Effector Cs02526 from Ciboria shiraiana induces cell death and modulates plant immunity.

Sclerotinia disease is one of the most devastating fungal diseases worldwide, as it reduces the yields of many economically important crops. Pathogen-secreted effectors play crucial roles in infection processes. However, key effectors of Ciboria shiraiana, the pathogen primarily responsible for sclerotinia disease in mulberry (Morus spp.), remain poorly understood. In this study, we identified and functionally characterized the effector Cs02526 in C. shiraiana and found that Cs02526 could induce cell deathin a variety of plants. Moreover, Cs02526-induced cell death was mediated by the central immune regulator BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 (BAK1), dependent on a 67-amino acid fragment. Notably, Cs02526 homologues were widely distributed in hemibiotrophic and necrotrophic phytopathogenic fungi, but the homologues failed to induce cell death in plants. Pre-treatment of plants with recombinant Cs02526 protein enhanced resistance against both C. shiraiana and Sclerotinia sclerotiorum. Furthermore, the pathogenicity of C. shiraiana was diminished upon spraying plants with synthetic dsRNA-Cs02526. In conclusion, our findings highlight the cell death-inducing effector Cs02526 as a potential target for future biological control strategies against plant diseases.

Low-frequency regular pulse and intermittent oscillation in a mid-infrared interband cascade laser with optoelectronic feedback.

In this work, we experimentally investigate the nonlinear dynamics of a mid-infrared interband cascade laser (ICL) subject to optoelectronic feedback (OEF) through inspecting the time series and power spectrum of the laser output. The results show that, within the range of feedback strength limited by the experiment condition, the ICL sequentially presents stable state, continuously periodical oscillation (CPO), low-frequency regular pulse (LF-RP) and intermittent oscillation state with the increase of feedback strength. For the LF-RP state, the peak-to-peak value and the oscillation period increase with the increase of feedback strength. For the intermittent oscillation state, the time series is composed of the laminar region and burst region appeared alternately, and the average value and standard deviation for the duration of burst region gradually decrease with the increase of feedback strength.

Inserting self-assembled InAs quantum dots into quantum cascade lasers to achieve a broadband free-running frequency comb and effective radio-frequency injection.

We present what we belive to be a new band design in which self-assembled InAs quantum dots (QD) are embedded in InGaAs quantum wells (QW) to fabricate broadband single-core quantum dot cascade lasers (QDCLs) operating as frequency combs. The hybrid active region scheme was exploited to form upper hybrid QW/QD energy states and lower pure QD energy states, which expanded the total laser bandwidth by up to 55 cm-1 due to a broad gain medium provided by the inherent spectral inhomogeneity of self-assembled QDs. The continuous-wave (CW) output power of these devices was as high as 470 mW with optical spectra centered at ∼7 µm, which allowed CW operation at temperatures up to 45 °C . Remarkably, measurement of the intermode beatnote map revealed a clear frequency comb regime extending over a continuous 200 mA current range. Moreover, the modes were self-stabilized with intermode beatnote linewidths of approximately 1.6 kHz. Furthermore, what we believe to be a novel π-shaped electrode design and coplanar waveguide transition way were used for RF signal injection. We found that RF injection modified the laser spectral bandwidth by up to 62 cm-1. The developing characteristics indicate the potential for comb operation based on QDCLs as well as the realization of ultrafast mid-infrared pulse.

Above 20†GHz high frequency operation of mid-infrared doughnut-shaped microcavity quantum cascade lasers.

Microresonator-based high-speed single-mode quantum cascade lasers are ideal candidates for on-chip optical data interconnection and high sensitivity gas sensing in the mid-infrared spectral range. In this paper, we propose a high frequency operation of single-mode doughnut-shaped microcavity quantum cascade laser at ∼4.6 µm. By leveraging compact micro-ring resonators and integrating with grounded coplanar waveguide transmission lines, we have greatly reduced the parasitics originating from both the device and wire bonding. In addition, a selective heat dissipation scheme was introduced to improve the thermal characteristics of the device by semi-insulating InP infill regrowth. The highest continuous wave operating temperature of the device reaches 288 K. A maximum -3 dB bandwidth of 11 GHz and a cut-off frequency exceeding 20 GHz in a microwave rectification technique are obtained. Benefiting from the notch at the short axis of the microcavity resonator, a highly customized far-field profile with an in-plane beam divergence angle of 2.4° is achieved.

High performance distributed feedback quantum cascade laser emitting at λ∼6.12um.

