens-Fresnel principle

            1.2 Different types of interference (stationary, instantaneous)

1. a) Light description and formalism
2. b) Monochromatic interference
3. c) Instantaneous interference (beat)
4. d) Interference between contra-propagating waves: longitudinal standing wave

            1.3 A typical approach to studying interference and diffraction

1. a) Run difference and phase shift
2. b) Sum of electric fields
3. c) Optical intensity evaluation
4. Interferences (3h)

            2.1 2-wave interference

1. a) Michelson interferometer
2. b) Transfer function of a 2-wave interferometer
3. c) Polychromatic interference 

            2.2 N-wave interference

1. a) Fabry-Perot cavity
2. b) Airy function
3. c) Fabry-Perot with gain (laser)

            2.3 Other common interferometers & applications

1. Diffraction (3h)

            3.1 Near field & far field

            3.2 Far-field slit diffraction

            3.3 Far-field Fourier transform

            3.4 Diffraction through a hole

            3.5 Young's cracks

            3.6 Diffraction grating

III. PRACTICAL WORK (12h)

            TP1. Polarization & Diffraction of light

            TP2. Mach-Zehnder amplitude modulator for optical communications

            TP3. Grating spectrometer

            TP4. Detection of weak optical signals