Scalable high-precision trimming of photonic resonances by polymer exposure to energetic beams

Integrated photonic circuits (PICs) have seen an explosion in interest, through to commercialization in the past decade. Most PICs rely on sharp resonances to modulate, steer, and multiplex signals. However, the spectral characteristics of high-quality resonances are highly sensitive to small variations in fabrication and material constants, which limits their applicability. Active tuning mechanisms are commonly employed to account for such deviations, consuming energy and occupying valuable chip real estate. Readily employable, accurate, and highly scalable mechanisms to tailor the modal properties of photonic integrated circuits are urgently required. Here, we present an elegant and powerful solution to achieve this in a scalable manner during the semiconductor fabrication process using existing lithography tools: by exploiting the volume shrinkage exhibited by certain polymers to permanently modulate the waveguide’s effective index. This technique enables broadband and lossless tuning with immediate applicability in wide-ranging applications in optical computing, telecommunications, and free-space optics

Different genes interact with particulate matter and tobacco smoke exposure in affecting lung function decline in the general population

BACKGROUND: Oxidative stress related genes modify the effects of ambient air pollution or tobacco smoking on lung function decline. The impact of interactions might be substantial, but previous studies mostly focused on main effects of single genes. OBJECTIVES: We studied the interaction of both exposures with a broad set of oxidative-stress related candidate genes and pathways on lung function decline and contrasted interactions between exposures. METHODS: For 12679 single nucleotide polymorphisms (SNPs), change in forced expiratory volume in one second (FEV(1)), FEV(1) over forced vital capacity (FEV(1)/FVC), and mean forced expiratory flow between 25 and 75% of the FVC (FEF(25-75)) was regressed on interval exposure to particulate matter >10 microm in diameter (PM10) or packyears smoked (a), additive SNP effects (b), and interaction terms between (a) and (b) in 669 adults with GWAS data. Interaction p-values for 152 genes and 14 pathways were calculated by the adaptive rank truncation product (ARTP) method, and compared between exposures. Interaction effect sizes were contrasted for the strongest SNPs of nominally significant genes (p(interaction)>0.05). Replication was attempted for SNPs with MAF<10% in 3320 SAPALDIA participants without GWAS. RESULTS: On the SNP-level, rs2035268 in gene SNCA accelerated FEV(1)/FVC decline by 3.8% (p(interaction) = 2.5x10(-6)), and rs12190800 in PARK2 attenuated FEV1 decline by 95.1 ml p(interaction) = 9.7x10(-8)) over 11 years, while interacting with PM10. Genes and pathways nominally interacting with PM10 and packyears exposure differed substantially. Gene CRISP2 presented a significant interaction with PM10 (p(interaction) = 3.0x10(-4)) on FEV(1)/FVC decline. Pathway interactions were weak. Replications for the strongest SNPs in PARK2 and CRISP2 were not successful. CONCLUSIONS: Consistent with a stratified response to increasing oxidative stress, different genes and pathways potentially mediate PM10 and tobac smoke effects on lung function decline. Ignoring environmental exposures would miss these patterns, but achieving sufficient sample size and comparability across study samples is challengin

Purinergic signalling and immune cells

This review article provides a historical perspective on the role of purinergic signalling in the regulation of various subsets of immune cells from early discoveries to current understanding. It is now recognised that adenosine 5'-triphosphate (ATP) and other nucleotides are released from cells following stress or injury. They can act on virtually all subsets of immune cells through a spectrum of P2X ligand-gated ion channels and G protein-coupled P2Y receptors. Furthermore, ATP is rapidly degraded into adenosine by ectonucleotidases such as CD39 and CD73, and adenosine exerts additional regulatory effects through its own receptors. The resulting effect ranges from stimulation to tolerance depending on the amount and time courses of nucleotides released, and the balance between ATP and adenosine. This review identifies the various receptors involved in the different subsets of immune cells and their effects on the function of these cells

Polorized Brillouin scattering in Salol: Effect of rotation-translation coupling

We have studied the 90 degree VV-polarized Brillouin scattering spectrum of the molecular glassformer salol and observed a previously unnoticed VV-dip feature at low frequencies for temperatures above 300K. This new feature is a consequence of rotation-translation coupling, as recently predicted by Pick, Franosch et al [Eur. Phys. J. B 31, 217, 229 (2003)], who showed its relationship to the Rytov dip that occurs in the corresponding VH spectrum. The analysis of the spectra shows good agreement with the theoretical prediction

Chalcogenide phase-change devices for neuromorphic photonic computing

The integration of artificial intelligence systems into daily applications like speech recognition and autonomous driving rapidly increases the amount of data generated and processed. However, satisfying the hardware requirements with the conventional von Neumann architecture remains challenging due to the von Neumann bottleneck. Therefore, new architectures inspired by the working principles of the human brain are developed, and they are called neuromorphic computing. The key principles of neuromorphic computing are in-memory computing to reduce data shuffling and parallelization to decrease computation time. One promising framework for neuromorphic computing is phase-change photonics. By switching to the optical domain, parallelization is inherently possible by wavelength division multiplexing, and high modulation speeds can be deployed. Non-volatile phase-change materials are used to perform multiplications and non-linear operations in an energetically efficient manner. Here, we present two prototypes of neuromorphic photonic computation units based on chalcogenide phase-change materials. First is a neuromorphic hardware accelerator designed to carry out matrix vector multiplication in convolutional neural networks. Due to the neuromorphic architecture, this prototype can already operate at tera-multiply-accumulate per second speeds. Second is an all-optical spiking neuron, which can serve as a building block for large-scale artificial neural networks. Here, the whole computation is carried out in the optical domain, and the device only needs an electrical interface for data input and readout

Reconfigurable nanophotonic cavities with nonvolatile response

The use of phase-change materials on waveguide photonics is presently being purported for a range of applications from on-chip photonic data storage to new computing paradigms. Photonic integrated circuits in combination with phase-change materials provide on-chip control handles, featuring nonvolatility and operation speeds down to the nano- and picosecond regime. Besides ultrafast control, efficient operation of nonvolatile elements is crucial and requires compact photonic designs. Here we embed phase-change materials in photonic crystal cavities to realize tunable nanophotonic devices which can be reconfigured on demand. The devices exploit strong light matter interactions between the resonant modes of the cavity and the evanescently coupled phase-change material cell. This results in an increased transmission contrast and a power reduction of 520% over conventional phase-change nanophotonic devices when reversibly switched with optical pulses. Such designs can thus open up new areas of reconfigurable nanophotonics without sacrificing the speeds or functionality for applications in optical memory cells, optical switches, and tunable wavelength filters

Integrated optical pattern generation on thin-film lithium niobate with electro-optic modulators and phase-change material cells

Reconfigurable photonic integrated circuits enable high-bandwidth signal shaping with the prospect for scalability and compact footprint. Co-integration of electro-optical tunability with non-volatile attenuation through functional materials allows for implementing photonic devices which operate both on phase and amplitude. Based on this approach, we propose an integrated photonic design for optical pattern generation deploying a continuous-wave laser and a single electrical function generator. We employ the non-volatile and reconfigurable phase-change material Ge2Sb2Te5 (GST) as a tunable attenuator for an integrated photonic circuit on the Lithium-Niobate-On-Insulator (LNOI) platform. The GST can be switched between its amorphous and crystalline phase, leading to an optical contrast of ≅18 dB. Combining this with integrated electro-optical modulators with a 4 GHz bandwidth in LNOI, enables the generation of short optical pulses, based on the principles of inverse discrete Fourier transform