The rapid advancement of ^9Be^+ ion-based quantum computing is creating a high demand for scalable and specialized laser sources. For this purpose, laser radiation at 313 nm is necessary which is generated by frequency doubling of 626 nm laser emission. Laser sources in this spectral region lack simplicity and need to be miniaturized. We carry out a systematic improvement of room temperature semiconductor laser structures emitting at 626 nm. They are based on a GaInP single quantum well embedded in AlGaInP grown on GaAs. We first investigate the structure theoretically and determine its limits and optima. We select the three most promising quantum well combinations, which are grown by metal-organic vapor-phase epitaxy. Furthermore, we fabricate broad-area lasers with dimensions of 1600 m × 100 m. All structures show laser operation around 626 nm. We are able to achieve a threshold current density of 721 A/cm2, a slope of 0.384 mW/mA and total maximum output power of 708 mW under pulsed excitation. Based on these results, we believe that quantum computing focusing on beryllium ions will highly benefit from these results.

We review approaches for the manipulation (flattening) of thermal profiles within broad-area-lasers for improved efficiency and brightness, illustrated with 1-cm wide, kW-class, 9xx-nm bars. Exemplary device structures yield 2° (~18%) reduced beam divergence (95% power) and 5%-point efficiency gain at 0.8kW compared to reference bars.

Increased optical output power $P_{\text{opt}}$ from single broad area GaAs-based diode lasers is demanded for material processing, with higher $P_{\text{opt}}$ and cost reduction in $/\mathrm{W}$ enabled by using devices with ever-wider apertures [1]. Device structures suitable for single emitters with very large footprints $(> 4\ \text{mm}^{2})$ that sustain high $P_{\text{opt}}$ and conversion efficiency $\eta_{\mathrm{E}}$ without exciting unwanted optical modes (e.g. ring oscillations) are also of interest as an enabling technology for high power photonic crystal surface emitting lasers [2]. We report here progress in broad area diode lasers with resonator length $L=4$ mm and emitting aperture of $W=1200\ \mu \mathrm{m}$ with wavelength $\lambda$ = 915 nm. An $\eta_{\mathrm{E}}$ -optimized highly vertically asymmetric epitaxial design was used, taken from [3]–[5], and grown using metal organic vapor phase epitaxy (MOVPE). To suppress lateral (e.g. ring) oscillations, following [6], the lateral current path was patterned periodically, with 9 $\mu \mathrm{m}$ current blocking stripes on a 29 $\mu \mathrm{m}$ period. Here, the lateral pattern was realised with a buried-regrown-implant-structure, BRIS, following [3]–[5], see schematic in Fig. 1a. After the first growth the p-side cladding and waveguide layers of the laser are implanted with $\mathrm{O}^{+}$ ions to block current flow, periodically within the stripe, and broadly outside the stripe, then the wafer is regrown to complete the structure. In contrast to approaches based on etched p-n junctions [7], the wafer is still planar, minimizing growth defects, and lateral refractive index steps are minimized. Thick (800 nm) highly-doped p-type material was regrown after implantation. The residual thickness is $d_{\text{res}}\sim 600$ nm (offset between current blocking and active region), sufficient to suppress 70 … 80% of lateral current spreading at the device edges [7]. After regrowth, single emitters lasers were fabricated using standard techniques, facet passivated (ZnSe) then coated for front and rear facet reflectivity of $R_{\mathrm{F}}=1.8\%$ and $R_{\mathrm{R}}=98\%$ . The devices were mounted with AuSn in a miniaturised $(6\times 8\times 3.2\ \text{mm})$ CuW -sandwich package. Fig. 1 b presents electro-optic characteristics at $25^{\circ}\mathrm{C}$ heatsink temperature, $P_{\text{opt}}$ is measured with a calibrated thermoelectric detector, in-pulse-power with a fast photodetector, voltage $U$ in 4-terminal configuration and far field with a goniometer. In quasi-continuous wave QCW test (10 Hz, 500 $\mu \mathrm{s})$ , peak $\eta_{\mathrm{E}}=P_{\text{opt}}/IU=69\%$ (current, I) at $P_{\text{opt}}=68\ \mathrm{W}$ and $\eta_{\mathrm{E}}=52\%$ at $P_{\text{opt}}=200\ \mathrm{W}$ are seen. In CW test, $P_{\text{opt}}=45\ \mathrm{W}$ at $\eta_{\mathrm{E}}=56\%$ , thermally limited (thermal resistance $R_{\text{th}}=1.1$ K/W, obtained from the wavelength shift). The CW lateral far-field is also shown in Fig. 1, and is $\leq 12^{\circ}$ (95% power) up to $P_{\text{opt}}=40\ \mathrm{W}$ , corresponding to a beam quality $M^{2} < 250($ for $W=1200\ \mu \mathrm{m})$ , suitable for low-loss coupling into a 1 mm NA 0.22 fiber. No evidence is seen for ring oscillations. Improved $\eta_{\mathrm{E}}$ is obtained at comparable $P_{\text{opt}}$ referred to earlier studies ([8]: $W=800\ \mu \mathrm{m},L=3.6$ mm, $\eta_{\mathrm{E}}=52\%$ at $P_{\text{opt}}=50\ \mathrm{W})$ , in spite of the use of $10\times$ smaller heatsink ([8]: 25 $\mathrm{x}\ 25$ mm). In Fig. 1 c, two far field peaks are observed up to $P_{\text{opt}}=30\ \mathrm{W}$ , indicating the strong contribution of a super-mode with 29 $\mu \mathrm{m}$ period, which is sustained to higher $P_{\text{opt}}$ than previously reported [9] (super-mode to $P_{\text{opt}}=5 \ \mathrm{W}$ , periodic implant in contact for $d_{\text{res}} > 1\ \mu \mathrm{m}$ ), promising for realising high brightness device and resonator configurations [2], [10], [11].

