Supercontinuum Generation in a Silica Spiral Waveguide

A low-loss silica spiral waveguide is used for demonstrating on-chip supercontinuum generation. The broadest measured spectrum spans an octave (936 – 1888 nm) at −50 dB from peak when 2.17 nJ pulses are launched

Coherent ultra-violet to near-infrared generation in silica ridge waveguides

Short duration, intense pulses of light can experience dramatic spectral broadening when propagating through lengths of optical fibre. This continuum generation process is caused by a combination of nonlinear optical effects including the formation of dispersive waves. Optical analogues of Cherenkov radiation, these waves allow a pulse to radiate power into a distant spectral region. In this work, efficient and coherent dispersive wave generation of visible to ultraviolet light is demonstrated in silica waveguides on a silicon chip. Unlike fibre broadeners, the arrays provide a wide range of emission wavelength choices on a single, compact chip. This new capability is used to simplify offset frequency measurements of a mode-locked frequency comb. The arrays can also enable mode-locked lasers to attain unprecedented tunable spectral reach for spectroscopy, bioimaging, tomography and metrology

Supercontinuum generation in an on-chip silica waveguide

Supercontinuum generation is demonstrated in an on-chip silica spiral waveguide by launching 180 fs pulses from an optical parametric oscillator at the center wavelength of 1330 nm. With a coupled pulse energy of 2.17 nJ, the broadest spectrum in the fundamental TM mode extends from 936 to 1888 nm (162 THz) at −50  dB from peak. There is a good agreement between the measured spectrum and a simulation using a generalized nonlinear Schrödinger equation

An optical-frequency synthesizer using integrated photonics

Optical-frequency synthesizers, which generate frequency-stable light from a single microwave-frequency reference, are revolutionizing ultrafast science and metrology, but their size, power requirement and cost need to be reduced if they are to be more widely used. Integrated-photonics microchips can be used in high-coherence applications, such as data transmission, highly optimized physical sensors and harnessing quantum states, to lower cost and increase efficiency and portability. Here we describe a method for synthesizing the absolute frequency of a lightwave signal, using integrated photonics to create a phase-coherent microwave-to-optical link. We use a heterogeneously integrated iii–v/silicon tunable laser, which is guided by nonlinear frequency combs fabricated on separate silicon chips and pumped by off-chip lasers. The laser frequency output of our optical-frequency synthesizer can be programmed by a microwave clock across 4 terahertz near 1,550 nanometres (the telecommunications C-band) with 1 hertz resolution. Our measurements verify that the output of the synthesizer is exceptionally stable across this region (synthesis error of 7.7 × 10^(−15) or below). Any application of an optical-frequency source could benefit from the high-precision optical synthesis presented here. Leveraging high-volume semiconductor processing built around advanced materials could allow such low-cost, low-power and compact integrated-photonics devices to be widely used

Asymptomatic Middle East Respiratory Syndrome coronavirus infection using a serologic survey in Korea

OBJECTIVES The rates of asymptomatic infection with Middle East Respiratory Syndrome (MERS) coronavirus vary. A serologic study was conducted to determine the asymptomatic MERS infection rate in healthcare workers and non-healthcare workers by exposure status. METHODS Study participants were selected from contacts of MERS patients based on a priority system in 4 regions strongly affected by the 2015 MERS outbreak. A sero-epidemiological survey was performed in 1,610 contacts (average duration from exposure to test, 4.8 months), and the collected sera were tested using an enzyme-linked immunespecific assay (ELISA), immunofluorescence assay (IFA), and plaque reduction neutralization antibody test (PRNT). Among the 1,610 contacts, there were 7 ELISA-positive cases, of which 1 exhibited positive IFA and PRNT results. RESULTS The asymptomatic infection rate was 0.060% (95% confidence interval, 0.002 to 0.346). The asymptomatic MERS case was a patient who had been hospitalized with patient zero on the same floor of the hospital at the same time. The case was quarantined at home for 2 weeks after discharge, and had underlying diseases, including hypertension, angina, and degenerative arthritis. CONCLUSIONS The asymptomatic infection was acquired via healthcare-associated transmission. Thus, it is necessary to extend serologic studies to include inpatient contacts who have no symptoms

Comparison of Ertapenem and Ceftriaxone Therapy for Acute Pyelonephritis and Other Complicated Urinary Tract Infections in Korean Adults: A Randomized, Double-Blind, Multicenter Trial

The efficacy and safety of ertapenem, 1 g once daily, were compared with that of ceftriaxone, 2 g once daily, for the treatment of adults with acute pyelonephritis (APN) and complicated urinary tract infections (cUTIs) in a prospective, multicenter, double-blinded, randomized study. After ≥ 3 days of parenteral study therapy, patients could be switched to an oral agent. Of 271 patients who were initially stratified by APN (n = 210) or other cUTIs (n = 61), 66 (48.9%) in the ertapenem group and 71 (52.2%) in the ceftriaxone group were microbiologically evaluable. The mean duration of parenteral and total therapy, respectively, was 5.6 and 13.8 days for ertapenem and 5.8 and 13.8 days for ceftriaxone. The most common pathogen was Escherichia coli. At the primary efficacy endpoint 5-9 days after treatment, 58 (87.9%) patients in the ertapenem group and 63 (88.7%) in the ceftriaxone had a favorable microbiological response. When compared by stratum and severity, the outcomes in the two groups were equivalent. The frequency and severity of drug-related adverse events were generally similar in both treatment groups. The results indicate that ertapenem is highly effective and safe for the treatment of APN and cUTIs

An Integrated-Photonics Optical-Frequency Synthesizer

Integrated-photonics microchips now enable a range of advanced functionalities for high-coherence applications such as data transmission, highly optimized physical sensors, and harnessing quantum states, but with cost, efficiency, and portability much beyond tabletop experiments. Through high-volume semiconductor processing built around advanced materials there exists an opportunity for integrated devices to impact applications cutting across disciplines of basic science and technology. Here we show how to synthesize the absolute frequency of a lightwave signal, using integrated photonics to implement lasers, system interconnects, and nonlinear frequency comb generation. The laser frequency output of our synthesizer is programmed by a microwave clock across 4 THz near 1550 nm with 1 Hz resolution and traceability to the SI second. This is accomplished with a heterogeneously integrated III/V-Si tunable laser, which is guided by dual dissipative-Kerr-soliton frequency combs fabricated on silicon chips. Through out-of-loop measurements of the phase-coherent, microwave-to-optical link, we verify that the fractional-frequency instability of the integrated photonics synthesizer matches the $7.0*10^{-13}$ reference-clock instability for a 1 second acquisition, and constrain any synthesis error to $7.7*10^{-15}$ while stepping the synthesizer across the telecommunication C band. Any application of an optical frequency source would be enabled by the precision optical synthesis presented here. Building on the ubiquitous capability in the microwave domain, our results demonstrate a first path to synthesis with integrated photonics, leveraging low-cost, low-power, and compact features that will be critical for its widespread use.Comment: 10 pages, 6 figure