This PDF file contains the front matter associated with SPIE Proceedings Volume 12681, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

In this study, we developed a new technique to analyze spatial correlation between metabolic activities of multiple biomolecules. Using a multimodal imaging platform integrating Stimulated Raman Scattering (SRS), Multiphoton Fluorescence (MPF), and Second Harmonic Generation (SHG), together with an image deconvolution algorithm, we obtained super resolution images of biomolecular metabolism and investigated the correlations between metabolic activities and distributions of metabolites in tissues such as breast cancer tissues. Further, we developed a Pearson’s Correlation Coefficient based algorithm to examine the co-registration and co-regulation of metabolic activities in multiple channels of super-resolved images of nanoscopic Regions of Interest (ROIs). The multimodal imaging platform and Pearson’s correlation coefficient-based algorithm potentially facilitate early-stage breast cancer detection, and mechanistic understanding of breast cancer.

We present a comparative experimental study of supercontinuum generation in undoped KGW and YVO₄ crystals pumped with near-IR femtosecond laser pulses. We demonstrate that KGW and YVO₄ crystals, compared to commonly used sapphire and YAG, have significantly lower supercontinuum generation thresholds, produce remarkably larger red-shifted spectral broadenings and exhibit durable damage-free long-term operation at 2 MHz and 76 MHz repetition rates. Our results show that KGW and YVO₄ crystals are excellent nonlinear materials for high repetition rate infrared supercontinuum generation which could be used for the design of high average power optical parametric amplifiers as well as for the development of ultrafast ultrafast spectroscopic and high-speed imaging systems.

We report a novel Reservoir Computing (RC) processor exploiting nonlinearity and memory effects in a thin liquid film cladding integrated with a Si-Photonic device. We report the multiphysics processes resulting in a Thermocapillary (TC) effect that serve as a source of nonlinear response and a short-term memory at the same time.

Recently, much attention has been drawn to deep learning models, namely deep Convolutional Neural Networks (CNNs) trained in a supervised fashion. Supervised learning is time consuming, requires a large dataset where the answer is already known, and often fails to generalize to new cases with patterns or noise statistics that were not foreseen in the training data. Unsupervised learning, on the other hand, does not use prior knowledge of the answer, can adapt to new data at hand, and can learn from single examples. A CNN can solve inverse problems in this way by learning to produce a result that, when passed through a forward model, recovers the experimental measurement. For example, a CNN can be trained in a supervised fashion to recover the complex field of a pulse from its Frequency-Resolved Optical Gating (FROG) measurement, by training it on thousands of examples of FROG measurements (the network inputs) and their corresponding optical pulses (the target outputs). In unsupervised learning, the network learns to transform a FROG measurement into an optical pulse, that, when passed through a forward model, recovers the original FROG measurement. We find this succeeds even on single FROG measurements, opening up new possibilities for analyzing measurements that fall outside the foreseeable distribution of training data.

Optical Second Harmonic Generation (SHG) is a nonlinear optical effect widely used for nonlinear optical microscopy and laser frequency conversion. The closed-form analytical solution of the nonlinear optical responses is essential for evaluating the optical responses of new materials whose optical properties are unknown a priori. Many approximations have therefore been employed in the existing analytical approaches, such as slowly varying approximation, weak reflection of the nonlinear polarization, transparent medium, high crystallographic symmetry, Kleinman symmetry, easy crystal orientation along a high-symmetry direction, phase matching conditions and negligible interference among nonlinear waves, which may lead to large errors in the reported material properties. To avoid these approximations, we have developed an open-source package named Second Harmonic Analysis of Anisotropic Rotational Polarimetry (♯SHAARP) for single interface (si) and in multilayers (ml) for homogeneous crystals. The reliability and accuracy are established by experimentally benchmarking with both the SHG polarimetry and Maker fringes predicted from the package using standard materials. SHAARP.si and SHAARP.ml are available through GitHub https://github.com/Rui-Zu/SHAARP and https://github.com/bzw133/SHAARP.ml, respectively.

