3D-printed optical probes for wafer-level testing of photonic integrated circuits.

Wafer-level probing of photonic integrated circuits is key to reliable process control and efficient performance assessment in advanced production workflows. In recent years, optical probing of surface-coupled devices such as vertical-cavity lasers, top-illuminated photodiodes, or silicon photonic circuits with surface-emitting grating couplers has seen great progress. In contrast to that, wafer-level probing of edge-emitting devices with hard-to-access vertical facets at the sidewalls of deep-etched dicing trenches still represents a major challenge. In this paper, we address this challenge by introducing a novel concept of optical probes based on 3D-printed freeform coupling elements that fit into deep-etched dicing trenches on the wafer surface. Exploiting the design freedom and the precision of two-photon laser lithography, the coupling elements can be adapted to a wide variety of mode-field sizes. We experimentally demonstrate the viability of the approach by coupling light to edge-emitting waveguides on different integration platforms such as silicon photonics (SiP), silicon nitride (TriPleX), and indium phosphide (InP). Achieving losses down to 1.9 dB per coupling interface, we believe that 3D-printed coupling elements represent a key step towards highly reproducible wafer-level testing of edge-coupled photonic integrated circuits.

Photonic-integrated circuit for continuous-wave THz generation.

We demonstrate a photonic-integrated circuit for continuous-wave (cw) terahertz (THz) generation. By comprising two lasers and an optical phase modulator on a single chip, the full control of the THz signal is enabled via a unique bidirectional operation technique. Integrated heaters allow for continuous tuning of the THz frequency over 570 GHz. Applied to a coherent cw THz photomixing system operated at 1.5 µm optical wavelength, we reach a signal-to-noise ratio of 44 dB at 1.25 THz, which is identical to the performance of a standard system based on discrete components.

Stimulation of suicidal erythrocyte death by trans-cinnamaldehyde.

Trans-cinnamaldehyde, a component of leaves from Cinnamomum osmophloeum kaneh, has been shown to counteract tumor growth. The substance exerts its effect at least in part by triggering apoptosis. The propapoptotic signaling involves altered gene expression and mitochondrial depolarization. In analogy to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine-exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+)-activity ([Ca(2+)]i). The present study explored, whether trans-cinnamaldehyde triggers eryptosis. Cell volume has been estimated from forward scatter, phosphatidylserine-exposure from annexin-V-binding, hemolysis from hemoglobin release, and [Ca(2+)]i from Fluo3-fluorescence. A 48 h exposure to trans-cinnamaldehyde (30 µM) significantly decreased forward scatter and increased annexin-V-binding, effects paralleled by increase of [Ca(2+)]i. Trans-cinnamaldehyde exposure was followed by a slight but significant increase of hemolysis. Removal of extracellular Ca(2+) virtually abolished the effect of trans-cinnamaldehyde (30 µM) on annexin-V-binding. The present observations show that trans-cinnamaldehyde triggers suicidal death of erythrocytes, i.e. cells devoid of mitochondria and gene expression.

Effect of dermaseptin on erythrocytes.

Dermaseptin, an antimicrobial peptide participating in the host defence against pathogens, interacts with the membrane of target cells, leading to membrane permeabilization and eventual cell lysis. Dermaseptin has previously been shown to trigger haemolysis. Prior to haemolysis, erythrocytes may enter suicidal death or eryptosis, which is characterized by cell shrinkage and by cell membrane scrambling leading to phosphatidylserine exposure at the erythrocyte surface. Triggers of eryptosis include increase in cytosolic Ca²âº activity [(Ca²âº)](i) and formation of ceramide. This study explored whether dermaseptin modifies [Ca²âº](i) and elicits eryptosis. Cell volume has been estimated from forward scatter, phosphatidylserine exposure from annexin-V binding, haemolysis from haemoglobin release, ceramide formation from binding of fluorescent antibodies and [Ca²âº](i) from Fluo3-fluorescence. A 48-hr exposure to dermaseptin (50 µM) was followed by a significant increase in [Ca²âº](i), a significant increase ceramide abundance, a significant decrease in forward scatter and a significant increase in annexin-V binding. The annexin-V binding after dermaseptin treatment was significantly blunted but not abrogated in the nominal absence of extracellular Ca²âº. Dermaseptin triggers eryptosis, an effect at least partially due to entry of extracellular Ca²âº.