Maximum Slope Research Articles

Perturbation-based pH control systems for buffer and equivalence points

The dynamics of the pH process is well-described by the Wiener model, in which a nonlinear static function follows a linear dynamic subsystem. Gain scheduling applied to the process output, or equivalently to the controller gain, has to be used to keep the pH process at a given set point under the severe static nonlinearity of the titration curve. The present study investigates two control problems of keeping the pH process on the buffer and equivalence points. The proposed method uses extremum seeking control techniques to find the first and second derivatives with continuous process input perturbations. It finds and maintains process operating points where the second derivatives of pH with respect to the process input changes are zero, the local points of minimum and maximum slopes. The performances of the proposed method are verified with simulation and experiment.

A Thermal Profile across the Idaho-Montana Fold-Thrust Belt Reveals a Low-Relief Orogenic Wedge That Developed atop a Pre-Orogenic Basement High

Abstract Growing orogenic wedges cool rocks during exhumation of thrust hanging walls and heat them during burial of footwalls, leaving behind a resilient thermal record of earlier deformation in fold-thrust belts. In order to investigate early burial of deformed strata within the retroarc Idaho-Montana fold-thrust belt, we use Raman spectroscopy of carbonaceous material to construct a maximum temperature profile that constrains the thicknesses of eroded rocks structurally above the Lemhi arch, a pre-thrusting basement high. In the eastern portion of the study area, a sharp maximum temperature change of ~120°C occurs across the Johnson thrust, signifying that regional burial and heating predated late-stage faulting. West of here, cumulative exhumation is irregular, varying by up to 5 km over large (~75 km) wavelength folds; however, maximum temperatures in this same region are consistently ~200°C higher than correlative stratigraphic units in the adjacent foreland. The pre-thrusting, low-relief unconformity above the Lemhi arch, which served as the early décollement to the fold-thrust belt, was everywhere buried to at least ~6.5 km depth, which is ~1.5-5.0 km deeper than can be explained by stratigraphic burial. We hypothesize that between ~145 and 80 Ma, a combination of Cretaceous deposition and folding and thrusting at higher structural levels buried the décollement of the Medicine Lodge-McKenzie thrust system to this depth. These results suggest that the early orogenic wedge had exceptionally low taper. We propose that thin strata over the low-relief Lemhi arch limited the availability of potential décollements, which restricted the maximum surface slope that could be constructed in a thin-skinned system. Subsequent growth of the orogenic wedge required activation of a much deeper décollement and a switch to a thick-skinned structural style, promoting a shift from burial to exhumation of the former décollement and the underlying Lemhi arch. This suggests that the growth of an orogenic wedge is dependent on the thicknesses of the preexisting strata and the availability of potential décollements, with sedimentation and burial heating potentially playing a key role.

High-power CW 1048 nm Yb:YAG Dual-Ended Diode-pumped zigzag slab Laser

We developed a high-power continuous-wave (CW) 1048 nm Yb:YAG laser oscillator with a folded cavity structure. Based on a surface gain slab structure of Yb:YAG, the CW laser output property of 1030 and 1048 nm wavelengths is theoretically analyzed. In order to achieve a CW single-wavelength laser output at 1048 nm, a high-power pump and the suppression of laser oscillations at other wavelengths were required. In our experiments at 4200 W of pump power, we obtained a maximum output power of 1330 W, with an optical–optical conversion efficiency of 31 %, a maximum slope efficiency of 46.4 % and a beam quality (β) of 1.7 times the diffraction limit. We also proposed a laser oscillator. To the best of our knowledge, we obtained the highest power and beam quality for Yb:YAG laser oscillators at 1048 nm. This work could provide a useful platform for developing 1048 nm lasers with higher power and beam quality and increasing the accessibility of the 1048 nm regime.

