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Detection of retinal laser lesions is necessary in both the evaluation of the extent of damage from high power laser sources, and in validating treatments involving the placement of laser lesions. However, such lesions are difficult to detect using Color Fundus cameras alone. Deep learning-based segmentation can remedy this, by highlighting potential lesions in the image.A unique database of images collected at the Air Force Research Laboratory over the past 30 years was used to train deep learning models for classifying images with lesions and for subsequent segmentation. We investigate whether transferring weights from models that learned classification would improve performance of the segmentation models. We use Pearson's correlation coefficient between the initial and final training phases to reveal how the networks are transferring features.The segmentation models are able to effectively segment a broad range of lesions and imaging conditions.Deep learning-based segmentation of lesions can effectively highlight laser lesions, making this a useful tool for aiding clinicians.

Molecular vibrational spectroscopy is widely used in various sensing and imaging applications, providing intrinsic information at the molecular level. Nonlinear optical interactions using ultrashort laser pulses facilitate the selective coherent excitation of molecular vibrational modes by focusing energy into specific molecular bonds, boosting the signal level for multiple orders of magnitude. The dephasing of such coherence, which is susceptible to the local molecular environment, however, is often neglected. The unique capability of vibrational dephasing dynamics to serve as a unique probe for complex molecular interactions and the effect of local nano- and microenvironments are beyond the reach of conventional, intensity-based spectroscopy. Here, we developed a novel multiorder coherent Raman spectroscopy platform with a special focus on the temporal evolution of molecular vibrational dephasing, termed as time-resolved coherent Raman scattering (T-CRS) spectroscopy. By utilizing a high dynamic range detection, molecular vibrational dynamics and the environmental effects are demonstrated with multidimensional spectroscopic sensing, which promises a new range of applications in biology, materials, and chemical sciences.

Quantum coherence in quantum optics is an essential part of optical information processing and light manipulation. Alkali metal vapors, despite the numerous shortcomings, are traditionally used in quantum optics as a working medium due to convenient near-infrared excitation, strong dipole transitions and long-lived coherence. Here, we proposed and experimentally demonstrated photon retention and subsequent re-emittance with the quantum coherence in a system of coherently excited molecular nitrogen ions (N2+) which are produced using a strong 800 nm femtosecond laser pulse. Such photon retention, facilitated by quantum coherence, keeps releasing directly-unmeasurable coherent photons for tens of picoseconds, but is able to be read-out by a time-delayed femtosecond pulse centered at 1580 nm via two-photon resonant absorption, resulting in a strong radiation at 329.3 nm. We reveal a pivotal role of the excited-state population to transmit such extremely weak re-emitted photons in this system. This new finding unveils the nature of the coherent quantum control in N2+ for the potential platform for optical information storage in the remote atmosphere, and facilitates further exploration of fundamental interactions in the quantum optical platform with strong-field ionized molecules.

We propose and demonstrate, first on simulated spectra and then experimentally, a novel approach to correct the undesired background distortions in the Brillouin spectra caused by molecular filter’s absorption, fluorescent emission, ambient room light or any other constant contaminant. The developed multi-wavelength excitation Brillouin spectroscopy method computationally reconstructs the pure Brillouin component of the signal from multiple Brillouin spectra acquired using different excitation wavelengths. By removing the baseline distortions, the approach improves the goodness of fit of the Brillouin peaks, enabling accurate Brillouin shift and linewidth measurements from a wide range of challenging samples. In the present report, we explain the principle behind the method on a set of simulated spectra and present experimental application on an intentionally strongly-distorted spectrum. Utilizing the multi-excitation Brillouin spectroscopy approach, we successfully reconstruct Brillouin spectra of a highly-scattering sample, initially rendered not analyzable by excessive iodine absorption and contamination by out-of-focus light.

The widespread use of antibiotics drives the evolution of antimicrobial-resistant bacteria (ARB), threatening patients and healthcare professionals. Therefore, the development of novel strategies to combat resistance is recognized as a global healthcare priority. The two methods to combat ARB are development of new antibiotics or reduction in existing resistances. Development of novel antibiotics is a laborious and slow-progressing task that is no longer a safe reserve against looming risks. In this research, we suggest a method for reducing resistance to extend the efficacious lifetime of current antibiotics. Antimicrobial photodynamic therapy (aPDT) is used to generate reactive oxygen species (ROS) via the photoactivation of a photosensitizer. ROS then nonspecifically damage cellular components, leading to general impairment and cell death. Here, we test the hypothesis that concurrent treatment of bacteria with antibiotics and aPDT achieves an additive effect in the elimination of ARB. Performing aPDT with the photosensitizer methylene blue in combination with antibiotics chloramphenicol and tetracycline results in significant reductions in resistance for two methicillin-resistant

