Lasers emitting in the mid-infrared ( mid-IR ) wavelength domain ( 2 - 5 micron ) are of great interest due to their potential applications in telecommunications and molecular spectroscopy. Gas detection with a high resolution can be developed using these mid-IR lasers because the strong absorption lines of many polluting gases and combustion products falls in this wavelength domain. A good spectral purity, contimuous wave ( cw ) output powers at room temperature and a good tuning range are the requirments for high resolution gas detection.The III-V compound semiconductor material system ( Al, Ga, In, As, Sb ) forms an ideal basis for the realization of diode lasers emitting in this wavelength range. The structure of a typical multi quantum well semiconductor laser is shown in the figure(??). The emitted wavelength depends on the dimensions and material system of the multi quantum wells which forms the active layer of the diode laser.

 

 

 

Figure 1: Multi Quantum Well semiconductor laser structure ( dimensions not to scale )

 

The objective our group is to develop Sb-based III-V semiconductor lasers operating in the mid-IR range for possible gas detection applications.