100-GHz ultra-short high-peak-power colliding-pulse mode-locked laser with asymmetric coating.

By using colliding-pulse mode-locking (CPM) configuration with asymmetric cladding layer and coating, 1.5-µm AlGaInAs/InP multiple quantum well (MQW) CPM lasers with high-power and ultra-short pulse generation capability at a repetition rate of 100 GHz are reported. The laser adopts a high-power epitaxial design, with four pairs of MQWs and an asymmetrical dilute waveguide cladding layer to reduce the internal loss, maintaining good thermal conductivity while increasing the saturation energy of the gain region. The asymmetric coating is introduced, as compared to conventional CPM laser with symmetric reflectivity, to further increase the output power and shorten the pulse width. With a high reflection (HR) coating of 95% on one facet and another facet as cleaved, 100-GHz sub-picosecond optical pulses with peak power on a Watt level are demonstrated. Two mode-locking states, the pure CPM state and the partial CPM state, are investigated. Pedestal-free optical pulses are obtained for both states. For the pure CPM state, a pulse width of 564 fs, an average power of 59 mW, a peak power of 1.02 W, and an intermediate mode suppression ratio over 40 dB are demonstrated. For the partial CPM state, a pulse width of 298 fs is demonstrated.

Polarization-stable single-mode 795†nm grating-coupled surface-emitting laser for quantum sensing.

We demonstrate a polarization-stable and single-mode grating-coupled surface-emitting laser (GCSEL) with high side-mode suppression ratio (SMSR) of ∼40 dB and orthogonal polarization suppression ratio (OPSR) of ∼25 dB around 795 nm. The fabricated devices have low threshold current of ∼4.8 mA and low electrical resistance of 53 Ω at 25 °C. Meanwhile, a low thermal resistance of ∼1 K/mW is achieved, which is comparable with that of the record of ever reported for vertical-cavity surface-emitting lasers (VCSELs). The far-field divergence angle of surface-emitting beam is ∼14.5°x14.7° at an injection current of 12 mA indicating a relatively good beam quality. Our results open what we believe is a new way to produce polarization-stable single-mode surface-emitting lasers with simple fabrication process. While the GCSEL is specifically designed for quantum sensing applications such as atomic clocks, magnetometers, and gyroscope, its performance in terms of low-power consumption, low thermal resistance, good beam qualities, and wafer-level testing are of particular interest for a wide range of applications.

Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser.

We report, to the best of our knowledge, the first demonstration of a 1555-nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a sidewall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.2% was obtained at IDFB = 180 mA. A particular advantage of this device is that only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching are required for the whole integrated device fabrication, significantly reducing complexity and cost.

Millimeter-wave generation based on a monolithic dual-wavelength DFB laser with four phase-shifted sampled gratings and equivalent chirp technology.

A dual-wavelength DFB laser array based on four phase-shifted grating and equivalent chirp technology is first proposed, fabricated, and experimentally demonstrated. The dual-wavelength emitting is achieved by symmetrically introducing two π phase shifts into a chirped four phase-shifted sampled grating cavity. Meanwhile, the beating signal of the dual-wavelength output is stabilized by applying an electro-absorption modulator integrated at the rear of the cavity. Under different grating chirp rates, a series of RF signals from 66.8 GHz to 73.6 GHz with a linewidth of less than 210 kHz is obtained.

Extraction of silver losses at cryogenic temperatures through the optical characterization of silver-coated plasmonic nanolasers.

We report on the extraction of silver losses in the range 10 K-180 K by performing temperature-dependent micro-photoluminescence measurements in conjunction with numerical simulations on silver-coated nanolasers around near-infrared telecommunication wavelengths. By mapping changes in the quality factor of nanolasers into silver-loss variations, the imaginary part of silver permittivity is extracted at cryogenic temperatures. The latter is estimated to reach values an order of magnitude lower than room-temperature values. Temperature-dependent values for the thermo-optic coefficient of III-V semiconductors occupying the cavity are estimated as well. This data is missing from the literature and is crucial for precise device modeling. Our results can be useful for device designing, the theoretical validation of experimental observations as well as the evaluation of thermal effects in silver-coated nanophotonic structures.

DFB laser array based on four phase-shifted sampled Bragg gratings with precise wavelength control.