Distributed feedback quantum cascade lasers emitting at a wavelength of 6.12 µm are reported. Benefitted from the optimized materials epitaxy and the modified bound to continuum transition active region design along with three pairs of phonon scattering, high device performance is achieved. For a 2-mm-long, 8.4-µm-wide device, the threshold current is as low as 130 mA, the corresponding threshold current density is only 0.77 kA/cm2, and the optical output power is 69 mW at 20 °C in continuous wave mode. The temperature of continuous wave operation can reach 100 °C, where the optical output power is still more than 8 mW. In addition, it maintains a stable single mode operation from 20 to 100 °C without mode hopping, corresponding to a total wavelength shift of 41 nm. Such low-threshold quantum cascade lasers are highly beneficial to portable and highly integrated system sensor applications.

Continuous-wave microcavity quantum cascade lasers in whispering-gallery modes up to 50 °C.

Micro-resonator-based lasers are well suited for high-density optoelectronic integration because of their small volumes and low thresholds. However, microcavity quantum cascade lasers for on-chip sensing have high thermal loads that make continuous-wave operation challenging. In this work, we designed an selective thermal dissipation scheme for the selective electrical isolation process to improve the thermal conductivity of the devices. The lasers operated at 50 °C, with 4.7-µm emission. They were fabricated as a notched elliptical resonator, resulting in a highly unidirectional far-field profile with an in-plane beam divergence of 1.9°. Overall, these directional-emission quantum cascade lasers pave the way for portable and highly integrated sensing applications.

Phase-locked terahertz quantum cascade laser array integrated with a Talbot cavity.

Increasing the power of a quantum cascade laser by widening laser ridges will lead to the degradation of the beam quality because of the operation of high-order transverse modes. We report on a phase-locked array scheme of terahertz quantum cascade laser (THz QCL) utilizing Talbot effect. By adjusting the absorbing boundary width of each ridge in the array, stable operation of the fundamental supermode is realized. A five-element array shows 4 times power amplification than that of a single ridge device. Due to the large power amplification efficiency, stable mode selection, and simple fabricating process, the phase-locked array scheme is very promising to further improve the performance of THz QCL.

Monolithically integrated mid-infrared sensor with a millimeter-scale sensing range.

On-chip sensors based on quantum cascade laser technology are attracting broad attention because of their extreme compactness and abundant absorption fingerprints in the mid-infrared wavelength range. Recent continuous wave operation microcavity quantum cascade lasers are well suited for high-density optoelectronic integration because their volumes are small and thresholds are low. In this experimental work, we demonstrate a monolithically integrated sensor comprising a notched elliptical resonator as transmitter, a quantum cascade detector as receiver, and a surface plasmon structure as light-sensing waveguide. The sensor structure is designed to exploit the highly unidirectional lasing properties of the notched elliptical resonator to increase the optical absorption path length. Combined with the evanescent nature of the dielectric loaded surface plasmon polariton waveguides, the structure also ensures a strong light-matter interactions. The sensing transmission distance obtained is approximately 1.16 mm, which is about one order of magnitude improvement over the traditional Fabry-Perot waveguide. This sensor opens new opportunities for long-range and high-sensitivity on-chip gas sensing and spectroscopy.

High-performance quantum cascade lasers at λ ∼ 9†µm grown by MOCVD.

We demonstrate a high power InP-based quantum cascade laser (QCL) (λ ∼ 9 µm) with high characteristic temperature grown by metalorganic chemical vapor deposition (MOCVD) in this article. A 4-mm-long cavity length, 10.5-µm-wide ridge QCL with high-reflection (HR) coating demonstrates a maximum pulsed peak power of 1.55 W and continuous-wave (CW) output power of 1.02W at 293 K. The pulsed threshold current density of the device is as low as 1.52 kA/cm2. The active region adopted a dual-upper-state (DAU) and multiple-lower-state (MS) design and it shows a wide electroluminescence (EL) spectrum with 466 cm-1 wide full-width at half maximum (FWHM). In addition, the device performance is insensitive to the temperature change since the threshold-current characteristic temperature coefficient, T0, is as high as 228 K, and slope-efficiency characteristic temperature coefficient, T1, is as high as 680 K, over the heatsink-temperature range of 293 K to 353 K.

Broad tuning range, high power quantum cascade laser at λ ∼ 7.4 µm.

In this article, we report a high power quantum cascade laser (QCL) at λ∼7.4 µm with a broad tuning range. By carefully designing and optimizing the active region and waveguide structure, a continuous-wave (CW) output power up to 1.36 W and 0.5 W is achieved at 293 K and 373 K which shows the excellent temperature stability. A high wall-plug efficiency (WPE) of 8% and 13.6% in CW and pulsed mode at 293 K are demonstrated. The laser shows a characteristic temperature T0 of 224 K and T1 of 381 K over a temperature range from 283 K to 373 K. In addition, a far field of pure zero order transverse mode and a fairly wide external cavity (EC) tuning range (280 cm-1) from 6.54 µm to 8 µm are achieved in pulsed operation. In addition, an EC single mode output power of 226 mW is obtained under CW operation at 293K.

