VCSEL arrays are being considered for use in interconnect applications that require high speed, high bandwidth, high density, and high reliability. In order to better understand the reliability of VCSEL arrays, we initiated an internal project at SUN Microsystems, Inc. In this paper, we present preliminary results of an ongoing accelerated temperature-humidity-bias stress test on VCSEL arrays from several manufacturers. This test revealed no significant differences between the reliability of AlGaAs, oxide confined VCSEL arrays constructed with a trench oxide and mesa for isolation. This test did find that the reliability of arrays needs to be measured on arrays and not be estimated with the data from singulated VCSELs as is a common practice.
Charge-transfer polymers are a new class of nonlinear optical materials which can be used for generating femtosecond holographic gratings. Using semiconducting polymers sensitizes with varying concentrations of C<SUB>60</SUB>, holographic gratings were recorded by individual ultrafast laser pulses; the diffraction efficiency and time decay of the gratings were measured using non-degenerate four-wave mixing. Using a figure of merit for dynamic data processing, the temporal diffraction efficiency, this new class of materials exhibits between two and 12 orders of magnitude higher response than previous reports. The charge transfer range at polymer/C<SUB>60</SUB> interfaces was further studied using transient absorption spectroscopy. The fact that charge-transfer occurs in the picosecond-time scale in bilayer structures implies that diffusion of localized excitations to the interface is not the dominant mechanism; the charge transfer range to be 80 angstrom and interpret that range as resulting from quantum delocalization of the photoexcitations.
Holographic recording has been demonstrated in conducting polymer/C60 blends. These materials allow ultrafast holographic recording and the ability to tailor the decay dynamics of the recorded hologram. Diffraction efficiencies up to 1.6 percent have been measured in these materials for gratings recorded with individual laser pulses. Results are presented that demonstrate that an improved signal-to-noise ratio is obtained when holographic detection is used to observe the dynamics of photo-induced absorption.