Large Emission Bandwidth Research Articles

Polarized spectral properties and 2.3 µm laser performance of the Tm:YVO4 crystal

The polarized spectral properties and ∼2.3 µm high-power continuous-wave laser operation of Tm3+-doped yttrium orthovanadate crystal (Tm:YVO4) are reported. For the 3H4 → 3H5 transition, the stimulated-emission cross-section σSE is 1.01 × 10−20 cm2 at 2276 nm corresponding to a large emission bandwidth of 52 nm (for π-polarization). Pumped by a 794 nm laser diode, the 1.5 at.% Tm:YVO4 laser delivered 5.52 W at 2.29 µm with a slope efficiency of 19.9%, a laser threshold of 8.70 W, and a linear laser polarization (π). The Tm laser operated on the cascade scheme (on the 3H4 → 3H5 and 3F4 → 3H6 transitions) which was mainly responsible for the observed high laser slope efficiency. We also report on the first passively Q-switched Tm:YVO4 laser at 2.3 µm by employing porous nano-grained cuprous selenide (PNG-Cu2Se) as a saturable absorber. The shortest pulse duration and the highest single pulse energy amounted to 706 ns and 3.65 µJ, respectively, corresponding to a pulse repetition rate of 62.8 kHz.

Multifunctional aggregation-based fluorescent probe for visualizing intracellular calcium dynamic fluctuations.

Calcium ion (Ca2+) is an indispensable second messenger in living organisms. The impaired Ca2+ handling can induce many diseases. In this paper, we developed a simple and effective method to encapsulate a coumarin-based Ca2+ probe ((E)-2-hydroxy-N'-((7-hydroxy-2-oxo-2H-chromen-8-yl)methylene)-2-phenylacetohydrazide, CPM) into nanoparticles (NPs), and CPM NPs with blue fluorescence were obtained, whose maximum excitation and maximum emission wavelengths were characterized at 365nm and 450nm, respectively. The CPM NPs show significant fluorescence enhancement toward Ca2+ over other metal ions, with a limit of determination (LOD) of 0.04μM. To optimize the optical property of the NPs, CPM and curcumin, which were introduced as the Förster resonance energy transfer (FRET) donor and acceptor, respectively, were co-encapsulated, and bright green CPM@Cur NPs with large stokes shift and narrow emission band width were constructed. Due to their low cytotoxicity and excellent stability, CPM NPs and CPM@Cur NPs were further successfully used to discriminate the primary aortic smooth muscle cells isolated from mice with abnormal Ca2+ homeostasis from their littermate controls. It is worth noting that CPM@Cur NPs exhibit stronger fluorescence signal and diminished background interference, which make them have great potential in the Ca2+ monitoring during biological processes. This strategy opens a new way to synthesize NPs with high brightness and has a potential application prospect in composite sensing and intracellular imaging. CPM@Cur NPs are developed and applied in biological sensing and intracellular Ca2+ imaging, as well as discriminating the cells with abnormal calcium homeostasis.

Transparent Nd,Y-Codoped Ca1-xSrxF2 glass-ceramic with large emission bandwidth tailored by a controllable spontaneous precipitation under supersaturated state

A highly transparent Nd,Y-codoped Ca1-xSrxF2 glass-ceramic with excellent optical properties was fabricated by the controllable spontaneous precipitation (CSP) under supersaturated state. The micron-sized Ca1-xSrxF2 crystal provides a favorable emission environment for Nd3+ ions. Meanwhile, the buffer ions Y3+ effectively addressed the fluorescence quenching originating from [Nd3+-Nd3+] clusters. The corresponding sample exhibited high transmittance (T@1053 nm = 83%), large absorption coefficient (9 cm−1@796 nm), intense 1.053 μm photoluminescence, large emission bandwidth (~32 nm), and moderate lifetime (167 μs), implying the glass ceramic would be powerful candidates for application in ultrashort pulse lasers. In addition, the sample also showed low phonon energy (IR-cut edge~4.5 μm), a low absorption coefficient of –OH (α-OH~1.0 × 10−4 cm−1), and high mid-infrared transmittance (T@2700 nm = 85.4%), which is expected to be applied in the field of mid-infrared.

Thermal and spectroscopic characteristics of disordered melilite Nd:BaLaGa3O7 crystal

1 at% Nd:BaLaGa3O7 disordered crystal has a large emission bandwidth of 32 nm at 1060 nm.