AlxGa1_xAs-based lasers are typically used for emission wavelengths of 730 nm and above, e.g. using GaAsyP1_y quantum wells (QW), while lasers emitting below 700 nm rely on (AlxGa1_x)0.5In0.5P in combination with GaxIn1_xP quantum wells. The 690 nm to 730 nm spectral range could basically be addressed from both ends, but this is practically limited by the tensile (GaAsyP1_y) and compressive (GaxIn1_xP) strains necessary to reach this spectral range. In this work we report on our efforts in growing GaxIn1_xAsyP1_y for emission around 700 nm. As this quaternary material is prone to phase separation, we first studied the growth of lattice matched bulk layers. We show that phase separation is kinetically triggered and can be avoided by staying below a critical thickness. Compressively strained GaxIn1_xAsyP1_y QWs can be grown if strain is kept below a critical value. The quantum well strain, which drives kinetic phase separation, is adjusted by a combination of X-ray diffraction and elec-troluminescence evaluated by modelling of the transition energies. Finally, we present LIV characteristics of uncoated edge-emitting broad area lasers (100 x 1000 mu m2) reaching output powers up to P = 900 mW at I = 2 A for emission wavelengths ranging from 690 to 726 nm.

We present high-power GaAs-based broad-area diode lasers with a novel variant of the enhanced self-aligned lateral structure ‘eSAS’, having a strongly reduced lasing threshold and improved peak conversion efficiency and beam quality in comparison to their standard gain-guided counterparts. To realize this new variant (eSAS-V2), a two-step epitaxial growth process involving in situ etching is used to integrate current-blocking layers, optimized for tunnel current suppression, within the p-Al 0.8 GaAs cladding layer of an extreme-triple-asymmetric epitaxial structure with a thin p-side waveguide. The blocking layers are thus in close proximity to the active zone, resulting in strong suppression of current spreading and lateral carrier accumulation. eSAS-V2 devices with 4 mm resonator length and varying stripe widths are characterized and compared to previous eSAS variant (eSAS-V1) as well as gain-guided reference devices, all having the same dimensions and epitaxial structure. Measurement results show that the new eSAS-V2 variant eliminates an estimated 89% of lateral current spreading, resulting in a strong threshold current reduction of 29% at 90 μ m stripe width, while slope and series resistance are broadly unchanged. The novel eSAS-V2 devices also maintain high conversion efficiency up to high continuous-wave optical power, with an exemplary 90 μ m device having 51.5% at 20 W. Near-field width is significantly narrowed in both eSAS variants, but eSAS-V2 exhibits a wider far-field angle, consistent with the presence of index guiding. Nonetheless, eSAS-V2 achieves higher beam quality and lateral brightness than gain-guided reference devices, but the index guiding in this realization prevents it from surpassing eSAS-V1. Overall, the different performance benefits of the eSAS approach are clearly demonstrated.

