Search results for "Upconversion"

Parametric conversion in micrometer and sub-micrometer structured ferroelectric crystals by surface poling

2012

We report on recent technological improvements concerning nonlinear patterning of lithium niobate and lithium tantalate in the micrometer and submicrometer scales using surface periodic poling for ferroelectric domain inversion. The fabricated samples were employed for frequency doubling via quasiphase-matching both in bulk and guided wave geometries, including forward and backward configurations and wavelength conversion in bands C and L. We also investigated short-period quasiperiodic samples with randomly distributed mark-to-space ratios.

Upconversion luminescent nanoparticles in physical sensing and in monitoring physical processes in biological samples.

2015

The most frequently used strategy for sensing is based on the emission variation of a photoactive system and it can be classified as chemical or physical depending on its response to either a chemical or a physical stimulus. There are a large number of luminescent nanomaterials that respond to chemical species, but comparatively, with the exception of temperature sensing, to date there are few examples showing the capacity of photoactive nanosystems responsive to physical stimuli, such as magnetic and electric fields, high radiation energy, tension/pressure, viscosity, etc, and very few of them comprise upconversion nanoparticles (UCNPs). These nanomaterials consist of an inorganic matrix d…

Study of upconversion in highly Er-doped photonic crystal fibers through laser-transient dynamics

2014

The dynamic response after pump switch-on of a 980 nm pumped-ring laser based on an active photonic crystal fiber with an Er3+ ion concentration of ≈1020 ions cm−3 was registered. Then a numerical fitting procedure of a theoretical model was followed to the experimental values of the relaxation oscillation parameters as a function of the input pump power. Non-radiative energy-transfer mechanisms’ coefficients: homogeneous upconversion coefficient (Cup) and critical radii for upconversion (Ru) and migration (Rm) were determined. The calculated best-fit coefficients (Cup = 1.3  ×  10−24 m3 s−1, Ru = 9  ×  10−10 m, Rm = 13  ×  10−10 m) were compared to those obtained with other steady-state an…

Photovoltaics: Photonic Crystal-Driven Spectral Concentration for Upconversion Photovoltaics (Advanced Optical Materials 4/2015)

2015

Lengthening the Lifetime of Common Emissive Probes to Microseconds by a Jigsaw‐Like Construction of NIR‐Responsive Nanohybrids

2020

Excited-state absorption in erbium-doped silica fiber with simultaneous excitation at 977 and 1531 nm

2009

We report a study of the excited-state absorption (ESA) in erbium-doped silica fiber (EDF) pumped at 977 nm, when the fiber is simultaneously excited by signal radiation at 1531 nm. We show, both experimentally and theoretically, that ESA efficiency at 977 nm gets strongly enhanced only in the presence of signal power. Experimentally, this conclusion is supported through the detection of upconversion emission, a “fingerprint” of the ESA process, and through the measurements of the EDF nonlinear transmission coefficient for the pump wavelength, which is sensitive to the ESA value. It is shown that the experimental data are precisely modeled with an advanced five-level Er3+ model developed fo…

Phase transitions and upconversion luminescence in oxyfluoride glass ceramics containing Ba4Gd3F17 nanocrystals

2017

This is the peer reviewed version of the following article: G. Krieke, A. Sarakovskis, R. Ignatans, J. Gabrusenoks "Phase transitions and upconversion luminescence in oxyfluoride glass ceramics containing Ba4Gd3F17 nanocrystals", Journal of the European Ceramic Society, 2017, 37 (4), which has been published in final form at https://www.sciencedirect.com/science/article/abs/pii/S0955221916306768 This article may be used for non-commercial purposes in accordance with Elsevier Terms and Conditions for Sharing and Self-Archiving.

Ultrafast Relaxation Dynamics of Osmium−Polypyridine Complexes in Solution

2013

We present steady-state absorption and emission spectroscopy and femtosecond broadband photoluminescence up-conversion spectroscopy studies of the electronic relaxation of Os(dmbp)(3) (Os1) and Os(bpy)(2)(dpp) (Os2) in ethanol, where dmbp is 4,4'-dimethyl-2,2'-biypridine, bpy is 2,2'-biypridine, and dpp is 2,3-dipyridyl pyrazine. In both cases, the steady-state phosphorescence is due to the lowest (MLCT)-M-3 state, whose quantum yield we estimate to be <= 5.0 x 10(-3). For Os1, the steady-state phosphorescence lifetime is 25 ns. In both complexes, the photoluminescence excitation spectra map the absorption spectrum, pointing to an excitation wavelength-independent quantum yield. The ultrafa…

Temperature and impurity concentration effects on upconversion luminescence in LaInO3 doped with Er3+

2016

In this paper a novel method for synthesis of LaInO3:Er3+ is reported and upconversion luminescence properties of the synthesized material at different temperatures (9–300 K) are studied. The samples were prepared by co-precipitation and subsequent heat treatment of lanthanum, indium and erbium hydroxides. It is shown that the excitation at 980 nm leads to a strong green upconversion luminescence in the material. At the concentrations above 0.1 mol. % of Er3+ the energy transfer upconversion mechanism of the luminescence becomes evident. Further increase of Er3+ content in the material leads to higher red-to-green upconversion luminescence intensity ratio. The mechanisms responsible for the…

Observation of Ligand-Centred Fluorescence and Intramolecular Relaxation at Sub-Vibrational Time Scales

2016

Using broadband photoluminescence upconversion, we observe fluorescence from a high-lying ligand-centred state in Ir(ppy)3. This result allows us to clock the electronic relaxation to the lowest 3MLCT state, occurring at sub-vibrational time scales.