The super luminescent diode (SLD) is an infrared emitter that has the advantages of both the laser diode and the LED; high radiant flux density and low coherency. The SLD was developed as a device that compensates for the disadvantages of laser diodes such as their coherent noise and is therefore ideal for applications where a higher S/N ratio is essential, for example in light-applied measurements and optical communications. A photodiode chip has also been mounted within the same package for monitoring the SLD output.