Bottom-Illuminated Photothermal Nanoscale Chemical Imaging with a Flat Silicon ATR in Air and Liquid.

We demonstrate a novel approach for bottom-illuminated atomic force microscopy and infrared spectroscopy (AFM-IR). Bottom-illuminated AFM-IR for measurements in liquids makes use of an attenuated total reflection setup where the developing evanescent wave is responsible for photothermal excitation of the sample of interest. Conventional bottom-illuminated measurements are conducted using high-refractive-index prisms. We showcase the advancement of instrumentation through the introduction of flat silicon substrates as replacements for prisms. We illustrate the feasibility of this technique for bottom-illuminated AFM-IR in both air and liquid. We also show how modern rapid prototyping technologies enable commercial AFM-IR instrumentation to accept these new substrates. This new approach paves the way for a wide range of experiments since virtually any established protocol for Si surface functionalization can be applied to this sample carrier. Furthermore, the low unit cost enables the rapid iteration of experiments.

Electrically driven source of time-energy entangled photons based on a self-pumped silicon microring resonator.

Time-energy entangled photon pairs are fundamental resources for quantum communication protocols since they are robust against environmental fluctuations in optical fiber networks. Pair sources based on spontaneous four-wave mixing in silicon microring resonators usually employ expensive external tunable lasers to compensate for ambient fluctuations; adopting self-pumped configurations, instead, lifts the need for such external source. Here we demonstrate the emission of time-energy entangled photon pairs at telecom wavelengths from a silicon self-pumped ring, obtaining a Franson interference fringe with 93.9%±0.9% visibility.