Figure 2

From: Mid-infrared surface transmitting and detecting quantum cascade device for gas-sensing

Figure 2

Emission spectrum of the single mode ring-QCL and absorption spectrum of the detector element (a). Detector signal over laser current (b) for the integrated detector element in comparison with an external detector. If the mirror is shielded the remaining detector signal is due to reflections from the gas-cell windows. The laser threshold is at 3 kA/cm2.