Quantum-cascade lasers emit between 2.75 and 2.97 µm

To fill the gap in high-performance mid-infrared lasers, researchers at Université Montpellier (Montpellier, France) have demonstrated quantum-cascade (QC) lasers emitting between 2.75 and 2.97 µm. The QC lasers were formed by heavily doped n+ indium arsenide (InAs) cladding layers and spacers made of short-period InAs/aluminum antimonide (InAs/AlSb) superlattices. Compared with inter-band diode lasers, the performance of QC lasers is more stable at high operating temperatures. Several structures of this nature were tested in pulsed mode at a repetition rate of 1 kHz with a pulse duration of 100 ns. The lasers emitting at 2.75 µm operated at a threshold current density of 2 kA/cm² with a peak output power of 0.3 W/facet at 78 K. Other samples showed emission between 2.88 and 2.97 µm with a similar threshold current density and an operating temperature between 80 K and 285 K; the peak optical power of these samples exceeded 1.5 W/facet because of the larger dynamic range. Single-frequency lasers in this regime are ideal for spectroscopic applications operating at elevated temperatures such as those in oil wells or exposed to direct sunlight in space. Contact Alexei Baranov at [email protected].