Optica最新文献

Optics that allow us to see clearly along one viewing direction while obscuring others' view of us are useful in numerous settings, including privacy-preserving window screens and one-way mirrors for psychological studies. Additionally, due to the rise of cameras that are able to see outside the visible spectrum, there is a need for optics that can also provide one-way visibility at these wavelengths. This is particularly challenging for thermal (i.e., infrared) imaging because most existing methods require precise control of scene illumination, which is difficult to achieve in the infrared. To address this challenge, we demonstrate broadband, passive one-way visibility by precisely tuning the position and optical parameters of a single optical scatterer. We show the benefits of our approach in both a simulated and an experimental testbed. With experimental data, we demonstrate a 5.22× and 5.23× improvement in the degree of asymmetry for midwave infrared (MWIR) and visible (VIS) wavelengths, respectively. Ultimately, our method introduces a robust, passive one-way visibility system at midwave infrared (MWIR), which can aid in numerous privacy preservation applications.

Volumetric fluorescence imaging techniques, such as confocal, multiphoton, light sheet, and light field microscopy, have become indispensable tools across a wide range of cellular, developmental, and neurobiological applications. However, it is difficult to scale such techniques to the large 3D fields of view (FOV), volume rates, and synchronicity requirements for high-resolution 4D imaging of freely behaving organisms. Here, we present reflective Fourier light field computed tomography (ReFLeCT), a high-speed volumetric fluorescence computational imaging technique. ReFLeCT synchronously captures entire tomograms of multiple unrestrained, unanesthetized model organisms across multi-millimeter 3D FOVs at 120 volumes per second. In particular, we applied ReFLeCT to reconstruct 4D videos of fluorescently labeled zebrafish and Drosophila larvae, enabling us to study their heartbeat, fin and tail motion, gaze, jaw motion, and muscle contractions with nearly isotropic 3D resolution while they are freely moving. To our knowledge, as a novel approach for snapshot tomographic capture, ReFLeCT is a major advance toward bridging the gap between current volumetric fluorescence microscopy techniques and macroscopic behavioral imaging.

In optical diffraction tomography (ODT), a sample's 3D refractive index (RI) is often reconstructed after illuminating it from multiple angles, with the assumption that the sample remains static throughout data collection. When the sample undergoes dynamic motion during this data-collection process, significant artifacts and distortions compromise the fidelity of the reconstructed images. In this study, we develop a space-time inverse-scattering technique for ODT that compensates for the translational motion of multiple-scattering samples during data collection. Our approach involves formulating a joint optimization problem to simultaneously estimate a scattering sample's translational position at each measurement and its motion-corrected 3D RI distribution. Experimental results with weak- and multiple-scattering samples demonstrate the technique's effectiveness, yielding reconstructions with reduced artifacts, enhanced spatial resolution, and improved quantitative accuracy for samples undergoing continuous translational motion during imaging.

Wide-field (WF) imaging is pivotal for observing dynamic biological events. While WF chemical microscopy offers high molecular specificity, it lacks the sensitivity for single-molecule detection. In contrast, WF fluorescence microscopy provides live-cell dynamic mapping but fails to leverage the rich chemical information necessary for functional interpretations. To address these limitations, we introduce Wide-Field Bond-selective Fluorescence-detected Infrared-Excited (WF-BonFIRE) spectro-microscopy. This technique combines rationally optimized imaging speed and field-of-view (FOV) to achieve single-molecule sensitivity with bond-selective contrast. We demonstrate WF-BonFIRE's capabilities in imaging single molecules, cells, astrocytes, and live neurons, capturing single FOVs up to 50 μm × 50 μm, with further expansion via multi-FOV mosaicking. Additionally, we have implemented a new temporal-delay modulation scheme that allows real-time kilohertz WF-BonFIRE imaging with speeds up to 1500 Hz. We showcase the millisecond temporal resolution through monitoring the random motion of live Escherichia coli. Leveraging its ability to distinguish molecules through distinct narrow-band BonFIRE signals, we further demonstrate multicolor real-time E. coli tracking. WF-BonFIRE should significantly broaden the boundary for chemical imaging, enabling high-speed observations at unparalleled sensitivity levels.

Optical metasurfaces provide novel solutions to label-free biochemical sensing by localizing light resonantly beyond the diffraction limit, thereby selectively enhancing light-matter interactions for improved analytical performance. However, high-Q resonances in metasurfaces are usually achieved in the reflection mode, which impedes metasurface integration into compact imaging systems. Here, we demonstrate a novel metasurface platform for advanced biochemical sensing based on the physics of the bound states in the continuum (BIC) and electromagnetically induced transparency (EIT) modes, which arise when two interfering resonances from a periodic pattern of tilted elliptic holes overlap both spectrally and spatially, creating a narrow transparency window in the mid-infrared spectrum. We experimentally measure these resonant peaks observed in transmission mode (Q~734 @ λ~8.8 μm) in free-standing silicon membranes and confirm their tunability through geometric scaling. We also demonstrate the strong coupling of the BIC-EIT modes with a thinly coated PMMA film on the metasurface, characterized by a large Rabi splitting (32 cm^-1) and biosensing of protein monolayers in transmission mode. Our new photonic platform can facilitate the integration of metasurface biochemical sensors into compact and monolithic optical systems while being compatible with scalable manufacturing, thereby clearing the way for on-site biochemical sensing in everyday applications.

The scattering and absorption of light within biological tissue severely limits the penetration depth of optical imaging techniques. Recently, it has been found that water-soluble, strongly absorbing dye molecules, such as tartrazine, can achieve in vivo tissue transparency by increasing the refractive index of aqueous components in tissue, as predicted by the Lorentz oscillator model and Kramers-Kronig relations. In this study, we topically applied absorbing dye molecules to the abdominal skin of pigmented and non-pigmented mice to enhance the penetration depth of optical coherence tomography (OCT) and photoacoustic microscopy (PAM). In both types of mice, the penetration depth of OCT was significantly improved using tartrazine and 4-aminoantipyrine. As predicted by the Kramers-Kronig relations and absorption spectra of the dyes, mice treated with 4-aminoantipyrine showed significantly improved penetration depth compared to mice treated with tartrazine for the PAM system with 532 nm excitation. These findings further demonstrate the use of absorbing dye molecules for achieving tissue transparency to enhance the penetration depth of depth-resolved optical imaging modalities in skin, thus accelerating the translation of these technologies in clinical areas, such as dermatology.

X-ray dark-field imaging highlights sample structures through contrast generated by sub-resolution features within the inspected volume. Quantifying dark-field signals generally involves multiple exposures for phase retrieval, separating contributions from scattering, refraction, and attenuation. Here, we introduce an approach for non-interferometric X-ray dark-field imaging that presents a single-parameter representation of the sample. This fuses attenuation and dark-field signals, enabling the reconstruction of a unified three-dimensional volume. Notably, our method can obtain dark-field contrast from a single exposure and employs conventional back projection algorithms for reconstruction. Our approach is based on the assumption of a macroscopically homogeneous material, which we validate through experiments on phantoms and on biological tissue samples. The methodology is implemented on a laboratory-based, rotating anode X-ray tube system without the need for coherent radiation or a high-resolution detector. Utilizing this system with streamlined data acquisition enables expedited scanning while maximizing dose efficiency. These attributes are crucial in time- and dose-sensitive medical imaging applications and unlock the ability of dark-field contrast with high-throughput lab-based tomography. We believe that the proposed approach can be extended across X-ray dark-field imaging implementations beyond tomography, spanning fast radiography, directional dark-field imaging, and compatibility with pulsed X-ray sources.