A four-laser array based on sampled Bragg grating distributed feedback (DFB) lasers in which each sampled period contains four phase-shift sections is proposed, fabricated, and experimentally demonstrated. The wavelength spacing between adjacent lasers is accurately controlled to 0.8 nm ± 0.026 nm and the lasers have single mode suppression ratios larger than 50 dB. Using an integrated semiconductor optical amplifier, the output power can reach 33 mW and the optical linewidth of the DFB lasers can be as narrow as 64 kHz. This laser array uses a ridge waveguide with sidewall gratings and needs only one metalorganic vapor-phase epitaxy (MOVPE) step and one III-V material etching process, simplifying the whole device fabrication process, and meeting the requirements of dense wavelength division multiplexing systems.

Resonances at Fundamental and Harmonic Frequencies for Selective Imaging of Sine-Wave Illuminated Reversibly Photoactivatable Labels.

We introduce HIGHLIGHT as a simple and general strategy to selectively image a reversibly photoactivatable fluorescent label associated with a given kinetics. The label is submitted to sine-wave illumination of large amplitude, which generates oscillations of its concentration and fluorescence at higher harmonic frequencies. For singularizing a label, HIGHLIGHT uses specific frequencies and mean light intensities associated with resonances of the amplitudes of concentration and fluorescence oscillations at harmonic frequencies. Several non-redundant resonant observables are simultaneously retrieved from a single experiment with phase-sensitive detection. HIGHLIGHT is used for selective imaging of four spectrally similar fluorescent proteins that had not been discriminated so far. Moreover, labels out of targeted locations can be discarded in an inhomogeneous spatial profile of illumination. HIGHLIGHT opens roads for simplified optical setups at reduced cost and easier maintenance.

Family Resilience and Its Association with Psychosocial Adjustment of Children with Chronic Illness: A Latent Profile Analysis.

PURPOSE: The purpose of this study was to investigate the characteristics of family resilience in a sample of Chinese families with children diagnosed with chronic illness using Latent Profile Analysis (LPA). In particular, we examined the association of family resilience profiles with the psychosocial adjustment of children, and identified the socio-demographic correlates of these latent profiles. DESIGN AND METHODS: A cross-sectional study was conducted at comprehensive hospitals and children hospitals in three cities (Hangzhou, Ningbo and Wenzhou) of Zhejiang province, China. Parents (n = 277) of children diagnosed with a chronic illness completed a socio-demographic questionnaire, the Chinese version of the family resilience assessment scale, and the Strengths and Difficulties Questionnaire. RESULTS: A three-class solution was found to demonstrate the best fit [low family resilience (74.7%), moderate family resilience (14.1%), and high family resilience (11.2%)]. One-way ANOVA revealed significant differences between the three groups with respect to peer relationship problems and pro-social behaviors of children. On multinomial logistic regression analysis, the type of childhood chronic disease, time since diagnosis, family monthly income, medical insurance, and parents employment status significantly predicted the profile membership. CONCLUSION: Inadequate family resilience was found to be a common phenomenon in families with children affected by chronic illness. Family resilience profiles were associated with psychological adjustment of children. PRACTICE IMPLICATION: Our findings may help inform tailored family-strength based interventions to promote better psychosocial adjustment of children with chronic illness.

Frequency comb with 100 GHz spacing generated by an asymmetric MQW passively mode-locked laser.

A L-band two-section AlGaInAs/InP asymmetric multiple quantum well (QW) passively mode-locked laser has been used to generate a frequency comb with a 100 GHz spacing at a central wavelength of 1610 nm. The comb contains 10 optical lines within a -3dB bandwidth of 8.05 nm and 34 optical lines within a -20dB bandwidth of 30 nm. The mode-locked pulse duration was 440 fs. To the best of our knowledge, this is the shortest pulse duration from any directly electrically pumped QW semiconductor mode-locked laser.

Photoelectrochemical Catalysis toward Selective Anaerobic Oxidation of Alcohols.

Selective oxidation of alcohols to aldehydes plays an important role in perfumery, pharmaceuticals, and agrochemicals industry. Different from traditional catalysis or photocatalytic process, here we report an effective photoelectrochemical (PEC) approach for selective anaerobic oxidation of alcohols accompanied with H2 production by means of solar energy. By using TiO2 nanowires modified with graphitic carbon layer as photoanode, benzyl alcohol (BA) has been oxidized to benzaldehyde with high efficiency and selectivity (>99 %) in aqueous media at room temperature, superior to individual electrocatalytic or photocatalytic processes. Moreover, this PEC synthesis method can be effectively extended to the oxidation of several other aryl alcohols to their corresponding aldehydes under mild conditions. The electron spin resonance (ESR) results indicate the formation of intermediate active oxygen (O2.- ) on the photoanode, which further reacts with alcohols to produce final aldehyde compounds.

