Tandem Pumping Research Articles

CALCULATION OF THREE-DIMENSIONAL HYDRAULIC ACTUATOR OF THE WORKING BODIES OF ATTACHMENTS AND TRAILERS IN THE MACHINE-TRACTOR UNIT

Using the RT-M-160 tractor power take-off shaft, a series of tandem hydraulic pumps has been installed. This made it possible to improve the conditions of use of the unit: the tractor RT-M-160 with the hook-up combine "Space" when performing field work. A hydraulic schematic diagram of a volumetric hydraulic drive of a rotary motion with a closed circuit of the working fluid circulation, an unregulated pump and a flow controller to maintain a constant speed of rotation, regardless of the value of the resistance of the working body. The definitions of the working volume of the hydraulic motor, which are rounded to the nearest greater value from the nomenclature series of hydraulic motors, are made, are given by the manufacturer in the catalog. On the basis of the specified value of the working volume and the corresponding value of the hydromechanical efficiency (in the catalogs of manufacturers of hydromotors give the dependence of the change of the hydromechanical efficiency on the differential pressure and the speed of rotation) determine the actual differential pressure on the hydromotor. The flow rate that must be applied to the hydromotors from the pump is determined to ensure the maximum speed of the working body and find the maximum theoretical supply of the pump. The working volume of the pump providing the necessary supply of working fluid at a given maximum speed of rotation of the drive motor is determined. The working volume of the pump is specified by the catalog, rounding to the nearest greater value from the nomenclature series. The maximum mechanical power of the volume hydraulic actuator and the maximum power consumed by the pump have been determined. Total efficiency of the three-dimensional hydraulic actuator was found. The installed power of the drive motor with the applied factor of reserve is determined. The diameter of the pipelines was calculated, which was then rounded according to the values of conditional passes according to GOST. Simplified calculations of the volume of the hydro tank and the choice of cooler.

Burkholderia collagen-like protein 8, Bucl8, is a unique outer membrane component of a putative tetrapartite efflux pump in Burkholderia pseudomallei and Burkholderia mallei.

Bacterial efflux pumps are an important pathogenicity trait because they extrude a variety of xenobiotics. Our laboratory previously identified in silico Burkholderia collagen-like protein 8 (Bucl8) in the hazardous pathogens Burkholderia pseudomallei and Burkholderia mallei. We hypothesize that Bucl8, which contains two predicted tandem outer membrane efflux pump domains, is a component of a putative efflux pump. Unique to Bucl8, as compared to other outer membrane proteins, is the presence of an extended extracellular region containing a collagen-like (CL) domain and a non-collagenous C-terminus (Ct). Molecular modeling and circular dichroism spectroscopy with a recombinant protein, corresponding to this extracellular CL-Ct portion of Bucl8, demonstrated that it adopts a collagen triple helix, whereas functional assays screening for Bucl8 ligands identified binding to fibrinogen. Bioinformatic analysis of the bucl8 gene locus revealed it resembles a classical efflux-pump operon. The bucl8 gene is co-localized with downstream fusCDE genes encoding fusaric acid (FA) resistance, and with an upstream gene, designated as fusR, encoding a LysR-type transcriptional regulator. Using reverse transcriptase (RT)-qPCR, we defined the boundaries and transcriptional organization of the fusR-bucl8-fusCDE operon. We found exogenous FA induced bucl8 transcription over 80-fold in B. pseudomallei, while deletion of the entire bucl8 locus decreased the minimum inhibitory concentration of FA 4-fold in its isogenic mutant. We furthermore showed that the putative Bucl8-associated pump expressed in the heterologous Escherichia coli host confers FA resistance. On the contrary, the Bucl8-associated pump did not confer resistance to a panel of clinically-relevant antimicrobials in Burkholderia and E. coli. We finally demonstrated that deletion of the bucl8-locus drastically affects the growth of the mutant in L-broth. We determined that Bucl8 is a component of a novel tetrapartite efflux pump, which confers FA resistance, fibrinogen binding, and optimal growth.