Nitrogen vacancy diamonds have emerged as sensitive solid-state magnetic field sensors capable of producing diffraction limited and sub-diffraction field images. Here, for the first time, to our knowledge, we extend those measurements to high-speed imaging, which can be readily applied to analyze currents and magnetic field dynamics in circuits on a microscopic scale. To overcome detector acquisition rate limitations, we designed an optical streaking nitrogen vacancy microscope to acquire two-dimensional spatiotemporal kymograms. We demonstrate magnetic field wave imaging with micro-scale spatial extent and ∼ 400 μs temporal resolution. In validating this system, we detected magnetic fields down to 10 μT for 40 Hz magnetic fields using single-shot imaging and captured the spatial transit of an electromagnetic needle at streak rates as high as 110 μm/ms. This design has the capability to be readily extended to full 3D video acquisition by utilizing compressed sensing techniques and a potential for further improvement of spatial resolution, acquisition speed, and sensitivity. The device opens opportunities to many potential applications where transient magnetic events can be isolated to a single spatial axis, such as acquiring spatially propagating action potentials for brain imaging and remotely interrogating integrated circuits.

Brillouin microscopy has recently emerged as a powerful tool for mechanical property measurements in biomedical sensing and imaging applications. Impulsive stimulated Brillouin scattering (ISBS) microscopy has been proposed for faster and more accurate measurements, which do not rely on stable narrow-band lasers and thermally-drifting etalon-based spectrometers. However, the spectral resolution of ISBS-based signal has not been significantly explored. In this report, the ISBS spectral profile has been investigated as a function of the pump beam’s spatial geometry, and novel methodologies have been developed for accurate spectral assessment. The ISBS linewidth was found to consistently decrease with increasing pump-beam diameter. These findings provide the means for improved spectral resolution measurements and pave the way to broader applications of ISBS microscopy.

Hydrogen bonding plays an essential role in biological processes by stabilizing proteins and lipid structures as well as controlling the speed of enzyme catalyzed reactions. Dimethyl sulfoxide-water (DMSO-H2O) solution serves as a classical model system by which the direct and indirect effects of hydrogen bonding between water hydrogens and the sulfoxide functional group can be explored. The complex transition from self-bonding to heterogeneous bonding is important, and multiple spectroscopic approaches are needed to provide a detailed assessment of those interactions. In this report, for the first time, hyper-Raman scattering was successfully employed to investigate molecular interactions in DMSO-H2O system. We measured the improper blueshift of the C–S and C–H stretching modes of DMSO caused by partial charge transfer and enhanced bond polarization. By detecting differences in the frequency shifts of C–S and C–H modes for low DMSO concentrations (

Molecular, morphological and physiological heterogeneity is the inherent property of cells, which governs differences in their response to external influence. The tumor cells metabolic heterogeneity is of a special interest due to its clinical relevance to the tumor progression and therapeutic outcomes. Rapid, sensitive and non-invasive assessment of metabolic heterogeneity of cells is of a great demand for biomedical sciences. Fluorescence lifetime imaging (FLIM), which is an all-optical technique is an emerging tool for sensing and quantifying cellular metabolism by measuring fluorescence decay parameters (FDPs) of endogenous fluorophores, such as NAD(P)H. To achieve the accurate discrimination between metabolically diverse cellular subpopulations, appropriate approaches to FLIM data collection and analysis are needed. In this report, the unique capability of FLIM to attain the overarching goal of discriminating metabolic heterogeneity has been demonstrated. This has been achieved using a novel approach to data analysis based on the non-parametric analysis, which revealed a much better sensitivity to the presence of metabolically distinct subpopulations as compare more traditional approaches of FLIM measurements and analysis. The new approach was further validated for imaging cultured cancer cells treated with chemotherapy. Those results pave the way for an accurate detection and quantification of cellular metabolic heterogeneity using FLIM, which will be valuable for assessing therapeutic vulnerabilities and predicting clinical outcomes.

We demonstrate exotic edge states in two-dimensional spatial-frequency space constructed by one-dimensional modulated waveguide arrays, which exhibits a distinct topological protected one-way transmission along spatial boundary, and Bloch oscillation along the frequency dimension.

We theoretically propose the construction of the optical neural network architecture for deep learning in a single ring resonator, with the concept of temporal synthetic dimension formed by arrival times of optical pulses.

