Simple technique for measuring cavity loss in semiconductor lasers

A new technique for measuring the cavity loss of semiconductor lasers is introduced. The cavity loss is deduced from the Fabry-Perot oscillations in the spontaneous emission well below the bandgap of the active region. This approach, referred to as the below-bandgap technique, is simple, applicable to both Fabry-Perot and DFB lasers, and is capable of measuring cavity losses with few restrictions on laser bias current