Basal-IQ technology in the real world: satisfaction and reduction of diabetes burden in individuals with type 1 diabetes.

To describe person-reported outcomes of the Basal-IQ predictive low-glucose-suspend system (Tandem Diabetes Care, San Diego, CA, USA) in real-world use. Adults with type 1 diabetes/caregivers of minors with type 1 diabetes completed the Diabetes Impact and Device Satisfaction questionnaire (11 items scored on 10-point Likert scales) prior to Basal-IQ system initiation, and at 2, 4 and 6 months post-initiation. Analysis was stratified by previous insulin treatment method. Beta mixed models were used to measure change in device satisfaction (e.g. trust, ease of use) and diabetes impact (e.g. hypoglycaemia fear, poor sleep) scores between time points, adjusting for baseline covariates. A total of 967 adults and caregivers [54% women, mean (sd) age 36 (17) years, 57% Tandem pump users, 27% non-Tandem pump users, 17% multiple daily injection users] completed surveys. Device satisfaction significantly increased from baseline to 2 months in all groups (P<0.001 multiple daily injection and non-Tandem pump users; P=0.048 Tandem pump users), and was sustained from 2 to 6 months in all groups. Diabetes impact decreased significantly from baseline to 2 months in all groups (P<0.001 for all), was sustained from 2 to 6 months in multiple daily injection and Tandem pump users, and increased slightly at 4 months/decreased at 6 months in non-Tandem users. The Basal-IQ system increased device satisfaction and reduced diabetes impact in all users in the first 2 months of use, and satisfaction was sustained over 6 months, with small fluctuations.

High absorption large-mode area step-index fiber for tandem-pumped high-brightness high-power lasers

A short absorption length ytterbium (Yb)-doped large-mode area (LMA) fiber is presented as a step forward to mitigate the stern problem of nonlinear scatterings in a tandem pumping scheme adopted for high-power fiber laser. The short absorption length was realized by incorporating high Yb concentration in the fiber core. Furthermore, by replacing the inherent silica cladding with a Ge-doped cladding, we were able to obtain low core numerical aperture (NA) and negate the detrimental effect of index-raising by high Yb concentrations. This overcomes the long-standing limitation in step-index Yb-doped fibers (YDFs) where high cladding absorption inevitably results in high NA, thus hampering single-mode operation. We report an LMA ( ∼ 575 μm 2 ) YDF with NA of 0.04 and absorption of 27 dB/m at 976 nm—both traits promote power scaling of single-mode tandem pumped fiber lasers. To our knowledge, this is the highest cladding absorption attained in a low-NA step-index fiber to date. An all-fiber tandem-pumped amplifier was built using only ∼ 14 m of the YDF. The amplifier delivered a near-Gaussian beam ( M 2 ∼ 1.27 ) at 836 W output power (pump power limited) with a high slope efficiency of ∼ 83 % . Thanks to the short length and the tandem pumping, no indication of limiting factors such as stimulated Raman scattering, photodarkening, and transverse mode instability was observed.

An Analysis of 2019 FDA Adverse Events for Two Insulin Pumps and Two Continuous Glucose Monitors.

US Food and Drug Administration adverse event data for 2019 were analyzed for two insulin pumps and two continuous glucose monitors (CGMs). The analyses were selective-they were guided by the text described in the adverse events. They included (1) percent using auto mode for the Medtronic 670G pump, (2) distributions of hyper and hypo glucose values for Medtronic and Tandem pumps, (3) a Parkes error grid for Dexcom CGM vs glucose meter when the complaint was inaccuracy, and (4) the most frequent events for Abbott Freestyle. We found that for the 670G pump, there were more hypo events when auto mode was on than when auto mode was off. With Dexcom CGMs, users complained about inaccurate result when most results were in the B zone. With the Abbott Freestyle, the most frequent adverse event was an allergic skin reaction.

