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We report InAs-based quantum cascade lasers (QCLs) operating near 14 µm with a threshold current density Jth as low as 0.6 kA/cm2 at room temperature. The threshold obtained is lower than the Jth of the best reported InP-based QCLs to date without facet treatment. The achieved performance improvement is partially due to an increased separation between the upper transition level and the next one in the active quantum wells of the employed QCL design.

Benzene is a gas known to be highly pollutant for the environment, for the water and cancerogenic for humans. In this paper, we present a sensor based on Quartz Enhanced Photoacoustic Spectroscopy dedicated to benzene analysis. Exploiting the infrared emission of a 14.85 µm quantum cascade laser, the sensor is working in an off-beam configuration, allowing easy alignment and stable measurements. The technique provides a very good selectivity to the sensor and a limit of detection of 30 ppbv in 1 s, i.e. a normalized noise equivalent absorption of 1.95 × 10−8 W.cm−1.Hz−1/2. The achieved performances of the sensor have enabled measurements on several air samples of a gas station showing a non-neglectable risk in case of long exposure.

Silicon (Si) photonics can have a major impact on the development of mid-IR photonics by leveraging on the reliable and high-volume fabrication technologies already developed for microelectronic integrated circuits. Germanium (Ge), already used in Si photonics, is a prime candidate to extend the operating wavelength of Group IV-based photonic integrated circuits beyond 8 µm, and potentially up to 15 µm. High performance quantum cascade lasers (QCLs) and interband cascade lasers grown on Si have been demonstrated, whereas no QCLs monolithically integrated on Ge have been reported yet. In this work, we present InAs-based QCLs directly grown on Ge by molecular beam epitaxy. The lasers emitting near 14 µm exhibited threshold current densities as low as 0.8-0.85 kA/cm2 at room temperature.