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Selective photothermolysis has limitations in efficacy and safety for dermal targets. We describe a novel concept using scanned focused laser microbeams for precise control of dermal depth and pattern of injury, using a 1550 nm laser that generates an array of conical thermal zones while minimizing injury to the epidermis. To characterize the conical thermal zones in vivo and determine safe starting parameters to transition to a second phase to explore potential clinical indications. A focused toroidal (ring) laser beam was delivered through a cold sapphire window, sparing epidermal injury in a central zone. Pulse energy, lesion depth, density, and energy delivery were titrated in ex vivo human skin and subsequently on the backs of 21 human subjects. Histology showed microscale patterns of thermal injury, which varied predictably with laser parameters. Time-course healing through histology and skin surface imaging demonstrated the ability of the device to deliver high energies without sequelae. Clinical data are currently being collected to further explore the safety and efficacy of the device. The 1550 nm laser with focal point technology enables precise control of lesion depth while simultaneously sparing a large portion of the epidermis, lowering the risk of adverse effects. [ABSTRACT FROM AUTHOR]

Information on forest structure is vital for sustainable forest management. Currently, airborne LiDAR remote sensing has been well established as an effective tool to characterize the structure of canopies and forest inventory variables. Radiometry and geometry are highly intertwined in LiDAR remote sensing of forest vegetation and phenology influences the geometric-optical properties of deciduous and evergreen trees causing seasonal variation in LiDAR observations. This variation may be considered as a nuisance or exploited in for example tree species identification. Airborne LiDAR data are also influenced by sensor functioning, acquisition settings, scan geometry and the atmosphere. Reliable estimation of subtle phenological effects calls for data in which the impact of the external factors is minimal. We experimented with such data and explored LIDAR waveforms (WFs) in boreal trees in winter, early summer and late summer. Our objectives were to i) assess the match of the multitemporal LiDAR data for observing true changes in vegetation; ii) quantify the influence of phenology in deciduous and evergreen trees; iii) study the effect of varying scan zenith angle (SZA) and canopy age on WF features in different phenostates; iv) assess the temporal feature correlation in individual living and dead standing trees. A WF-recording pulsed LiDAR sensor unit operating at the wavelength of 1550 nm was used in repeated acquisitions. WF attributes such as energy, peak amplitude and echo width were derived for each pulse and were localized vertically to crown, understory and ground components. Silver and downy birch, black alder, European aspen, Siberian larch, Scots pine, Norway spruce and dead standing spruce formed our strata. Results showed that phenology caused more variation in WF features of deciduous trees compared to evergreen conifers. Deciduous trees displayed substantial between-species variation that was linked with differences in branching pattern, leaf orientation and bark reflectance. Pine displayed a possible winter-early summer anomaly in canopy backscattering that may be linked with changes in foliage clumping or with the role of stamens in early summer trees. Trees displayed positive temporal correlation in WF features and correlations were the strongest in evergreen and deciduous conifers and decreased with time. SZA had minor influence on WF features whereas age exercised a strong effect on many features with parallel variation between species and phenostates. Structural changes following death, i.e. 'aging' changed the geometric WF features of dead standing trees. Our results provide new insights for enhancing tree species identification by using WF LiDAR and for LiDAR time-series analysis of vegetation. • Multitemporal waveform (WF) LiDAR data with high radiometric and geometric match. • Effects of phenology on WF features at 1550 nm investigated. • Phenological effects are larger in deciduous than in evergreen trees. • WFs vary seasonally also in evergreen trees, but geometric WF features are stable. • WF features of dead standing trees change over time. [ABSTRACT FROM AUTHOR]

• The ternary sulfide of NaYS 2 was adopted as a novel host for high-efficient UCL. • Er3+ single-doped NaYS 2 was designed to avoid luminescence quenching via CTS. • Breakthrough upconversion brightness and efficiency were achieved in the NaYS 2 :Er3+. • The mechanisms for high-efficiency UCL and color stability were studied. Optimizing the host lattice is the most efficient strategy to break through the intrinsic characteristic of low efficiency up-conversion luminescence (UCL). In principle, ternary sulfide, e.g. NaYS 2 , is an ideal UCL host matrix due to its low phonon energy and highly asymmetrical crystal structure. However, it was found that the low lying S2-→Yb3+ charge transfer state (CTS) existing in the ternary sulfide material severely quenches the UCL under 980 nm excitation, which generally employs Yb3+ ion as the conventional sensitizer. Herein, we design Er3+ single-doped NaYS 2 phosphors for highly efficient UCL under 1550 nm excitation. This novel NaYS 2 :Er3+ phosphor excited at 1550 nm exhibits a 94-fold enhancement of UCL intensities compared to that of conventional NaYS 2 :Yb3+,Er3+ under 980 nm excitation. More encouragingly, compared to the commercial β-NaYF 4 :Yb3+,Er3+ phosphors, the UCL efficiency and brightness of NaYS 2 :Er3+ excited at 1550 nm are twice that of β-NaYF 4 :Yb3+,Er3+ excited at 980 nm. Such extraordinary efficient UCL is accomplished by taking advantages of the intrinsic low phonon energy (279 cm−1) of the NaYS 2 host and the highly asymmetrical trigonal crystal system. Furthermore, in the Er3+ single-doped NaYS 2 system, the S2-→Er3+ CTS lies at a high state of ≈34500 cm−1, which will not quench the efficient UCL from Er3+ ions. The large absorption cross-section at 4I 13/2 energy level (high response to 1550 nm radiation) and long lifetime of the metastable state of 4I 9/2 also contribute to the population of the emission levels (2H 11/2 /4S 3/2). These findings provide a new class of host materials for achieving highly efficient UCL. [ABSTRACT FROM AUTHOR]

