Mid-infrared intersubband emission from optically pumped asymmetric coupled quantum wells

A. Sa'ar*, Y. Lavon, F. H. Julien, P. Boucaud, J. Wang, J. P. Leburton, R. Planel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Mid-infrared optical emission due to intersubband transitions between excited conduction subbands of a coupled quantum well structure is studied. The emission process is based on optical pumping of free carriers from the ground subband into the third subband followed by a radiative transition from the third subband into the second subband and a fast phonon assisted relaxation into the ground subband. We have observed spontaneous emission at 14 μm that persists up to room temperature. Our results indicate that population inversion between conduction subbands and large stimulated gain can be achieved.

Original languageAmerican English
Pages (from-to)517-525
Number of pages9
JournalSuperlattices and Microstructures
Issue number4
StatePublished - Jun 1997

Bibliographical note

Funding Information:
In conclusion, we have demonstrated intersubband mid-infrared luminescence in ACQW structure that is optically pumped by a CO2 laser. The emission signal persists from low temperatures up to room temperature. The conditions to have a population inversion can be achieved by intersubband scattering time engineering that allows fast relaxation from the second subband relative to a slower relaxation rate of the third subband. However, we found that the phonon bottleneck effect causes a critical slowdown of the relaxation rate between the second and the ground subband. As a result the carriers are heated up, leading to thermal population of the second subband that destroys the population inversion. A possible solution to this problem may be achieved by using a four level system in which the carrier heating effect can significantly be reduced .[30].. Acknowledgements—This work has been supported by a joint grant of the Commission of European Com- munities (EC No. CI1 -CT93-0072) and the Israeli ministry of science and by grant No. 95-00361 from the United States–Israel Binational Science Foundation (BSF), Jerusalem, Israel. J. Wang and J.-P. Leburton acknowledge the support by the Engineering center of compound semiconductors microelectronics under grant No. NSF EEC 89-43166.


  • Intersubband transitions
  • Optical properties of quantum wells
  • Semiconductor lasers


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