Abstract
Since the first demonstration of the quantum cascade laser (QCL) in 1994, three main material families have been used. Each of these three materials best suits a specific wavelength range, due to differences in electronic effective mass, conduction band offset and index of refraction. The material of choice for mid-infrared (mid-IR) applications is InGaAs/AlInAs, with excellent performances demonstrated from =3.5 μm to =10 μm and beyond. The GaAs/AlGaAs system is the preferred material for THz applications (65 μm<λ<250 μm). In combination with the metal–metal waveguide geometry, maximum operating temperatures (Tmax) of almost 200K have been achieved. Finally, InAs-based QCLs were originally developed for short infrared wavelengths (λ ~ 2.6–3.5 μm)1, benefiting of the large conduction band-offset. Another advantage of the InAs/AlSb system is the low electronic effective mass in the InAs quantum wells (0.023 m0, where m0 is the electron mass), which provides elevated optical gain2.
© 2015 Optical Society of America
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