Different diagnostic methods were investigated in order to evaluate their potential as aging sensitive tool for the analysis of high-power laser diode arrays. The well-known method of photocurrent spectroscopy, i.e. the measurement of the spectral sensitivity of a laser diode acting as a detector, was found to monitor aging properties of high power laser diode arrays in a convenient way. Photocurrent spectra of high power laser diode arrays emitting at 808 nm (1.53 eV) were investigated in the 0.8 - 3.0 eV photon energy range. Aging induced changes in different spectral regions reveal the influence of difference mechanisms affecting the structure. One aging effect--the growth of the defect concentration within the optically active layers of the devices--is monitored. Conclusions on the microscopic nature of the changes are drawn and several applications are discussed.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.