Author(s):

Vlieg, Redmar C. & van Noort, John

Abstract:

“Plasmonic metallic nanoparticles are commonly used in (bio-)sensing applications because their localized surface plasmon resonance is highly sensitive to changes in the environment. Although optical detection of scattered light from single particles provides a straightforward means of detection, the two-photon luminescence (TPL) of single gold nanorods (GNRs) has the potential to increase the sensitivity due to the large anti-Stokes shift and the non-linear excitation mechanism. However, two-photon microscopy and spectroscopy are restricted in bandwidth and have been limited by the thermal stability of GNRs. Here, we used a scanning multi-focal microscope to simultaneously measure the two-photon excitation spectra of hundreds of individual GNRs with sub-nanometer accuracy. By keeping the excitation power under the melting threshold, we show that GNRs were stable in intensity and spectrum for more than 30 min, demonstrating the absence of thermal reshaping. Spectra featured a signal-to-noise ratio of >10 and a plasmon peak width of typically 30 nm. Changes in the refractive index of the medium of less than 0.04, corresponding to a change in surface plasmon resonance of 8 nm, could be readily measured and over longer periods. We used this enhanced spectral sensitivity to measure the presence of neutravidin, exploring the potential of TPL spectroscopy of single GNRs for enhanced plasmonic sensing.”

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Author(s):

Deliyski, Dimitar D.; Shishkov, Milen; Mehta, Daryush D.; Ghasemzadeh, Hamzeh; Bouma, Brett; Zañartu, Matias; de Alarcon, Alessandro & Hillman, Robert E.

Abstract:

“Summary

The design specifications and experimental characteristics of a newly developed laser-projection transnasal flexible endoscope coupled with a high-speed videoendoscopy system are provided. The hardware and software design of the proposed system benefits from the combination of structured green light projection and laser triangulation techniques, which provide the capability of calibrated absolute measurements of the laryngeal structures along the horizontal and vertical planes during phonation. Visual inspection of in vivo acquired images demonstrated sharp contrast between laser points and background, confirming successful design of the system. Objective analyses were carried out for assessing the irradiance of the system and the penetration of the green laser light into the red and blue channels in the recorded images. The analysis showed that the system has irradiance of 372 W/m2 at a working distance of 20 mm, which is well within the safety limits, indicating minimal risk of usage of the device on human subjects. Additionally, the color penetration analysis showed that, with probability of 90%, the ratio of contamination of the red channel from the green laser light is less than 0.002. This indicates minimal effect of the laser projection on the measurements performed on the red data channel, making the system applicable for calibrated 3D spatial-temporal segmentation and data-driven subject-specific modeling, which is important for further advancing voice science and clinical voice assessment.”

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Author(s):

Kolesnichenko, Pavel V.; Wittenbecher, Lukas & Zigmantas, Donatas

Abstract:

“Michelson interferometers have been routinely used in various applications ranging from testing optical components to interferometric time-resolved spectroscopy measurements. Traditionally, plate beamsplitters are employed to redistribute radiation between the two arms of an interferometer. However, such an interferometer is susceptible to relative phase fluctuations between the two arms resulting from vibrations of the beamsplitter. This drawback is circumvented in diffraction-grating-based interferometers, which are especially beneficial in applications where highly stable delays between the replica beams are required. In the vast majority of grating-based interferometers, reflective diffraction gratings are used as beamsplitters. Their diffraction efficiency, however, is strongly wavelength dependent. Therefore transmission-grating interferometers can be advantageous for spectroscopy methods, since they can provide high diffraction efficiency over a wide spectral range. Here, we present and characterize a transmission grating-based Michelson interferometer, which is practically dispersion-free, has intrinsically high symmetry and stability and moderate throughput efficiency, and is promising for a wide range of applications.”