GaSb surface grating distributed feedback interband cascade laser emitting at 3.25 µm.

A second-order distributed feedback interband cascade laser emitting at 3.25 µm was designed, grown, and fabricated. By coherent epitaxy of a GaSb cap layer instead of the conventional thin InAs cap on top of the laser structure, a high-quality surface grating was made of GaSb and gold. Enough coupling strength and a significant inter-modal loss difference were predicted according to the simulation within the framework of couple-wave theory. Lasers having 2-mm-long cavities and 4.5-µm-wide ridges with high-/anti-reflection coatings were fabricated. The continuous-wave threshold current and maximum single-mode output power were 60 mA and 24 mW at 20°C, respectively. The output power of 5 mW was still kept at 55°C. Continuous tuning free from mode hopping and high single-mode suppression ratios (>20 dB) were realized at all injection currents and heat-sink temperatures, covering a spectral range of over 20 cm-1.

Lateral waveguide scanner integration on surface-emitting mid-infrared lasers.

In this paper, a novel, to the best of our knowledge, monolithic non-mechanical semiconductor laser scanner in the mid-infrared (MIR) spectrum is proposed. A deflector above the active region at the substrate side is used for coupling the vertical light into a lateral substrate waveguide, which creates a chain of coherent emitters such as optical phased arrays (OPAs) for beam steering. The numerical simulation reveals that GaSb-based surface-emitting interband cascade lasers (SE-ICLs) are an excellent platform for waveguide scanner integration. Due to the hundreds of micrometers of optical path difference and the narrow gap between each emitter, an extremely high angle tuning coefficient of 0.84°/nm covering the whole 28.6° steering range is obtained. This work theoretically verifies the feasibility of integrating an OPA scanner into the GaSb-based SE-ICLs, providing a practical solution to fabricate compact steerable MIR laser sources. Note that this substrate OPA concept has strong adaptation potential to extend to even longer wavelength devices such as InP and GaAs-based quantum cascade lasers.

Dual-wavelength switchable, mid-infrared quantum cascade laser with two shallow-etched distributed Bragg reflectors.

A dual-wavelength quantum cascade laser (QCL) with two shallow-etched distributed Bragg reflectors is designed and fabricated. Based on a heterogeneous active region within a single waveguide, single-mode emission at 7.6µm and 8.2µm was achieved. The two wavelengths can be independently controlled by selective current injection on different regions of the device, which are electrically isolated. High optical powers of about 275mW and 218mW at room temperature were obtained for the single-mode emission at 7.6µm and 8.2µm, respectively. The presented design concept for high power, dual-wavelength switchable, mid-infrared QCLs is significant in developing miniaturized multi-species gas detection systems.

Mid-wave/long-wave dual-color infrared quantum cascade detector enhanced by antenna-coupled microcavity.

We have demonstrated a mid-wave/long-wave dual-color infrared quantum cascade detector enhanced by antenna-coupled microcavity. By optimizing the size of patches, the coupling wavelength of the antenna-coupled microcavity can be conveniently tuned to match the targeted intersubband transition energy. At 77 K, the peak responsivity of our detector is 4.1 mA/W for long wave (10.4 µm) and 0.6 mA/W for mid wave (5.8 µm), while the detectivity is 1.8×109 cm·Hz1/2/W (Jones) and 2.6×108 cm·Hz1/2/W (Jones), respectively. Compared with a reference device with a 45° multi-pass geometry, the responsivity of our detector has been increased by a factor of 9.1 for the long wave and 2.7 for the mid wave. Our results illustrate how to realize a dual-color infrared detector and improve the optoelectronic performance through the concept of antenna-coupled microcavity.

Watt-level, high wall plug efficiency, continuous-wave room temperature quantum cascade laser emitting at 7.7µm.

In this article, a InP based strain-balanced In0.58Ga0.42As/In0.47Al0.53As quantum cascade laser emitting at 7.7µm is reported. The active region is based on a slightly-diagonal bound to continuum design with 50 cascade stages and a low voltage defect Δinj of 96 meV. By optimizing the active region and waveguide structure, the waveguide loss αw of 1.18cm-1 are obtained, which contribute to a high wall-plug efficiency (WPE) of 9.08% and low threshold current of only 1.09 kA/cm2 in continuous-wave(CW) operation at 293K. The maximum single facet output power of 1.17W in CW operation and 2.3W in pulsed operation are measured at 293K. The narrow ridge and buried ridge structure epi-side-down-mounted on the diamond heatsink improved the heat dissipation of the device. A beam of pure zero order mode and a broad external-cavity tuning range from 7.16µm to 8.16µm are also achieved.

Ultralow power consumption of a quantum cascade laser operating in continuous-wave mode at room temperature.