Isotopes-based characterization of precipitation compositions and atmospheric water vapor sources over typical Eurasian steppes in south mongolian Plateau

An inland river grassland basin is a fragile ecosystem, and precipitation is of great significance to its resilience. However, the knowledge of where precipitation-forming water vapor originated is not well understood, limiting the predictability of future precipitation provided climate change. The objective of this study was to characterize the hydrogen (δD) and oxygen (δ18O) isotopes and hydro-chemical compositions of precipitation as well as decipher atmospheric water vapor sources in a typical Eurasian steppe river basin. In this regard, this study collected 59 water samples from 44 storm events in 2019 and 2020. The samples were analyzed in our laboratory for ions, δD, and δ18O, which in turn were used to examine the stable isotopic features, hydro-chemical characteristics, and water vapor transport at different temporal scales by a backward trajectory model and correlation and redundancy analyses. The results showed negative δD and δ18O during the wet season with a trend of positive deuterium excess, indicating that precipitation effect was significant. In comparison with a linear model of global meteoric water levels, the local meteoric water lines had smaller slopes and intercepts, with a maximum slope in August and a minimum slope in July. In addition, HCO3− and Ca2+ were the primary hydro-chemical ions in precipitation. Ca2+ and Mg2+ were significantly correlated with HCO3− and Na+, indicating that they shared terrestrial and marine sources. NH4+ originated mainly from human activities and chemical reactions, whereas K+ originated primarily from continental and marine processes. Further, the atmospheric water vapor was mainly transported from the northeast, northwest, and southeast directions into the study basin, as affected by the westerly wind circulation, the East Asian summer monsoon, northeast anticyclone circulation, and local evapotranspiration. Moreover, the water vapor was from both onsite and offsite sources: over 40% from Eurasia, 10 to 25% from the Arctic Ocean, and 35 to 45% from the Pacific Ocean.

Functional MRI radiomics-based assessment of pelvic bone marrow changes after concurrent chemoradiotherapy for cervical cancer

ObjectivesTo quantify the dose-response relationship of changes in pelvic bone marrow (PBM) functional MR radiomic features (RF) during concurrent chemoradiotherapy (CCRT) for patients with cervical cancer and establish the correlation with hematologic toxicity to provide a basis for PBM sparing.MethodsA total of 54 cervical cancer patients who received CCRT were studied retrospectively. Patients underwent MRI IDEAL IQ and T2 fat suppression (T2fs) scanning pre- and post-CCRT. The PBM RFs were extracted from each region of interest at dose gradients of 5–10 Gy, 10–15 Gy, 15–20 Gy, 20–30 Gy, 30–40 Gy, 40–50 Gy, and > 50 Gy, and changes in peripheral blood cell (PBC) counts during radiotherapy were assessed. The dose-response relationship of RF changes and their correlation with PBC changes were investigated.ResultsWhite blood cell, neutrophils (ANC) and lymphocyte counts during treatment were decreased by 49.4%, 41.4%, and 76.3%, respectively. Most firstorder features exhibited a significant dose-response relationship, particularly FatFrac IDEAL IQ, which had a maximum dose-response curve slope of 10.09, and WATER IDEAL IQ had a slope of − 7.93. The firstorder-Range in FAT IDEAL IQ and firstorder-10Percentile in T2fs, showed a significant correlation between the changes in ANC counts under the low dose gradient of 5–10 Gy (r = 0.744, -0.654, respectively, p < 0.05).ConclusionFunctional MR radiomics can detect microscopic changes in PBM at various dose gradients and provide an objective reference for bone marrow sparing and dose limitation in cervical cancer CCRT.

Abstract 11617: Chronic Spinal Cord Stimulation Mitigates Cardiac Sympathoexcitation and Reduces Ventricular Arrhythmias Induced by Myocardial Infarction

