Vertical cavity surface-emitting lasers (VCSELs) are only effectively lasing, when the emission wavelength of the quantum well (QW) coincides with the Fabry-Perot resonances of the inner cavity and with the maximum reflectivity wavelength of the Bragg reflectors. In order to characterise epitaxial structures before laser processing a method for the rapid determination of quantum well emission and thicknesses of i./4-layers in the mirror is developed. The in-plane photoluminescence spectrum of a complete VCSEL structure is measured at room temperature by optical excitation perpendicular to the sample surface. Since the PL spectrum consists of the Q W luminescence and additional features originating from interferences in the Bragg reflector the thicknesses of the mirror layers can be determined.Oberflachenemittierende Halbleiterlaser mit vertikaler Resonatoranordnung zeigen optimale Lasertatigkeit nur bei einer ubereinstimmung der Quantentopf-Emissionswellenlinge mit der Wellenlange der Fabry-Perot-Mode des inneren Resonators sowie der Wellenlange des maximalen Reflexionsvermogens der Bragg-Reflektoren, Zur Charakterisierung der Epitaxiestrukturen vor der Prozessierung wird eine Methode zur schnellen Bestimmung der Quantentopf-Emissionswellenllnge und der Dicken der i/4-Schichten im Bragg-Spiegel entwickelt. Dabei wird bei Raumtemperatur das parallel zur Oberflache abgestrahlte Photolumineszenzspektrum einer kompletten VCSEL-Struktur bei optischer Anregung senkrecht zur Oberflache gemessen. Dieses Spektrum zeigt die Quantentopf-Lumineszenz und zusatzliche Intensitatsmaxima, die durch die Interferenz im Bragg-Reflektor-System entstehen und eine Bestimmung der Spiegelschichtdicken gestatten. I ) Rudower Chaussee 5,
The effect of (NH4)2Sx treatment of the facet of InGaAs/AlGaAs ridge waveguide (RW) laser diodes on the nonradiative current and catastrophic optical damage (COD) level is reported. Using the power–voltage–current (P–V–I) characteristics of the electroluminescence at low injection levels, changes in the density of surface states at the laser facets are described.
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