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A new nonlinear optical process, named enhanced stimulated Raman scattering (ESRS), is reported for the first time from resonance Raman in β-carotene-methanol solution. It is well known that absorption decreases the efficiency of the nonlinear optical and laser processes; however, we observed enhanced stimulated Raman peaks at the first and second Stokes from methanol solvent at 2834 cm−1 with the addition of β-carotene solutes. This enhanced SRS effect in methanol is attributed to the resonance Raman (RR) process in β-carotene, which creates a significant number of vibrations from RR and the excess vibrations are transferred to methanol from anharmonic vibrational interactions between the β-carotene solutes and the methanol solvent, and consequently leads to the increased Raman gain.

Key optical properties of calcite were measured to unravel the difference between stimulated Raman scattering (SRS) and self-phase modulation (SPM) for the supercontinuum (SC) for ordinary (O) wave and extraordinary (E) wave. These properties are group velocity dispersion, walk-off, spontaneous Raman spectra and cross section, optical 1086 c m − 1 phonon linewidth, nonlinear susceptibility ( χ 3 ), steady-state and transient SRS, and SC caused from SPM. These are investigated for O-waves and E-waves from a 2.7 cm thick calcite crystal. Using 390 fs pulses ( ∼ 0.8 µ J pulse energy) at 517 nm, the O-wave produced a stronger sharp SRS peak at 1086 c m − 1 and a weaker SC spectrum in the visible range than the E-wave. The salient difference found between the O- and E-waves for SRS and SPM in calcite is attributed to the larger Raman cross section and the size of nonlinear susceptibility ( χ 3 ) for O-waves as compared to E-waves.

Triple-negative breast cancer (TNBC) is an aggressive subset of breast cancer that is more common in African-American and Hispanic women. Early detection followed by intensive treatment is critical to improving poor survival rates. The current standard to diagnose TNBC from histopathology of biopsy samples is invasive and time-consuming. Imaging methods such as mammography and magnetic resonance (MR) imaging, while covering the entire breast, lack the spatial resolution and specificity to capture the molecular features that identify TNBC. Two nonlinear optical modalities of second harmonic generation (SHG) imaging of collagen, and resonance Raman spectroscopy (RRS) potentially offer novel rapid, label-free detection of molecular and morphological features that characterize cancerous breast tissue at subcellular resolution. In this study, we first applied MR methods to measure the whole-tumor characteristics of metastatic TNBC (4T1) and nonmetastatic estrogen receptor positive breast cancer (67NR) models, including tumor lactate concentration and vascularity. Subsequently, we employed for the first time in vivo SHG imaging of collagen and ex vivo RRS of biomolecules to detect different microenvironmental features of these two tumor models. We achieved high sensitivity and accuracy for discrimination between these two cancer types by quantitative morphometric analysis and nonnegative matrix factorization along with support vector machine. Our study proposes a new method to combine SHG and RRS together as a promising novel photonic and optical method for early detection of TNBC.

In this paper, a projection-type dual-view holographic three-dimensional (3D) display consisting of a single spatial light modulator (SLM) and a grating light-guide plate is proposed and implemented. A synthetic phase-only hologram of two different 3D objects is calculated by the layer-based Fresnel diffraction method and uploaded onto the SLM for 3D reconstruction. A grating with special design and fabrication is used as the light-guide plate to re-direct the two reconstructed 3D images into the two separated viewing zones simultaneously. Optical experiments demonstrate that the proposed system can realize the function of dual-view holographic 3D display, and it can present 3D images to the human eye with sufficient depth cues, which enables the observers free of the accommodation-vergence conflict and visual fatigue problem. Furthermore, the proposed dual-view holographic 3D display system is applied to the see-through display for augmented reality (AR) applications, and the performance of this system is also tested in the experiments and the results show that the system can provide the dual-view AR 3D sensation successfully.