Macromolecular crowding and ionic strength in living cells influence a myriad of biochemical processes essential to cell function and survival. For example, macromolecular crowding is known to affect diffusion, biochemical reaction kinetics, protein folding, and protein-protein interactions. In addition, enzymatic activities, protein folding, and cellular osmosis are also sensitive to environmental ionic strength. Recently, genetically encoded mCerulean3-linker-mCitrine constructs have been developed and characterized using time-resolved fluorescence measurements as a function of the amino acid sequence of the linker region as well as the environmental crowding and ionic strength. Here, we investigate the thermodynamic equilibrium of structural conformations of mCerulean3-linker-mCitrine constructs in response to the environmental macromolecular crowding and ionic strength. We have developed a theoretical framework for thermodynamic equilibrium of the structural conformations of these environmental sensors. In addition, we tested these theoretical models for thermodynamic analysis of these donor-linker-acceptor sensors using time-resolved fluorescence measurements as a function of the amino acid sequence of the linker region. Employing ultrafast time-resolved fluorescence measurements for gaining thermodynamic energetics would be helpful for Förster Resonance Energy Transfer (FRET) studies of protein-protein interactions in both living cells and controlled environments.

We present results of classical Coulomb explosion simulations to demonstrate that Coulomb explosion imaging can serve as a robust method for differentiating molecular structures and following structural changes in pump-probe experiments by tracking the motion of individual atoms within the molecule.

We develop an optical temperature mapping modality, termed Single-shot Photoluminescence Lifetime Imaging Thermometry (SPLIT). Synergistically combining dual-view optical streak imaging with compressed sensing, SPLIT records wide-field luminescence decay of Er³⁺, Yb³⁺ co-doped NaGdF₄ upconverting nanoparticles in real time, from which a lifetime-based 2D temperature map is obtained in a single exposure. Largely advancing existing optical thermometry techniques in detection capabilities, SPLIT enables longitudinal 2D temperature monitoring beneath a thin scattering medium and dynamic temperature tracking of a moving biological sample at single-cell resolution. SPLIT will be applied to early melanoma diagnosis and extended to the near-infrared spectral region.

Using ultrafast double-pulse spectroscopy, our experiment showcases coherent control over the 2.39 THz optical phonon mode within bulk WTe₂. Through precise manipulation of the delay between successive pump pulses, we successfully achieve modulation of the phonon amplitude at room temperature by a factor of two. This breakthrough showcases the potential for all-optical control and modulation of the unique properties in WTe₂ that are directly bound to its structural degrees of freedom.

High-speed multiplex Stimulated Raman Scattering (SRS) microscopy has emerged as a powerful imaging technique in the field of biomedical research. This cutting-edge technology combines the benefits of traditional Raman spectroscopy with the high speed and resolution of microscopy, enabling real-time, label-free, and non-invasive visualization of biological samples at the molecular level. In this article, we delve into the principles, advantages, and applications of high-speed multiplex SRS microscopy in the context of biomedical studies.

The integration of photonic materials in applications traditionally dominated by electronic components, such as light emitting diodes, photovoltaic cells and all-optical switches has emerged as a compelling area of study, unlocking new possibilities. Crystalline organic compounds are of particular interest for many applications where their performance is impacted by the crystalline properties. However, investigating crystallization processes in solution remains challenging because their rapid and complex dynamics are difficult to quantify. To this end, we developed an innovative multimodal optical setup capable of in-situ measurements of dynamic processes. Our approach combines a tunable femtosecond pulsed laser and a continuous wave laser, leveraging spectrally resolved scattering and fluorescence detection to measure up to nine different optical effects: second and third harmonic scattering and their depolarization ratios, linear light scattering, multi- and one photon excitation fluorescence, optical rotation and transmission. In this study, we aim to discover the crystallization dynamics of regioregular poly(3-hexylthiophene) through anti-solvent addition. Our findings demonstrate the capability of our setup to provide valuable insights for the optimization of photonic materials.

The self-assembly and transport of species at oil/aqueous interfaces represent key mechanistic steps in processes spanning from liquid extraction to soft-matter neuromorphic electrical devices. While technologically and fundamentally important, there is a notable lack of chemical understanding regarding these buried interfaces due to challenges in differentiating species located at the surface from the nearby bulk phases. In this work, we will describe some of the challenges in probing chemistry at these liquid/liquid interfaces and detail the approaches we have developed using vibrational sum frequency generation to enable studies of these complex interfaces at and away from equilibrium. From these spectroscopic developments, new insight into solvation, ion pairing, aggregation, complexation, and transport will be discussed in the context of solvent extraction chemistry. Notably, we show how the presence of both oil and aqueous phases provides an environment to drive fundamentally different phenomena from what is observed at model air/aqueous interfaces. This difference arises from key differences in solvation and bulk populations that feedback onto the surface to drive emergent and often functional molecular assemblies.