Coherence of VCSEL's for holographic interconnects
Temporal and spatial coherence measurements were conducted on the emission from AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSEL's). Results of both CW and pulsed conditions from devices of 8- and 15-μm diameter are reported. Coherence length of 0.6 mm for multi-mode and ~75 cm for single-mode were obtained. Thermal chirp reduces the single-mode coherence to 16 mm for 5 ns pulses. For holograms smaller than 0.6 mm in size the density of information that can be read by the VCSEL's is diffraction-limited by the size of the holographic element.