Laser waveguides based on surface plasmons at a metal–semiconductor interface have been demonstrated by use of quantum cascade (QC) lasers emitting in the 8–11.5-µm wavelength range. The guided modes are transverse magnetic polarized surface waves that propagate at the metal (Pd or Ti–Au)–semiconductor interface between the laser top contact and the active region without the necessity for waveguide cladding layers. The resultant structure has the advantages of a strong decrease in the total layer thickness and a higher confinement factor of the laser-active region compared with those of a conventional layered semiconductor waveguide, and strong coupling to the active material, which could be used in devices such as distributed-feedback lasers. These advantages have to be traded against the disadvantage of increased absorption losses. A peak output power exceeding 25 mW at 90 K and a maximum operating temperature of 150 K were measured for a QC laser with an emission wavelength λ ≈ 8 µm . At λ ≈ 11.5 µm the peak power levels are several milliwatts and the maximum operating temperature is 110 K.
© 1998 Optical Society of America
Carlo Sirtori, Claire Gmachl, Federico Capasso, Jérôme Faist, Deborah L. Sivco, Albert L. Hutchinson, and Alfred Y. Cho, "Long-wavelength (λ ≈ 8–11.5 µm) semiconductor lasers with waveguides based on surface plasmons," Opt. Lett. 23, 1366-1368 (1998)