MWP true time delay implemented in PbS-SU8 waveguides

A new kind of microwave true time delay (TTD) device based on the dispersion of PbS colloidal quantum dots (QDs) in the commercially available photoresist SU8 is presented. For this purpose PbS-SU8 nanocomposites are integrated on a silicon platform in the form of ridge waveguides. When these structures are pumped at wavelengths below the band-gap of the PbS QDs, a phase shift in an optically conveyed (at 1550 nm) microwave signal is performed and therefore a temporal delay is produced. Furthermore, results are improved by implementing a novel ridge bilayer waveguide composed by a PbS-SU8 nanocomposite and a SU8 passive layer that reduces the losses due to the pump beam, and hence to improve the excitation of the QDs. The resulting device shows potential benefits respect to the current TTD technologies since it allows a fast tunability of the temporal delay by controlling the pump power and a high level of integration due to its small size and the material used.