Introduction: Spinal cord stimulation (SCS) is effective neuromodulation therapy for pain, but little is known about the effectiveness of SCS for arrhythmia prevention in chronic myocardial infarction (MI). Hypothesis: Chronic SCS reduces MI-induced cardiac sympathoexcitation and reduces ventricular arrhythmias. Methods: Yorkshire pigs were randomized to chronic left circumflex coronary artery MI alone (n=11) or MI + chronic SCS (n=9). Epidural SCS lead was placed percutaneously T1-T4 of the spinal cord and reactive SCS was performed at 10 kHz, 0.03ms, and 2.5mA after MI. Holter ECG was recorded for heart rate variability (HRV) analysis, performed throughout 4-5 weeks post-MI. To create acute stress in chronic MI, epicardial extraventricular programmed stimulus (S1/S2 pacing), and acute left anterior descending coronary artery (LAD) ischemia(1h)+reperfusion(2h) (I/R) injury were conducted during terminal experiment. SCS was continued throughout terminal experiment. Cardiac electrophysiological data (activation recovery interval (ARI) and dispersion of repolarization (DOR)), as well as ventricular arrhythmia quantification were measured by placing a 56-electrode mesh sock over the heart . Data is shown as mean±SEM. Results: 1 week after MI, 30min HRV showed a higher high-frequency band and lower very-low and low-frequency band with SCS (%HF: MI 25±4 vs SCS 51±4, p=0.0028. %VLF: 50±4 vs 30±3, p=0.0015. %LF: 22±2 vs 14±2, p=0.047). In the terminal experiment, SCS reduced the maximum slope (Smax) of the electrical restitution curve described by S1/S2 pacing (Smax: MI 0.6±0.03 vs SCS 0.4±0.05, p=0.023). After acute LAD ischemia, SCS reduced global %ARI change (MI -19±3% vs SCS -11±1%, p=0.019), specifically in the ischemic region (MI -31±4% vs SCS -16±3%, p=0.008), and global %DOR (MI 1513±288% vs SCS 595±144%, p=0.011). Chronic SCS also reduced ventricular tachycardia and ventricular fibrillation during acute I/R (MI 15±3 vs SCS 5±0.8, p=0.014). Conclusions: Reactive SCS therapy mitigates cardiac autonomic imbalance in chronic MI and protects from new acute ischemia induced cardiac sympathoexcitation and ventricular arrhythmias.

Fast differential scanning calorimetry: new solutions in data treatment and applications to molecular glass-formers

Fast scanning calorimetry is an experimental technique very appreciated for its capability of suppressing reorganization processes, thanks to its wide interval of scanning rates, several orders higher than that of conventional calorimeters; nevertheless, drawbacks still exist. In this paper we propose a novel way to estimate the dynamical thermal lag by using the temperatures of maximum slope of the heat flow through the glass transition when we are not in the optimal conditions to apply the existing methods based on a reference material added on both cells of the chip or on the fictive temperature. Moreover, a novel interpretation of the heat flow losses due to the sample depending on the scanning rate sign is provided, in order to rescale the measured specific heat capacity to that from conventional calorimetry. Finally, the use of the glass to liquid transition measured on heating is shown as a new manner to reveal static thermal gradients.

Critical soil moisture thresholds of plant water stress in terrestrial ecosystems.

Plant water stress occurs at the point when soil moisture (SM) limits transpiration, defining a critical SM threshold (θcrit). Knowledge of the spatial distribution of θcrit is crucial for future projections of climate and water resources. Here, we use global eddy covariance observations to quantify θcrit and evaporative fraction (EF) regimes. Three canonical variables describe how EF is controlled by SM: the maximum EF (EFmax), θcrit, and slope (S) between EF and SM. We find systematic differences of these three variables across biomes. Variation in θcrit, S, and EFmax is mostly explained by soil texture, vapor pressure deficit, and precipitation, respectively, as well as vegetation structure. Dryland ecosystems tend to operate at low θcrit and show adaptation to water deficits. The negative relationship between θcrit and S indicates that dryland ecosystems minimize θcrit through mechanisms of sustained SM extraction and transport by xylem. Our results further suggest an optimal adaptation of local EF-SM response that maximizes growing-season evapotranspiration and photosynthesis.

Spectroscopy and 2.1 µm laser operation of Czochralski-grown Tm3+:YScO3 crystals.