Investigation of photodarkening in tandem-pumped Yb-doped fibers

Investigation of photodarkening (PD) in Yb-doped fibers tandem-pumped at 1018 nm is reported. For a homemade Yb-doped aluminosilicate double-clad fiber (YADF), the transmitted power of a 633 nm probe beam is reduced by 2.4% over 2 hours for the tandem pumping configuration at 1018 nm, which is significantly smaller than 33.3% for a laser diode (LD) pumping at 976 nm. A tandem-pumped Yb fiber amplifier also shows a much smaller decrease in the amplified output power over time than a LD-pumped Yb fiber amplifier. Based on fluorescence spectra of the YADF, we can not only associate PD of the YADF to intrinsic oxygen deficiency centers or Tm3+ impurities but also confirm the impact of the excited Yb3+ ion density on PD. The benefits of the tandem pumping in a high-power Yb fiber laser system will be discussed.

Real-World Improvements in Hypoglycemia in an Insulin-Dependent Cohort With Diabetes Mellitus Pre/Post Tandem Basal-Iq Technology Remote Software Update

Software updatable insulin pumps, such as the t:slim X2 pump from Tandem Diabetes Care, enable access to new technology as soon as it is commercialized. The remote software update process allows for minimal interruption in therapy compared to purchasing a new pump; however, little quantitative data exist on the software update process or on pre/post therapeutic outcomes. We examined real-world usage and impact of a remote software updatable predictive low-glucose suspend (PLGS) technology designed to reduce hypoglycemic events in people with insulin-dependent diabetes. Approximately 15,000 U.S. Tandem pump users remotely updated their t:slim X2 software to Basal-IQ PLGS technology since its commercial release. We performed a retrospective analysis of users who uploaded at least 21 days of pre/post PLGS update usage data to the Tandem t:connect web application between August 28, 2018, and October 21, 2019 (N = 6,170). Insulin delivery and sensor-glucose values were analyzed per recent international consensus and American Diabetes Association guidelines. Software update performance was also assessed. Median software update time was 5.36 minutes. Overall glycemic outcomes for pre and post software update showed a decrease in sensor time <70 mg/dL from 2.14 to 1.18% (-1.01; 95% confidence interval &lsqb;CI], -0.97, -1.05; P<.001), with overall sensor time 70 to 180 mg/dL increasing from 57.8 to 58.5% (0.64; 95% CI, 0.04, 1.24; P<.001). These improvements were sustained at 3, 6, and 9 months after the update. Introduction of a software updatable PLGS algorithm for the Tandem t:slim X2 insulin pump resulted in sustained reductions of hypoglycemia. ADA = American Diabetes Association; CGM = continuous glucose monitoring; CI = confidence interval; PLGS = predictive low-glucose suspend; SG = sensor glucose; T1D = type 1 diabetes; T2D = type 2 diabetes; TIR = time-in-range.

Influence of Bragg reflection of chirped tilted fiber Bragg grating on Raman suppression in high-power tandem pumping fiber amplifiers.

The key remaining technological challenge to the realization of further power scaling for high-power fiber laser systems is overcoming the stimulated Raman scattering (SRS) effect. In past years, chirped and tilted fiber Bragg gratings (CTFBGs) have been demonstrated to be a simple and effective way to suppress SRS in high-power fiber amplifiers. However, the weak reflection at the Bragg wavelength could be strongly amplified, which not only limits the power and efficiency but also degrades the beam quality. We report here, for the first time to the best of our knowledge, the influence of the residual Bragg reflection of CTFBGs on SRS suppression in high-power fiber laser systems. Two groups of CTFBGs with different Bragg reflection wavelengths are fabricated and used for the comparison experiments. Test results show that the CTFBGs of longer Bragg wavelengths have a better suppression effect, in particular, at a higher power level. By further moving the Bragg wavelength of a CTFBG out of the Raman gain spectral range, a better suppression effect and a promotion in laser efficiency could be achieved, which is very useful for further power scaling.

