|
The CSIR houses a core of laser technology knowledge and expertise
accumulated through research, development and implementation
of laser-based technologies. The organisation continues to
form partnerships to strengthen the science, engineering and
technology base in this research domain. Current laser-based
research focuses on: Novel laser sources
Ultra short physics spectroscopy
Mathematical optics
Biophotonics
Lasers Material
Processing
Novel laser sources
Currently, CSIR research into novel laser sources concentrates
on robust and efficient pulsed lasers. The researchers concentrate
their efforts on mid-infrared (MIR) laser sources,
on robust ultra-short pulse lasers and on electronic
feedback control.
Mid-infrared (MIR) laser sources
A number of applications in industry, medicine and defence
require laser sources, which operate in the mid-infrared
wavelength region of 2 to 4 µm. CSIR research focuses
on improved laser sources for the 2 µm region and
on ’non-linear’ wavelength conversion to longer
wavelengths.
Robust ultra-short pulse lasers
Lasers that emit pulses of a few pico-seconds (ps, 10-12s)
in length and have a relatively high energy per pulse are
very effective in a number of applications. The largest
market for these lasers is in materials processing for micro-machining
applications, since ultra-short pulse lasers are able to
machine much finer structures than conventional lasers.
Current commercial ultra-short pulse laser systems are very
complex and therefore expensive and not very reliable. In
addition, many applications require more average power than
current commercial systems can deliver. CSIR research in
this area concentrates on novel concepts for robust high-power
operation of these lasers. Another application that requires
a similar type of laser is lunar laser ranging (LLR). The
CSIR is involved in an LLR project, where the aim is to
measure the distance to the moon within a few millimetres
in accuracy using a novel ultra-short pulse laser.
Electronic control of lasers
Electronic feedback control has the potential to substantially
enhance the stability and performance of lasers. In collaboration
with academia, CSIR electronic engineers and laser physicists
perform joint research on novel control concepts for lasers.
These will enable the group to develop new lasers with improved
performance.
The synchronisation of pulsed lasers with external systems
with high accuracy is also under investigation.
Ultra-short science and spectroscopy
A group of researchers at the CSIR are focusing their research
efforts on:
- Pump-probe spectroscopy of biological samples with a
specific emphasis on light harvesting complexes
- Femtosecond chemistry with the primary aim of understanding
the reaction dynamics of specific chemical reactions
- The development of high-power femtosecond systems based
on OPCPA amplified techniques
A well-equipped laboratory comprising a femtosecond laser
system delivering 1 mJ per pulse at 1000Hz and 100 fs as
well as a TOPAS OPA system has been established. In addition,
a multi-purpose pump-probe experiment is currently being
constructed.
The group has well established local research links with
both the Laser Research Institute of the University of Stellenbosch
and the School of Chemistry of North-West University. The
group is currently pursuing joint research collaborations
with various international groups.
In addition the group also performs research in atomic
and molecular spectroscopy using more conventional laser
systems. This is done primarily as a support function for
the femtosecond spectroscopy work. The group is supported
by a computational chemistry team.
Mathematical optics
In the Mathematical Optics research group, researchers study
the various aspects of modern optics, including laser beam
shaping, laser beam propagation and novel resonators. Researchers
are interested in both the mathematical basis of these fields
as well as applications of this research in such diverse
areas as optical tweezing in bio-photonics, high energy
laser delivery through a turbulence atmosphere, novel gas
lenses for variable focal lengths and flat-top beams for
studies in high pressure and high temperature physics. Research
undertaken is building competency in mathematical algorithms
applied in optics, both theoretically and computationally,
novel laser resonators, non-linear optics, diffractive optical
elements, micro optics, adaptive optics, refractive beam
shapers, digital holograms, spatial light modulators and
wavefront sensing.
Biophotonics
Applications of optically-based techniques in surgery and
medicine continue to increase rapidly. This is mainly due
to the fact that such techniques hold a series of inherent
advantageous properties compared to more conventional medical
techniques. For instance, by applying optical techniques,
treatments and diagnostic procedures can be done non-invasively,
reducing the inconvenience for the patients as well as the
risk of spreading infectious diseases. Furthermore, optically-based
medical equipment is typically relatively inexpensive and
can also be made transportable, which allows for outpatient
treatment and early diagnostics at first level patient care.