Luminescence of La0.2Y1.8O3 nanostructured scintillators.

For the first time, transparent La0.2Y1.8O3 nanostructured polycrystalline scintillators were fabricated by sintering nanoparticle powders at high temperatures and their scintillation properties are reported. La0.2Y1.8O3 is a host material that has never been investigated as scintillators for radiation detection. Our observations found that La0.2Y1.8O3 has an intense scintillation luminescence, a detection efficiency higher than that of YAG:Ce and a comparable energy resolution to NaI and CsI scintillators. In addition, La0.2Y1.8O3 is stable and has luminescence decay lifetime in the picosecond range which is favorable for radiation detection. The luminescence of La0.2Y1.8O3 has a large Stokes-shift and a large emission bandwidth, and the luminescence is highly temperature dependent. Different from most doped scintillators, the luminescence of La0.2Y1.8O3 is most likely from the self-trapped excitons. The discovery of La0.2Y1.8O3 scintillators opens a new door for the research of new materials for radiation detection.

Enhancement of 1.53 μm emission in erbium/cerium-doped germanosilicate glass pumped by common 808 nm laser diode.

Erbium-doped germanosilicate glasses with various cerium ions contents have been prepared. Optical absorption and 1.53 μm emission spectra were measured to characterize the spectroscopic performances of prepared samples. A detailed study of 1.53 μm spectroscopic properties was carried out when pumped by an 808 nm laser diode. Moreover, an energy level diagram and an energy transfer mechanism between Er3+ and Ce3+ were proposed to elucidate the enhanced 1.53 μm fluorescence. It is found that the prepared samples have optimal spectroscopic properties when the Ce3+ concentration is fixed to 0.5 mol. %. High spontaneous radiative transition probability (172.66 s(-1)), large effective emission bandwidth (74 nm), and emission cross section (9.49×10(-21) cm(2) indicate that 808 nm pumped Er3+/Ce3+ codoped germanosilicate glass might be a suitable material for a broadband optical amplifier.

Spectroscopic properties of Tm,Ho:CaYAlO4 single crystal

A Tm,Ho:CaYAlO4 single crystal was grown using the Czochralski (CZ) method. The absorption spectra, the fluorescence spectrum around 2 μm, the upconversion spectrum and energy‐transfer (ET) schemes between Tm3+ ions and Ho3+ ions have been studied. The crystal boule was free from cracks, inclusions and scattering centers. The broad FWHM of the 797‐nm absorption band (with E//c polarization is 19 nm and with E//a polarization is 18 nm), the large emission bandwidth (about 600 nm) and the intense ET from Tm3+ ions to Ho3+ ions make Tm,Ho:CaYAlO4 a promising media for tunable and ultrashort pulses.

Anomalous photoluminescence inBaS:Eu

The photoluminescence emission properties of $\mathrm{BaS}:\mathrm{Eu}$ powders have been studied. At room temperature, several weak emission bands related to impurities or intrinsic defects are observed in the visible part of the spectrum. The strongest emission band is situated mainly in the infrared with a peak emission wavelength of $878\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ and is related to ${\mathrm{Eu}}^{2+}$ centers. From the viewpoint of the large Stokes shift, the large emission bandwidth, and the temperature quenching profile, the ${\mathrm{Eu}}^{2+}$ emission in $\mathrm{BaS}:\mathrm{Eu}$ is totally different than what can be expected from the analogy with the similar materials $\mathrm{CaS}:\mathrm{Eu}$ and $\mathrm{SrS}:\mathrm{Eu}$. Hence the emission in $\mathrm{BaS}:\mathrm{Eu}$ is anomalous. Photoluminescence excitation and electron paramagnetic resonance spectra show that the incorporation of ${\mathrm{Eu}}^{2+}$ in $\mathrm{BaS}$ is not radically different from $\mathrm{SrS}:\mathrm{Eu}$ or $\mathrm{CaS}:\mathrm{Eu}$. The appearance of infrared emission is related to the position of the $5d$ excited level of ${\mathrm{Eu}}^{2+}$ relative to the conduction band of $\mathrm{BaS}$, which leads to autoionization of the ${\mathrm{Eu}}^{2+}$ centers upon $4{f}^{7}\text{\ensuremath{-}}4{f}^{6}5d$ excitation and the formation of impurity trapped excitons. The influence of trap levels was studied by thermoluminescence and a major trap with an activation energy of $0.51\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ was found. The thermal quenching behavior was evaluated as well.

