Efficient 1.7 µm pumping of 2 µm thulium lasers.

Solid-state 2 µm lasers based on thulium-doped active media Tm:YAG, Tm:YAP, and Tm:YLF were investigated under 1.7 µm resonant diode pumping. In contrast with standard 0.8 µm pump wavelength, a high slope efficiency was achieved, up to 80% in the case of Tm:YAP and Tm:YLF, nearing a quantum limit without relying on Tm3+-Tm3+ cross-relaxation energy transfer. Low thermal load allowed for stable continuous-wave operation with good beam quality and output power up to 6 W (Tm:YAG, Tm:YLF), and 8 W (Tm:YAP).

Alexandrite microchip lasers.

We report on a continuous-wave alexandrite (Cr3+:BeAl2O4) microchip lasers operating at 680.4 nm and 749.5 nm laser wavelengths. Microchip resonators were realized by dielectric mirrors directly deposited on the alexandrite crystal surfaces. InGaN laser diode providing up to 3.5 W of the output power at ∼445 nm wavelength was used as a pump source. More than 210 mW and 570 mW of the laser radiation have been extracted from the microchip laser systems at 680.4 nm and 749.5 nm wavelengths, respectively. The corresponding slope efficiencies related to absorbed pump power were 15 % and 39 %.

Long-pulse 4.4-4.6 µm laser oscillations of Fe2+ ions in a Zn1-xMnxSe (x = 0.3) crystal pumped by a 1940 nm Tm fiber laser through Cr2+ → Fe2+ energy transfer.

Millisecond-pulse laser operation of Fe2+ ions at 78 K is demonstrated in the Zn1-xMnxSe:Fe2+,Cr2+ (x=0.3) crystal under a Tm fiber 1940 nm laser pumping through a Cr2+→Fe2+ energy transfer process for the first time, to the best of our knowledge. The laser slope efficiency was 1% with respect to absorbed pumping energy at 1940 nm. The laser central wavelength shift from 4450 nm at 78 K up to 4510 nm at 110 K was observed. Tunability from 4350 up to 4670 nm at 78 K was achieved using an intracavity tuning element.

Influence of the pumping wavelength on laser properties of Fe2+ ions in ZnSe crystal.

ZnSe:Fe2+ active laser crystal properties at different excitation wavelengths (2.94 and 4.1 µm) were investigated, and noticeable variations of the fluorescence spectra shape and their maxima positions, as well as changes in decay times, were observed. A stepwise shift of the laser oscillation wavelength from 4.7 µm at 2.94 µm pumping to 4.95 µm at 4.1 µm pumping was achieved at room temperature.

Line-tunable Er:GGAG laser.

In this Letter, for the first time, to the best of our knowledge, a pulse and CW laser based on an Er-doped Gd3Ga2.7Al2.3O12 (Er:GGAG) active medium emitting laser radiation at 2.8 µm are presented. With the longitudinal diode pumping, the maximal output energy of 4.9 mJ and slope efficiency of 13.5% in the pulse regime were reached. Using the birefringent MgF2 plate, the line tunability of Er:GGAG at several spectral bands of 2800-2822 nm, 2829-2891 nm, and 2917-2942 nm were obtained.

Thulium fiber pumped tunable Ho:CaF2 laser.

The paper reports the first room-temperature operation of the in-band pumped Ho:CaF2 laser. A set of Ho:CaF2 crystals varying in holmium concentrations (from 0.1 up to 2.5 mol. % of HoF2), synthesized using the Bridgeman technique, was used for lasing and related spectroscopy investigation. A pulsed 1.94 µm thulium fiber laser system was used for Ho:CaF2 longitudinal pumping. For 1.5 mol. % of Ho:CaF2, the maximal wavelength tunability (from 2073 to 2114 nm) and output energy (1.6 mJ at 2113 nm) were obtained for absorbed pumping energy 34 mJ. Without the tuning element, the slope efficiency up to 30% in respect to absorbed power was obtained using this sample.