We report an ultralow power consumption of a quantum cascade laser (QCL) emitting at λ ∼ 4.6 µm operating in continuous-wave mode at room temperature. The ultralow power consumption is achieved by using a high gain active region and shortening the device size. For the device with a 0.5-mm-long cavity and 3.2-µm-wide ridge, the threshold power consumption is as low as 0.26 W with an optical output power of 12.6 mW at 10 °C in continuous-wave mode, which represents the world's most advanced level. Furthermore, the threshold power consumption varies linearly with the operating temperature, where the linear change rate of 2.3 mW/K from 10 to 40 °C is low. As a result, the devices also show low threshold power consumption values of 0.33 W even at 40 °C in continuous-wave mode with an optical output power of 6.1 mW. In addition, the lasers can maintain a single-mode operation due to the short cavity length even if no distributed feedback grating is applied.

Low voltage-defect quantum cascade lasers based on excited-states injection at λ ∼ 8.5 µm.

A quantum cascade laser emitting at λ∼8.5 µm based on the excited-state injection is presented. The operating voltage is reduced for a low-voltage defect in the excited-state design, compared with the conventional ground-state injection design. The threshold voltage and voltage defect are as low as 6.3 V and 54 mV for a 30-stage active region, respectively. Devices were fabricated through standard buried-heterostructure processing to decrease the heat accumulation. A continuous-wave optical power of 340 mW is obtained at 283 K with a threshold current density of 2.7 kA/cm2. Such a design has the potential to further improve the wall plug efficiency for increased voltage efficiency.

Room temperature continuous wave quantum dot cascade laser emitting at 7.2 µm.

We demonstrate a quantum cascade laser with active regions consisting of InAs quantum dots deposited on GaAs buffer layers that are embedded in InGaAs wells confined by InAlAs barriers. Continuous wave room temperature lasing at the wavelength of 7.2 µm has been demonstrated with the threshold current density as low as 1.89 kA/cm2, while in pulsed operational mode lasing at temperatures as high as 110 °C had been observed. A phenomenological theory explaining the improved performance due to weak localization of states had been formulated.

Resistant starch alters gut microbiome and metabolomic profiles concurrent with amelioration of chronic kidney disease in rats.

Patients and animals with chronic kidney disease (CKD) exhibit profound alterations in the gut environment including shifts in microbial composition, increased fecal pH, and increased blood levels of gut microbe-derived metabolites (xenometabolites). The fermentable dietary fiber high amylose maize-resistant starch type 2 (HAMRS2) has been shown to alter the gut milieu and in CKD rat models leads to markedly improved kidney function. The aim of the present study was to identify specific cecal bacteria and cecal, blood, and urinary metabolites that associate with changes in kidney function to identify potential mechanisms involved with CKD amelioration in response to dietary resistant starch. Male Sprague-Dawley rats with adenine-induced CKD were fed a semipurified low-fiber diet or a high-fiber diet [59% (wt/wt) HAMRS2] for 3 wk (n = 9 rats/group). The cecal microbiome was characterized, and cecal contents, serum, and urine metabolites were analyzed. HAMRS2-fed rats displayed decreased cecal pH, decreased microbial diversity, and an increased Bacteroidetes-to-Firmicutes ratio. Several uremic retention solutes were altered in the cecal contents, serum, and urine, many of which had strong correlations with specific gut bacteria abundances, i.e., serum and urine indoxyl sulfate were reduced by 36% and 66%, respectively, in HAMRS2-fed rats and urine p-cresol was reduced by 47% in HAMRS2-fed rats. Outcomes from this study were coincident with improvements in kidney function indexes and amelioration of CKD outcomes previously reported for these rats, suggesting an important role for microbial-derived factors and gut microbe metabolism in regulating host kidney function.

High efficiency, single-lobe surface-emitting DFB/DBR quantum cascade lasers.

We demonstrate a surface-emitting quantum cascade laser (QCL) based on second-order buried distributed feedback/distributed Bragg reflector (DFB/DBR) gratings for feedback and outcoupling. The grating fabricated beneath the waveguide was found to fundamentally favor lasing in symmetric mode either through analysis or experiment. Single-lobe far-field radiation pattern with full width at half maximum (FWHM) of 0.18° was obtained along the cavity-length direction. Besides, the buried DFB/DBR grating structure successfully provided an efficient vertical outcoupling mechanism with low optical losses, which manages to achieve a high surface outcouping efficiency of 46% in continuous-wave (CW) operation and 60% in pulsed operation at room temperature. Single-mode emission with a side-mode suppression ratio (SMSR) about 25 dB was continuously tunable by heat sink temperature or injection current. Our work contributes to the realization of high efficiency surface-emitting devices with high far-field beam quality that are significantly needed in many application fields.