Les patients atteints de cancer du pancréas présentent souvent une perte de poids et de masse musculaire. L'objectif de cette étude était d'évaluer le rôle de la sarcopénie sur les résultats postopératoires après pancréatectomie oncologique. Cette étude rétrospective inclut des patients opérés d'un cancer du pancréas entre 01/2015 et 12/2018. L'index musculaire squelettique (IMS ; quantité musculaire) a été mesuré au niveau de la troisième vertèbre lombaire (L3) sur des CT scans préopératoires. La sarcopénie a été définie sur la base de seuils préétablis, et son impact sur la morbidité postopératoire et la durée de séjour a été évalué. Les facteurs de risque indépendants pour des complications majeures (Clavien ≥ IIIa) ont été identifiés par analyse uni- et multivariée. Au total, 136 patients ont été inclus et 76 (56 %) étaient sarcopéniques. Ces patients étaient plus âgés (69 vs 64 ans, p = 0,004) et avaient un IMC plus faible (23 vs 26 kg/m2, p < 0,001). La durée médiane de séjour et le taux de complications majeures étaient comparables (16 vs 17 jours, p = 0,397, et 38 vs 40 %, p = 1,000). Les facteurs de risque indépendants de complications majeures identifiés étaient la fistule pancréatique (OR 6,811, < 0,001) et l'hémorragie postopératoire (OR 40,379, p < 0,001). L'augmentation de l'atténuation radiologique des muscles squelettiques (ARMS, qualité musculaire) était un facteur de protection (OR 0,909, p = 0,008). La sarcopénie préopératoire n'avait pas d'impact sur la morbidité et la durée de séjour après pancréatectomie oncologique. Cependant, la qualité musculaire était plus faible chez les patients avec complications majeures et semblait prévaloir sur la quantité musculaire.

Introduction: According to the Barcelona Clinic Liver Cancer (BCLC) staging system, liver resection (LR) is recommended for early-stage (BCLC-A) hepatocellular carcinoma (HCC) but is not a standard treatment for intermediate-stage (BCLC-B). The study aim was to assess surgical and oncological outcomes of LR in BCLC-A and B patients. Methods: This retrospective multicenter study included HCC patients with LR between January 2010 and December 2020 in four tertiary referral centers. Surgical outcomes of LR were assessed according to the Clavien classification. The overall survival (OS) and disease-free survival (DFS) were calculated by the Kaplan-Meier method. Results: Among 614 patients included, 564 were classified as BCLC-A and 50 as BCLC-B. Despite a higher clinically relevant complication (≥3b) rate in BCLC-B group (20.0 vs 8.0%, p=0.009), the incidence of overall complications (56.0 vs 41.5%, p=0.053) and mortality (0.0 vs 1.6%, p=1.000) did not differ between the two groups. Length of stay was significantly longer in BCLC-B group (12.9 vs 9.8 days, p<0.001). DFS was similar between BCLC-A and BCLC-B group (1-, 3-, and 5-year DFS: 66%, 24%, and 15% vs 67%, 35%, and 24%; p=0.766). OS was longer in BCLC-A group (1-, 3-, and 5-year OS of 93%, 70%, and 39% vs 83%, 48%, and 32%; p=0.015). Conclusions: LR for early and intermediate-stage HCC is safe providing careful preoperative selection. Despite better OS in BCLC-A patients, results of surgery in BCLC B patients were acceptable. These results will help to refine the BCLC staging system, which is probably too restrictive for surgery.

Purpose: Preoperative sarcopenia has been proposed as predictor for adverse outcomes. The aim of this study was to assess the role of preoperative sarcopenia on postoperative outcomes in patients undergoing liver resection. Methods: This retrospective mono-center study included consecutive patients undergoing liver resection between January 2014 and March 2020. Skeletal muscle index (SMI) was measured at the level of the third lumbar vertebra (L3) on preoperative computed tomographic (CT) scans. Preoperative sarcopenia was defined based on pre-established cut-offs, and its impact on postoperative morbidity and length of stay (LOS) was assessed. Major complications were defined as Clavien grade ≥ 3b. Results: A total of 355 patients were included and 212 (59.7%) were determined to have preoperative CT-based sarcopenia. Patients with sarcopenia were significantly older (63.5 years) and had lower BMI (23.9 kg/m2) than those without sarcopenia (59.3 years, p<0.01 and 27.7 kg/m2, p<0.01, respectively). There were significantly more men and ASA score ≥ 3 in the sarcopenic group (65.6 vs 49.9%, p<0.01, and 24.5 vs 7.0%, p<0.01, respectively). There was no difference in LOS and major complications rates between the 2 groups (8 vs 8 days, p=0.753 and 11.2 vs 11.3%, p=1.00, respectively). Conclusion: Sarcopenia had no impact on major complications and LOS in patients undergoing liver surgery. Therefore, its preoperative assessment may not provide clinically important information for all comers and should not be part of the standard preoperative workup.

