Beyond the partial light intensity imager: eliminating Moiré patterns

A partial light intensity imager (PLII) was proposed in our previous research for enhancing the dynamic range to 2.2x105 lx in strong light. Moiré patterns may occur, however, since the PLII employs both a liquid crystal display (LCD) and a charge-coupled device (CCD) camera as its key devices, which can be regarded as two gratings. This research calculates the fringe widths and spectra for both the LCD and the CCD, and analyzes the relationship between the fringe width and the applied voltage on each pixel of the LCD. According to the theoretical results, we find that changing the rotational angle of the liquid crystal (LC) molecule by regulating the applied voltage is an effective method to eliminate the Moiré patterns in the PLII. Based on this principle, an experiment has been designed, and the Moiré patterns fringe width is alleviated from 20 pixels to10 pixels distance before and after, and the results verify the correctness of the theoretical analysis

Enhancing the generating and collecting efficiency of single particle upconverting luminescence at low power excitation

Upconverting luminescent nanoparticles are photostable, nonblinking, and low chemically toxic fluorophores that are emerging as promising fluorescent probes at the single molecule level. High luminescence intensity upconversion nanoparticles (UCNPs) have previously been achieved by doping with high amounts of rare-earth ions using high excitation power (>2.5 MW/cm2). However, such particles are inadequate for in vitro live-cell imaging and single-particle tracking, as high excitation power can cause photodamage. Here, we compared UCNP luminescence intensities with different dopant concentrations and presented more efficient (about seven times) UCNPs at low excitation power by increasing the concentrations of Yb3+ and Tm3+ dopants (NaYF4: 60% Yb3+, 8% Tm3+) and adding a core-shell structure

STED optical super-resolution microscopy with fluorescent NV-centers

In this work, we present the application of RESOLFT nanoscopy in subcellular organelle imaging. Fluorescent nano-diamond (FND) has been imaged as a photostable inorganic dye, with large stimulated emission cross-section. FND nanoparticles as well as bulk FNDs grown in a large diamond have been studied with our STED system. ? OSA 2013.EI

Mitochondrial dynamics quantitatively revealed by STED nanoscopy with an enhanced squaraine variant probe

Live cell imaging of mitochondrial cristae is challenged by the unsuitability of current fluorescent probes and high phototoxicity. Here the authors develop a squarine variant probe (MitoESq-635) that is capable of longitudinal imaging of cristae with STED with minimal phototoxicity

Amplified stimulated emission in upconversion nanoparticles for super-resolution nanoscopy

Lanthanide-doped glasses and crystals are attractive for laser applications because the metastable energy levels of the trivalent lanthanide ions facilitate the establishment of population inversion and amplified stimulated emission at relatively low pump power. At the nanometre scale, lanthanide-doped upconversion nanoparticles (UCNPs) can now be made with precisely controlled phase, dimension and doping level. When excited in the near-infrared, these UCNPs emit stable, bright visible luminescence at a variety of selectable wavelengths, with single-nanoparticle sensitivity, which makes them suitable for advanced luminescence microscopy applications. Here we show that UCNPs doped with high concentrations of thulium ions (Tm3+), excited at a wavelength of 980 nanometres, can readily establish a population inversion on their intermediate metastable 3H4 level: The reduced inter-emitter distance at high Tm3+ doping concentration leads to intense cross-relaxation, inducing a photon-avalanche-like effect that rapidly populates the metastable 3H4 level, resulting in population inversion relative to the 3H6 ground level within a single nanoparticle. As a result, illumination by a laser at 808 nanometres, matching the upconversion band of the 3H4 - 3H6 transition, can trigger amplified stimulated emission to discharge the 3H4 intermediate level, so that the upconversion pathway to generate blue luminescence can be optically inhibited. We harness these properties to realize low-power super-resolution stimulated emission depletion (STED) microscopy and achieve nanometre-scale optical resolution (nanoscopy), imaging single UCNPs; the resolution is 28 nanometres, that is, 1/36th of the wavelength. These engineered nanocrystals offer saturation intensity two orders of magnitude lower than those of fluorescent probes currently employed in stimulated emission depletion microscopy, suggesting a new way of alleviating the square-root law that typically limits the resolution that can be practically achieved by such techniques