Interband Cascade Lasers for gas sensing

The Interband Cascade Laser (ICL) [1, 2] combines the interband transition as in a conventional diode laser with the cascading scheme of a Quantum Cascade Laser. ICLs allow for an external quantum efficiency greater than which is enabled because of the special band alignment of GaInSb/AlAs/InAs-interfaces that separates hole and electron injector and internally feed each cascade with carriers. This makes ICLs a unique with great design flexibility. By changing the InAs layer thickness of the typically used W-shaped quantum well (W-QW) the emission wavelength can be tuned within the entire mid infrared region which is known as the fingerprint region of a variety of industrially relevant molecules. Absorption spectra of two prominent ones (acetone and nitric oxide) are shown in Figure 1 together with room temperature spectra of broad area ICLs driven under pulsed condition. Meanwhile GaSb-based ICLs that are operational in continuous wave mode at room temperature have been realized from 2.8 μm [3] to 5.6 μm [4].