Near-Infrared Quenching Effects on Mid-Infrared Quantum Cascade Lasers

We report in this work the near-Infrared optical quenching effects on mid-Infrared Quantum Cascade Lasers (QCLs). The quenching effect is both intensity and wavelength dependent. A group of strain-compensated InGaAs/InAlAs, 4.8 mu m mid-IR QCLs, were used in the experiment. The pump lasers are near-IR lasers with wavelengths ranging from 1550nm to visible wavelength around 500nm. When the pump lasers have their lasing wavelengths shorter than 950 nm, it seems that majority of the generated electrons are excited above the conduction band edge of the InAlAs material and be swept off as photoconductive current without significantly affecting the QCL intersubband operations. So their quenching effect is weaker. We also observe that a near-IR laser with good quenching ability can modulate the mid-IR laser with speeds way above 100 MHz, which excludes the possibility of a thermal origin of these results.