We report on growth, temperature-dependent spectroscopy, and laser experiments of Tm3+-doped YScO3 mixed sesquioxide crystals. For the first time, cm3-scale laser quality Tm3+:YScO3 crystals with 2.2 at.% and 3.1 at.% doping levels were grown by the Czochralski method from iridium crucibles. We reveal that the structural disorder in the mixed crystals allows for broad and smooth spectral features even at cryogenic temperatures. We obtained the first continuous wave laser operation in this material at wavelengths around 2100 nm using a laser diode emitting at 780 nm as a pump source. A maximum slope efficiency of 45% was achieved using a Tm3 + (3.1 at.%):YScO3 crystal. Our findings demonstrate the high potential of Tm3+-doped mixed sesquioxides for efficient ultrafast pulse generation in the 2.1 µm range.

Multiparametric MRI enables for differentiation of different degrees of malignancy in two murine models of breast cancer.

The objective of this study was to non-invasively differentiate the degree of malignancy in two murine breast cancer models based on identification of distinct tissue characteristics in a metastatic and non-metastatic tumor model using a multiparametric Magnetic Resonance Imaging (MRI) approach. The highly metastatic 4T1 breast cancer model was compared to the non-metastatic 67NR model. Imaging was conducted on a 9.4 T small animal MRI. The protocol was used to characterize tumors regarding their structural composition, including heterogeneity, intratumoral edema and hemorrhage, as well as endothelial permeability using apparent diffusion coefficient (ADC), T1/T2 mapping and dynamic contrast-enhanced (DCE) imaging. Mice were assessed on either day three, six or nine, with an i.v. injection of the albumin-binding contrast agent gadofosveset. Ex vivo validation of the results was performed with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), histology, immunhistochemistry and electron microscopy. Significant differences in tumor composition were observed over time and between 4T1 and 67NR tumors. 4T1 tumors showed distorted blood vessels with a thin endothelial layer, resulting in a slower increase in signal intensity after injection of the contrast agent. Higher permeability was further reflected in higher Ktrans values, with consecutive retention of gadolinium in the tumor interstitium visible in MRI. 67NR tumors exhibited blood vessels with a thicker and more intact endothelial layer, resulting in higher peak enhancement, as well as higher maximum slope and area under the curve, but also a visible wash-out of the contrast agent and thus lower Ktrans values. A decreasing accumulation of gadolinium during tumor progression was also visible in both models in LA-ICP-MS. Tissue composition of 4T1 tumors was more heterogeneous, with intratumoral hemorrhage and necrosis and corresponding higher T1 and T2 relaxation times, while 67NR tumors mainly consisted of densely packed tumor cells. Histogram analysis of ADC showed higher values of mean ADC, histogram kurtosis, range and the 90th percentile (p90), as markers for the heterogenous structural composition of 4T1 tumors. Principal component analysis (PCA) discriminated well between the two tumor models. Multiparametric MRI as presented in this study enables for the estimation of malignant potential in the two studied tumor models via the assessment of certain tumor features over time.

Improving the built environment for manual wheelchair users: A review

The aim of Universal Design is to make the built environment accessible to all people regardless of disability. This is a laudable aim, but most people are unaware of the many barriers manual wheelchair users actually face when accessing the built environment. The main challenges for manual wheelchair users arise from three areas. Firstly, there are intrinsic limitations arising from the manual wheelchair user’s condition and capability. Secondly, there are features such as ramps and cross slopes in the built environment that fail to comply with building codes relating to wheelchair access. Thirdly, there are cosmetic features such as cracked paths, obstructions and poorly placed signage that place an additional burden on manual wheelchair navigation. Each of these three areas is discussed in this article.The intrinsic limitations of user condition and capability include a wide range of physical impairments and an inherently inefficient manual wheelchair propulsion mechanism. The typical code compliance requirements for wheelchair access in the built environment range from limitations on minimum path widths to maximum permissible ramp slopes. However, even when these features comply with code requirements they may be compromised by temporary obstructions or by poor maintenance so that they become insurmountable challenges to manual wheelchair users. An understanding of these challenges is necessary to improve the built environment so that it is more accessible to manual wheelchair users in the future.