Pulmonary dysfunction in patients after cervical spinal cord injury: serial follow-up measurement within the first year post-injury.

OBJECTIVES: Respiratory complications are most common cause of morbidity/mortality in patients with cervical spinal cord injury (cSCI) due to respiratory muscle weakness and lower diaphragm position resulting in limited availability of inspiration, reduced thorax mobility and limited forced expiration. Differences in respiratory dysfunctions (RDs) in patients with motor complete versus incomplete cSCI were assessed. DESIGN: Prospective longitudinal study, serial measurement. SETTING: University hospital and ambulatory departments. METHODS: Twenty two patients with acute cSCI were recruited. Neurological level of injury and severity according to ISNCSCI were used as criteria for recruitment. Patients were divided into two groups - motor complete and incomplete. Standardized pulmonary function tests (PFT) were used - spirometry and respiratory muscle strength (RMS) measurement. Motor score of key muscles assessments for upper (UEMS) and lower (LEMS) limbs were used. Tests were performed in 5 measurement sessions starting on (medians) 14.5 days (M1), then 6.7 weeks, 3.2 months, 6.3 months and 1.0 year (M5). RESULTS: Significant differences in measurement sessions M2-M5 between groups in forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), expiratory reserve volume (ERV), maximal static inspiratory/expiratory pressures (MIP, MEP) and UEMS were proved. Consequently, prominent differences in courses of particular parameters were found. No intergroup changes in UEMS were found during study. CONCLUSIONS: Obvious differences in parameters of spirometry, respiratory muscles and limb muscles strength between motor complete and incomplete group were found. Carefull monitoring of RDs by functional assessments (i.e., PFT and UEMS/LEMS tests) within one year after SCI seems to be clinically important.

Pr:YAlO3 laser generation in the green spectral range.

A continuous-wave 37 mW Pr:YAlO

Dysprosium-doped PbGa2S4 laser generating at 4.3 µm directly pumped by 1.7 µm laser diode.

In this Letter, we demonstrate the pulsed and CW operation of the Dy:PbGa(2)S(4) laser directly pumped by the 1.7 µm laser diode. In the pulsed regime (pulse duration 5 ms; repetition rate 20 Hz), the maximum mean output power of 9.5 mW was obtained with the slope efficiency of 9.3% with respect to the absorbed pump power. The generated wavelength was 4.32 µm, and the laser beam cross section was approximately Gaussian on both axes. Stable CW laser generation was also successfully obtained with the maximum output power of 67 mW and the slope efficiency of 8%. Depopulation of the lower laser level by 1.7 µm pump radiation absorption followed by 1.3 µm upconversion fluorescence was demonstrated. These results show the possibility of construction of the compact diode-pumped solid-state pulsed or CW laser generating at 4.3 µm in the power level of tens mW operating at room temperature.

Diode-pumped Er:CaF2 ceramic 2.7 µm tunable laser.

Spectroscopic and laser properties of a newly developed high optical quality Er:CaF2 hot-formed ceramic were investigated. Under pulsed 968 nm laser diode pumping, the mid-infrared (2.7 µm) radiation was obtained with a slope efficiency of 3%. Laser tunability was reached using a birefringent filter and the laser tuning range of 118 nm, from 2687 up to 2805 nm, was demonstrated. The maximal output energy reached was 0.48 mJ at 2730 nm for the absorbed pumping energy 34 mJ.

The effect of abdominal bracing on respiration during a lifting task: a cross-sectional study.

