Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Harnessing randomness to improve lasers

17.01.2014
Developed at A*STAR, the first electrically pumped random lasers for mid-infrared radiation are set to enable applications in sensing and imaging

Randomly arranged items usually have poor optical properties. The rough—or random—surface of a frosted-glass window, for example, obscures the view of an object.


Computed optical light fields in a random laser overlaid on black circles, which represent the nanoholes drilled into a semiconductor quantum cascade laser, to produce a laser pattern with low spatial coherence.

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The optical industry therefore expends considerable effort reducing any surface irregularities in optical devices to avoid the uncontrollable scattering of light characteristic of random structures.

But now, a research group led by Ying Zhang from the A*STAR Singapore Institute of Manufacturing Technology (SIMTech) has made good use of randomness by studying how random structures can improve the performance of lasers. Together with a team led by Qijie Wang at Nanyang Technical University in Singapore, the group has demonstrated the world’s first electrically pumped mid-infrared random laser, which operates at a 10-micrometer wavelength. The laser is as bright as conventional diode lasers but produces less-speckled images.

Light waves from a conventional laser oscillate in perfect synchronicity, across both time and space. Perfect alignment of the light waves at different time and different locations across the beam profile is known as temporal and spatial coherence, respectively. When a laser illuminates a surface, a speckled pattern is typically visible, which indicates spatial coherence. The speckles result from the laser beam reflecting from different parts of the surface. Because the waves are in sync, they create spatial interference effects in the eye of an observer. This distortion is undesirable, particularly in biomedical imaging applications conducted in the infrared region of the spectrum.

Random lasers are the solution to this type of distortion, says Zhang. “Random lasers show the same high temporal coherence as that of other lasers but have a lower spatial coherence,” he explains. “High temporal coherence gives the desirable brightness but it is the low spatial coherence that removes the speckles caused by interferences.”

To realize a random laser in the mid-infrared spectrum, Zhang and co-workers used a semiconductor quantum cascade laser into which they had drilled a random pattern of nanoholes. At a sufficiently high density, these holes prevent the formation of a regular laser pattern within the semiconductor (see image). Instead, the pattern of a random laser forms, with low spatial coherence.

Employing a quantum cascade laser to realize the random lasers allows for the polarization of the laser light perpendicular to the laser surface. This propagation minimizes losses owing to the air-hole structure.

The research team’s wafer-fabrication competencies enabled them to drill holes deep enough into the laser chip, with sufficiently smooth side walls to minimize losses in the laser itself. By introducing these perfections and overcoming a number of other practical hurdles, Zhang and his colleagues succeeded in making the lasers efficient enough to provide lasing during electrical operation.

Nevertheless, notes Hou Kun Liang of SIMTech, who invented the mid-infrared random laser, more work is needed to bring random lasers to market. “We are working on a random laser that operates at room temperature. And in the long-term, we plan to extend random lasers from the infrared to even longer wavelengths and can be used for inspection of various polymer packaging quality-control of printed electronics, biomedical imaging, among other applications.”

About the Singapore Institute of Manufacturing Technology

The A*STAR Singapore Institute of Manufacturing Technology (SIMTech) develops high-value manufacturing technology and human capital to contribute to the competitiveness of Singapore’s industry. It collaborates with universities as well as multinational and local companies in the precision engineering, electronics, semiconductor, medical technology, aerospace, automotive, marine, logistics and other sectors.

Journal information

Liang, H. K., Meng, B., Liang, G., Tao, J., Chong, Y., Wang, Q. J. & Zhang, Y. Electrically pumped mid-infrared random lasers. Advanced Materials 25, 6859—6863 (2013).

A*STAR Research | Research asia research news
Further information:
http://www.research.a-star.edu.sg/feature-and-innovation/6889
http://www.researchsea.com

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

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>