Efficiently up-conversion luminescence can be achieved by replacing the traditional sensitizer Yb 3+ ions with Er 3+ ions in LaVO 4 host under 1550 nm excitation. In contrast to other up-conversion luminescence materials, such as Y 2 O 2 S:Er 3+ , Y 2 O 3 :Er 3+ , YOCl:Er 3+ , which exhibit red emission, LaVO 4 :Er 3+ samples present an abnormal green emission under 1550 nm excitation. Excited state absorption is the dominating up-conversion luminescence mechanism at low doping concentrations of Er 3+ , whereas energy transfer up-conversion predominates at high concentrations of Er 3+ . Infrared thermal imaging is adopted to investigate the thermal effects of LaVO 4 :Er 3+ sample under 1550 nm irradiation. It shows a rapid heating process within 1 ∼ 5 s and LaVO 4 :0.21Er 3+ sample yields a temperature rising of ΔT = 66.46 °C under 1550 nm irradiation (207 mW) within 60 s. Therefore, the temperature sensor based on up-conversion luminescence of Er 3+ ions 2 H 11/2 / 4 S 3/2 thermally coupled levels produced significant measurement errors at low temperatures because of the thermal effects and non-uniform temperature of the incident light spot area. [ABSTRACT FROM AUTHOR]

Red emission with high color purity in Y 2 Ti 2 O 7 :Yb 3+ ,Er 3+ material is successfully obtained by high-concentration doping of Yb 3+ and Er 3+ under 980 and 1550 nm excitation based on the special layer structure of pyrochlore crystal. It shows that Yb 3+ ion content and excitation wavelength greatly influence the red emission percent of total up-conversion luminescence intensity of Y 2 Ti 2 O 7 :Yb 3+ ,Er 3+ . Y 2 Ti 2 O 7 :Yb 3+ ,Er 3+ shows much better red color purity at 1550 nm excitation than at 980 nm. Furthermore, the co-doping of Yb 3+ ions considerably boosts the red emission under 980 or 1550 nm pumping with different luminescence mechanisms compared with Y 2 Ti 2 O 7 :Er 3+ sample. The red emission percent of total up-conversion luminescence intensity gradually increases with the increment of Yb 3+ concentration at both excitation sources. The red-to-green emission ratio of the sample is 6.97 (980 nm) and 23.26 (1550 nm) when the Yb 3+ content is 30 mol%. [ABSTRACT FROM AUTHOR]

• Multi-component fluoride nanocrystal Pb x Na y-n Li n Y z F 2x+y+3z+3m : Er3+ m with a response in the 1.5 μm band was synthesized by the low temperature combustion synthesis method. • When the concentration of Li+ ion is 2.07 mol%, the up-conversion luminescence intensity is obviously improved. • The hypothetical physical mechanism model for the luminescence intensity of Li+ ion enhanced materials was confirmed. • Innovatively established a dual-fuel system, and systematically analyzed the heat release characteristics of each fuel system, and prepared nanocrystals with high luminous intensity and fine particles. A 1.5 μm multi-component fluoride nanocrystal Pb x Na y-n Li n Y z F 2x+y+3z+3m : Er3+ m was synthesized by the low temperature combustion synthesis (LCS) method. On the basis of the orthogonal experiment and optimization experiment, Li+ ion was introduced into the matrix and the dual-fuel system was established, and the up-conversion luminescence intensity was enhanced by changing the matrix composition and improving the process methods. The results show that when the concentration of Li+ ion is 2.07 mol%, the fuel consumption in the dual-fuel system is 2.2 stoi., 0.7 stoi., the up-conversion luminescence intensity is obviously improved. The structure and morphology of samples were analyzed by the X-ray diffraction (XRD) and scanning electron microscopy (SEM), and a schematic model of physical mechanism for the luminescence intensity of Li+ ion enhanced materials was confirmed. The exothermic characteristics of the dual-fuel system were analyzed by the differential scanning calorimetry and thermogravimetric analysis (DSC-TGA). The influence of the introduction of Li+ ion and the dual-fuel system on the luminescence intensity was discussed in detail. [ABSTRACT FROM AUTHOR]