Leakage current detection in InGaAsP laser diodes by imaging of the optical emission within the confining InP layers

The optical emission at 950 nm due to charge carrier recombination within the confining InP layers has been measured for buried heterostructure and ridge waveguide 1300 nm InGaAsP Multi Quantum Well Fabry-Perot laser diodes as a function of the temperature and of the injected current. Above laser threshold, this emission does only weakly depend on laser current for the ridge waveguide type while it increases exponentially with injection current in the case of Double Channel Planar Buried Heterostructure and Facet Selective Buried Heterostructure laser diodes. At high current densities, the 950 nm emission is mainly due to lateral leakage currents. For buried heterostructure laser diodes, a direct correlation has been found between the sublinearity of the optical emission vs. laser current characteristics and the integral of the InP emission. Second harmonic generation with a conversion efficiency below 10^-9 has been observed