1.3-µm dual-wavelength DFB laser chip with modulation bandwidth enhancement by integrated passive optical feedback.

We report a 1.3-µm dual-wavelength distributed feedback (DFB) photonic integrated chip with modulation bandwidth enhancement using integrated optical feedback section. The dual-wavelength DFB lasers were realized using the upper separate confinement heterostructure (SCH) selective area growth (SAG) approach. A modified butt-joint technique was also adopted to achieve high-quality active-passive interface and minimize unintentional intra-cavity optical feedbacks. The fabricated photonic chip exhibited stable single mode operations with a wavelength separation of 2.06 nm. The 3-dB modulation bandwidth was enhanced through the photon-photon resonance effect with f3dB > 17 GHz and open eyes up to 25 Gbit/s for both channels were also obtained. The design can also be scaled up to higher channel counts and higher data rate.

Hierarchical Conducting Polymer@Clay Core-Shell Arrays for Flexible All-Solid-State Supercapacitor Devices.

A sophisticated hierarchical nanoarray consisting of a conducting polymer (polypyrrole, PPy) core and layered double hydroxide (LDH) shell are synthesized via a facile two-step electrosynthesis method. The obtained PPy@LDH-based flexible all-solid-state supercapacitor meets the requirements of both high energy/power output and long-term endurance, which can be potentially used in highly-efficient and stable energy storage.

Preparation of paramagnetic ferroferric oxide-calcined layered double hydroxide core-shell adsorbent for selective removal of anionic pollutants.

Adsorption is one of the most common methods of pollution treatment. The selectivity for pollutants and recyclability of adsorbents are crucial to reduce the treatment cost. Layered double hydroxide (LDH) materials are one type of adsorbent with poor recyclability. Prussian blue (PB) is a sturdy and inexpensive metal-organic framework material that can be used as the precursor for synthesizing paramagnetic ferroferric oxide (Fe3O4). It is intriguing to build some reusable adsorbents with magnetic separation by integrating LDH and PB. In this work, paramagnetic Fe3O4-calcined LDH (Fe3O4@cLDH) core-shell adsorbent was designed and prepared by the calcination of PB-ZnAl layered double hydroxide (PB@LDH) core-shell precursor, which exhibits high anionic dyes selectivity in wastewater solutions. The paramagnetism and adsorption capability of Fe3O4@cLDH come from the Fe3O4 core and calcined ZnAl-LDH shell, respectively. Fe3O4@cLDH shows an adsorption capacity of 230 mg g-1 for acid orange and a high selectivity for anionic dyes in cation-anion mixed dye solutions. The regeneration process indicates that the high selectivity for anions is related to the specific hydration recovery process of ZnAl-LDH. The synergistic effect of the paramagnetic Fe3O4 core and calcined ZnAl-LDH shell makes Fe3O4@cLDH an excellent magnetic separation adsorbent with high selectivity to anions.

Extra kinetic dimensions for label discrimination.

Due to its sensitivity and versatility, fluorescence is widely used to detect specifically labeled biomolecules. However, fluorescence is currently limited by label discrimination, which suffers from the broad full width of the absorption/emission bands and the narrow lifetime distribution of the bright fluorophores. We overcome this limitation by introducing extra kinetic dimensions through illuminations of reversibly photoswitchable fluorophores (RSFs) at different light intensities. In this expanded space, each RSF is characterized by a chromatic aberration-free kinetic fingerprint of photochemical reactivity, which can be recovered with limited hardware, excellent photon budget, and minimal data processing. This fingerprint was used to identify and discriminate up to 20 among 22 spectrally similar reversibly photoswitchable fluorescent proteins (RSFPs) in less than 1s. This strategy opens promising perspectives for expanding the multiplexing capabilities of fluorescence imaging.

Preparation of LDO@TiO2 core-shell nanosheets for enhanced photocatalytic degradation of organic pollution.