BACKGROUND: Abdominal bracing is a maneuver widely used by rehabilitation specialists and sports trainers to improve spinal stability. This study aimed to investigate how lifting tasks with and without abdominal bracing affect the respiratory function of the diaphragm. METHODS: M-mode ultrasonographic assessment of diaphragmatic motion combined with spirometry was performed on 31 healthy adults. Participants were asked to breathe continuously whilst lifting a load with spontaneous abdominal muscle contraction (natural loaded breathing) and abdominal bracing (AB loaded breathing). RESULTS: Pearson's correlations revealed strong correlations between ultrasonography and spirometry measures (p < 0.001) for all types of breathing: tidal breathing (r = 0.709, r2 = 0.503), natural loaded breathing (r = 0.731, r2 = 0.534) and AB loaded breathing (r = 0.795, r2 = 0.632). Using paired-samples t-tests, the natural loaded breathing ultrasonography revealed more caudal diaphragm positions during inspiration (p < 0.001) but not during expiration (p = .101). Spirometry demonstrated lower lung volumes (L) at the end of inspiration and expiration (p < 0.001), with no changes in total lung volume (p = 0.06). The AB loaded breathing ultrasonography revealed more caudal diaphragm positions during inspiration (p = 0.002) but not during expiration (p = 0.05). Spirometry demonstrated lower lung volumes at the end of inspiration (p < 0.001), expiration (p = 0.002), and total lung volumes (p = 0.019). CONCLUSION: This study demonstrated that abdominal bracing performed during a lifting task reduces lung volume despite an increase in diaphragmatic motion. Diaphragm excursions strongly correlate with lung volumes even under postural loading. TRIAL REGISTRATION: The study was prospectively registered on 8 April 2021 at ClinicalTrials.gov with identification number NCT04841109.

Postural-respiratory function of the diaphragm assessed by M-mode ultrasonography.

OBJECTIVES: The diaphragm changes position and respiratory excursions during postural loading. However, it is unclear how it reacts to lifting a load while breath-holding or breathing with simultaneous voluntary contraction of the abdominal muscles (VCAM). This study analyzed diaphragm motion in healthy individuals during various postural-respiratory situations. METHODS: 31 healthy participants underwent examination of the diaphragm using M-mode ultrasonography, spirometry, and abdominal wall tension (AWT) measurements. All recordings were performed simultaneously during three consecutive scenarios, i.e., 1. Lifting a load without breathing; 2. Lifting a load and breathing naturally; 3. Lifting a load and breathing with simultaneous VCAM. RESULTS: Using paired-samples t-tests, lifting a load without breathing displaced the diaphragm's expiratory position more caudally (P < .001), with no change noted in the inspiratory position (P = .373). During lifting a load breathing naturally, caudal displacement of the diaphragm's inspiratory position was presented (P < .001), with no change noted in the expiratory position (P = 0.20) compared to tidal breathing. Total diaphragm excursion was greater when loaded (P = .002). Lifting a load and breathing with VCAM demonstrated no significant changes in diaphragm position for inspiration, expiration, or total excursion compared to natural loaded breathing. For all scenarios, AWT measures were greater when lifting a load (P < .001). CONCLUSION: In healthy individuals, caudal displacement and greater excursions of the diaphragm occurred when lifting a load. The postural function of the diaphragm is independent of its respiratory activity and is not reduced by the increase in AWT.

Symptomatic preterm infants suffer from lung function deficits, regardless of bronchopulmonary dysplasia.

BACKGROUND: The long-term respiratory consequences for children with bronchopulmonary dysplasia (BPD) are well known. However, there is little emphasis on monitoring preterm infants without BPD. Few studies have explored the lung function status of infants with the symptoms of chronic lung disease of prematurity (CLD). OBJECTIVE: To evaluate functional lung deficits in preterm infants with CLD, and to assess the perinatal determinants of diminished lung function. METHODS: In our cross-sectional study, 132 preterm infants with symptomatic CLD underwent infant pulmonary function testing (iPFT) at a median post-term age of 0.9 years. The iPFT included bodypletysmography, compliance measurement, tidal breath analysis, and rapid thoracoabdominal compression. The relationships between the respective z scores of the iPFT parameters and perinatal characteristics, postnatal treatment, and BPD status were investigated. RESULTS: Seventy-three patients (55.3%) were born before the 28th week of gestation, and 92 (69.7%) met the BPD criteria. Functional deficits were detected in 85.8%. The obstructive ventilatory pattern was more prevalent than restrictive (36.3 vs. 12.4%, p < 0.001). Infants with restriction had lower birth weight (BW) and required a longer duration of oxygenotherapy. In a univariate model, the lung function correlated with the duration of invasive mechanical ventilation, gestational week, and BW. In a general linear model, BPD status was not an additional determinant of the iPFT results. CONCLUSION: IPFT may reveal significant functional deficits in preterm infants with CLD even without BPD. The current symptoms and perinatal factors may be more important determinants of functional deficits than the BPD status itself.