195-OR: Safety and Performance of the Tandem T:slim X2 with Control-IQ Automated Insulin Delivery System in Preschoolers, Age 2-6 Years Old

Glycemic control is particularly challenging for young children with T1DM. We studied the Tandem Control-IQ AP system (CIQ) in children ages 2-5.9 years old during 48hr of supervised outpatient hotel/Airbnb use (SH) followed by 3 days of at home use (H). A minimum of 48hr Tandem standard pump therapy at home (B) preceded the SH phase. Meals and snacks were chosen by parents, without restrictions, and boluses were estimated per parents’ routine. While on closed-loop, all participants were remotely monitored by study staff. There were at least 30 minutes of exercise each day of SH phase. Twelve participants with &amp;gt;3 months of T1D, mean age 4.7±1y, A1C 7.3±0.8%, weight 19.3±3.1kg were enrolled at 3 sites. All were using sensor augmented pumps before entry, with or without automation. All participants completed the study with no adverse events. Outcomes are reported below. CIQ improved mean glucose and TIR without an increase in hypoglycemia during the SH phase; at home CIQ improved all hypoglycemia outcomes as well as TIR, with a tendency towards a better mean glucose. All overnight outcomes were further improved. The Tandem Control IQ system was safe and significantly improved glycemic control in these young children in both the supervised hotel/Airbnb and the home setting. Disclosure L. Ekhlaspour: None. G.P. Forlenza: Advisory Panel; Self; Medtronic. Consultant; Self; Dexcom, Inc., Insulet Corporation, Tandem Diabetes Care. Research Support; Self; Abbott, Dexcom, Inc., Insulet Corporation, Medtronic, Tandem Diabetes Care. M. Schoelwer: Research Support; Self; Tandem Diabetes Care. M.D. DeBoer: Research Support; Self; Tandem Diabetes Care. L. Hsu: Stock/Shareholder; Self; Dexcom, Inc., Insulet Corporation, Tandem Diabetes Care. R.S. Kingman: None. E. Boranian: Other Relationship; Self; American Diabetes Association. E. Emory: None. R. Wadwa: Advisory Panel; Self; Eli Lilly and Company, Medtronic. Research Support; Self; Dexcom, Inc., Eli Lilly and Company, MannKind Corporation, Medtronic, Novo Nordisk Inc., Tandem Diabetes Care. B.A. Buckingham: Advisory Panel; Self; ConvaTec Inc., Medtronic. Research Support; Self; Beta Bionics, Inc., Dexcom, Inc., Insulet Corporation, Medtronic, Tandem Diabetes Care. M.D. Breton: Research Support; Self; Dexcom, Inc., Novo Nordisk A/S, Sanofi, Tandem Diabetes Care. Speaker’s Bureau; Self; Dexcom, Inc., Tandem Diabetes Care. Funding Tandem Diabetes Care

Substantiation of the methodology for modeling and calculating the optimal operating modes of a tandem pumping installation when mining uranium

The research was performed at the expense of grant fun-ding from the Ministry of Education and Science of the Republic of Kazakhstan under the project No. AR05131363 “Research and development of techniques and technologies for pumping-out productive solutions in bore-hole in-situ leaching using combined jet pumping installations” on priority “Systems for prospecting, exploration and development of mineral deposits”. The authors express their gratitude to L.A. Krupnik, Doctor of Technical Sciences, Professor of the Department of Technological Machines and Equipment at Satbayev University in the Republic of Kazakhstan for valuable advice and comments when conducting research and writing this paper.