GeO2–PbO–Bi2O3 glasses doped with Yb3+ for laser applications

Glasses of heavy metal oxide GeO2–PbO–Bi2O3 doped with different concentrations of Yb3+ were prepared as materials for IR emission. Absorption and fluorescence emission spectra were measured. The spectroscopic properties and laser parameters are calculated; the disagreement between the reciprocity method and Fuchtbauer–Ladenburg formula in calculations of Yb3+ emission cross-sections is discussed using the radiation trapping effect. GeO2–PbO–Bi2O3 glass doped with Yb3+ is a promising material for laser action at 1021nm, with properties similar to other known glasses (phosphate and tellurite laser glasses) used as active laser media; the high absorption cross-section (of 1.5×10−20 cm2) and the large emission bandwidth (of 70nm) are properties appropriate for short pulse generation.

Spectroscopic properties of lead fluoroborate and heavy metal oxide glasses doped with Yb 3+

A new glass of heavy metal oxide (25.0Bi 2O 3–57.0PbO–18.0Ga 2O 3 (mol%)) doped with Yb 3+ is presented and compared with lead fluoroborate glass (43.5H 3BO 3–22.5PbCO 3–34.0PbF 2 (mol%)), also doped with ytterbium. The interest in Yb 3+ for laser action and short pulse generation under diode pumping has been reported in the literature. Spectroscopic properties were studied for both glasses doped with 0.5 mol% of Yb 2O 3. The absorption cross-section of the heavy metal oxide glass is (2.20±0.15)×10 −20 cm 2 at the absorption peak wavelength of 968 nm and its emission cross-section is (0.75±0.05)×10 −20 cm 2 at the extraction wavelength of 1012 nm. A fluorescence effective linewidth of 86 nm and a fluorescence lifetime of 0.40 ms were measured. In the case of the lead fluoroborate glass used for comparison, these values change to (2.56±0.18)×10 −20 cm 2 (absorption cross-section), (1.07±0.08)×10 −20 cm 2 (emission cross-section at 1022 nm), 60 nm (fluorescence effective linewidth) and 0.81 ms (fluorescence lifetime). Calculations of the minimum pump intensity are also presented. Both have spectroscopic properties for laser applications that are similar to those of other known glasses (phosphate and tellurite laser glasses) used as active laser media. The large emission bandwidth measured for the heavy metal oxide is of interest for tunable lasers.

Évolution des techniques de micromesures thermiques au travers de quelques applications

The thermoelectric sensors made at present in our laboratory have junction dimensions from a few micrometers to 0.5 μm. Two techniques are used: welding of ultra-thin wires and vacuum deposition (PVD). Two applications related to the first one will be presented: the detection of periodic field of temperature for photothermal microscopy and acoustic resonator characterization. In the latter, the comparison of simultaneous pressure and temperature will lead us to improve the knowledge of thermoacoustic phenomena. The deposition technique allows us to create either simple thermoelectric couples, multiple as thermopiles; or heat (and light) flow sensors. Our work is presented in that field, with the development of a laser light sensor designed to image its light profile for large emission bandwidth and power densities. Finally, the description followed by an example of application is shown in the case of the heat flow measurement between a laminar gaseous flow and a wall. By comparison, we show that the use of such sensors could be worthwhile to replace the usual temperature sensors in the estimation of the heat transfer coefficient at the gas-wall boundary.

N-(9-acridinyl)-bromoacetamide—A powerful reagent for phase-transfer-catalyzed fluorescence labeling of carboxylic acids for liquid chromatography

Phase-transfer-catalyzed esterification of various carboxylic acids has been carried out on a microanalytical scale with a new reagent, N-(9-acridinyl)-bromoacetamide, in aqueous/organic two-phase systems. The procedure gives esters showing very high fluorescence intensity in acid solution. The large Stokes' shift (>120 nm) means that a low background can be achieved even when using a large emission bandwidth. These derivatives show very good chromatographic behavior on reversed-phase liquid chromatographic columns with the use of aqueous acetonitrile, containing 0.2% of phosphoric acid, as the mobile phase. Detection limits ( S N = 2 ) as low as 10 fmol can be obtained under optimal conditions.