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1. Surface-enhanced Raman scattering sensing platform for detecting amyloid-β peptide interaction with an aggregation inhibitor

   https://doi.org/10.1364/AO.399307  

   de Oliveira, Marcos A. Soares ; Hilt, Silvia ; Chang, Che-Wei ; Lee, Changwon ; Voss, John C. ; Chan, James W. ( August 2020 , Applied Optics)

   Soluble, small amyloid-$\mathrm{\beta <\#comment/>}$oligomers ($\mathrm{A}\mathrm{\beta <\#comment/>}\mathrm{O}$) are recognized as significant contributors to the pathology of Alzheimer’s disease (AD). Although drugs for treating AD symptoms have been approved, no therapy targeting amyloid-$\mathrm{\beta <\#comment/>}$($\mathrm{A}\mathrm{\beta <\#comment/>}$) capable of modifying the course of the disease is available. In an effort to develop a label-free method for screening new anti-AD therapeutic agents, we show the use of a surface-enhanced Raman scattering (SERS) active substrate for detecting the interactions between$\mathrm{A}\mathrm{\beta <\#comment/>}$peptides and spin-labeled fluorine (SLF), a peptide aggregation inhibitor. Changes in the peak positions and intensity ratios of two spectral peaks near$1600\mathrm{c}{\mathrm{m}}^{-<\#comment/>1}$and$2900\mathrm{c}{\mathrm{m}}^{-<\#comment/>1}$can be used to monitor the molecular interactions between SLF and$\mathrm{A}\mathrm{\beta <\#comment/>}$. This study demonstrates the potential of SERS spectroscopy for rapidly screening and identifying new anti-$\mathrm{A}\mathrm{\beta <\#comment/>}$therapeutic agents.

    

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2. Variability of relationship between the volume scattering function at 180° and the backscattering coefficient for aquatic particles

   https://doi.org/10.1364/AO.383229  

   Hu, Lianbo ; Zhang, Xiaodong ; Xiong, Yuanheng ; Gray, Deric J. ; He, Ming-Xia ( February 2020 , Applied Optics)

   Properly interpreting lidar (light detection and ranging) signal for characterizing particle distribution relies on a key parameter,${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$, which relates the particulate volume scattering function (VSF) at 180° (${\mathrm{\beta <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$) that a lidar measures to the particulate backscattering coefficient ($b_{\mathit{\text{bp}}}$). However,${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$has been seldom studied due to challenges in accurately measuring${\mathrm{\beta <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$and$b_{\mathit{\text{bp}}}$concurrently in the field. In this study,${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$, as well as its spectral dependence, was re-examined using the VSFs measuredin situat high angular resolution in a wide range of waters.${\mathrm{\beta <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$, while not measured directly, was inferred using a physically sound, well-validated VSF-inversion method. The effects of particle shape and internal structure on the inversion were tested using three inversion kernels consisting of phase functions computed for particles that are assumed as homogenous sphere, homogenous asymmetric hexahedra, or coated sphere. The reconstructed VSFs using any of the three kernels agreed well with the measured VSFs with a mean percentage difference$<<\#comment/>5\mathrm{\%<\#comment/>}$at scattering angles$<<\#comment/>{170}^{\circ <\#comment/>}$. At angles immediately near or equal to 180°, the reconstructed${\mathrm{\beta <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$depends strongly on the inversion kernel.${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$derived with the sphere kernels was smaller than those derived with the hexahedra kernel but consistent with${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$estimated directly from high-spectral-resolution lidar andin situbackscattering sensor. The possible explanation was that the sphere kernels are able to capture the backscattering enhancement feature near 180° that has been observed for marine particles.${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$derived using the coated sphere kernel was generally lower than those derived with the homogenous sphere kernel. Our result suggests that${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$is sensitive to the shape and internal structure of particles and significant error could be induced if a fixed value of${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$is to be used to interpret lidar signal collected in different waters. On the other hand,${\mathrm{\chi <\#comment/>}}_p(\mathrm{\pi <\#comment/>})$showed little spectral dependence.

    

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3. Rapid acquisition of broadband two-dimensional electronic spectra by continuous scanning with conventional delay lines

   https://doi.org/10.1364/OL.391360  

   Spencer, Austin P. ; Chen, Lin X. ( May 2020 , Optics Letters)

   A passively phase-stable, broadband ($\sim <\#comment/>7\mathrm{f}\mathrm{s}$,$><\#comment/>2000{\mathrm{c}\mathrm{m}}^{-<\#comment/>1}$) two-dimensional (2D) electronic spectroscopy apparatus that achieves rapid acquisition rates by continuously—rather than step-wise—scanning the Fourier-transform dimension is demonstrated for the first time, to the best of our knowledge. This is made possible through use of a partially common path interferometer design in which the coherence time$\mathrm{\tau <\#comment/>}$is sampled in a “rotating frame.” Rapid, continuous scanning of$\mathrm{\tau <\#comment/>}$increases the duty cycle of signal collection, rejects the majority of excitation pulse scatter, and enables the measurement of a complete 2D spectrum in 92 ms, which minimizes the influence of pulse intensity and delay fluctuations on the 2D spectrum. In practice, these improvements make possible the acquisition of hundreds of 2D spectra in tens of minutes, which opens the door to dense sampling of ultrafast relaxation dynamics and to generating extremely broadband 3D Fourier-transform spectra.