Tandem-Pumped High-Power Narrow-Linewidth Fiber Laser Tunable From 1060–1090 nm

Tandem pumping is a promising technique for gaining higher power from ytterbium-doped fiber (YDF) lasers. However, the characteristics of tandem pumped laser light, especially their variation with the lasing wavelengths, were not thoroughly investigated. We investigated the characteristics with the first 1018-nm tandem-pumped high-power tunable YDF laser. The 1018-nm tandem pumping was not applicable in tunable fiber lasers before because its much-lower absorption requires compensation of long YDFs, which enhances destructive nonlinear effects as a barrel effect for tuning wavelengths. Here, the setup used a fiber ring-cavity as seed, which was much more cost-effective than conventional setups, and only three stages of amplification, of which the last stage was unidirectional tandem-pumped. By deliberate system design, it gained over 1-kW output powers at wavelengths tuning from 1060–1090 nm with ∼100-pm 3 dB linewidths and 79.4%∼85.6% slope efficiencies. Amplified spontaneous emissions (ASE) and stimulated Brillouin scattering (SBS) caused no limits for further scaling powers. Variations of spectra and beam qualities of the outputs with the tuning wavelengths were revealed in detail in the experiment. Drastically varying linewidths at ∼1062 and ∼1080 nm suggested complex evolution of the nonlinear effects with the pump light. This study offers not only an economic seed setup to high-power narrow-linewidth tunable fiber lasers, but detailed characteristics of laser amplified with 1018-nm pump in YDFs. The knowledge of the characteristics can usefully guide future design of high-performance tandem-pumped fiber lasers.

Study of flow ripple characteristics in an innovative two-dimensional fuel piston pump

To meet the requirements of fuel pumps with high efficiency, high power density, and low flow ripple for modern advanced aircraft, we hereby propose a two-dimensional piston pump (called 2D pump). A single piston with both rotary and linear motions is used to combine the flow distributing and volumetric varying functions together. The leakage spots are reduced to the clearance between the piston and the cylinder. As the radial force of the piston is balanced, a small piston clearance is selected to reduce leakage. Furthermore, a 2D tandem pump formed by two 2D pump units connected in series was introduced to eliminate the geometric flow ripple. The flow ripple characteristics were studied through analytical techniques, CFD numerical methods, and experiments. The results show that the flow ripple of 2D pump obtained by the measured pressure wave is 6.3%, while the pump has a high volumetric efficiency of up to 96% within a speed range of 1000–8000 r/min, indicating that reducing the leakage increases the average actual flow and reduces the flow ripple. Therefore, the proposed 2D pump is suitable for modern advanced aircraft.

Transverse mode instability, thermal lensing and power scaling in Yb3+-doped high-power fiber amplifiers.

Transverse mode instability (TMI) is compared to thermal lensing (TL) power threshold and used to derive power scaling limits in high-power fiber amplifiers. The TMI power threshold is shown to be ~65% of the TL one and dominates power scaling. In addition to commonly used limiting effects, we introduce a bend-induced mechanical reliability criterion, which limits the maximum allowable cladding diameter to ~600μm. This also results in the introduction of a critical pump brightness, the minimum required pump brightness at which the maximum signal power is achieved. The maximum achievable power depends primarily on the choice of pumping wavelength, amplifier gain and heat coefficient. Maximum signal powers of ~28kW to ~38kW, for diode pumping (λp = 976nm), and ~35kW to ~52kW, for tandem pumping (λp = 1018nm), are predicted for single-mode fiber amplifiers operating at signal wavelength λs = 1070nm, when the amplifier gain is increased from 10dB to 20dB. For an amplifier gain of 10dB, the maximum achievable signal power varies from 85kW to 25kW for tandem pumping and 35kW to 20kW for diode pumping, when the heat coefficient varies from 1% to 15% and 5.5% to 20%, respectively. The corresponding critical pump brightness varies from ~0.50 W/(μm2 sr) to ~0.14 W/(μm2 sr) for tandem pumping and ~0.25 W/(μm2 sr) to ~0.13 W/(μm2 sr) for diode pumping.