In this paper, a viewing angle enlargement method of holographic display using an off-axis holographic lens is proposed, and verification experiment of viewing angle enlargement is developed by using a single spatial light modulator (SLM) and an off-axis holographic lens fabricated by the holographic recording. The experimental results indicate that the viewing angle of holographic reconstructed image is increased to 11.2°, which is about 3.8 times as wide as the original viewing angle formed by the single SLM only. Furthermore, a see-through holographic display system for augmented reality (AR) is constructed, where virtual image is generated by holographic projection. The real scene and the virtual image will fuse together by using the off-axis holographic lens as the image combiner. The results prove that the proposed system can reconstruct virtual three-dimensional (3D) image with correct depth cues, solve the accommodation-vergence conflict problem effectively, and achieve the holographic AR 3D display effect without visual fatigue.

In this paper, a multi-plane optical see-through holographic three-dimensional (3D) display system for augmented reality (AR) applications is proposed and implemented. This system is composed of a holographic projection module and an optical see-through display module. The holographic projection module manages to reconstruct the multi-plane 3D scene by using a spatial light modulator (SLM), and the correct depth information can be expressed by programmable zoom lenses encoded on the SLM. The reconstructed 3D scene and the real physical world will fuse together through the optical see-through display module. An experimental verification system for the proposed multi-plane optical see-through holographic 3D display is demonstrated. The experimental results prove that the proposed system can achieve the multi-plane AR holographic 3D display effect without any image bearing structure, and can solve the accommodation-vergence conflict problem effectively. This system has the advantages of large depth range, continuous expression capacity of depth information and no visual fatigue.

In this paper, an autostereoscopic three-dimensional (3D) display system based on synthetic hologram reconstruction is proposed and implemented. The system uses a single phase-only spatial light modulator to load the synthetic hologram of the left and right stereo images, and the parallax angle between two reconstructed stereo images is enlarged by a grating to meet the split angle requirement of normal stereoscopic vision. To realize the crosstalk-free autostereoscopic 3D display with high light utilization efficiency, the groove parameters of the grating are specifically designed by the rigorous coupled-wave theory for suppressing the zero-order diffraction, and then the zero-order nulled grating is fabricated by the holographic lithography and the ion beam etching. Furthermore, the diffraction efficiency of the fabricated grating is measured under the illumination of a laser beam with a wavelength of 532 nm. Finally, the experimental verification system for the proposed autostereoscopic 3D display is presented. The experimental results prove that the proposed system is able to generate stereoscopic 3D images with good performances.

This study aimed to use self-absorption correction to determine the Raman enhancement of β-carotene. The Raman spectra of β-carotene solutions were measured using 488nm, 514nm, 532nm and 633nm laser beams, which exhibited significant resonance Raman (RR) enhancement when the laser energy approaches the electronic transition energy from S0 to S2 state. The Raman intensity and the actual resonance Raman gain without self-absorption from S2 state by β-carotene were also obtained to evaluate the effect of self-absorption on RR scattering. Moreover, we observed the Raman intensity strength followed the absorption spectra. Our study found that, although 488nm and 514nm pumps seemed better for stronger RR enhancement, 532nm would be the optimum Raman pump laser with moderate RR enhancement due to reduced fluorescence and self-absorption. The 532nm excitation will be helpful for applying resonance Raman spectroscopy to investigate biological molecules in tissues.

A two-color vibrational imaging technique for simultaneously mapping glucose uptake and incorporation activity inside single living cells is reported. Heterogeneous patterns of glucose metabolism are directly visualized from the ratiometric two-color images for various cell types, cells undergoing epithelia-to-mesenchymal transitions and live mouse brain tissues. The two-color imaging of glucose metabolism here demonstrates the development of multi-functional vibrational probes for multicolor imaging of cellular metabolism.