Brillouin microscopy is an emerging label-free imaging technique to assess local viscoelastic properties. Quantum-enhanced stimulated Brillouin scattering is demonstrated for the first time using low power continuous-wave lasers at 795~nm. A signal to noise ratio enhancement of 3.4~dB is reported by using two-mode intensity-difference squeezed light generated with the four-wave mixing process in atomic rubidium vapor. The low optical power and the excitation wavelengths in the water transparency window has the potential to provide a powerful bio-imaging technique for probing mechanical properties of biological samples prone to phototoxicity and thermal effects. The performance enhancement affordable through the use of quantum light may pave the way for significantly improved sensitivity that cannot be achieved classically. The proposed new way of utilizing squeezed light for enhanced stimulated Brillouin scattering can be easily adapted for both spectroscopic and imaging applications in materials science and biology., 12 pages, 8 figures

In contrast to previous studies that focused on classical machine learning algorithms and hand-crafted features, we present an end-to-end neural network classification method able to accommodate lesion heterogeneity for improved oral cancer diagnosis using multispectral autofluorescence lifetime imaging (maFLIM) endoscopy. Our method uses an autoencoder framework jointly trained with a classifier designed to handle overfitting problems with reduced databases, which is often the case in healthcare applications. The autoencoder guides the feature extraction process through the reconstruction loss and enables the potential use of unsupervised data for domain adaptation and improved generalization. The classifier ensures the features extracted are task-specific, providing discriminative information for the classification task. The data-driven feature extraction method automatically generates task-specific features directly from fluorescence decays, eliminating the need for iterative signal reconstruction. We validate our proposed neural network method against support vector machine (SVM) baselines, with our method showing a 6.5%-8.3% increase in sensitivity. Our results show that neural networks that implement data-driven feature extraction provide superior results and enable the capacity needed to target specific issues, such as inter-patient variability and the heterogeneity of oral lesions.Clinical relevance- We improve standard classification algorithms for in vivo diagnosis of oral cancer lesions from maFLIm for clinical use in cancer screening, reducing unnecessary biopsies and facilitating early detection of oral cancer.

The electronic or molecular mechanisms that initiate photobiomodulation (PBM) in cells are not yet fully understood. The porcine complex III (C-III) of the electron transport chain was characterized with transient absorption spectroscopy (TAS). We then applied our recently developed continuous wave laser coupled TAS procedure (CW-TAS) to investigate the effect of red light irradiances on the heme dynamics of C-III in its c1 reduced state. The time constants were found to be 3.3 ± 0.3 ps for vibrational cooling of the oxidized state and 4.9 ± 0.4 ps for rebinding of the photodissociated axial ligand of the c1 reduced state. The analysis of the CW-TAS procedure yielded no significant changes in the C-III heme dynamics. We rule out the possibility of 635 nm CW light at 4.7 mW/cm2 inducing a PBM effect on the heme dynamic of C-III, specifically with the photodissociation of its axial ligand.

Fundamental understanding of biological pathways requires minimally invasive nanoscopic optical resolution imaging. Many approaches to high-resolution imaging rely on localization of single emitters, such as fluorescent molecule or quantum dot. Exact determination of the number of such emitters in an imaging volume is essential for a number of applications; however, in a commonly employed intensity-based microscopy it is not possible to distinguish individual emitters without initial knowledge of system parameters. Here we explore how quantum measurements of the emitted photons using photon number resolving detectors can be used to address this challenging task. In the proposed new approach, the problem of counting emitters reduces to the task of determining differences between the emitted photons and the Poisson limit. We show that quantum measurements of the number of photons emitted from an ensemble of emitters enable the determination of both the number of emitters and the probability of emission. This method can be applied for any type of emitters, including Raman and infrared emitters, which makes it a truly universal way to achieve super-resolution optical imaging. The scaling laws of this new approach are presented by the Cramer-Rao Lower Bounds and define the extent this technique can be used for quantum optical imaging with nanoscopic resolution.