Beam Transmission Properties in High Power Ytterbium-Doped Tandem-Pumping Fiber Amplifier

This paper presented beam evolution in entire fiber laser from a more qualitative perspective. Specifically, the beam transmission properties under the condition of the disturbances of the refraction index, during the full length of active fiber in tandem pumping fiber amplifier were shown. The refractive index change was calculated considering the laser gain and the thermal effect. The simulations confirmed the superiority on beam transmission when employing the tandem-pumping configuration, which indicated that tandem-pumping fiber lasers might have better control on beam quality than direct-pumping fiber lasers for further power scaling. Moreover, to verify the model, we set a 1080-nm tandem-pumping fiber amplifier with an output power of 5.4 kW and the beam quality M 2 was measured to be 2.2. The experimental result implied a rationality of the model.

Modelling and validation of a roller-cam rail mechanism used in a 2D piston pump

The 2D principle is a new concept in hydrostatic pump design. It features a piston with a compound motion of both rotation and reciprocation to realize the functions of pumping and distribution. The compound motion is achieved through a specially designed roller-cam rail mechanism. Compared with conventional axial piston pumps, the 2D pump avoids sliding friction pairs completely and optimizes the force balanced conditions in the pump, making it easier to operate at the condition of higher speeds. The pump is also highly integrated for four cycles of suction and delivery for each round of the piston and thus has increased power density. Additionally, by applying a pair of pump units in tandem, the pump eliminates the structural flow ripple, caused by the limited number of pump elements, which exists in traditional pumps. The performance of the proposed 2D pump is highly dependent upon the motion conversion mechanism, especially the roller-cam rail mechanism. A mathematical model of the cam rail is developed and compared with its experimental counterpart to demonstrate its precision. Then, the performance of the piston and the no-load flow characteristics of the tandem pump are tested and analyzed to show the effectiveness of the roller-cam rail mechanism and the viability of the tandem pump. Although the curves of no-load flow characteristic of the tandem pump include a lot of clutter, by analyzing the frequency spectrogram of the curves of flow and revolving speed, they can be smoothed by applying a band-pass filter to remove that clutter. For comparison, the flow ripple in the experimental and simulation results of the tandem pump is smaller than that in simulation results of the traditional piston pump at low pressure. Both the theoretical analysis and experimental results indicate that the surface of the cam rail is precise and the pump has the potential advantage of eliminating sliding friction pairs and flow ripple.

Effective suppression of stimulated Raman scattering in half 10 kW tandem pumping fiber lasers using chirped and tilted fiber Bragg gratings

The average power of fiber lasers has been scaled deeply into the kW regime in the past years. However, stimulated Raman scattering (SRS) is still a major factor limiting further power scaling. Here, we have demonstrated for the first time, to the best of our knowledge, the suppression of SRS in a half 10 kW tandem pumping fiber amplifier using chirped and tilted fiber Bragg gratings (CTFBGs). With specially self-designed and manufactured CTFBGs inserted between the seed laser and the amplifier stage, a maximum SRS suppression ratio of >15 dB in spectrum is observed with no reduction in laser efficiency. With one CTFBG, the effective output power is improved to 3.9 kW with a beam quality M2 factor of ∼1.7 from 2; with two CTFBGs, the effective laser power reaches 4.2 kW with an increasing ratio of 20% and an M2 factor of ∼1.8, and further power improvement is limited by the power and performance of the 1018 nm pump sources. This work provides an effective SRS suppression method for high-power all-fiber lasers, which is useful for further power scaling of these systems.

Design and Clinical Evaluation of the Interoperable Artificial Pancreas System (iAPS) Smartphone App: Interoperable Components with Modular Design for Progressive Artificial Pancreas Research and Development.

