Courses and
Projects
Within Research Center COM, there
is a selection of courses related to general as well as more
specific topics within optical communications.
A number of courses and projects given at COM are either
related to SCOOP or directly linked to the SCOOP project.
This page tells you what projects are related to SCOOP.
The SCOOP project is a collaboration between Research
Center COM and industry, represented by the Danish
semiconductor manufacturer GIGA A/S. Hence, SCOOP presents a
great opportunity for students who are keen on doing a project
with industry relations.
If you have any questions or if you are
just interested in seeing what we are doing, please do not
hesitate to contact us by phoning, writing, or emailing to:
| Jørn Hvam |
| Phone |
+45 4525 5758 |
| E-mail |
hvam@com.dtu.dk |
| Snail Mail |
SCOOP
Att. Jørn Hvam
COM, DTU
Bldg. 345
east
DK-2800
Lyngby
Denmark |
| Title |
Quantum Dot
Lasers |
| Points |
To be agreed upon |
| Duration |
Contact teachers |
| Requirements |
Background in opto-electronics and
semiconductor physics |
| Description |
Click
here |
| Supervisors |
Svend Bischoff and Jesper Mørk
|
| Contact |
Svend Bischoff (4525 5736,
sb@com.dtu.dk) or
Jesper Mørk (4525 5767,
jm@com.dtu.dk) |
|
| Title |
Semiconductor laser
mode-locking and clock recovery |
| Points |
To be agreed upon |
| Duration |
Contact teachers |
| Requirements |
Background in opto-electronics and/or
scientific computing |
| Description |
Click
here |
| Supervisors |
Svend Bischoff and Jesper Mørk
|
| Contact |
Svend Bischoff (4525 5736,
sb@com.dtu.dk) or
Jesper Mørk (4525 5767,
jm@com.dtu.dk) |
|
| Title |
All-optical signal
regeneration |
| Points |
To be agreed upon |
| Duration |
Contact teacher |
| Requirements |
Background in opto-electronics and/or
scientific computing |
| Description |
Click
here |
| Supervisors |
Svend Bischoff and Jesper Mørk
|
| Contact |
Svend Bischoff (4525 5736,
sb@com.dtu.dk) or
Jesper Mørk (4525 5767,
jm@com.dtu.dk) |
|
| Title |
Optical Coatings of
Semiconductor Lasers |
| Points |
To be agreed upon |
| Duration |
Contact teacher |
| Requirements |
Background in opto-electronics and/or
semiconductor technology |
| Description |
Click
here |
| Supervisor |
Peter M.W. Skovgaard, 345/154, +45 4525
5734,mailto:ps@mic.dtu.dk |
| Contact |
See above |
|
| Title |
Optimizing Growth
Techniques for Advanced Optoelectronics |
| Points |
To be agreed upon |
| Duration |
Contact teacher |
| Requirements |
Background in opto-electronics and/or
semiconductor technology |
| Description |
Click
here |
| Supervisors |
Peter M.W. Skovgaard, 345/154, +45 4525
5734,mailto:ps@mic.dtu.dk
Jesper Hanberg, GIGA, jh@giga.dk |
| Contact |
See
above |
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to the top...
