Lead Chalcogenide Mid-Infrared Vertical External Cavity Surface Emitting Lasers
Sprache des Titels:
Mid-infrared vertical cavity surface emitting lasers (VECSELs) with various lead salt active region structures including quantum wells (QWs) and quantum dots (QDs) were fabricated and analyzed regarding their laser performance. The fabricated PbSe and PbS VECSELs are based on a modular design, which enables to grow the active region and the bottom Bragg mirror on two different substrates. The VECSEL emission covers a spectral range between 3 µm and 5.2 µm. Continuously tunable single mode VECSELs were obtained by applying very short optical cavity lengths. In this case, the free spectral range is sufficiently large that only one single longitudinal mode is supported by the spectral gain. Single mode tuning is achieved by changing slightly the cavity length using a Piezo actuator. Furthermore, we realized the first QD VECELs operating in the mid-infrared. The active regions consist of PbTe quantum dots epitaxially embedded in a CdTe host matrix. The highest operation temperature of 240 K was reached using QDs with a diameter of 22 nm. The fabricated QD VECSELs emit in a wavelength range from 4.2 µm to 2.7 µm. The combination of narrow-gap PbTe and wide-gap CdTe also allows fabricating QW active structures. In contrast to ternary lead salt barriers, CdTe barriers offer a very high charge carrier confinement. The QW VECSELs cover a wavelength range from 3.3 µm to 4.5 µm and the highest operation temperature is 300 K.