Up-conversion nanoparticles are highly attractive for application cases in bio sensing and imaging without autofluorescence. Characterizing the photophyiscial properties of such nanoparticles is essential to enhance the efficiency of preparation methods as well as their electronic and optical properties. We will demonstrate the performance of a spectrometer-microscope assembly for characterization and analysis of up-conversion nanoparticles in terms of lifetime, spectral, and spatial resolution, which provides more information than when using only lifetime or steady-state experiments.

This work presents an AI-driven framework to extract the biological tissue's refractive index and thickness maps from a single RGB image. This approach is based on a physical light-trapping surface and an unsupervised inverse search projector which projects given RGB pixel to the sample's refractive index and thickness at the corresponding coordinate.

Thermal effects need to be accurately measured and/or controlled to generate continuous kinetic binding curves with whispering gallery mode (WGM) microcavity sensors. We use a high spatial resolution optical frequency domain reflectometry system at 780 nm to capture the Rayleigh backscattering signal within a microtoroid optical resonator for temperature calibration. It is shown that this system has a temperature detection accuracy of 30 mK. This technique characterizes thermal effects in the microcavity and the surrounding environment, thus enabling lower limits of detection to be achieved.

Many schemes have been proposed to measure physiological pH by conjugating pH-sensitive dyes with Upconverting Nanoparticles (UCNPs). However, the signal transduction is typically achieved by a combination of photon reabsorption and Förster resonant energy transfer (FRET) between UCNPs and dyes. While FRET senses the pH in the immediate vicinity of the sensor, photon reabsorption is strongly affected by the global environment, potentially obscuring the local pH values. In this presentation, we report a new sensing scheme that detects only the contributions by FRET and is insensitive to photon reabsorption, making it the first demonstration of truly local pH measurements.

We demonstrate a proof-of-concept design of a new type of nanophotonic molecular sensors with the functionality of trapping target biomolecules to the device regions of highly enhanced field intensity, and hence facilitating improvement of sensing performance. Our experimental results show that these devices are capable of effectively accumulating precipitated L-Proline after the analyte solution of various concentrations dries on the device surface. Specifically, our devices produce a few percentage reflection (absorption) change in response to picogram level amino acid proline. Our work demonstrates a new strategy for designing optical sensors for detecting and sensing trace amount of analyte such as molecules in solutions.

Current 3D fabrication approaches either do not have nanoscale resolution, or are severely limited in terms of materials or structure. Here we present optical positioning and linking (OPAL), which uses optical tweezers and biotin-avidin linkage chemistry to assemble previously infeasible metamaterial and biosensor structures out of building blocks. These building blocks include polystyrene microspheres, gold nanospheres, and silica-gold nanoshells. We present the precision assembly of >440 particles into a 3D structure, as well as the fastest published optical tweezer nanoparticle manipulation speeds. Structures are designed using the coupled dipole method, which is particularly fast for these types of structures.

Scattering from nanoparticles has previously been utilized to achieve sub-wavelength resolution in microscopy, sub-diffraction beam widths in focused laser beams, and improved sensitivity in biological sensing. However, these applications often require time-consuming detailed vectorial simulation of the interaction of incident fields with the nanoparticles to achieve the desired performance. On the other hand, the scalar angular spectrum method is widely used for rapid holographic reconstruction, but can be inaccurate for sub-wavelength features, depending on the light-matter interaction model. Here we establish the domains of accuracy of three scalar light-matter interaction models for arrays of randomly distributed dielectric and metallic nanoparticles.

Cell migration is an essential cellular process that help cells to develop complex organisms, organs, and tissues, arrange cells into specialized architecture and help organize the nervous system. Nanoscale imaging has the potential to provide new insight into the mechanics of cell migration. However, quantification over time in nanoscale imaging remains difficult. Here, we visualize cell migration by non-bleaching nanoscale imaging. We present a set of quantitative metrics - length, branching, gaps, distribution, and curvature - to quantitatively analyze cell migration at the nanoscale over time.

This talk will present work on in vivo fluorescence/luminescence biological imaging in the 1000-1700 nm NIR-II/SWIR window to benefit from suppressed light scattering at these long wavelengths combined with diminished autofluorescence. I will show in vivo NIR-II imaging with millimeter tissue depth, single-cell spatial resolution, and real-time temporal resolution using a wide range of nano-scale fluorescent/luminescent nanoprobes emitting > 1000 nm including carbon nanotubes, quantum dots, rare-earth down-conversion nanoparticles, and donor-acceptor organic molecules. New imaging tools such as light sheet microscopy and confocal microscopy in NIR-II/SWIR will be presented for non-invasive molecular imaging in vivo down to mm's depths. Finally, I will show some recent results on imaging guided surgery with tumor/normal tissue signal ratios exceeding 100.