Mid-Infrared Laser Generation of Zn1-xMnxSe and Zn1-xMgxSe (x ≈ 0.3) Single Crystals Co-Doped by Cr2+ and Fe2+ Ions-Comparison of Different Excitation Wavelengths.

Two different mid-infrared (mid-IR) solid-state crystalline laser active media of Cr2+, Fe2+:Zn1-xMnxSe and Cr2+, Fe2+:Zn1-xMgxSe with similar amounts of manganese or magnesium ions of x ≈ 0.3 were investigated at cryogenic temperatures for three different excitation wavelengths: Q-switched Er:YLF laser at the wavelength of 1.73 µm, Q-switched Er:YAG laser at 2.94 µm, and the gain-switched Fe:ZnSe laser operated at a liquid nitrogen temperature of 78 K at ∼4.05 µm. The temperature dependence of spectral and laser characteristics was measured. Depending on the excitation wavelength and the selected output coupler, both laser systems were able to generate radiation by Cr2+ or by Fe2+ ions under direct excitation or indirectly by the Cr2+→ Fe2+ energy transfer mechanism. Laser generation of Fe2+ ions in Cr2+, Fe2+:Zn1-xMnxSe and Cr2+, Fe2+:Zn1-xMgxSe (x ≈ 0.3) crystals at the wavelengths of ∼4.4 and ∼4.8 µm at a temperature of 78 K was achieved, respectively. The excitation of Fe2+ ions in both samples by direct 2.94 µm as well as ∼4.05 µm radiation or indirectly via the Cr2+→ Fe2+ ions' energy transfer-based mechanism by 1.73 µm radiation was demonstrated. Based on the obtained results, the possibility of developing novel coherent laser systems in mid-IR regions (∼2.3-2.5 and ∼4.4-4.9 µm) based on AIIBVI matrices was presented.

Influence of Y2O3 Content on Structural, Optical, Spectroscopic, and Laser Properties of Er3+, Yb3+ Co-Doped Phosphate Glasses.

The influence of the addition of Y2O3 on the structural, spectroscopic, and laser properties of newly prepared Er, Yb-doped strontium-sodium phosphate glass was investigated. While the addition of Y2O3 has a small influence on the absorption spectra and fluorescence lifetime, it has a strong impact on the emission cross-section and on OH- content. The glasses were used as the active medium for diode-pumped laser emitting at 1556 nm. The increase in Y2O3 content leads to a significant 35% increase in laser slope efficiency up to 10.4%, but at the expense of the substantial reduction of the wavelength tunability from 82 to 54 nm.

Effect of Waterjet Machining Parameters on the Cut Quality of PP and PVC-U Materials Coated with Polyurethane and Acrylate Coatings.

The article focuses on the machining of polymeric materials polypropylene (PP) and un-plasticized poly vinyl chloride (PVC-U) after surface treatment with polyurethane and acrylate coatings using waterjet technology. Two types of waterjet technologies, abrasive waterjet (AWJ) and waterjet without abrasive (WJ), were used. The kerf width and its taper angle, at the inlet and outlet of the waterjet from the workpiece, were evaluated. Significant differences between AWJ and WJ technology were found. WJ technology proved to be less effective due to the creation of a nonuniform cutting gap and significant burrs. AWJ technology was shown to be more efficient, i.e., more uniform cuts were achieved compared to WJ technology, especially at a cutting head traverse speed of 50 mm·min-1. The most uniform kerf width or taper angle was achieved for PP + MOBIHEL (0.09°). The materials (PP and PVC-U) with the POLURAN coating had higher values of the taper angle of the cutting gap than the material with the MOBIHEL coating at all cutting head traverse speeds. The SEM results showed that the inappropriate cutting head traverse speed and the associated WJ technology resulted in significant destruction of the material to be cut on the underside of the cut. Delamination of the POLURAN and MOBIHEL coatings from the base material PP and PVC-U was not demonstrated by SEM analysis over the range of cutting head traverse speeds, i.e., 50 to 1000 mm·min-1.