There is an unmet need for a modular artificial pancreas (AP) system for clinical trials within the existing regulatory framework to further AP research projects from both academia and industry. We designed, developed, and tested the interoperable artificial pancreas system (iAPS) smartphone app that can interface wirelessly with leading continuous glucose monitors (CGM), insulin pump devices, and decision-making algorithms while running on an unlocked smartphone. After algorithm verification, hazard and mitigation analysis, and complete system verification of iAPS, six adults with type 1 diabetes completed 1 week of sensor-augmented pump (SAP) use followed by 48 h of AP use with the iAPS, a Dexcom G5 CGM, and either a Tandem or Insulet insulin pump in an investigational device exemption study. The AP system was challenged by participants performing extensive walking without exercise announcement to the controller, multiple large meals eaten out at restaurants, two overnight periods, and multiple intentional connectivity interruptions. Even with these intentional challenges, comparison of the SAP phase with the AP study showed a trend toward improved time in target glucose range 70-180 mg/dL (78.8% vs. 83.1%; P = 0.31), and a statistically significant reduction in time below 70 mg/dL (6.1% vs. 2.2%; P = 0.03). The iAPS system performed reliably and showed robust connectivity with the peripheral devices (99.8% time connected to CGM and 94.3% time in closed loop) while requiring limited user intervention. The iAPS system was safe and effective in regulating glucose levels under challenging conditions and is suitable for use in unconstrained environments.

Bendable large-mode-area fiber with a non-circular core.

We investigate mode-area-scaling and bending performances of a Yb-doped large-mode-area fiber with an elongated non-circular core. Such fiber can be bent in the plane of its short axis to suppress bending effects, such as mode area reduction and mode profile distortion. Meanwhile, the other orthogonal axis can be stretched for mode area scaling. Calculations show that for fibers with the same mode area, the higher the aspect ratio between the long axis and short axis, the less sensitive the fiber will be to bending effects. However, mode area scaling is limited by the increased beat length (BL) between the fundamental mode (FM) and the second-order mode, leading to mode degeneracy at higher aspect ratios. Within the 100mm BL, the FM area is scalable to 3000 μm2 in a bent fiber. To facilitate FM operation, we study mode-selective gain through confined doping. Thanks to the small bending distortions, the confined-doping approach works well in the bent large-mode-area fiber. In addition, the advantage of tandem pumping is also discussed in terms of preferential modal gain. A non-circular core fiber with a 41μm short axis and 120μm long axis was fabricated in-house. We evaluated the fiber in a linear laser cavity pumped by a 975nm laser diode. The maximum output power obtained was 191W, with slope efficiency of approximately 67% with respect to launched pump power. The output signal has good beam qualities with M2 of ∼1.5 and ∼3.1, respectively, along the short and long axis.

Efficient Ho:CaF2 laser intracavity-pumped by a Tm:LuAG laser in-band pumped at 1.6 µm

In this paper we demonstrate an efficient intra-cavity pumped Ho:CaF2 laser based on a tandem in-band pumping scheme for the first time. The laser diode at 1.6 µm was employed to pump a Tm:LuAG crystal. At an incident laser diode pump power of 9.5 W, the in-band pumped Tm:LuAG laser realizes a maximum output power of 2.3 W and a slope efficiency of 33.4%. With the same incident pump power, a maximum output power of 1.5 W at 2085 nm was achieved with a slope efficiency of 24.2% in the Ho:CaF2 laser intra-cavity pumped by the Tm:LuAG laser. The beam quality factor of the Ho:CaF2 laser at the maximum output level was measured to be 1.3 and 1.2 in the horizontal and vertical directions, respectively.

656 W Er-doped, Yb-free large-core fiber laser.

A continuous-wave erbium-doped ytterbium-free fiber laser generates a record-breaking pump-power-limited output power of 656W at ∼1601 nm when cladding pumped by 0.98μm diode lasers. The slope efficiency was 35.6% with respect to launched pump power, and the beam quality factor (M2) was ∼10.5. This M2 value excludes a fraction ∼25% of the power that emerged from the cladding, which we attribute in part to mode coupling between the 146μm core and 700μm inner cladding. Whereas these parameters are adequate for in-band tandem pumping of Tm-doped fiber lasers, we predict that an output power of over 1kW is possible through pumping with state-of-the-art 0.98μm diode lasers, even with a smaller core that allows for improved beam quality.