| A collaboration of Mid-InfraRed
Technologies for Health and the Environment (MIRTHE) Engineering Research
Center (ERC) partners including Johns Hopkins University, AdTech Optics,
Inc., and Princeton University has led to the development of a new design
for power-efficient Quantum Cascade lasers.
Quantum Cascade lasers are
based in large part on cascaded optical transitions between sub-bands.
Because of the nature of the process, laser devices are not highly power-efficient:
the cascading process involves non-radiative energy loss, the intersub-band
transition has a strong non-radiative component, and optical losses are
high.
To overcome these inefficiencies,
Center collaborators leveraged work done on the Defense Advanced Research
Projects Agency (DARPA) Efficient Mid Infrared Laser (EMIL) program and
employed new quantum design strategies to raise the lasers’ wall-plug efficiency.
With a new understanding of the inter- and intrasub-band scattering processes,
the researchers were able to speed up transit of electrons through the
injector regions. A strongly decreased injection barrier thickness
led to better coupled injector and upper laser sub-bands (top figure).
For pulsed mode operation, one of the best-performing lasers had a peak
wall-plug efficiency (WPE) of 47% at 80K (bottom figure).
Researchers tested a considerable
number of Quantum Cascade lasers, and the majority had a peak WPE greater
than 40% at 80K. Previously, wall-plug efficiency had not exceeded
35%. The collaborators’ work was published in the January 2010 Issue
of the journal Nature Photonics. |