    

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4. Mid-IR spectroscopy of Er 3+ doped low-phonon CsCdCl 3 and CsPbCl 3 crystals

   https://doi.org/10.1364/JOSAB.470152  

   Brown, Ei Ei ; Fleischman, Zackery D. ; McKay, Jason ; Hommerich, Uwe ; Kabir, Al Amin ; Riggins, Jazmine ; Trivedi, Sudhir ; Dubinskii, Mark ( September 2022 , Journal of the Optical Society of America B)

   The mid-IR spectroscopic properties of${\mathrm{E}\mathrm{r}}^{3+}$doped low-phonon${\mathrm{C}\mathrm{s}\mathrm{C}\mathrm{d}\mathrm{C}\mathrm{l}}_3$and${\mathrm{C}\mathrm{s}\mathrm{P}\mathrm{b}\mathrm{C}\mathrm{l}}_3$crystals grown by the Bridgman technique have been investigated. Using optical excitations at$\sim <\#comment/>800\mathrm{n}\mathrm{m}$and$\sim <\#comment/>660\mathrm{n}\mathrm{m}$, both crystals exhibited IR emissions at$\sim <\#comment/>1.55$,$\sim <\#comment/>2.75$,$\sim <\#comment/>3.5$, and$\sim <\#comment/>4.5\text{µ<\#comment/>}\mathrm{m}$at room temperature. The mid-IR emission at 4.5 µm, originating from the${}^4{\mathrm{I}}_{9/2}\to <\#comment/>{}^4{\mathrm{I}}_{11/2}$transition, showed a long emission lifetime of$\sim <\#comment/>11.6\mathrm{m}\mathrm{s}$for${\mathrm{E}\mathrm{r}}^{3+}$doped${\mathrm{C}\mathrm{s}\mathrm{C}\mathrm{d}\mathrm{C}\mathrm{l}}_3$, whereas${\mathrm{E}\mathrm{r}}^{3+}$doped${\mathrm{C}\mathrm{s}\mathrm{P}\mathrm{b}\mathrm{C}\mathrm{l}}_3$exhibited a shorter lifetime of$\sim <\#comment/>1.8\mathrm{m}\mathrm{s}$. The measured emission lifetimes of the${}^4{\mathrm{I}}_{9/2}$state were nearly independent of the temperature, indicating a negligibly small nonradiative decay rate through multiphonon relaxation, as predicted by the energy-gap law for low-maximum-phonon energy hosts. The room temperature stimulated emission cross sections for the${}^4{\mathrm{I}}_{9/2}\to <\#comment/>{}^4{\mathrm{I}}_{11/2}$transition in${\mathrm{E}\mathrm{r}}^{3+}$doped${\mathrm{C}\mathrm{s}\mathrm{C}\mathrm{d}\mathrm{C}\mathrm{l}}_3$and${\mathrm{C}\mathrm{s}\mathrm{P}\mathrm{b}\mathrm{C}\mathrm{l}}_3$were determined to be$\sim <\#comment/>0.14\times <\#comment/>{10}^{-<\#comment/>20}{\mathrm{c}\mathrm{m}}^2$and$\sim <\#comment/>0.41\times <\#comment/>{10}^{-<\#comment/>20}{\mathrm{c}\mathrm{m}}^2$, respectively. The results of Judd–Ofelt analysis are presented and discussed.

    

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5. Needle-based deep-neural-network camera

   https://doi.org/10.1364/AO.415059  

   Guo, Ruipeng ; Nelson, Soren ; Menon, Rajesh ( March 2021 , Applied Optics)

   We experimentally demonstrate a camera whose primary optic is a cannula/needle ($\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{m}\mathrm{e}\mathrm{t}\mathrm{e}\mathrm{r}=0.22\mathrm{m}\mathrm{m}$and$\mathrm{l}\mathrm{e}\mathrm{n}\mathrm{g}\mathrm{t}\mathrm{h}=12.5\mathrm{m}\mathrm{m}$) that acts as a light pipe transporting light intensity from an object plane (35 cm away) to its opposite end. Deep neural networks (DNNs) are used to reconstruct color and grayscale images with a field of view of 18° and angular resolution of$\sim <\#comment/>{0.4}^{\circ <\#comment/>}$. We showed a large effective demagnification of$127\times <\#comment/>$. Most interestingly, we showed that such a camera could achieve close to diffraction-limited performance with an effective numerical aperture of 0.045, depth of focus$\sim <\#comment/>16\text{µ<\#comment/>}\mathrm{m}$, and resolution close to the sensor pixel size (3.2 µm). When trained on images with depth information, the DNN can create depth maps. Finally, we show DNN-based classification of the EMNIST dataset before and after image reconstructions. The former could be useful for imaging with enhanced privacy.

    

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