| Title |
MODELLING OF GAIN SWITCHED
SEMICONDUCTOR LASERS |
| Number of Students |
3-5 |
| Points |
10-15 |
| Duration |
1 or 2 semesters |
| Exam |
Written report and oral
presentation |
| Requirements |
Basic knowledge of opto- or
semiconductor -electronics and interest in computer
modeling |
| Description |
Click
here |
| Tutors |
Svend Bischoff and Jesper Mørk
|
| Contact |
Svend Bischoff (4525 5736,
sb@com.dtu.dk) or
Jesper Mørk (4525 5767,
jm@com.dtu.dk) |
|
| Title |
OPTICAL TRANSITIONS IN
QUANTUM DOTS |
| Number of
Students |
3-5 |
| Points |
10-15 |
| Duration |
1 or 2 semesters |
| Exam |
Written report and oral
presentation |
| Requirements |
Basic quantum mechanics and interest in
computer modeling |
| Description |
Click
here |
| Tutors |
Svend Bischoff and Jesper Mørk
|
| Contact |
Svend Bischoff (4525 5736,
sb@com.dtu.dk) or
Jesper Mørk (4525 5767,
jm@com.dtu.dk) |
|
| Title |
MODELING OF SATURABLE
ABSORBERS FOR OPTICAL PROCESSING |
| Number of Students |
3-5 |
| Points |
10-15 |
| Duration |
1 or 2 semesters |
| Exam |
Written report and oral
presentation |
| Requirements |
Basic knowledge of opto- or
semiconductor-electronics and interest in computer
modeling |
| Description |
Click
here |
| Tutors |
Sune Højfeldt and Jesper Mørk
|
| Contact |
Sune Højfeldt (4525 5736,
sh@com.dtu.dk) or
Jesper Mørk (4525 5767,
jm@com.dtu.dk) |
Back
to the top...
| 3 week courses and special
projects |
| To be published. For inquries, please
contact
us |
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to the top...
Project Descriptions
MODELLING OF GAIN SWITCHED SEMICONDUCTOR LASERSFuture optical communication systems may be based on
the use of very short optical pulses that are closely packed
in time. This necessitates the development of reliable and
easily controllable lasers that can generate short optical
pulses, down to the range of a picosecond or less. A
gain-switched semiconductor laser is one of the possible pulse
sources that are under investigation. It works by operating
the laser close to threshold and exciting it by a fast
electrical pulse. This leads to an even shorter optical pulse,
than can be further compressed by propagation in an optical
fiber or reflection in a Bragg grating.
The purpose of the project is to set up a model for the
gain-switched laser and develop a computer program for the
numerical solution of the resulting equations. The simulation
tool will subsequently be used for investigating the optimum
way of compressing the pulses externally and assessing the
minimum pulsewidths achievable. Since the processes limiting
the gain-switched laser performance are not well understood
yet, it is important for further optimisation to have a good
simulation tool for the gain-switched laser. The project will
provide a good practical introduction to semiconductor laser
dynamics and optical pulse propagation in fibers.
Keywords: Scientific computing, semiconductor
lasers, opto-electronics, optical communications.
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OPTICAL TRANSITIONS IN QUANTUM DOTSQuantum dots can be considered man-made artificial
atoms and have several unique properties, which make them
highly interesting for a number of different applications.
Semiconductor lasers based on quantum dots are thus expected
to have low threshold current and high modulation speed. CW
operation of quantum dots lasers has been experimentally
demonstrated. However, the high modulation potential of
quantum dot lasers has not been explored yet, and a lot of
research is still devoted to the basic characterisation of
quantum dot devices. More detailed experimental and
theoretical investigations are thus required to understand the
characteristics and limitations of components based on
semiconductor quantum dots.
The aim of this project is to develop a basic tool for
calculating optical transitions in quantum dots. This involves
setting up a computer program for the numerical solution of
the Schrödinger equation for the eigen-functions and
eigen-energies of electrons and holes in quantum dots of
different geometry. These results will subsequently be used
for calculating optical transition strengths and absorption
and gain spectra for collections of excited quantum dots. The
project will provide the possibility to work in practise with
a quantum mechanical system of technological importance.
Keywords: Scientific computing, semiconductor
physics, opto-electronics.
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MODELING OF SATURABLE ABSORBERS FOR OPTICAL
PROCESSINGAn electro-absorption modulator
(EAM) is a semiconductor waveguide, in which changing the
externally applied voltage significantly changes the
absorption. Experimentally, these devices have been operated
at speeds of up to 80 Gbit/s with high extinction ratios,
externally modulating a CW signal from for instance a
semiconductor laser. Besides coming up with exciting ideas for
applications which include such devices, one of the key
issues, which is currently being investigated, is how to
design EAMs to optimize the speed at which they can be
operated. In the project, we will investigate the properties
of optically controlled EAMs. This mode of operation uses that
the transmission of one optical beam (the signal) can be
controlled by another beam (the control), since the absorption
of the waveguide is reduced when the control beam is absorbed
(absorber bleaching). Such all-optical - or photonic - devices
may become key elements in future all-optical networks.
