Femtosecond two-photon photocurrent imaging of VCSELs

Summary form only given.Two-photon photocurrent imaging is used to quantitatively study VCSELs on a microscopic level. Similar to two-photon backside imaging of ICs, two-photon excitation provides a convenient way of injecting localized carriers through the GaAs substrate, circumventing the problems caused by the opacity of the substrate and the top metal layer. Backside illumination allows the use of ordinary microprobes to contact the VCSELs on the front side, without the restriction of the probe movement and the requirement of long working distance lenses. Thus, high numerical aperture objectives can be used to achieve high spatial resolution (/spl les/1 /spl mu/m). Furthermore, the required peak and average power levels for testing can be easily satisfied by available compact ultrafast laser sources, making the technique practical and user friendly.