Highly power-efficient quantum cascade lasers

• Published in: Nature photonics Vol. 4; no. 2; pp. 95 - 98
• Main Authors: Liu, Peter Q, Hoffman, Anthony J, Escarra, Matthew D, Franz, Kale J, Khurgin, Jacob B, Dikmelik, Yamac, Wang, Xiaojun, Fan, Jen-Yu, Gmachl, Claire F
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2010; Nature Publishing Group
• Subjects: 639/624/1020/1092; 639/766/930/1032; Applied and Technical Physics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Lasers; letter; Light sources; Optics; Photonics; Physics; Physics and Astronomy; Quantum cascade lasers; Quantum Physics; Semiconductor lasers; laser diodes; Transport processes; Diagnostic techniques; Transport processes; Semiconductor lasers; Interface roughness; Radiation sources; Quantum cascade laser
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2009.262

Quantum cascade lasers
1
are promising mid-infrared semiconductor light sources for molecular detection in applications such as environmental sensing or medical diagnostics. For such applications, researchers have been striving to improve device performance
2
. Recently, improvements in wall plug efficiency have been pursued with a view to realizing compact, portable, power-efficient and high-power quantum cascade laser systems
3
,
4
. However, advances have largely been incremental, and the basic quantum design has remained unchanged for many years, with the wall plug efficiency yet to reach above 35%. A crucial factor in quantum cascade laser performance is the efficient transport of electrons into the laser active regions. We recently theoretically described this transport process as limited by the interface-roughness-induced detuning of resonant tunnelling
5
. Here, we report that an ‘ultrastrong coupling’ design strategy overcomes this limiting factor and leads to the experimental realization of quantum cascade lasers with 40–50% wall plug efficiency when operated in pulsed mode at temperatures of 160 K or lower.
A quantum cascade laser with a wall-plug efficiency of up to 50% is experimentally realized when operated at low temperatures and in pulsed mode. The high-efficiency performance is achieved by implementing an ultrastrong coupling between the injector and active regions.