Monolithic quantum-dot distributed feedback laser array on silicon

Electrically-pumped lasers directly grown on silicon are key devices interfacing silicon microelectronics and photonics. We report here, for the first time, an electrically-pumped, room-temperature, continuous-wave (CW) and single-mode distributed feedback (DFB) laser array fabricated in InAs/GaAs quantum-dot (QD) gain material epitaxially grown on silicon. CW threshold currents as low as 12 mA and single-mode side mode suppression ratios (SMSRs) as high as 50 dB have been achieved from individual devices in the array. The laser array, compatible with state-of-the-art coarse wavelength division multiplexing (CWDM) systems, has a well-aligned channel spacing of 20 0.2 nm and exhibits a record wavelength coverage range of 100 nm, the full span of the O-band. These results indicate that, for the first time, the performance of lasers epitaxially grown on silicon is elevated to a point approaching real-world CWDM applications, demonstrating the great potential of this technology

Electrically pumped continuous-wave O-band quantum-dot superluminescent diode on silicon

High-power, broadband quantum-dot (QD) superluminescent diodes (SLDs) are ideal light sources for optical coherence tomography (OCT) imaging systems but have previously mainly been fabricated on native GaAs- or InP-based substrates. Recently, significant progress has been made to emigrate QD SLDs from native substrates to silicon substrates. Here, we demonstrate electrically pumped continuous-wave InAs QD SLDs monolithically grown on silicon substrates with significantly improved performance thanks to the achievement of a low density of defects in the III-V epilayers. The fabricated narrow-ridge-waveguide device exhibits a maximum 3 dB bandwidth of 103 nm emission spectrum centered at the O-band together with a maximum single facet output power of 3.8 mW at room temperature. The silicon-based SLD has been assessed for application in an OCT system. Under optimized conditions, a predicted axial resolution of ∼5.3µm is achieved with a corresponding output power of 0.66 mW/facet

Efficient Thermal Conductance in Organometallic Perovskite CH3NH3PbI3 Films

Perovskite-based optoelectronic devices have shown great promise for solar conversion and other optoelectronic applications, but their long-term performance instability is regarded as a major obstacle to their widespread deployment. Previous works have shown that the ultralow thermal conductivity and inefficient heat spreading might put an intrinsic limit on the lifetime of perovskite devices. Here, we report the observation of a remarkably efficient thermal conductance, with conductivity of 11.2 +/- 0.8 W m^-1 K^-1 at room temperature, in densely-packed perovskite CH3NH3PbI3 films, via noncontact time-domain thermal reflectance measurements. The temperature-dependent experiments suggest the important roles of organic cations and structural phase transitions, which are further confirmed by temperature-dependent Raman spectra. The thermal conductivity at room temperature observed here is over one order of magnitude larger than that in the early report, suggesting that perovskite device performance will not be limited by thermal stability

Multi-wavelength 128 Gbit s−1 λ−1 PAM4 optical transmission enabled by a 100 GHz quantum dot mode-locked optical frequency comb

Semiconductor mode-locked lasers (MLLs) with extremely high repetition rates are promising optical frequency comb (OFC) sources for their usage as compact, high-efficiency, and low-cost light sources in high-speed dense wavelength-division multiplexing transmissions. The fully exploited conventional C- and L- bands require the research on O-band to fulfil the transmission capacity of the current photonic networks. In this work, we present a passive two-section InAs/InGaAs quantum-dot (QD) MLL-based OFC with a fundamental repetition rate of ∼100 GHz operating at O-band wavelength range. The specially designed device favours the generation of nearly Fourier-transform-limited pulses in the entire test range by only pumping the gain section while with the absorber unbiased. The typical integrated relative intensity noise of the whole spectrum and a single tone are −152 and −137 dB Hz−1 in the range of 100 MHz–10 GHz, respectively. Back-to-back data transmissions for seven selected tones have been realised by employing a 64 Gbaud four-level pulse amplitude modulation format. The demonstrated performance shows the feasibility of the InAs QD MLLs as a simple structure, easy operation, and low power consumption OFC sources for high-speed fibre-optic communications