The project involves setting up a computer model, which can
simulate the propagation of pulses through an EAM to
investigate the different physical processes, which influence
the performance of the device, especially at higher bit-rates.
This includes computing basic properties like the absorption
spectrum at different carrier densities, and accounting for
the so-called recovery of the device, which means describing
with more or less simple, often phenomenological models, what
happens to excited carriers as a function of time. The
resulting simulation tool can be used to investigate a number
of different device functionalities, and testing out possible
new ideas.
Keywords: Opto-electronics, computer simulation,
semiconductors, optical communications.
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Quantum Dot Lasers
Experimental demonstration of a semiconductor laser based
on quantum dots has recently been accomplished. Quantum dots
can be considered man-made artificial atoms and have several
unique properties which make them highly interesting for a
number of different applications as well as for basic science.
Lasers based on quantum dots may thus offer advantages such as
higher power, lower threshold current, and higher modulation
speed. Further investigations are, however, required to
understand the characteristics and limitations of these novel
devices.
Project description:
The aim of the project is to develop a model for
semiconductor lasers or amplifiers based on quantum dots and
use it to investigate and understand the characteristics of
such devices. The particular focus can be placed on different
aspects, more closely related to the applications or to the
physics of these novel devices, depending on the interest and
background of the student. For instance, the goal may be to
set up a complete working model for a quantum dot laser or
amplifier, but treating some of the physical processes on a
rather phenomenological level. Such a model may take its
starting point in conventional semiconductor laser models, but
incorporating a simplified treatment of the gain of
semiconductor quantum dots. This will still allow to
investigate a number of interesting features of these devices,
in particular relating to their potential in replacing
standard bulk or quantum well materials. Investigations on the
ultrafast dynamical properties of quantum dot lasers require
an additional effort on the microscopic modeling of the
carrier dynamics of the quantum dots. It has been proposed
that such lasers are limited in their response by bottleneck
effects associated with getting the carriers into the quantum
dots. Recent experimental investigations, for instance carried
out at COM, indicate this not to be the case, and it is an
important task to develop materials dynamics model that
explain these observations.
The project is closely related to experimental activities
at COM related to the characterization of quantum dot lasers
and amplifiers.
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Semiconductor laser mode-locking and clock
recovery
Background:
It is a challenging and important task to develop
semiconductor lasers that can generate short optical pulses
with a width on the order of a few picoseconds or less. Such
lasers are needed as sources in high-speed optical
communication systems but also have a range of other
applications related to optical signal processing. For
instance they can be used for all-optical clock recovery,
where a passively modelocked laser is injection locked to an
incoming signal, and thereby generates the basic signal
period. This is a very elegant alternative to complex
electronic clock recovery, which is furthermore limited in
bandwidth to a few tens of GHz.
Project description:
The aim of the project is to develop a simulation tool for
mode-locked semiconductor laser devices. The simulator should
be used to investigate the mechanisms that are responsible for
the modelocking and the quality of the generated pulses, since
these are presently not very well understood. Issues such as
output power, pulse width, chirp, noise and timing jitter are
very important. A number of different device geometries should
be investigated and compared, eventually resulting in new or
optimized device designs. One of the device geometries of
interest involves coupling to an external Bragg grating made
in a glass waveguide, since it offers additional freedom in
terms of tuneability and wavelength control. It will also be
of significant interest to identify the issues that are of
importance for mode-locked lasers intended for clock recovery.
A good numerical model requires careful treatment of pulse
shaping and pulse propagation effects in the semiconductor
laser and this in turn requires a detailed treatment of the
underlying ultrafast gain and index dynamics.
