Figure 1

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

Figure 1

Scanning electron microscopy (SEM) image of the device (a) comprising a ring-QCL and a detector. The detector element with extended top contact is surrouded by the detector bottom contact (second bond wire from left). The metal hole grating couples the surface incident reflected beam to the detector element. The device cross section (b) of the region indicated by the red dashed line in the SEM image with the emitting and detecting areas marked by the red arrows. The AR (active region) is covered by a cladding layer to provide the waveguiding for the ring cavity of the laser. The ring-QCL is contacted by the extended top contact and the InP-substrate. The detector element has a separated bottom contact. The detector bottom contact is surrounded by an optional guard ring.