Numerical simulations of water waves generated by subaerial granular and solid-block landslides: Validation, comparison, and predictive equations

We compare waves generated by subaerial solid-block and granular landslides and propose equations for predicting their maximum initial wave amplitudes. The recent Anak Krakatau subaerial landslide tsunami in December 2018, which resulted in more than 450 deaths, demonstrated the knowledge gap on this subject and motivated this study. Here, we make numerical models using the numerical package FLOW3D-Hydro for solid-block and granular landslides and validate them using physical experiments. Results indicate that the maximum initial wave amplitudes generated by solid-block landslides are 107% larger than those generated by granular landslides in our experiments. The relationship between maximum initial wave amplitude and slope angle is inverse for solid-block slides whereas, it is direct for granular slides. However, a critical angle of 60° is achieved for granular slides, and for slope angles more than this critical value, the maximum wave amplitudes start to decrease. Regarding wave period, our results show that it remains nearly unchanged for both types of landslides as water depth and slide volume vary. The period generated by solid-block slides increases as the slope angle decreases; however, it remains unchanged for granular slides. The predictive equations are applied to real landslide tsunamis and resulted in satisfactory performances.

Crystallographic texture and structure formed in rolled sheets of zirconium alloys during annealing

This paper examines the processes of recrystallization in sheets of Zr &ndash; 2.5% Nb alloy rolled down to a 50&ndash;90% deformation and annealed at 610 oC for 1, 3 and 5 hours. The heating rate varied from 10 to 100 oC/min. With the help of X-ray structure and texture analysis, the authors looked at optimizing the crystal structure of the deformed alloy while examining changes in the crystallographic texture. It was established that annealing of Zr &ndash; 2.5% Nb alloy sheets performed at the temperature that corresponds to the dual phase region&nbsp;&alpha; +&nbsp;&beta; of an equilibrium phase diagram also leads to recrystallization, as it happens when applying the annealing temperature of 580 oC. However, an 11% increase in the concentration of the additional phase suppresses changes in the crystallographic texture, which may be due to the predominant precipitation of &beta;-zirconium at grain boundaries. At the same time, the growth of recrystallized grains still follows the main regularities of orientation: the orientation of growing grains corresponds to the texture maximum slopes of the direct pole figure (0001); an increased pole density was observed on the difference charts of the direct pole figure {10.0}, which is indicative of the presence of grains that are disoriented to the deformed matrix at 30o around the base normals. It is shown that the contribution of the above mentioned processes is determined by the type of initial texture, the annealing temperature, the heating rate and the amount of &beta;-phase. An extended annealing time (from 1 to 5 hours) at the temperature of the dual phase region does not cause any significant change in the crystallographic texture.This research was funded by the Ministry of Science and Higher Education of&nbsp;the Russian Federation; Agreement No. 075-15-2021-1352.

Determination of the Agricultural Land Potential Index Using a Geographic Information System: A Case Study of Aceh Tengah Regency, Indonesia

Agricultural problems that often arise are due to a lack of suitable and strategic agricultural land for its use, which results in poor agricultural production in the area. A land potential index that classifies existing land potentials from high to low class can be used to overcome this. This study aims to build an agricultural land potential index using a geographic information system in the Regency of Aceh Tengah, Indonesia, using a geographic information system. The method used in this research is a survey approach to collect information in the form of rainfall data, slope, lithology, soil type, land use and administrative maps of the Aceh Tengah Regency. The land potential index is obtained by overlaying the slope parameters, lithology, soil type, hydrology, and susceptibility to erosion into a land map unit that can classify it into five classes of a land potential index. The results of this study indicate that the Regency of Aceh Tengah is included in the very wet climate type. Maximum erosion was 1,213.6 tons per ha per year. The land potential index with very low criteria was 23.38% (102,002.42 ha) with a slope greater than 40%. The land potential index with very high criteria has an area of 3,807.80 ha (0.87%) with a maximum slope of 15%. A land potential index with very high criteria was found in the Linge, Atu Lintang, Lut Tawar, Pegasing, Bintang, Jagong Jeget, Kebayakan, Ketol, and Celala districts with an area of 2,014.26 ha, 1,266.33 ha, 174.81 ha, 148.07 ha, 77.86 ha, 73.63 ha, 46.77 ha, 4.14 ha and 1.94 ha, respectively. Meanwhile, the land potential index with very low criteria is found in all districts except Kute Panang and Atu Lintang.

