MWP phase shifters integrated in PbS-SU8 waveguides

Abstract

Abstract:We present new kind of microwave phase shifters (MPS) based on dispersion of PbS colloidal quantum dots (QDs) in commercially available photoresist SU8 after a ligand exchange process. Ridge PbS-SU8 waveguides are implemented by integration of the nanocomposite in a silicon platform. When these waveguides 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 produced. The strong light confinement produced in the ridge waveguides allows an improvement of the phase shift as compared to the case of planar structures. Moreover, a novel ridge bilayer waveguide composed by a PbS-SU8 nanocomposite and a SU8 passive layer is proposed to decrease the propagation losses of the pump beam and in consequence to improve the microwave phase shift up to 36.5º at 25 GHz. Experimental results are reproduced by a theoretical model based on the slow light effect produced in a semiconductor waveguide due to the coherent population oscillations. The resulting device shows potential benefits respect to the current MPS technologies since it allows a fast tunability of the phase shift and a high level of integration due to its small size. 2015 Optical Society of America References and links1.

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

“…Results were even improved by exploiting the better confinement of the light provided by the PbS-SU8 ridge structures [88]. Here, the QD-polymer active waveguides presented potential benefits with respect to other technologies, such as a continuous scan of the phase delay or its small size.…”

“…Nevertheless, properties of perovskite look promising in these directions, since they not only present interesting light emitting properties but also a high electron mobility and diffusion lengths, already exploited to develop solar cells [88], LEDs [89,92] or photodetectors [90,91].…”

Optical Amplification in Hollow-Core Negative-Curvature Fibers Doped with Perovskite CsPbBr3 Nanocrystals

“…Alternatively, third-order nonlinear effects in PNCs may also explain the experimental results presented here, at least to be considered as another phenomenological model until being confirmed by other different experiments. In previous works, we demonstrated that similar pumping conditions can change the effective refractive index of colloidal QDs integrated in plasmonic [44] or dielectric waveguides [48] due to a nonlinear interaction of pump plus probe beams with QDs. On the other hand, a Four Wave Mixing (FWM) third-order nonlinear process has been commonly proposed to provide parametric gain in Fiber-based optical devices [49] or the generation of high energy femtosecond pulses [50].…”

Propagation length enhancement of surface plasmon polaritons in gold nano-/micro-waveguides by the interference with photonic modes in the surrounding active dielectrics

“…Indeed, we observe waveguided photoluminescence under TPA in dielectric waveguides containing our CdSe/ZnS QDs (see Section S8.4 in the Supplementary Information). Furthermore, in similar PMMA-QD waveguides, we demonstrated that it is possible to induce a change in the effective refractive index of the mode at the signal frequency when the active medium is strongly and efficiently pumped at the pump frequency [49], in analogy of a four-wave mixing process [50]. This type of nonlinear modulation can be taken into account by adding an extra term proportional to I PUMP to the waveguide mode propagation constant at the signal frequency, due to the change of its effective refractive index.…”