Modulation of a group of cells or tissue needs to be very precise in order to exercise effective control over the cell population under investigation. Optogenetic tools have already demonstrated to be of great value in the study of neuronal circuits and in neuromodulation. Ideally, they should permit very accurate resolution, preferably down to the single cell level. Further, to address a spatially distributed sample, independently addressable multiple optical outputs should be present. In current techniques, at least one of these requirements is not fulfilled. In addition to this, it is interesting to directly monitor feedback of the modulation by electrical registration of the activity of the stimulated cells. Here, we present the fabrication and characterization of a fully integrated silicon-based multi-electrode-optrode array (MEOA) for in vitro optogenetics. We demonstrate that this device allows for artifact-free electrical recording. Moreover, the MEOA was used to reliably elicit spiking activity from ChR2-transduced neurons. Thanks to the single cell resolution stimulation capability, we could determine spatial and temporal activation patterns and spike latencies of the neuronal network. This integrated approach to multi-site combined optical stimulation and electrical recording significantly advances today’s tool set for neuroscientists in their search to unravel neuronal network dynamics.
We demonstrate a novel transmission
color filter design that exploits
both dielectric and plasmonic resonances to establish a highly color-selective
device, reaching an experimental full-width at half-maximum (fwhm)
that is only half that of previously demonstrated cost-effective color
filter devices for the same peak transmission and better out-of-band
rejection. The measured fwhm is only 25 nm, and the peak transmission
reaches up to 53%. The filter uses the interference of Fabry-Pérot
resonances and guided-mode resonances in two separated dielectric
slabs to achieve this excellent fwhm while relying on propagating
surface plasmon polaritons to achieve the excellent out-of-band rejection.
A simulation study elucidates the nature of the optical modes in the
device and their interference mechanisms and reveals the most important
design considerations. Fabrication was done in a CMOS pilot line and
is cost-effective, as it requires only two metal patterning steps.
Fabrication imperfections are discussed, together with strategies
to mitigate them. We show the correct mitigation of these imperfections
leads to further performance gain, enabling a full-width at half-maximum
down to 20 nm and a peak transmission beyond 60%. We believe this
novel filter design is a powerful concept to improve the spectral
resolution of color filters for cost-effective multispectral imaging.
Beyond multispectral imaging, the design could be adapted for other
applications that require on-chip spectral filtering in a thin form
factor.
We report on phase-change material scatterers in a half-wave plate design. A simulation study shows the cross-polarization of circularly polarized light reaches close to 20% around 800 nm in the ON state. Characterization is ongoing.
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