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Author(s):

Arias-Alpizar, Gabriela; Kong, Li; Vlieg, Redmar C.; Rabe, Alexander; Papadopoulou, Panagiota; Meijer, Michael S.; Bonnet, Sylvestre; Vogel, Stefan; van Noort, John; Kros, Alexander & Campbell, Frederick

Abstract:

“Surface charge plays a fundamental role in determining the fate of a nanoparticle, and any encapsulated contents, in vivo. Herein, we describe, and visualise in real time, light-triggered switching of liposome surface charge, from neutral to cationic, in situ and in vivo (embryonic zebrafish). Prior to light activation, intravenously administered liposomes, composed of just two lipid reagents, freely circulate and successfully evade innate immune cells present in the fish. Upon in situ irradiation and surface charge switching, however, liposomes rapidly adsorb to, and are taken up by, endothelial cells and/or are phagocytosed by blood resident macrophages. Coupling complete external control of nanoparticle targeting together with the intracellular delivery of encapsulated (and membrane impermeable) cargos, these compositionally simple liposomes are proof that advanced nanoparticle function in vivo does not require increased design complexity but rather a thorough understanding of the fundamental nano-bio interactions involved.”

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Author(s):

Berzinš, Jonas; Indrišiūnas, Simonas; van Erve, Koen; Nagarajan, Arvind; Fasold, Stefan; Steinert, Michael; Gerini, Giampiero; Gečys, Paulius; Pertsch, Thomas; Bäumer, Stefan M. B. & Setzpfandt, Frank

Abstract:

“High-index dielectric metasurfaces featuring Mie-type electric and magnetic resonances have been of great interest in a variety of applications such as imaging, sensing, photovoltaics, and others, which led to the necessity of an efficient large-scale fabrication technique. To address this, here we demonstrate the use of single-pulse laser interference for direct patterning of an amorphous silicon film into an array of Mie resonators a few hundred nanometers in diameter. The proposed technique is based on laser-interference-induced dewetting. A precise control of the laser pulse energy enables the fabrication of ordered dielectric metasurfaces in areas spanning tens of micrometers and consisting of thousands of hemispherical nanoparticles with a single laser shot. The fabricated nanoparticles exhibit a wavelength-dependent optical response with a strong electric dipole signature. Variation of the predeposited silicon film thickness allows tailoring of the resonances in the targeted visible and infrared spectral ranges. Such direct and high-throughput fabrication is a step toward a simple realization of spatially invariant metasurface-based devices.”

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Author(s):

Suzuki, Takakazu; Nemoto, Hirofumi; Takasawa, Kazuki & Kannari, Fumihiko

Abstract:

“We demonstrated real-time, in-situ operation of a single-shot, frequency-time-encoding burst imaging method of sequentially timed all-optical mapping photography utilizing spectral filtering (SF-STAMP) by employing a high-speed camera with the frame rate of a 1000 fps as a detector. We obtained single-shot burst images of a pulse-by-pulse femtosecond laser ablation of a glass by a chirped probe laser pulse with a 1–2-ps frame interval or by a spectrally sweeping burst laser pulse train with a 300-ps interval. We observed burst images of plasma generation during the early stage of laser ablation in a glass with a short frame interval by a chirped probe laser pulse. We also captured burst images of plume and shock-wave generation in air with a 1.5-ns observation time window by a spectrally sweeping probe laser pulse train.”

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Author(s):

Chen, Zhenyue; Mc Larney, Benedict; Rebling, Johannes; Deán-Ben, Xosé Luis; Zhou, Quanyu; Gottschalk, Sven & Razansky, Daniel

Abstract:

“Abstract Scanning optical microscopy techniques are commonly restricted to a sub-millimeter field-of-view (FOV) or otherwise employ slow mechanical translation, limiting their applicability for imaging fast biological dynamics occurring over large areas. A rapid scanning large-field multifocal illumination (LMI) fluorescence microscopy technique is devised based on a beam-splitting grating and an acousto-optic deflector synchronized with a high-speed camera to attain real-time fluorescence microscopy over a centimeter-scale FOV. Owing to its large depth of focus, the approach allows noninvasive visualization of perfusion across the entire mouse cerebral cortex, not achievable with conventional wide-field fluorescence microscopy methods. The new concept can readily be incorporated into conventional wide-field microscopes to mitigate image blur due to tissue scattering and attain optimal trade-off between spatial resolution and FOV. It further establishes a bridge between conventional wide-field macroscopy and laser scanning confocal microscopy, thus it is anticipated to find broad applicability in functional neuroimaging, in vivo cell tracking, and other applications looking at large-scale fluorescent-based biodynamics.”