The predictive value of pressure recording analytical method for the duration of mechanical ventilation in children undergoing cardiac surgery with an XGBoost-based machine learning model.

Prolonged mechanical ventilation in children undergoing cardiac surgery is related to the decrease in cardiac output. The pressure recording analytical method (PRAM) is a minimally invasive system for continuous hemodynamic monitoring. To evaluate the postoperative prognosis, our study explored the predictive value of hemodynamic management for the duration of mechanical ventilation (DMV). This retrospective study included 60 infants who underwent cardiac surgery. Cardiac index (CI), the maximal slope of systolic upstroke (dp/dtmax), and cardiac cycle efficiency (CCE) derived from PRAM were documented in each patient 0, 4, 8, and 12 h (T0, T1, T2, T3, and T4, respectively) after their admission to the intensive care unit (ICU). A linear mixed model was used to deal with the hemodynamic data. Correlation analysis, receiver operating characteristic (ROC), and a XGBoost machine learning model were used to find the key factors for prediction. Linear mixed model revealed time and group effect in CI and dp/dtmax. Prolonged DMV also have negative correlations with age, weight, CI at and dp/dtmax at T2. dp/dtmax outweighing CI was the strongest predictor (AUC of ROC: 0.978 vs. 0.811, p < 0.01). The machine learning model suggested that dp/dtmax at T2 ≤ 1.049 or < 1.049 in combination with CI at T0 ≤ 2.0 or >2.0 can predict whether prolonged DMV (AUC of ROC = 0.856). Cardiac dysfunction is associated with a prolonged DMV with hemodynamic evidence. CI measured by PRAM immediately after ICU admission and dp/dtmax 8h later are two key factors in predicting prolonged DMV.

Double-Clad Bismuth-Doped Fiber with a Rectangular Inner Cladding for Laser Application

In this paper, we report the latest research results on the fabrication of double-clad Bi-doped germanosilicate core fibers with a rectangular inner cladding design for improved laser performance in the near-IR spectral region. Detailed comparative analysis of the absorption characteristics of the Bi-doped fibers with a circular- and rectangular-shaped inner cladding was performed. A series of cladding-pumped, Bi-doped fiber lasers emitting near 1.46 µm was developed using the semiconductor’s multi-mode fiber-coupled laser diodes at λ = 808 nm. The peculiarities of the laser parameters of the fabricated active fibers with the double-clad design were thoroughly studied by analyzing the dependencies of the slope efficiency of the lasers, namely the pump power, active fiber length and core-to-inner-cladding area ratio. The obtained results show that the rectangular design provided enhanced cladding absorption and improvements in laser performance. In particular, we achieved maximal slope efficiencies of 5.5% and 4.3% for the absorbed pump power introduced into the inner cladding with cross-section areas of 80 × 80 µm2 and 125 × 125 µm2, respectively. Multi-wavelength lasing operation in a free-running cavity due to a few modes’ propagation regimes was found using the Bi-doped fiber with an 80 × 80 µm2 inner cladding.

Monitoring and Analysis of Water Surface Slope of the Yarlung Zangbo River Based on Remote Sensing

