Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Record-breaking tuning lasers lead to better data flow

11.03.2004


A novel process for fabricating tuneable lasers using micro-machined mirrors was developed by IST project TUNVIC. Part of a special two-part device, it allows variable wavelengths of emitted light that will ultimately allow increased volumes of data to be sent through a single optical fibre cable.



High-capacity data links between networked routers are part of the Internet’s backbone. These links use optical fibre cables through which information is sent using semiconductor lasers. By deploying several lasers of different wavelengths, it is possible to multiply the volume of data that can be sent through a single optical fibre. And with increased Internet traffic, ever increasing amounts of data will need to be exchanged.

"There is a clear need for this [TUNVIC] fabrication process," says Prof. Peter Meissner of the Technical University of Darmstadt and project coordinator. "For example, in WDM [wavelength division multiplexed] communication links, separate semiconductor lasers are used to generate light for each wavelength. Reliability is a key consideration in operational data links, and the system design incorporates pairs of lasers for each wavelength: one in use, the other as a ’hot’ standby. In the event of a failure, the standby laser can take over and maintain the link until the fault is fixed."


The problem is that the lasers, together their associated control systems, are expensive. A solution would be to use a single tuneable laser to act as the hot standby for all the lasers. In the event of a failure, the tuneable laser could be set to the wavelength of the failed component and the service could be resumed.

Two-chip process

At the heart of the TUNVIC process is the idea of using a two-part device. The first is a vertical-cavity surface-emitting laser (VCSEL), where light emitted from the surface, as opposed to the edge, is used for the laser action. This has the advantage of high coupling efficiency to the optical fibre. The second part is a lasing cavity defined by a micro-mechanical structure on which a mirror surface has been created.

There are clear advantages to separating these functionalities. The performance of the VCSEL amplifier and the micro-mechanical structure can be individually optimised, without having to make compromises. Furthermore, the design leads to a relatively long resonator length, which in turn leads to a smaller laser line width, (i.e. purer spectral light output). This has to be balanced against additional assembly steps, which inevitably increase process costs.

Technically speaking, the VCSEL uses an Indium Phosphide substrate. The mirrors are diffused Bragg reflectors, which are fabricated from 40 pairs of layers. The micro-mechanical structure is machined from a membrane. It consists of a central circular area that is suspended by four supports; the length of these supports, and hence the length of the laser cavity, can be modified by passing a small heating current through the substrate. A dissipation of 2mW is sufficient to displace the mirror by around 2 microns. The whole system can provide 0.5 mW light output over a tuning range of 30 nm.

"We set out to produce a laser that could be pumped both electrically and optically," adds Meissner. Pumping is the input of energy that is necessary for the lasing action to take place. "We succeeded in these objectives and managed to get some very nice results. We currently hold the world record for tuning long-wavelength lasers."

"The first application for the devices made with the process is to check the stability and reproducability," says Meissner. "We would need to cycle it through a sequence of wavelengths and monitor the performance. The devices don’t suffer from mode hopping, as one might expect with external cavity lasers."

In the longer term, devices such as these could be used in a number of areas. Wavelength routing is one possibility. Another application might be gas sensing. There are a number of gases that have spectral absorption lines in the region of 1.5 microns. A tuneable laser could scan through a range of wavelengths and specific gases could be identified by measuring the wavelength at which absorption occurs.

Contact:
Peter Meissner
Technische Universitaet Darmstadt
Institut fuer Hochfrequenztechnik
Karolinenplatz 5
D-64289 Darmstadt
Germany
Tel: +49-6151-162462
Fax: +49-6151-164367
Email: meissner@hrz1.hrz.tu-darmstadt.de

Tara Morris | IST Results
Further information:
http://istresults.cordis.lu/index.cfm?section=news&tpl=article&BrowsingType=Features&ID=62960

More articles from Process Engineering:

nachricht Quick, Precise, but not Cold
17.05.2017 | Fraunhofer-Institut für Lasertechnik ILT

nachricht A laser for divers
03.05.2017 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>