This is of course of substantial importance with regards
to South African conditions, for example in the deployment
of medical diagnostic and therapeutic equipment in remote/rural
areas.
CSIR researchers in biophotonics focus on the development
and improvement of various therapeutic and diagnostic medical
applications of lasers. These applications include low level
laser therapy for wound healing and photodynamic therapy
(PDT) for noninvasive cancer treatment . To facilitate this
and future research in novel medical laser applications,
a generic biomedical optics test bed facility (BioBed) is
currently being established for convenient, risk-free, and
cost-effective development and preclinical testing of such
applications.
As implied, the field of Biophotonics is highly multidisciplinary.
Therefore, to succeed, collaboration between various disciplines,
for example physics, medicine, biology, and engineering
is crucial. Accordingly, one of the key drivers for establishing
the BioBed facility at the CSIR is to facilitate this multidisciplinary
biophotonics research collaboration in South Africa. Several
local collaborations have already been established with
the universities of Rhodes, Johannesburg, Pretoria, and
Stellenbosch and the Tshwane University of Technology, together
with a number of international collaborations, e.g. with
the universities of Lund (Sweden), Ulm (Germany), and St.
Andrews (UK).
Laser Materials Processing
Since the invention of the laser in 1960, laser technology
has had a profound impact on virtually all spheres of modern
life. Because of its spectacular successes over a broad
range of applications, laser technology was soon identified
as an enabler and a key technology to global competitiveness.
This realisation led to the implementation of government
sponsored R&D programmes in laser technology in practically
every industrialised country around the world. In fields
as diverse as telecommunications, medicine and entertainment,
laser technology opened up new frontiers. Manufacturing
proved to be no exception. In each of the basic disciplines
of cutting, joining, milling and drilling, laser technology
introduced significant advantages as well as new possibilities.
At the heart of the competitive advantage that laser technology
offers over conventional manufacturing techniques, lies
exceptional precision and control. To illustrate this point
it should be mentioned that the beam from a standard industrial
laser source of 4 kW power can readily be focused onto a
spot size as small as 0.2 mm in diameter. This gives rise
to a power density of over 10 million W/cm2 - enough to
overcome the thermal properties of all known engineering
materials resulting in melting and vaporisation.
The advantages of a laser-based manufacturing process can
be wide and varied depending on the particular application,
but more often than not, it includes a combination of high
levels of productivity and quality.
In 2000, the CSIR National Laser Centre embarked on a programme
aimed at introducing the competitive advantages of advanced
laser materials processing to the South African manufacturing
industry. Today the materials processing technology in the
CSIR is at the forefront of laser-based materials processing
in Africa. Laser-based manufacturing processes that were
specifically targeted are:
- Deep penetration welding
- Surface modification (cladding, hardening, alloying
and cleaning)
- Laser milling
- Specialised laser cutting, including thick section
cutting and 3D profile cutting of sheet metal
The first objective was to establish a capacity for the
practical demonstration and application of these processes.
This required the establishment of infrastructure in the
form of appropriate equipment as well as human capital development
(HCD). The HCD process was fast tracked through a technology
transfer agreement between the CSIR National Laser Centre
and the Fraunhofer Institut für Laser Technik in Aachen,
Germany. The infrastructure currently includes:
- Trumpf TLC 1005 Lasercell: five-axis gantry robot equipped
with 5 kW CO2 laser for deep penetration welding of ferrous
metals and 3D cutting
- High-power Nd:YAG facility: eight-axis articulated
arm robot equipped with 4.4 kW Nd:YAG laser for deep penetration
welding of light metals, laser cladding and transformation
hardening
- Deckel Maho Gildemaister: system for deep precision-laser
engraving.
As the respective capabilities gain in maturity, the emphasis
is shifting from demonstration and application to a focus
on R&D.
|
