ENGINEERING TRIPOS PART IIA – 2012/2013

Module 3B6 – Photonic Technology

AIMS

This course will introduce key aspects of photonics technology and its applications in fields such as communications, storage, medicine, environmental sensing and solar power.

The course will be concerned both with optical fibres and photonic components including light emitting diodes, lasers, photodiodes and solar cells.

The course will conclude with an introduction to photonic sub-systems including transmitters and receivers for use in applications such as wide area, metropolitan and local area networks.

SYLLABUS

• How and why optoelectronics fits within electronics: Outline of major applications areas within engineering, science and medicine. Examples of optoelectronic subsystems, solar cells, lighting, Communication transceivers.
• Optical processes in semiconductors: Direct and indirect band structures, comparison of Silicon, Germanium, GaAs based and InP based materials. Optical absorption, Optical emission, non-radiative transitions
• Light emitting diodes: Quantum efficiency, wavelength, optical linewidth, visible devices, modulation limits, device structures, materials.
• Laser diodes: Stimulated emission, optical gain. Laser as a feedback amplifier of spontaneous emission, Fabry-Perot laser cavities. Rate equations, modulation characteristics, dynamic linewidth. Examples of common diode laser types.
• Optical transmitter circuits: LED based circuits, LED types, transmitter power, bandwidth. Laser based circuits, laser types, biassing, feedback circuits. Noise in optical systems, shot noise, thermal noise, noise bandwidths, circuit effects.
• Photodetectors: PN junction photodiodes, photoconductors, solar cells, avalanche photodiodes, capacitance, transit time, leakage currents, avalanche gain and noise.
• Optical receiver circuits; Transimpedance amplifiers.
• Fibres and transmission: Multimode and single mode fibres: Attenuation, dispersion, interfaces to fibre.
• Transmission systems in a real environment: Power budgets, error rates, monitoring, power penalties, margins for temperature and ageing. Emerging technologies.

OBJECTIVES

On completion of the course students should be able to-

• Know of the main applications of optoelectronics
• Choose appropriate transmission media with reference to bandwidth and physical environment
• Know which semiconductors are used for what optoelectronic tasks and why.
• Be familiar with the construction of LEDs, and be able to estimate their linewidth, speed and external quantum efficiency.
• Be familiar with the construction of Fabry-Perot and grating based diode lasers, and how this relates to their spectra and light-current characteristics
• Estimate the response of semiconductor lasers to changes in their drive current or operating environment
• Be familiar with the construction of junction photodiodes, and hence be able to estimate the capacitance and responsivity, and know how to operate them for best sensitivity and speed.
• Be familiar with the relationship in construction and operation between junction photodiodes, avalanche photodiodes, solar cells and photoconductors.
• Perform noise calculations for typical optoelectronic circuits.
• Be aware of the design of typical receiver circuits with reference to the physical characteristics of photodetectors.
• Be familiar with the construction of firbres as well as the causes of attenuation and dispersion.
• Perform calculations of link budgets, dispersion and attenuation limits.

REFERENCES

Please see the Booklist for Part IIA Courses for references for this module.