Abstract:Morpho butterflies are well-known for their iridescence originating from nanostructures in the scales of their wings. These optical active structures integrate three design principles leading to the wide angle reflection: alternating lamellae layers, "Christmas tree" like shape, and offsets between neighboring ridges. We study their individual effects rigorously by 2D FEM simulations of the nanostructures of the Morpho sulkowskyi butterfly and show how the reflection spectrum can be controlled by the design of the nanostructures. The width of the spectrum is broad (≈ 90 nm) for alternating lamellae layers (or "brunches") of the structure while the "Christmas tree" pattern together with a height offset between neighboring ridges reduces the directionality of the reflectance. Furthermore, we fabricated the simulated structures by e-beam lithography. The resulting samples mimicked all important optical features of the original Morpho butterfly scales and feature the intense blue iridescence with a wide angular range of reflection.

Ultrafast single-photon detectors with high efficiency are of utmost importance for many applications in the context of integrated quantum photonic circuits. Detectors based on superconductor nanowires attached to optical waveguides are particularly appealing for this purpose. However, their speed is limited because the required high absorption efficiency necessitates long nanowires deposited on top of the waveguide. This enhances the kinetic inductance and makes the detectors slow. Here, we solve this problem by aligning the nanowire, contrary to usual choice, perpendicular to the waveguide to realize devices with a length below 1 μm. By integrating the nanowire into a photonic crystal cavity, we recover high absorption efficiency, thus enhancing the detection efficiency by more than an order of magnitude. Our cavity enhanced superconducting nanowire detectors are fully embedded in silicon nanophotonic circuits and efficiently detect single photons at telecom wavelengths. The detectors possess subnanosecond decay (∼120 ps) and recovery times (∼510 ps) and thus show potential for GHz count rates at low timing jitter (∼32 ps). The small absorption volume allows efficient threshold multiphoton detection.

Diamond integrated photonic devices are promising candidates for emerging applications in nanophotonics and quantum optics. Here, we demonstrate active modulation of diamond nanophotonic circuits by exploiting mechanical degrees of freedom in free-standing diamond electro-optomechanical resonators. We obtain high quality factors up to 9600, allowing us to read out the driven nanomechanical response with integrated optical interferometers with high sensitivity. We are able to excite higher order mechanical modes up to 115 MHz and observe the nanomechanical response also under ambient conditions

By reaction of MIICl2·x H2O (M = Fe (x = 4), Co, Ni (x = 6)) and LiOH·H2O in diethylene glycol (DEG) rod‐like crystals of the composition MII4Cl4(OCH2CH2OCH2CH2OH)4 are formed. According to X‐ray diffraction data obtained by both, single crystals and powders, the CoII and NiII compounds crystallize monoclinic with C2/c (CoII4Cl4(OCH2CH2OCH2CH2OH)4 (1): a = 2084.1(4), b = 919.0(2), c = 1754.0(4) pm, β = 124.3(1)°, Z = 4; NiII4Cl4(OCH2CH2OCH2CH2OH)4 (2): a = 2055.2(4), b = 932.1(2), c = 1727.4(4) pm, β = 125.2(1)°, Z = 4), whereas FeII4Cl4(OCH2CH2OCH2CH2OH)4 (3) crystallizes tetragonal with $\rm P{\bar 4}2_{1}c$ (a = 1251.4(2), c = 915.3(2) pm, Z = 2). All compounds exhibit analogous molecular structures which are built of a heterocubane‐type core consisting of four metal ions and four deprotonated oxygen atoms of four coordinated diethylene glycol molecules. Neutrality of charge is realized by additional coordination of four chloride anions. In addition to the structural characterization, the thermal and magnetical properties of the title compounds are investigated in detail.

We realize diamond electro-optomechanical resonators operated at frequencies above 100 MHz. The nanomechanical motion is read-out via on-chip diamond photonic circuits showing Q-factors above 1300

The sintering and melting of submicron-sized bismuth particles were studied in situ via scanning electron microscopy. The relevant bismuth particles were prepared via a polyol-mediated synthesis, which results in spherical and non-agglomerated particles, about 250 nm in size. The samples as well as suitable references were deposited on a heater stage assembly inside a scanning electron microscope. Both were investigated up to temperatures of 480 degrees C. Surprisingly, sample areas continuously scanned by the electron beam showed neither sintering nor melting of submicron-sized bismuth, whereas melting was observed at temperatures between 250 and 270 degrees C in non-scanned areas. This behavior was ascribed to an electron-beam-induced decomposition of organic stabilizers that adhered on the bismuth particles to form a thin layer of amorphous carbon. For experimental verification of this hypothesis, controlled carbon coating of submicron-sized bismuth particles was conducted.

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