Multidimensional near- and far-field measurements of broad ridge (Al,In)GaN laser diodes

Abstract

Broad (Al,In)GaN laser diodes (LD) with ridge widths of some micrometers show up multi mode patterns. We analyze (Al,In)GaN LDs with different ridge widths in the UV and blue spectral regime simultaneously with temporal, spectral and spatial resolution in the near- and far-field. We transform the laser beam of the LD by a lens system and get a magnified image of the near-field. By using a CCD camera we get the near-field intensity information of the image. In combination of an optical fiber with a photomultiplier or a spectrometer we get the temporal and spectral information. Additionally we can image the propagation from near- to far-field. In this paper we describe the properties of our setup and compare a near-field (SNOM) and far-field (imaging with a microscope objective) approach to the measurement of the LDs multi-dimensional characteristics (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)