Pr:YAlO(3) microchip laser.

A cw Pr:YAlO(3) microchip-laser operation in the near-IR spectral region is reported. A microchip resonator was formed by dielectric mirrors directly deposited on the Pr:YAlO(3) crystal surfaces. For active medium pumping, a GaN laser diode providing up to 1W of output power at approximately 448 nm was used. 139mW of laser radiation at 747nm wavelength has been extracted from the microchip-laser system. Slope efficiency related to the incident pumping power was approximately 25%.

Continuous-wave blue generation of intracavity frequency-doubled Pr:YAP laser.

We report the cw blue generation of Pr:YAP laser emission at room temperature, which has been achieved by intracavity frequency doubling of the near-IR-emitting Pr:YAP laser operating at a fundamental wavelength of 747 nm. For active medium pumping, a GaN laser diode providing up to 1 W of output power at approximately 448 nm was used. With beta barium borate crystal employed as a nonlinear medium, 12.3 mW of output power at 373.5 nm has been obtained.

Dysprosium-doped PbGa2S4 laser excited by diode-pumped Nd:YAG laser.

We realized a compact mid-IR room temperature operating Dy(3+):PbGa(2)S(4) laser, excited by a diode-pumped Nd:YAG laser at a wavelength of 1318 nm. The pumping laser was operating in pulsed mode with a pulse length of 4 ms and repetition rate of 20 Hz. Maximum pumping energy at a wavelength of 1318 nm was 15 mJ. Energy up to 90 µJ and mean output power of 1.8 mW was obtained at a wavelength of 4290 nm with a slope efficiency with respect to absorbed pumping energy better than 3%.

Cytokine gene polymorphisms and high-resolution-computed tomography score in idiopathic pulmonary fibrosis.

INTRODUCTION: Idiopathic pulmonary fibrosis (IPF) is a serious disease with unknown cause and the influence of cytokine gene polymorphisms is presumed in the etiology and pathogenesis of the disease. We used high-resolution computed tomography (HRCT) as a marker of disease stage and progression and compared the alveolar and interstitial score with IL-1, IL-4, IL-12, IL-1RA and IL-4RA cytokine gene polymorphisms. SUBJECTS AND METHODS: The IPF patients were all Caucasians from the Czech Republic and consisted of 20 females and 10 males, with a mean age of 65 years, range 36-85. The HRCT results were evaluated by an experienced viewer using the interstitial and alveolar score scales, which were based on the IPF HRCT description system from Gay SE, Kazerooni EA, Tows GB, Lynch JP, Gross BH, Cascade PN, et al. [Idiopathic pulmonary fibrosis. Predicting response to therapy and survival. Am J Respir Crit Care Med 1998;157:1063-72]. We evaluated the polymorphisms of cytokine genes utilizing a PCR with sequence-specific primers method. RESULTS: The HRCT alveolar score was more pronounced in IL-4 RA (+1902) AG heterozygotes. The HRCT interstitial score was less severe in the IL-12 (-1188) AA homozygotes. According to progression of the HRCT interstitial score, the CC homozygosity at IL-1 RA (mspa 111100), the AA homozygosity at IL-4 RA (+1902) and CC homozygosity at IL-4(+33) positions were more frequent in patients with stable disease compared to those with progressive disease. CONCLUSIONS: We assume from our data that the polymorphisms of IL-4, IL-4RA, IL-1RA and IL-12 genes (genes of cytokines with regulatory activity) might influence the phenotype of IPF as shown by measurable changes in HRCT investigations.