A diode laser module emitting 1.4 kW optical in-pulse power near 780 nm optimized for high (≥ 10%) duty-cycle operation in a micro-channel free design is presented. With full collimation, a beam quality with a nearly symmetric M2 of 205 × 295 (vertical × horizontal direction) for a wide range of pulse widths is found.

Studies balancing modal gain (confinement) and facet reflectivity in high power 940 nm lasers using extreme-triple-asymmetric epitaxial designs enable > 70% efficiency at 12 W output and low temperature sensitivity. Insight into carrier losses that limit device performance are discussed.

We present a bipolar-cascade distributed-Bragg reflector laser emitting near 905nm with a high slope efficiency. The wavelength stabilization by a surface grating was achieved by placing three active regions and two tunnel junctions into the nodes and antinodes, respectively, of the third-order vertical waveguide mode.

Epitaxial design development in 780 nm diode lasers for lower loss and lower bias-driven leakage enables increases in power (to 210 W) and conversion efficiency (to 57% at 60 W) in high repetition-rate (10 ms, 10 Hz), wide-aperture (1200 μm) devices ready for use in pumping high-energy-class thulium-doped solid-state lasers.

Einleitung Die Versorgungsqualität von Einwanderern und ihren direkten Nachkommen (E&dN) mit Diabetes ist unbefriedigend (1), Ursachen hierfür sind z.B. der oft niedrigere sozio-ökonomischer Status, Sprachdefizite kulturelle und religiöse Einflüsse (2,3). Eine schlechtere Versorgungsqualität könnte sich auch auf die gesundheitsbezogene Lebensqualität (gbLQ) von Kindern und Jugendlichen (KuJ) mit Diabetes mellitus Typ 1 (T1D) auswirken.

Introduction: Quality of care for immigrants and their direct descendants (I/DD patients) with diabetes is unsatisfactory. Causes include socioeconomic status, language deficits, and cultural influences. Poorer quality of care may also affect health-related quality of life (HRQOL) in children and adolescents (C/A patients) with type 1 diabetes mellitus (T1D). Method: A total of 219 young native and immigrant patients aged six and older and their parents were interviewed between 2017 and 2020. Direct descendants were defined as having at least one immigrant parent. Two variants of the KINDL (R) questionnaires were used, yielding scores from 0 to 100. Results: No statistical differences were found between the I/DD and native C/A groups for overall HRQOL. However, I/DD participants assessed their HRQOL as significantly higher than did native participants. External perception from parents scored significantly higher than self-perception in both groups. The I/DD group showed higher HbA1c levels than the native C/A group. Conclusion: The I/DD T1D group showed similar subjective health-related and better disease-specific QOL compared to the native C/A group. Even so, half of all HbA1c values lay outside the 7.5 % target, even in the native group. HbA1c values in the I/DD group were half a percentage point worse, possibly due to poorer care structure. This had no apparent relationship to low quality of life.

GaAs based high power broad area lasers are the most efficient source of optical energy and are used in many industrial applications. Despite considerable improvement in power and efficiency in recent years, further improvement is needed due to the high demand from industry. We review here progress in vertical epitaxial layer design, showing how higher performance is enabled by migrating from asymmetric large optical cavity (ASLOC) designs to the newly developed extreme-triple-asymmetric (ETAS) vertical structure. Building on earlier studies at 940 nm, we focus on gain-guided lasers that have operating wavelength 970 nm, have 90 μm stripe width and 4 mm resonator length. We can emphasize the positive impact of epitaxial layer design, without need for advanced lateral structures. We show how design improvement increases conversion efficiency ηΕ at 12 W output power from 56% to 66%, whilst peak (saturation) power increases from Popt = 14 to 19 W in continuous wave (CW) mode for p-down single emitters on CuW carriers (thermal resistance 3 K/W). Progress in epitaxial design also leads to smaller lateral beam parameter product (BP Plat) at higher bias, leading to lateral brightness Popt/BPPlat < 3 W/mm × mrad. Specifically, in these most recent ETAS structures, by design BPPlat increases more slowly with self-heating, and this leads directly to lower BPPlat at high bias. We will also review options for further increased performance, include efforts to understand and improve BPPlat, which is also limited by a non-thermal ground level BPP0 (here ∼ 1 mm × mrad).