Monolithic III–V quantum-dot light sources on silicon for silicon photonics

Epitaxial growth of III–V materials on silicon (Si) substrates is one of the most promising techniques for generating coherent light on Si and offers a low-cost and high-yield solution for Si photonics. The main challenge of this technique is the large material dissimilarity between group IV and III–V compounds. These differences between group IV and III–V tend to produce various types of defects which all generate non-radiative recombination centres and dramatically undermine the promise of III–V materials. Multiple strategies for novel epitaxial growth technologies have been employed in order to reduce the defect density, resulting in high-quality III–V materials on Si. Very recently, III–V quantum-dot (QD) structures have drawn increasing attention for the implementation of compound semiconductor lasers on Si, due to their low threshold current density and reduced temperature sensitivity. In addition, QD structures have also been proven to be less sensitive to defects than conventional bulk materials and quantum well structures, mainly due to the stronger carrier localisation and hence reduced interaction with the defects. As a result, high-performance Si-based QD laser devices have been developed intensively. In order to fully utilize the advantages of Si photonics, the next challenge is to monolithically integrate the high-performance III-V QD lasers with other components, such as modulators and waveguides on a Si platform for information processing and transmission systems

Electrically pumped continuous-wave 13 µm InAs/GaAs quantum dot lasers monolithically grown on on-axis Si (001) substrates

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Bulk segregant analysis coupled with transcriptomics and metabolomics revealed key regulators of bacterial leaf blight resistance in rice

Abstract Background Bacterial leaf blight (BLB) is a highly destructive disease, causing significant yield losses in rice (Oryza sativa). Genetic variation is contemplated as the most effective measure for inducing resistance in plants. The mutant line T1247 derived from R3550 (BLB susceptible) was highly resistant to BLB. Therefore, by utilizing this valuable source, we employed bulk segregant analysis (BSA) and transcriptome profiling to identify the genetic basis of BLB resistance in T1247. Results The differential subtraction method in BSA identified a quantitative trait locus (QTL) on chromosome 11 spanning a 27-27.45 Mb region with 33 genes and 4 differentially expressed genes (DEGs). Four DEGs (P < 0.01) with three putative candidate genes, OsR498G1120557200, OsR498G1120555700, and OsR498G1120563600,0.01 in the QTL region were identified with specific regulation as a response to BLB inoculation. Moreover, transcriptome profiling identified 37 resistance analogs genes displaying differential regulation. Conclusions Our study provides a substantial addition to the available information regarding QTLs associated with BLB, and further functional verification of identified candidate genes can broaden the scope of understanding the BLB resistance mechanism in rice

Biochar's role as an electron shuttle for mediating soil N₂O emissions

The functionality of biochar as an electron shuttle has been hypothesized to rationalize its suppressing effect on nitrous oxide (N₂O) emissions from soil denitrification. However, this hypothesis has not yet been experimentally confirmed in soil matrices. In this study, we weakened biochar's function as an electron shuttle using a hydrogen peroxide pretreatment. Biochar addition supressed soil N₂O emissions compare to a nil biochar control, but oxidized biochar increased soil N₂O emission rates and N₂O/(N₂O + N₂) emission ratio. The increasing extent of the soil N₂O emission rate significantly correlated positively with the abundance of the biochar's oxidative moieties (e.g., C=O groups). These results imply that addition of biochar with a strong electron shuttle function will decrease soil N₂O emissions whereas biochar aging will weaken or even reverse the suppressing effects on soil N₂O emissions

Multi-Functional and Highly Conductive Textiles With Ultra-High Durability Through \u27Green\u27 Fabricaiton Process

© 2020 Elsevier B.V. Conductive textiles with mechanical flexibility, long-term durability and stability under harsh conditions are highly desired for potential applications in wearable electronics and devices. One challenge associated with the development of such materials is their fabrication method, which requires to be low-cost, scalable, and environmental-friendly. Herein, we developed a full “green” route to fabricate machine-washable conductive textiles by coating textiles with a novel crosslinked and conductive polymer composite coating, using single-walled carbon nanotubes (SWNTs) and bio-mass derived glucaric acid/chitosan (GA-chitosan) organic salt aqueous solution with dip-coating or spray-coating. The crosslinked SWNTs/GA-chitosan polyamide coatings exhibit a high electrical conductivity of up to 7.4 × 102 S/m and high water/organic solvents resistance. The conductive textiles can achieve an exceptional Joule heating performance driven by moderate voltage and exhibit a high electromagnetic interference shielding efficiency of approximately 30 dB at X-band under optimized formulation. The high adhesive energy between the polymer composite coatings and textile substrates enables the ultra-high durability and stability of textiles, confirmed by mechanical deformation, rubbing, and washing tests. This simple and organic solvent-free processing method provides an environmentally friendly, cost-effective fabrication approach, holding great promise for large-scale production of multifunctional conductive wearable textiles for EMI shielding and/or personal heating applications