Near-field spectroscopic characterization of a 10 μm aperture selectively oxidized vertical cavity surface emitting laser

A 10μm square aperture selectively oxidized 850 nm vertical cavity surface emitting laser (VCSEL) was characterized by employing a near-field scanning optical microscope coupled to a spectrometer. The spatial distribution of various lasing modes was investigated with different wavelengths, both in the near field and far field, by analyzing a series of spectra as a function of position over the VCSEL emitting surface. The inhomogeneous gain distribution with localized regions of higher gain was found through two dimensional scan of the near-field total integrated intensity. It was also found that the VCSELs exhibit a rich transverse mode structure which can be classified as Hermite-Gaussian type.