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Author(s):

Krmpot, Aleksandar J.; Nikolić, Stanko N.; Oasa, Sho; Papadopoulos, Dimitrios K.; Vitali, Marco; Oura, Makoto; Mikuni, Shintaro; Thyberg, Per; Tisa, Simone; Kinjo, Masataka; Nilsson, Lennart; Terenius, Lars; Rigler, Rudolf & Vukojevic, Vladana

Abstract:

“Functional fluorescence microscopy imaging (fFMI), a time-resolved (21 μs/frame) confocal fluorescence microscopy imaging technique without scanning, is developed for quantitative characterization of fast reaction-transport processes in solution and in live cells. The method is based on massively parallel fluorescence correlation spectroscopy (FCS). Simultaneous excitation of fluorescent molecules in multiple spots in the focal plane is achieved using a diffractive optical element (DOE). Fluorescence from the DOE-generated 1024 illuminated spots is detected in a confocal arrangement by a matching matrix detector comprising 32 × 32 single-photon avalanche photodiodes (SPADs). Software for data acquisition and fast auto- and cross-correlation analysis by parallel signal processing using a graphic processing unit (GPU) allows temporal autocorrelation across all pixels in the image frame in 4 s and cross-correlation between first- and second-order neighbor pixels in 45 s. We present here this quantitative, time-resolved imaging method with single-molecule sensitivity and demonstrate its usefulness for mapping in live cell location-specific differences in the concentration and translational diffusion of molecules in different subcellular compartments. In particular, we show that molecules without a specific biological function, e.g., the enhanced green fluorescent protein (eGFP), exhibit uniform diffusion. In contrast, molecules that perform specialized biological functions and bind specifically to their molecular targets show location-specific differences in their concentration and diffusion, exemplified here for two transcription factor molecules, the glucocorticoid receptor (GR) before and after nuclear translocation and the Sex combs reduced (Scr) transcription factor in the salivary gland of Drosophila ex vivo.”

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Author(s):

Guo, Zhenkun; Zhou, Ninghao; Williams, Olivia F.; Hu, Jun; You, Wei & Moran, Andrew M.

Abstract:

“Carrier diffusion is imaged in a perovskite film and crystal using a newly developed transient absorption microscope. Wide-field imaging is combined with a diffractive optic-based beam geometry to conduct 41 transient absorption experiments in parallel in this experimental setup. This configuration allows statistics to be quickly compiled with a 1 kHz laser system. Diffusion coefficients of 0.01 and 0.20 cm2/s are obtained for the methylammonium lead iodide film and crystal, respectively. Our data suggest that the dynamics in the film are dominated by intensity dependence of the carrier lifetimes as opposed to carrier diffusion. The small diffusion coefficients determined in the film are attributed to the presence of grain boundaries.”

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Author(s):

Suzuki, Takakazu; Hida, Ryohei; Yamaguchi, Yuki; Nakagawa, Keiichi; Saiki, Toshiharu & Kannari, Fumihiko

Abstract:

“We captured ultrafast two-dimensional (2D)-burst images of the crystalline-to-amorphous phase transition of Ge2Sb2Te5. These transitions were induced by a femtosecond laser pulse, and the images, with a sub-picosecond temporal resolution, were acquired on a single-shot basis through the change in local optical transmittance. We employed a 2D-burst imaging method of sequentially timed all-optical mapping photography utilizing spectral filtering (SF-STAMP). The SF-STAMP system consists of a 25-beam-generating diffractive optical element, a band-pass filter, and two Fourier transform lenses. We used a frequency-chirped broadband pulse and achieved 25-frame burst imaging with an interval of 133 fs in a single-shot time window of 3.2 ps.”

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