Simple Summary Complete resection of dysplastic and malignant tissue improves overall survival and delays cancer recurrence in oral cancer patients; however, intraoperative surgical margin assessment is limited to visual inspection and palpation, making it difficult to achieve total resection. There is currently no tool capable of providing real-time, accurate, and continuous margin-assessment guidance during oral cancer resection surgery. Multispectral autofluorescence lifetime imaging (maFLIM) is a label-free imaging modality that enables quantifying a plurality of metabolic and compositional autofluorescence biomarkers of oral dysplasia and cancer. We have developed and validated a machine-learning assisted computer aided detection (CAD) system for automated discrimination of dysplastic and cancerous from healthy oral tissue based on in vivo widefield maFLIM endoscopy data. This CAD system can be potentially embedded into maFLIM endoscopes to enable continuous in situ detection of positive margins during oral cancer resection surgery, thus facilitating maximal tumor resection and improving surgical outcomes for oral cancer patients. Abstract Multispectral autofluorescence lifetime imaging (maFLIM) can be used to clinically image a plurality of metabolic and biochemical autofluorescence biomarkers of oral epithelial dysplasia and cancer. This study tested the hypothesis that maFLIM-derived autofluorescence biomarkers can be used in machine-learning (ML) models to discriminate dysplastic and cancerous from healthy oral tissue. Clinical widefield maFLIM endoscopy imaging of cancerous and dysplastic oral lesions was performed at two clinical centers. Endoscopic maFLIM images from 34 patients acquired at one of the clinical centers were used to optimize ML models for automated discrimination of dysplastic and cancerous from healthy oral tissue. A computer-aided detection system was developed and applied to a set of endoscopic maFLIM images from 23 patients acquired at the other clinical center, and its performance was quantified in terms of the area under the receiver operating characteristic curve (ROC-AUC). Discrimination of dysplastic and cancerous from healthy oral tissue was achieved with an ROC-AUC of 0.81. This study demonstrates the capabilities of widefield maFLIM endoscopy to clinically image autofluorescence biomarkers that can be used in ML models to discriminate dysplastic and cancerous from healthy oral tissue. Widefield maFLIM endoscopy thus holds potential for automated in situ detection of oral dysplasia and cancer.

The dimensionality of a physical system is one of the major parameters defining its physical properties. The recently introduced concept of synthetic dimension has made it possible to arbitrarily manipulate the system of interest and harness light propagation in different ways. It also facilitates the transformative architecture of system-on-a-chip devices enabling far reaching applications such as optical isolation. In this report, a novel architecture based on dynamically-modulated waveguide arrays with the Su-Schrieffer-Heeger configuration in the spatial dimension is proposed and investigated with an eye on a practical implementation. The propagation of light through the one-dimensional waveguide arrays mimics time evolution of the field in a synthetic two-dimensional lattice. The addition of the effective gauge potential leads to an exotic topologically protected one-way transmission along adjacent boundary. A cosine-shape isolated band, which supports the topological Bloch oscillation in the frequency dimension under the effective constant force, appears and is localized at the spatial boundary being robust against small perturbations. This work paves the way to improved light transmission capabilities under topological protections in both spatial and spectral regimes and provides a novel platform based on a technologically feasible lithium niobate platform for optical computing and communication.

Early detection is critical for improving the survival rate and quality of life of oral cancer patients; unfortunately, dysplastic and early-stage cancerous oral lesions are often difficult to distinguish from oral benign lesions during standard clinical oral examination. Therefore, there is a critical need for novel clinical technologies that would enable reliable oral cancer screening. The autofluorescence properties of the oral epithelial tissue provide quantitative information about morphological, biochemical, and metabolic tissue and cellular alterations accompanying carcinogenesis. This study aimed to identify novel biochemical and metabolic autofluorescence biomarkers of oral dysplasia and cancer that could be clinically imaged using novel multispectral autofluorescence lifetime imaging (maFLIM) endoscopy technologies. In vivo maFLIM clinical endoscopic images of benign, precancerous, and cancerous lesions from 67 patients were acquired using a novel maFLIM endoscope. Widefield maFLIM feature maps were generated, and statistical analyses were applied to identify maFLIM features providing contrast between dysplastic/cancerous vs. benign oral lesions. A total of 14 spectral and time-resolved maFLIM features were found to provide contrast between dysplastic/cancerous vs. benign oral lesions, representing novel biochemical and metabolic autofluorescence biomarkers of oral epithelial dysplasia and cancer. To the best of our knowledge, this is the first demonstration of clinical widefield maFLIM endoscopic imaging of novel biochemical and metabolic autofluorescence biomarkers of oral dysplasia and cancer, supporting the potential of maFLIM endoscopy for early detection of oral cancer.

We report a novel approach to coherent anti-Stokes spectroscopy based on multiple overtone resonances in both theory and experiment. A pump laser with the tunable wavelength at the near infrared range is used to excite the inner-band vibrational transition of the C-H stretching vibrations, commonly corresponding to biological molecules. Strong coherent signals with higher chemical specificity are observed in experiments Our work points to a new route for applying resonantly enhanced nonlinear optical spectroscopy in the deeper tissue optical imaging with near infrared lasers which is important for various biomedical applications. © 2021 SPIE.