Emphasis may be placed on understanding in detail how the
ultrafast carrier dynamics influence the modelocking
characteristics or on the use of the simulation tool for
various kinds of subsystem simulations.
The project is related to ongoing experimental work at COM
both on device fabrication and characterization and may, in
the case of a one year project, to some extent be combined
with experimental work.
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All-optical signal regeneration
Background:
All-optical communication networks require devices that can
perform various kinds of optical signal processing. Since the
transmission capacity of optical fibers significantly exceeds
the bandwidth of electronic devices, it is of significant
interest to develop devices that are based on all-optical
signal processing. The present project focuses on all-optical
regeneration. When an optical signal is transmitted over long
distances and through different optical devices in an optical
network it will be severely distorted. For instance,
attenuation, noise and dispersion destroy the signal quality.
It is therefore important to develop devices that can
regenerate the signal. Ultimately, both re-amplification,
re-shaping and re-timing of the signal is required. Today,
efficient optical amplifiers exist, but re-shaping and
re-timing of the signal requires additional optical signal
processing. Several optical components incorporating
semiconductor optical amplifiers or electro-absorption
modulators have been demonstrated as useful components for
re-shaping the optical signal, but simultaneous re-timing of
the optical signal requires an additional effort.
Project description:
The aim of the project is to set-up a simulation tool for a
signal regenerator based on a device incorporating
semiconductor optical amplifiers or electro-absorption
modulators. Either bulk or quantum well devices can be
considered. The mechanisms limiting the performance of the
regenerator should be investigated using the simulator, and
eventually result in improved regenerator designs or new ideas
for devices. The project requires development of detailed
models for the gain and index dynamics of the devices,
incorporating also ultra-fast carrier dynamic effects, and
careful treatment of propagation effects. Depending on
interests, the emphasis can be placed on improving the models
for the materials dynamics, e.g. by focusing on quantum well
devices, or on the application of the device models in system
simulations.
The project is related to ongoing experimental activities
at COM. For a full-year project, the investigations may be
combined with experimental device and systems investigations
(Contact: H.N. Poulsen, hnp@com.dtu.dk, or A. Buxens,
aba@com.dtu.dk).
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Optical Coatings of Semiconductor Lasers
Description:
The need for new and improved optical devices for the
rapidly expanding tele communication industries calls for
refinement of fabrication and processing technologies. The COM
center collaboration with the company GIGA A/S is focussing on
device fabrication. Therefore, the final and very important
processing steps towards implementation of useful devices for
communication purposes must be developed. Based at GIGA A/S
this project aims at developing high quality multi-layer
coatings with either high reflection or anti-reflection
properties over a wide range of wavelengths, typically at
around the communication wavelength of 1.55 ?m. The final
characterization of these efforts will be done on real devices
such as semiconductor optical amplifiers and wavegudies and
will be an integrated part of this project.
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Optimizing Growth Techniques for Advanced
Optoelectronics
Description:
To improve the functionality of optoelectronic components
for optical signal processing it is desirable to integrate
several devices on one chip. Such an integrated optoelectronic
device could include for example optical amplifiers,
electro-optical absorbers and passive waveguide sections. To
this end different parts of the device has to be made with
different bandgaps. The amplifier should have maximum gain at
a wavelength where the passive sections shows little loss and
where the absorber can be made to switch between low and high
loss by applying an electrical bias. One approach is the
so-called selective area growth technique. With this technique
areas on the wafer are masked off before growing the active
layers. During growth there will be no deposition on the mask,
but instead an increased deposition rate in the unmasked areas
due to diffusion of the materials. By controlling the
mask-layout, growth parameters etc. it is possible to tailor
the bandgap. This project is focused on developing the
selective area growth technique with special emphasis on
structures used for optical signal processing. The main part
of the practical work will take place at Giga A/S, Mileparken
22, 2740 Skovlunde.
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