Mid-infrared (MIR) solid state lasers based on thulium and holmium-doped crystals are of increasing interest in applications in medicine, material processing and particle physics. Thulium-doped lasers can be efficiently pumped at wavelengths around 780 nm and diode laser pumps with high conversion efficiency and high intensity are sought at this wavelength. Diode lasers integrated in laser stacks suitable for high duty cycle pumping are of particular interest for high energy class applications, especially when realizable without need for the additional cost and reliability hazard of microchannel cooling. However, high efficiency and reliable power is more challenging to realize at 780 nm than around 940...980 nm, due to limitations on the capability of the available semiconductor materials. Progress is therefore presented here in the design, realization and test of 780 nm pump sources suitable for high energy class pump applications, using GaAs-based TM-polarized diode lasers. We show how power per device can be increased from 4 W for conventional single emitters (90...100 mu m) up to 60 W at high duty cycle (10%) and long pulse length (10 ms) for high brightness large aperture emitters (with 1200 mu m aperture, equivalent to around 500 W per bar), at the cost of reduced operating efficiency (from 60 to 50%). We show progress in integrating these large aperture emitters into novel passively (macro-channel) edge-cooled stacks, that are then suitable for use in pumping high energy class Th:YAG laser systems.

We present 1 kW-emitting diode-laser bars optimized for higher conversion efficiency and smaller far-field angle Θ95% power content), as needed, e.g., for solid-state laser pumping (wavelength λ= 940 nm). First, we review the latest high-efficiency designs, targeting reduced series resistance Rs and less power saturation and then discuss developments for high brightness via tailored chip-internal heat distribution. Recent results include conversion efficiency η of 66% and far-field width Θ 95%= 8.8° at 1 kW (thermal resistance Rth ~ 0.02 K/W), as well as 64% efficiency and 10.8° divergence at Rth ~ 0.05 K/W, equivalent to CW operation with advanced packaging.

Broad-area diode lasers with increased brightness and efficiency are presented, which are fabricated using an enhanced self-aligned lateral structure by means of a two-step epitaxial growth process with an intermediate etching step. In this structure, current-blocking layers in the device edges ensure current confinement under the central stripe, which can limit the detrimental effects of current spreading and lateral carrier accumulation on beam quality. It also minimizes losses at stripe edges, thus lowering the lasing threshold and increasing conversion efficiency, while maintaining high polarization purity. In the first realization of this structure, the current block is integrated within an extreme-triple-asymmetric epitaxial design with a thin p-doped side, meaning that the distance between the current block and the active zone can be minimized without added process complexity. Using this configuration, enhanced self-aligned structure devices with 90 µm stripe width and 4 mm resonator length show up to 20% lower threshold current, 21% narrower beam waist, and slightly higher (1.03×) peak efficiency in comparison to reference devices with the same dimensions, while slope, divergence angle and polarization purity remain almost unchanged. These results correspond to an increase in brightness by up to 25%, and measurement results of devices with varying stripe widths follow the same trend.

A 780nm diode laser pump source is presented that uses passive side-cooling to enable Kilowatt-class output at >10% duty cycle (10ms, 10Hz). Beam quality is M2<360 (BPP<90mm-mrad) and initial reliability test extrapolates over GShot-class lifetime.

Over the last decades considerable efforts have been undertaken to increase output power, conversion efficiency and beam quality of GaAs based broad-area diode lasers by optimizing the epitaxial layer design as well as the lateral device structure. In this respect the reduction of current spreading is essential to meet future requirements for high power diode lasers. Lateral current spreading enhances the accumulation of carriers at the edges of the active region defined by the contact stripes which results in additional leakage current and lasing of higher-order lateral modes, reducing efficiency and beam quality. We address this issue by implementing a tailored deep implantation scheme as a current block, implanting O and Si, using two-step epitaxy. This work elucidates the effects of buried current apertures, fabricated by Si and O doping at different doses on the optoelectronic properties of broad area lasers. It will be shown how deep O-and Si-implantation significantly suppresses current spreading, leading to lower threshold currents and higher efficiency.