COVID-19 pandemic is calling for new methods of remote chemical sensing, which can potentially detect small number of viral particles in air at safe distances. Raman spectroscopy is a chemically specific spectroscopic technique;however, it is often difficult to apply it for remote sensing due to the non-directional scattering. We propose and demonstrate a novel way to achieve directional backward emission through nonlinear Raman interactions. © 2021 SPIE.

Raman spectroscopy is often considered as a powerful tool for chemical sensing and imaging and in the times of COVID- 19 pandemic is frequently suggested as the way to identify the presence of viral particles in solution. In this report, we evaluate the ability of Raman spectroscopy to quantitatively assess the presence of nanoparticles in colloidal solutions. © 2021 SPIE. All rights reserved.

Photodynamic inactivation (PDI) has been widely applied to localized infections, both internal and external. However, there is a notable knowledge gap when it comes to applying PDI to an entire organ system or even systemically throughout an organism. To study these treatment methods, an in vivo murine model of MHV-1 is planned. As a respiratory coronavirus, the model provides a suitable system for study, in addition to potential determination of systemic results. Specifically applied, MHV-1 has many key characteristics, such as symptoms and viral protein structures, that are in common or similar to other coronaviruses. Thus, this theorized model simultaneously addresses a key knowledge gap and provides useful insights into potential treatments for COVID-19 and similar disease-causing viruses. The risk of emergent viral threats and the necessity for rapidly developed, adaptable, affordable treatment methods are both now vividly evident. © 2021 SPIE.

Hydrogen bonding plays an essential role in biological processes. In this report we apply hyper-Raman scattering spectroscopy to probe the effects of the alkyl groups on hydrogen bonding in mixtures of DMSO-methanol. We characterize the dependence of hyper-Raman spectra on concentration and observe suppression of the hyper-Raman responses of the methanol alkyl group at intermediate concentrations. In addition, small frequency shifts in the vibrational frequencies of DMSO and methanol were detected. These results provide new insights into the nature of the hydrogen bonding in solution and into the details of the hydrogen bond’s interaction with the alkyl groups.

Brillouin spectroscopy has recently emerged as a valuable tool for assessing microscopic viscoelastic properties in biological tissues and cells. For many practical biomedical applications, the viscoelastic measurement techniques should be sensitive to low sample concentrations in biological media. In this report, we assess the sensitivity of a recently improved impulsive stimulated Brillouin scattering (ISBS) setup. We explored biologically relevant solutions in distilled water using citric acid, glycine, and sucrose, for which we performed Brillouin measurements. We detailed the peak fitting methodology and analyzed the Brillouin shift and linewidth as a function of concentration. We discuss the sensitivity of the ISBS setup to low concentration measurements and its implications to biological applications.

Dysfunctions in the endothelial cell lining of the vascular endothelium are linked with human pathogenesis of atherosclerosis, venous thrombosis, and several human viral infections. These diseases typically originate from abnormalities resulting from poor structural integrity of the tunica intima of the vascular endothelium. In this report, impulsive stimulated Brillouin scattering spectroscopy was used to assess viscoelastic properties of cells in a microfluidic chip which was designed to mimic the vascular endothelium tunica intima. Brillouin spectroscopy method enabled non-invasive data acquisition of viscoelastic measurements to understand the role of collagen type I on the anchoring of endothelial cells to the extracellular matrix.

Hyper-Raman spectroscopy is a nonlinear optical variant of vibrational spectroscopy to acquire information about molecular structures. Hyper-Raman spectroscopy complements existing infrared and Raman spectroscopy techniques due to differences in the selection rules. Performing hyper-Raman spectroscopy at 532 nm results in the signal emission in the UV spectral range (266 nm – 296 nm), which benefits from near-resonant conditions for many biomolecules. Even operating in the electronic resonant enhancement regime, hyper-Raman spectroscopy requires high average and peak power, picosecond laser systems to achieve reasonable collection times (1 minute – 30 minutes). In this report, we explore applications of hyper-Raman spectroscopy to aromatic structures (L-phenylalanine and imidazole) that experience significant two-photon absorption and two-photon fluorescence which can obstruct measurements of the hyper-Raman spectra of these molecules. Since competing two-photon processes could significantly limit future UV hyper-Raman applications, we explore mitigating strategies to circumvent the fluorescence background of Lphenylalanine and imidazole by applying a quenching agent (hydrogen peroxide). We also outline a more general solution to alleviate two-photon absorption and fluorescence by proposing tailored laser configurations where the excitation wavelength could be tuned to avoid two-photon absorption resonances while remaining in the UV regime.