• Leblanc Guzman posted an update 1 year, 6 months ago

    Advanced monolithic III-nitride asymmetric optical links can be developed toward Internet of Things (IoT) deployment based on such multifunction devices.Optical resolution photoacoustic microscopy (ORPAM) has demonstrated both high resolution and rich contrast imaging of optical chromophores in biologic tissues. To date, sensitivity remains a major challenge for ORPAM, which limits the capability of resolving biologic microvascular networks. In this study, we propose and evaluate a new ORPAM modality termed as optical resolution photoacoustic computed microscopy (ORPACM), through the combination of a two-dimensional laser-scanning system with a medical ultrasonographic platform. Apart from conventional ORPAMs, we record multiple photoacoustic (PA) signals using a 128-element ultrasonic transducer array for each pulse excitation. Then, we apply a reconstruction algorithm to recover one depth-resolved PA signal referred to as an A-line, which reveals more detailed information compared with conventional single-element transducer-based ORPAMs. In addition, we carried out both in vitro and in vivo experiments as well as quantitative analyses to show the advanced features of ORPACM.Motion contrast optical coherence tomography angiography (OCTA) entails a precise identification of dynamic flow signals from the static background, but an intermediate region with voxels exhibiting a mixed distribution of dynamic and static scatterers is almost inevitable in practice, which degrades the vascular contrast and connectivity. In this work, the static-dynamic intermediate region was pre-defined according to the asymptotic relation between inverse signal-to-noise ratio (iSNR) and decorrelation, which was theoretically derived for signals with different flow rates based on a multi-variate time series (MVTS) model. Then the ambiguous voxels in the intermediate region were further differentiated using a shape mask with adaptive threshold. Finally, an improved OCTA classifier was built by combining shape, iSNR, and decorrelation features, termed as SID-OCTA, and the performance of the proposed SID-OCTA was validated experimentally through mouse retinal imaging.We introduce a laser-based process relying on multiphoton-induced polymerization to produce complex three-dimensional (3D) glass parts. A focused, intense laser beam is used to polymerize a transparent resin, loaded with additives and silica nanoparticles, at the wavelength of the laser beam through nonlinear absorption processes. The object is created directly in the volume, overcoming the limitation of the layer-by-layer process. The process enables the production of silica parts with consecutive debinding and sintering processes. With bulk silica density and a resolution that depends on the laser spot size, 3D objects of centimetric dimensions are obtained.In this Letter, we demonstrate a method to combine a molecular iodine absolute frequency reference with a high-finesse optical cavity in a single laser to take advantage of the frequency stability properties of both systems at different time scales. see more The result is a laser exhibiting the long-term and short-term stability levels of the iodine frequency reference and optical cavity, respectively. The method uses frequency offset side-band locking and an acousto-optical modulator driven ac-coupled servo-loop to correct the iodine’s short-term frequency fluctuations. Experimental results show cavity-limited stability at 1 Hz of 10-151/Hz and iodine stability below 10 mHz of 10-131/Hz. In terms of the Allan deviation, this corresponds to stability levels close to the 10-15 at 1 s and 10-14 for observation times >100s.Here, we demonstrate a flat nanofocalizer for converging light field into a uniform subwavelength light spot array based on the fractional Talbot effect by developing a direct laser writing technique with 3D fabrication precision. The fractional Talbot effect endows the device with the merits of high compression ratio and modular design capability for transforming a plane wave into arrayed light focal spots. By combining a synergistic laser printing technique, we introduce a buffer layer for improving the fabrication precision of structural height in favor of accurately manipulating the phase delay. For a given light wavelength at 750 nm, by precisely producing a nanofocalizer consisting of periodic unit elements with the dimensions of 300(width)×600(length)×585(height)nm, we have achieved 5×6 light spot array with modular design, while the full width at half-maximum of a single focused light spot can be reduced to ∼0.82λ. Our research may pave the way for realizing subwavelength optical devices capable of being readily integrated to existing optical systems.A full polymeric optofluidic Fabry-Perot (FP) resonator with a high quality factor (Q) is proposed and tested. The device is based on multilayer optical polymeric films that act as high reflectivity interference mirrors. The all-polymeric laminated structure avoids any deposition or etching process, simplifying the fabrication procedure while retaining a high quality optical surface. The measured quality factor of the FP resonator is 3.03×104, and the finesse is 91 around 700 nm. The refractometric sensing properties have been measured, and a sensitivity of 314 nm/RIU with a limit of detection of 2.55×10-5RIU could be achieved. The device exhibits a very high figure of merit of 1.36×104RIU-1 that is comparable with the performance attainable with sensors based on photonic crystal and whispering gallery mode resonators.Heavily Tm3+-doped glass fibers are urgently desired for ∼2µm single-frequency fiber lasers and high-repetition-rate mode-locked fiber lasers. Here the structure of glass networks was tuned through controlling the numbers of non-bridging oxygens and bridging oxygens by adjusting the composition of the glasses, hence increasing the Tm3+ doping concentration of germanate glasses. The increased flexibility of the glass networks favors the distribution of Tm3+ ions to decrease fluorescence quenching, which was confirmed by the experimental and theoretical results. A heavily Tm3+ (9.8×1020ions/cm3)-doped germanate glass was successfully fabricated without quenching by tuning the components of the glass. To the best of our knowledge, the Tm3+ ion doping concentration is the highest reported level in Tm3+-doped glasses and fibers. The results suggest that the heavily Tm3+-doped germanate glass is highly promising for fabricating ∼2µm glass fibers with high gain per unit length.

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