DAC-Less amplifier-less generation and transmission of QAM signals using sub-volt silicon-organic hybrid modulators

We demonstrate generation and transmission of optical signals by directly interfacing highly efficient silicon-organic hybrid (SOH) modulators to binary output ports of a field-programmable gate array. Using an SOH Mach-Zehnder modulator (MZM) and an SOH IQ modulator we generate ON-OFF- keying and binary phase-shift keying signals as well as quadrature phase-shift keying and 16-state quadrature amplitude modulation (16QAM) formats. Peak-to-peak voltages amount to only 0.27 V-pp for driving the MZM and 0.41 V-pp for the IQ modulator. Neither digital-to-analog converters nor drive amplifiers are required, and the RF energy consumption in the modulator amounts to record-low 18 fJ/bit for 16QAM signaling

Teachers’ and students’ perceptions of students’ ability and importance value in math and reading: a latent difference score analysis of intra-individual cross-domain differences

Informed by Eccles and colleagues’ expectancy-value theory and Möller and Marsh’s dimensional comparison theory, we examined cross-domain intra-individual differences in elementary teachers’ (N = 57) and their students’ (N = 469) ratings of students’ ability and subjective importance of math and reading. Latent difference score analyses revealed that students perceived greater intra-individual differences in their own math versus reading ability than did their teachers. Analogous results emerged for students’ and teachers’ ratings of students’ valuing (i.e., perceived importance) of math versus reading, suggesting differing dimensional comparison processes for students’ self-judgments vs. their teachers’ judgments. Cross-domain differences in teachers’ and students’ perceptions were positively associated for ratings of students’ ability but not for ratings of students’ perceived importance. Moreover, intra-individual differences varied substantially across students, in both students’ and teachers’ ratings. Students’ gender and prior achievement in math and reading contributed to this variation.Auf Basis der Erwartungs-Wert-Theorie von Eccles et al. und der Theorie dimensionaler Vergleiche von Möller und Marsh untersucht dieser Beitrag intra-individuelle Differenzen der Lernenden zwischen Mathe und Lesen bezüglich ihrer fachspezifischen Fähigkeiten und subjektiven Wichtigkeit der Fächer, beurteilt von den Lernenden (N = 469) und ihren Grundschullehrkräften (N = 57). Latente Differenzmodelle ergaben, dass die Lernenden größere intra-individuelle Unterschiede zwischen Mathe und Lesen sowohl in ihrer Fähigkeit als auch der Wichtigkeit des Fachs wahrnahmen als ihre Lehrkräfte, was auf unterschiedliche dimensionale Vergleichsprozesse bei Selbst- und Lehrkrafturteilen hindeutet. Lernenden- und Lehrkraftbeurteilung der Differenzen zwischen Mathe und Lesen waren positiv assoziiert für die Beurteilung der Fähigkeiten, aber nicht für die Beurteilung der wahrgenommenen Wichtigkeit des Fachs. Darüber hinaus variierten die intra-individuellen Unterschiede zwischen den Lernenden, sowohl in den Beurteilungen der Lernenden als auch der Lehrkräfte. Das Geschlecht der Lernenden und ihre Vorleistungen in beiden Fächern erwiesen sich als Prädiktoren dieser inter-individuellen Unterschiede

Optical coherence tomography system mass-producible on a silicon photonic chip

Miniaturized integrated optical coherence tomography (OCT) systems have the potential to unlock a wide range of both medical and industrial applications. This applies in particular to multi-channel OCT schemes, where scalability and low cost per channel are important, to endoscopic implementations with stringent size demands, and to mechanically robust units for industrial applications. We demonstrate that fully integrated OCT systems can be realized using the state-of-the-art silicon photonic device portfolio. We present two different implementations integrated on a silicon-on-insulator (SOI) photonic chip, one with an integrated reference path (OCTint) for imaging objects in distances of 5 mm to 10 mm from the chip edge, and another one with an external reference path (OCText) for use with conventional scan heads. Both OCT systems use integrated photodiodes and an external swept-frequency source. In our proof-of-concept experiments, we achieve a sensitivity of −64 dB (−53 dB for OCTint) and a dynamic range of 60 dB (53 dB for OCTint). The viability of the concept is demonstrated by imaging of biological and technical objects

Ultra-short silicon-organic hybrid (SOH) modulator for bidirectional polarization-independent operation

We propose a bidirectional, polarization-independent, recirculating IQ-modulator scheme based on the silicon-organic hybrid (SOH) platform. We demonstrate the viability of the concept by using an SOH Mach-Zehnder modulator, operated at 10 GBd BPSK and 2ASK-2PSK

Limitations of Near Edge X Ray Absorption Fine Structure as a tool for observing conduction bands in chalcopyrite solar cell heterojunctions

A non optimized interface band alignment in a heterojunctionbased solar cell can have negative eff ects on the current and voltage characteristics of the resulting device. To evaluate the use of Near Edge X ray Absorption Fine Structure spectroscopy NEXAFS as a means to measure the conduction band position, Cu In,Ga S2 chalcopyrite thin film surfaces were investigated as these form the absorber layer in solar cells with the structure ZnO Buffer Cu In,Ga S2 Mo Glass. The composition dependence of the structure of the conduction bands of CuInxGa1 xS2 has been revealed for x 0, 0.67 and 1 with both hard and soft NEXAFS and the resulting changes in conduction band off set at the junction with the bu ffer layer discussed. A comprehensive study of the positions of the absorption edges of all elements was carried out and the development of the conduction band with Ga content was observed, also with respect to calculated densities of state

Silicon-Organic Hybrid (SOH) and Plasmonic-Organic Hybrid (POH) integration

Silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) integration combines organic clectro-optic materials with silicon photonic and plasmonic waveguides, The concept enables fast and power-efficient modulators that support advanced modulation formats such as QPSK and 16QAM

Silicon-Organic Hybrid (SOH) and Plasmonic-Organic Hybrid (POH) integration

Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration. Besides conventional dielectric waveguides, plasmonic structures can also be efficiently realized on the silicon photonic platform, reducing device footprint by more than an order of magnitude. However, nei-ther silicon nor metals exhibit appreciable second-order optical nonlinearities, thereby making efficient electro-optic modulators challenging to realize. These deficiencies can be overcome by the concepts of silicon-organic hybrid (SOH) and plasmonic-organic hybrid integration, which combine SOI waveguides and plasmonic nanostructures with organic electro-optic cladding materials

10 GBd modulator directly driven by an FPGA without electrical amplification

Using standard single-ended FPGA outputs with 270 mV(pp) we demonstrate 10GBd OOK and BPSK transmission by directly driving a low-voltage silicon-organic hybrid ( SOH) modulator. The scheme does not require electronic driver amplifiers, which paves the way to energy-efficient photonic-electronic integration

Silicon-organic hybrid electro-optical devices

Organic materials combined with strongly guiding silicon waveguides open the route to highly efficient electro-optical devices. Modulators based on the so-called silicon-organic hybrid (SOH) platform have only recently shown frequency responses up to 100 GHz, high-speed operation beyond 112 Gbit/s with fJ/bit power consumption. In this paper, we review the SOH platform and discuss important devices such as Mach-Zehnder and IQ-modulators based on the linear electro-optic effect. We further show liquid-crystal phase-shifters with a voltage-length product as low as V pi L = 0.06 V.mm and sub-mu W power consumption as required for slow optical switching or tuning optical filters and devices