Free Newsletter
Register for our Free Newsletters
Newsletter
Zones
Advanced Composites
LeftNav
Aerospace
LeftNav
Amorphous Metal Structures
LeftNav
Analysis and Simulation
LeftNav
Asbestos and Substitutes
LeftNav
Associations, Research Organisations and Universities
LeftNav
Automation Equipment
LeftNav
Automotive
LeftNav
Biomaterials
LeftNav
Building Materials
LeftNav
Bulk Handling and Storage
LeftNav
CFCs and Substitutes
LeftNav
Company
LeftNav
Components
LeftNav
Consultancy
LeftNav
View All
Other Carouselweb publications
Carousel Web
Defense File
New Materials
Pro Health Zone
Pro Manufacturing Zone
Pro Security Zone
Web Lec
Pro Engineering Zone
 
 
 
News

Heat-powered cascade laser needs no electric current

Institut Für Theoretische Physik, Universität Innsbruck : 21 November, 2012  (Technical Article)
In micro electronics heat often causes problems and engineers have to put a lot of technical effort into cooling, for example micro chips, to dissipate heat that is generated during operation. Innsbruck physicists have now suggested a concept for a laser that could be powered by heat. This idea may open a completely new way for cooling microchips.

Since its invention 50 years ago, lasers of varying wave lengths and power are used in many parts of our life, from consumer electronics to telecommunication and medicine. However, not all wave lengths have been equally well researched. For the far infrared and terahertz regime quantum cascade lasers are the most important source of coherent radiation. Light amplification in such a cascade laser is achieved through a repeated pattern of specifically designed semi-conductor layers of diverse doping through which electric current is running. “The electrons are transferred through this structure in a specific series of tunneling processes and quantum leaps, emitting coherent light particles,” explains Helmut Ritsch, Institute for Theoretical Physics, University of Innsbruck, the functioning of such a laser. “Between these layers the electrons collide with other particles, which heats the laser.” In this way, quantum cascade lasers only work as long as they are strongly cooled. When too much heat is produced, the laser light extinguishes.

Schematic picture of a quantum cascade laser. The layers of different semiconductor material constitute the bandstructure shown in the inset.When looking for ways to reduce heat in lasers, PhD student Kathrin Sandner and Ritsch came up with a revolutionary idea: using heat to power the laser. In their work, recently published in Physical Review Letters, the two physicists propose the theory that the heating effect in quantum cascade lasers could not only be avoided but, in fact, reversed through a cleverly-devised modification of the thickness of the semiconductor layers.

“A crucial part is to spatially separate the cold and warm areas in the laser,” explains Sandner. “In such a temperature gradient driven laser, electrons are thermally excited in the warm area and then tunnel into the cooler area where photons are emitted.”

This produces a circuit where light particles are emitted and heat is absorbed from the system simultaneously.

“Between the consecutive emissions of light particles a phonon is absorbed and the laser is cooled. When we develop this idea further, we see that the presence of phonons may be sufficient to provide the energy for laser amplification,” says Sandner. Such a laser could be powered without using electric current.

“Of course, it is quite a challenge to implement this concept in an experiment,” says Ritsch. “But if we are successful, it will be a real technological innovation.” The physical principle behind the idea could already be applied to existing quantum cascade lasers, where it could provide internal cooling. This simplified concept seems to be technically feasible and is already being examined by experimental physicists.

“Apart from the conceptual elegance of this idea, a completely new way may open up of using heat in microchips in a beneficial way instead of having to dissipate it by cooling,” adds Ritsch.

Attached files
Schematic picture of a quantum cascade laser. The layers of different semiconductor material constitute the bandstructure shown in the inset. Graphics: Christoph Deutsch
Full bibliographic information
Temperature Gradient Driven Lasing and Stimulated Cooling. K. Sandner, H. Ritsch. Phys. Rev. Lett. 109, 193601 (2012) DOI:10.1103/PhysRevLett.109.193601, http://dx.doi.org/10.1103/PhysRevLett.109.193601.

 

Bookmark and Share
 
Home I Editor's Blog I News by Zone I News by Date I News by Category I Special Reports I Directory I Events I Advertise I Submit Your News I About Us I Guides
 
   © 2012 NewMaterials.com
Netgains Logo