In this paper, we propose a projection-type multiview holographic three-dimensional (3-D) display using a single spatial light modulator (SLM) and a directional diffractive device, where a phase-only Fresnel hologram is calculated and displayed on the SLM to reconstruct the multiview hybrid image of a 3-D object for providing the amplitude information of a multiview light field, and a directional diffractive device covered with many pixelated gratings is designed to guide different reconstructed perspectives into different viewing zones for expressing the phase information of the light field. Furthermore, a four-view directional diffractive device is fabricated by using the pixelated holographic exposure method, and its optical properties are also measured under a collimated illumination of the green reconstruction laser with the designed wavelength. In addition, an experimental verification system is constructed to demonstrate a four-view 3-D display. The recorded experimental results confirm that a crosstalk-free four-view light field is created, which is beneficial from the precise alignment between the directional diffractive device and the reconstructed image. Moreover, the capability of dynamic display with the proposed system is also tested by refreshing the SLM with the sequential holograms, and the captured videos show a promising potential for the real-time multiview holographic 3-D projectors.

Significance Membranes can adopt distinct phases. The endoplasmic reticulum (ER) is the largest membrane system inside cells and also harbors the richest metabolic activity including lipid synthesis. Unlike plasma membrane where separated “lipid raft” domains have been predicted and observed, ER membrane is thought to be uniformly fluidic. However, such understanding is based on biophysical studies of model membrane under thermodynamic equilibrium. It remains unclear whether and how lipid synthesis activity perturbs the equilibrium and promotes phase segregation in ER membrane. Herein, we utilized coherent Raman imaging technique to track lipid synthesis and surprisingly revealed solid-like domains emerging from liquid ER membrane. Interestingly, this phenomenon can be tuned by the incoming nutrient source, demonstrating the susceptibility of ER membrane to nonequilibrium modulation., Membrane phase behavior has been well characterized in model membranes in vitro under thermodynamic equilibrium state. However, the widely observed differences between biological membranes and their in vitro counterparts are placing more emphasis on nonequilibrium factors, including influx and efflux of lipid molecules. The endoplasmic reticulum (ER) is the largest cellular membrane system and also the most metabolically active organelle responsible for lipid synthesis. However, how the nonequilibrium metabolic activity modulates ER membrane phase has not been investigated. Here, we studied the phase behavior of functional ER in the context of lipid metabolism. Utilizing advanced vibrational imaging technique, that is, stimulated Raman scattering microscopy, we discovered that metabolism of palmitate, a prevalent saturated fatty acid (SFA), could drive solid-like domain separation from the presumably uniformly fluidic ER membrane, a previously unknown phenomenon. The potential of various fatty acids to induce solid phase can be predicted by the transition temperatures of their major metabolites. Interplay between saturated and unsaturated fatty acids is also observed. Hence, our study sheds light on cellular membrane biophysics by underscoring the nonequilibrium metabolic status of living cell.

In this paper, a synthetic holographic display system for three-dimensional (3D) optical see-through augmented reality (AR) is proposed and implemented. The system is composed of a synthetic hologram reconstruction module and an optical see-through display module. The synthetic hologram reconstruction module utilizes a spatial light modulator (SLM) to present the virtual 3D image in the form of left and right stereo images, and the parallax angle between two stereo images can be enlarged by the zero-order nulled grating to meet the split angle requirement of normal stereoscopic vision. The virtual reconstructed scene and the real physical world will fuse together through the optical see-through display module. The zero-order nulled grating is specifically designed and fabricated, and its diffraction efficiency is measured. Furthermore, an experimental verification system for the proposed AR 3D display is presented. The experimental results prove that the proposed system can support virtual 3D display without crosstalk, and it is able to generate the realistic augmentation successfully.