TiO2-based nanosheet materials with a core-shell structure are expected to be one of the promising photocatalysts for the degradation of organic pollution. It is a challenge to synthesize TiO2 by the desired nucleation and growth process, so most reported TiO2 core-shell photocatalysts are prepared using TiO2 as a core material. Layered double hydroxides (LDHs) are considered ideal platforms to grow TiO2in situ and further serve as additional components to improve the separation of photogenerated charge carriers. In this work, we report the design and fabrication of anatase TiO2-coated ZnAl-layered double oxide (LDO@TiO2) nanosheets, which involve the in situ growth of TiO2 on ZnAl-LDH followed by subsequent calcination treatment. The resulting LDO@TiO2 photocatalyst yields typical core-shell nanosheet morphology with a mesoporous structure, exhibiting excellent photodegradation and mineralization efficiency for organic pollution.

Out-of-Phase Imaging after Optical Modulation (OPIOM) for Multiplexed Fluorescence Imaging Under Adverse Optical Conditions.

Fluorescence imaging has become a powerful tool for observations in biology. Yet it has also encountered limitations to overcome optical interferences of ambient light, autofluorescence, and spectrally interfering fluorophores. In this account, we first examine the current approaches which address these limitations. Then we more specifically report on Out-of-Phase Imaging after Optical Modulation (OPIOM), which has proved attractive for highly selective multiplexed fluorescence imaging even under adverse optical conditions. After exposing the OPIOM principle, we detail the protocols for successful OPIOM implementation.

Impact of oxygen vacancies on TiO2 charge carrier transfer for photoelectrochemical water splitting.

Oxygen vacancies are recognized as the most prevalent defects in oxide materials. The effect of oxygen vacancies on the physicochemical properties of metal oxide semiconductors has attracted considerable attention in the photocatalysis field. But so far, the impact of oxygen vacancies on charge carrier transfer for photoelectrochemical water splitting has been unclear. In this work, TiO2 photoanodes with various oxygen vacancy concentrations were studied as metal oxide models to clarify the impact of oxygen vacancies on charge carrier transfer behaviors. The potential distribution and electrochemical impedance spectroscopy results indicate that the oxygen vacancies facilitate charge carrier diffusion in TiO2, but are disadvantageous for the charge carrier drift in the TiO2/electrolyte interface. The TiO2-400 photoanode with intermediate oxygen vacancy concentration exhibits the highest photocurrent density. It is expected that this work will provide reference to design and fabricate oxide semiconductors as photoanodes for higher charge carrier utilization in the field of solar-to-chemical energy conversion.

The effect of the photochemical environment on photoanodes for photoelectrochemical water splitting.

Besides photoelectrode materials, realizing the synergy of the photochemical environment and photoelectrodes for high charge carrier utilization is crucial for enhancing the performance of photoelectrochemical (PEC) water splitting systems. However, few researchers have focused on this important aspect. Herein, the effect of the photochemical environment on photoanodes in PEC water splitting, including the redox potential of electrolytes and light direction, is rationally discussed. A combined study of the potential distribution and electrochemical impedance spectroscopy reveals that the low redox potential of electrolytes facilitates the interior charge transfer and surface charge utilization by enlarging the depletion layer. In addition, it is found that the optimum thickness of semiconductors in photoelectrodes is the length of the depletion layer plus diffusion layer.

Correction to "Dynamic Contrast for Plant Phenotyping".

[This corrects the article DOI: 10.1021/acsomega.0c00957.].

Dynamic Contrast for Plant Phenotyping.

Noninvasiveness, minimal handling, and immediate response are favorable features of fluorescence readout for high-throughput phenotyping of labeled plants.Yet, remote fluorescence imaging may suffer from an autofluorescent background and artificial or natural ambient light. In this work, the latter limitations are overcome by adopting reversibly photoswitchable fluorescent proteins (RSFPs) as labels and Speed OPIOM (out-of-phase imaging after optical modulation), a fluorescence imaging protocol exploiting dynamic contrast. Speed OPIOM can efficiently distinguish the RSFP signal from autofluorescence and other spectrally interfering fluorescent reporters like GFP. It can quantitatively assess gene expressions, even when they are weak. It is as quantitative, sensitive, and robust in dark and bright light conditions. Eventually, it can be used to nondestructively record abiotic stress responses like water or iron limitations in real time at the level of individual plants and even of specific organs. Such Speed OPIOM validation could find numerous applications to identify plant lines in selection programs, design plants as environmental sensors, or ecologically monitor transgenic plants in the environment.