Towards mid-infrared on-chip sensing utilizing a bi-functional quantum cascade laser/detector

Our recently demonstrated bi-functional quantum cascade laser/detector (QCLD) opens up a novel approach for monolithically integrated chemical and biological sensors. Simply by changing the applied bias, the structure switches between lasing (58 kV/cm) and detection (0 kV/cm). We have shown that it is possible to match the wavelength of the laser and the detector by a special design approach to decrease the intrinsic Stark-shift. In the QCLD the laser injector also acts as an efficient phonon-ladder extractor at zero bias. As the design is rather complicated, we have developed an optimizer based on a semi-classical Monte-Carlo transport simulator. With this simulator we are able to calculate gain/absorption, as well as the responsivity. By considering non-parabolic in-plane masses in the transport calculation, we can observe the temperature shift of the responsivity, which has to be considered to match the wavelength of the laser and the detector at room-temperature.