Global warming has led to an increase in interest in river hydrology. Water surface slope is a basic parameter of river morphology and is critical in understanding riverine ecosystems. The Yarlung Zangbo River is an important international river. Scientific understanding of its hydrology has been severely limited by its harsh topography and the sparse distribution of measurement stations. This paper describes the first attempt to use ICESat-2 satellite altimetry data to calculate river water slope and introduces a new technique for studying river hydrology. Water level data for different stretches of the Yarlung Zangbo River were obtained from high spatial resolution ICESat-2 altimetry data. The data were analyzed to determine the water surface slope of the Yarlung Zangbo River, and variation in the water surface slope was examined for several river sections. The water surface slope of the Yarlung Zangbo River was greatest in summer and autumn and least in winter and spring. There may be seasonal cyclic changes in the water surface slope. The range for water surface slope was large and the difference in extremes is significant; the maximum average water surface slope was 1935.17 cm/km and the minimum water surface slope was 0.08 cm/km. The water surface slope of the Yarlung Zangbo River can be characterized as small in the upper and middle reaches and large in the lower reaches; it is related to dry and wet conditions determined by topography and climate. The upper and middle reaches of the Yarlung Zangbo River are semi-arid and the lower reaches of the Yarlung Zangbo River span three climate zones: semi-arid, semi-humid and humid. In addition, the water level information measured by ICESat-2 data is basically similar to the water level information measured by Hydroweb data, except that the water level information of individual virtual stations is quite different due to special reasons. It was found that ICESat-2 data had higher-accuracy water level data results and more river location information. Therefore, ICESat-2 satellite altimetry data can provide a baseline reference for the study of the Yarlung Zangbo River hydrology, and the technique used is applicable to other rivers.

All-Fiber Wavelength-Tunable Narrow-Linewidth Polarization-Maintaining Tm-Doped Fiber MOPA System

An all-fiber wavelength-tunable narrow-linewidth polarization-maintaining (PM) Tm-doped fiber master oscillator power amplifier (MOPA) system is presented. We demonstrate an all-fiber ring cavity Tm-doped fiber master-oscillator (MO) with a tuning range of 110 nm (from 1925 to 2034 nm). The maximum output power of 459 mW is obtained at 1992.9 nm for 16 W of launched pump power at 793 nm, corresponding to a slope efficiency of 5.6% concerning launched pump power. By using a one-stage Tm-doped fiber amplifier combined with a high gain of &gt;10 dB, the maximum slope efficiency is 12.6% and the output power is 5.65 W at 1993 nm. The 3 dB linewidth is less than 0.5 nm, M2 ≈ 1.25, and the polarization extinction ratio (PER) reaches 21.4 dB. The influence of different active fiber lengths on laser amplification is also studied.

Watt-level diode-pumped Tm:YVO4 laser at 2.3 µm.

In this Letter, a watt-level laser diode (LD)-pumped ∼2.3-µm (on the 3H4→3H5 quasi-four-level transition) laser is reported based on a 1.5 at.% a-cut Tm:YVO4 crystal. The maximum continuous wave (CW) output power obtained is 1.89 W and 1.11 W with the maximum slope efficiency of 13.6% and 7.3% (versus the absorbed pump power) for the 1% and 0.5% transmittance of the output coupler, respectively. To the best of our knowledge, the CW output power of 1.89 W we obtained is the highest CW output power amongst the LD-pumped ∼2.3-µm Tm3+-doped lasers.

A Tunable Multi-Port Fano Resonator Based on Mach-Zehnder Interferometers Coupling with Micro-Ring Resonators

Fano resonance has an asymmetric and sharp resonance peak near the resonance wavelength, which can effectively enhance the all-optical signal processing capability and realize silicon photonic switches, sensors, and modulators. In this paper, a silicon photonic Fano resonator with Mach-Zehnder interferometer (MZI) structure coupling with micro-ring resonators (MRR) is designed. Two MRRs with different quality factors are coupled with two arms of an MZI, and the coupling zone is composed of two half-ring waveguides. Based on the transfer matrix method, the intrinsic and modulated transfer characteristics of the component are analyzed. By adjusting the optical amplitude and phase of MZIs and tuning the resonance wavelength of two MRRs, Fano resonance spectra are simulated at four output ports with the highest extinction ratios of 56.19 dB and maximum slope rates at 2175.74 dB/nm, and the transmission spectra of Fano resonance at the four output ports are experimentally demonstrated. As the four Fano resonance ports of the designed component have different performances, they can be used for various functions simultaneously. The advantage of the proposed scheme is the improvement of the multiplexing capacity and simultaneous utilization of the muti-port for the Fano resonator. Our four-port Fano resonator can be employed in the fields of optical switching, optical computing, and optical interconnect in the future.