Edge-Emitting laser diodes versus VCSELs

Traditional semiconductor lasers, such as DFB lasers used in telecommunications or the ones used in CD players, are edge-emitters that emit light parallel to the wafer surface. It is therefore necessary to cleave the wafer into laser bars, or chips, in order to complete the laser cavity with a reflective and transmitting mirror layer. Compared to the simple and cost-effective on-wafer testability of VCSELs, this requires much more effort and hence makes laser fabrication expensive. As a result, VCSEL technology combines the advantages of lasers and LEDs, making low-cost, high-perfomance laser devices feasible. In the short wavelength field of up to a ~1 µm wavelength, the GaAs (Galliumarsenid)-based multimode VCSELs were thus able to achieve commercial mass production and low prices falling within a 1 $ range.