On-chip CMOS-compatible all-optical integrator

One reason for using photonic devices is their speed—much faster than electronic circuits—but there are many challenges in integrating the two technologies. Ferrera et al. construct a CMOS-compatible monolithic optical waveform integrator, a key building block for photonic circuits

Using mechanical force to probe the mechanism of pausing and arrest during continuous elongation by Escherichia coli RNA polymerase

Escherichia coli RNA polymerase translocates along the DNA discontinuously during the elongation phase of transcription, spending proportionally more time at some template positions, known as pause and arrest sites, than at others. Current models of elongation suggest that the enzyme backtracks at these locations, but the dynamics are unresolved. Here, we study the role of lateral displacement in pausing and arrest by applying force to individually transcribing molecules. We find that an assisting mechanical force does not alter the translocation rate of the enzyme, but does reduce the efficiency of both pausing and arrest. Moreover, arrested molecules cannot be rescued by force, suggesting that arrest occurs by a bipartite mechanism: the enzyme backtracks along the DNA followed by a conformational change of the ternary complex (RNA polymerase, DNA and transcript), which cannot be reversed mechanically

CMOS-compatible integrated optical hyper-parametric oscillator

Integrated multiple-wavelength laser sources, critical for important applications such as high-precision broadband sensing and spectroscopy, molecular fingerprinting, optical clocks and attosecond physics, have recently been demonstrated in silica and single-crystal microtoroid resonators using parametric gain. However, for applications in telecommunications and optical interconnects, analogous devices compatible with a fully integrated platform do not yet exist. Here, we report a fully integrated, CMOS-compatible, multiple-wavelength source. We achieve optical hyper-parametric oscillation in a high-index silica-glass microring resonator with a differential slope efficiency above threshold of 7.4% for a single oscillating mode, a continuous-wave threshold power as low as 54mW, and a controllable range of frequency spacing from 200GHz to more than 6THz. The low loss, design flexibility and CMOS compatibility of this device will enable the creation of multiple-wavelength sources for telecommunications, computing, sensing, metrology and other areas

Low-power continuous-wave nonlinear optics in doped silica glass integrated waveguide structures

Photonic integrated circuits are a key component of future telecommunication networks, where demands for greater bandwidth, network flexibility, and low energy consumption and cost must all be met. The quest for all-optical components has naturally targeted materials with extremely large nonlinearity, including chalcogenide glasses and semiconductors, such as silicon and AlGaAs (ref. 4). However, issues such as immature fabrication technology for chalcogenide glass and high linear and nonlinear losses for semiconductors motivate the search for other materials. Here we present the first demonstration of nonlinear optics in integrated silica-based glass waveguides using continuous-wave light. We demonstrate four-wave mixing, with low (5 mW) continuous-wave pump power at λ=1,550nm, in high-index, doped silica glass ring resonators. The low loss, design flexibility and manufacturability of our device are important attributes for low-cost, high-performance, nonlinear all-optical photonic integrated circuits