Magnetic-field-assisted terahertz quantum cascade laser operating up to 225 K

• Published in: Nature photonics Vol. 3; no. 1; pp. 41 - 45
• Main Authors: Smirnov, D, Wade, A, Fedorov, G, Kumar, S, Williams, B. S, Hu, Q, Reno, J. L
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-01-2009; Nature Publishing Group
• Subjects: Applied and Technical Physics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); High temperature; Lasers; letter; Magnetic fields; Optics; Physics; Physics and Astronomy; Quantum Physics; Semiconductor lasers; laser diodes; Wavelengths; THz range; Semiconductor lasers; Population inversion; High field; Optoelectronic devices; Landau levels; Quantum cascade laser
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/nphoton.2008.251

Advances in semiconductor bandgap engineering have resulted in the recent development of the terahertz quantum cascade laser
1
. These compact optoelectronic devices now operate in the frequency range 1.2–5 THz, although cryogenic cooling is still required
2
,
3
. Further progress towards the realization of devices operating at higher temperatures and emitting at longer wavelengths (sub-terahertz quantum cascade lasers) is difficult because it requires maintaining a population inversion between closely spaced electronic sub-bands (1 THz ≈ 4 meV). Here, we demonstrate a magnetic-field-assisted quantum cascade laser based on the resonant-phonon design. By applying appropriate electrical bias and strong magnetic fields above 16 T, it is possible to achieve laser emission from a single device over a wide range of frequencies (0.68–3.33 THz). Owing to the suppression of inter-Landau-level non-radiative scattering, the device shows magnetic field assisted laser action at 1 THz at temperatures up to 215 K, and 3 THz lasing up to 225 K.
The application of a very strong magnetic field is experimentally demonstrated to enable operation of terahertz quantum cascade lasers at much higher temperatures than usual. Lasing at a frequency of 3 THz is reported at up to 225 K when a field of 19.3 T is applied. The results validate theoretical predictions that quantum confinement is a route towards room temperature operation.