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Lecture

Semiconductor Lasers: Rate Equations and Steady State Solutions

In course

EE-440: Photonic systems and technology

The physics of optical communication components and their applications to communication systems will be covered. The course is intended to present the operation principles of contemporary optical communication systems employing optical fibers and modern op ...

Description

This lecture covers the rate equations describing the behavior of semiconductor lasers, focusing on photon and electron densities in the active volume. It discusses the steady state solutions, including the conditions for small current and lasing threshold. The dynamic behavior is explored through modulation response analysis with a time-dependent current. Laser dynamics topics such as modulation bandwidth, turn-on delay, and relative intensity noise are also addressed. Additionally, the lecture explains the operation of semiconductor lasers, their optical feedback mechanism, and their application in optical communications. The differences between light emitting diodes (LEDs) and lasers are highlighted, emphasizing their emission processes and characteristics.

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Instructor

Camille Sophie Brès

Prof. Camille-Sophie Brès is an Associate Professor in the Institute of Electrical Engineering within the School of Engineering of EPFL. Her primary research interests are centered optical communications and on parametric and nonlinear processes in optical fiber and non-silica platforms for ultrafast signal processing, all optical networks, sensing and light sources. She has authored over thirty peer-reviewed journal articles and has presented more than 15 papers at international conferences. She received the Gordon Wu Fellowship for her graduate studies, the NSF CIANs Diversity Postdoctoral Fellowship in 2009, the Early Career Woman in Engineering Award in 2016. She is a senior member of the IEEE and OSA. 2019 - present: Associate Professor in the Institute of Electrical Engineering, EPFL 2011 - 2018: Assistant Professor in the Institute of Electrical Engineering, EPFL 2010 - 2011: Assistant Project Scientist, University of California San Diego (UCSD) 2007 - 2010: Postdoc in ECE, University of California San Diego (UCSD) 2002 - 2007: Ph.D in Electrical Engineering, Princeton University 1998 - 2002: B.Eng with Honours in Electrical Engineering, McGill University

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Related concepts (32)

Stimulated emission

Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level. The liberated energy transfers to the electromagnetic field, creating a new photon with a frequency, polarization, and direction of travel that are all identical to the photons of the incident wave. This is in contrast to spontaneous emission, which occurs at a characteristic rate for each of the atoms/oscillators in the upper energy state regardless of the external electromagnetic field.

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word laser is an anacronym that originated as an acronym for light amplification by stimulated emission of radiation. The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light that is coherent.

Spontaneous emission

Spontaneous emission is the process in which a quantum mechanical system (such as a molecule, an atom or a subatomic particle) transits from an excited energy state to a lower energy state (e.g., its ground state) and emits a quantized amount of energy in the form of a photon. Spontaneous emission is ultimately responsible for most of the light we see all around us; it is so ubiquitous that there are many names given to what is essentially the same process.

Maser

A maser (ˈmeɪzər; acronym of microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves (i.e. microwaves), through amplification by stimulated emission. The first maser was built by Charles H. Townes, James P. Gordon, and Herbert J. Zeiger at Columbia University in 1953. Townes, Nikolay Basov and Alexander Prokhorov were awarded the 1964 Nobel Prize in Physics for theoretical work leading to the maser.

Laser diode

A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction. Driven by voltage, the doped p–n-transition allows for recombination of an electron with a hole. Due to the drop of the electron from a higher energy level to a lower one, radiation, in the form of an emitted photon is generated. This is spontaneous emission.

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