Dual-color cross-correlation spectroscopy allows the detection and quantification of labeled biomolecules at ultra-low concentrations, whereby the sensitivity of the assay correlates with the measurement time. We now describe a parallel multifocal dual-color spectroscopic configuration employing multiple avalanche photodiodes and hardware correlators. Cross-correlation curves are obtained from several dual-color excitation foci simultaneously. Multifocal dual-color excitation is achieved by splitting each of two laser beams (488 and 633 nm) into four sub-beams with the help of two 2×2 fan-out diffractive optical elements (DOEs), and subsequent superposition of the two sets of four foci. The fluorescence emission from double-labeled biomolecules is detected by two 2×2 fiber arrays.
The optical part of a high-speed, inter-chip optical interconnection scheme was tested. In the scheme, electronic data processing units are interconnected by laser beams via a transparent substrate. All the electronic and optoelectronic chips are mounted on one side of the transparent substrate, reflective diffractive optical elements for shaping and deflecting the laser beams located on the other side. To both allow close packing of VCSELs and low reflection losses, physically the transparent substrate is made-up of a thinner quartz plate positioned on top of and in direct contact with a thicker one. The insertion loss on imaging a VCSEL-simulating point source located on the upper side of the substrate onto an 8 mm laterally displaced position on the same side of the substrate via transmission through the substrate was found to be ~10 dB.