Spectrally resolved confocal microscopy for laser mode imaging and beam characteristic investigations

In this letter, confocal optical microscopy is used to investigate the intensity patterns of an infrared vertical cavity surface emitting laser in three dimensions with high spectral resolution. The measurements were performed between the near field (Fresnel) regime and the far field (Fraunhofer) regime. The calculated intensity patterns were found to be in good agreement with the measured intensity distribution. The calculations together with the measurements can be used to determine the phase relation between different positions inside the gain medium.