Glioma is one of the most refractory types of brain tumor. Accurate tumor boundary identification and complete resection of the tumor are essential for glioma removal during brain surgery. We present a method based on visible resonance Raman (VRR) spectroscopy to identify glioma margins and grades. A set of diagnostic spectral biomarkers features are presented based on tissue composition changes revealed by VRR. The Raman spectra include molecular vibrational fingerprints of carotenoids, tryptophan, amide I/II/III, proteins, and lipids. These basic in situ spectral biomarkers are used to identify the tissue from the interface between brain cancer and normal tissue and to evaluate glioma grades. The VRR spectra are also analyzed using principal component analysis for dimension reduction and feature detection and support vector machine for classification. The cross-validated sensitivity, specificity, and accuracy are found to be 100%, 96.3%, and 99.6% to distinguish glioma tissues from normal brain tissues, respectively. The area under the receiver operating characteristic curve for the classification is about 1.0. The accuracies to distinguish normal, low grade (grades I and II), and high grade (grades III and IV) gliomas are found to be 96.3%, 53.7%, and 84.1% for the three groups, respectively, along with a total accuracy of 75.1%. A set of criteria for differentiating normal human brain tissues from normal control tissues is proposed and used to identify brain cancer margins, yielding a diagnostic sensitivity of 100% and specificity of 71%. Our study demonstrates the potential of VRR as a label-free optical molecular histopathology method used for in situ boundary line judgment for brain surgery in the margins.

This paper extends the concept of entangled vector vortex beams as a form of Majorana-like photons. Majorana photon quasi particles are introduced and attributed to a class of entangled vector beams and show higher transmission. These photons and the antiphotons are identical. A Majorana photon has within itself both right and left handed twists. These majorana beams travel at speeds other than speed of light, c in free space. Light transmission of Majorana photon vortex beams with orbital angular momentum (OAM) are investigated in a mouse brain at different local regions showing enhanced transmission and properties of being entangled. This work is new interpretation of our past paper of mixed photon beam states. The transmission change observed with Majorana structured light other than linear polarization is attributed to the nonseparable and mixed nature of radial and azimuthal polarizations with OAM and the handedness of the light passing through chiral brain media. These mixed nonhomogeneous beams are entangled in OAM and polarization. Majorana photons may play an important role in the future for quantum and optical computing and sub and super luminal speeds due to its traversal wave vector, k.

Majorana like photons are introduced from class of classically entangled Cylindrical Vector Vortex Beams. An enhanced transmission is observed in mouse brain from Majorana vector photons with orbital angular momentum due to their non-separability.

Majorana-like photons are introduced in this paper, which are attributed to the polarization and wavefront of special function class of optical vector vortex beams. A Majorana photon is a photon that is identical to its anti-photon. It has within itself both chirality, right and left-handed twist in polarization and wavefront. A theory is presented which reveals that certain types of cylindrical vector vortex photons that are spin–orbit coupled beams – radial, and azimuthal Laguerre-Gaussian, hybrid π -vector beams, and Airy beams – are Majorana-like based on their SAM (polarization) and OAM (wavefront) modes Majorana-like vector photons may play an important role in free-space fiber communication, propagation, quantum computing, optical computing, and imaging in turbid and bio-media as non-separable entangled polarized photons— a quantum mechanical entity.

Being able to image chemical bonds with high sensitivity and speed, stimulated Raman scattering (SRS) microscopy has made a major impact in biomedical optics. However, it is well known that the standard SRS microscopy suffers from various backgrounds, limiting the achievable contrast, quantification and sensitivity. While many frequency-modulation (FM) SRS schemes have been demonstrated to retrieve the sharp vibrational contrast, they often require customized laser systems and/or complicated laser pulse shaping or introduce additional noise, thereby hindering wide adoption. Herein we report a simple but robust strategy for FM-SRS microscopy based on a popular commercial laser system and regular optics. Harnessing self-phase modulation induced self-balanced spectral splitting of picosecond Stokes beam propagating in standard single-mode silica fibers, a high-performance FM-SRS system is constructed without introducing any additional signal noise. Our strategy enables adaptive spectral resolution for background-free SRS imaging of Raman modes with different linewidths. The generality of our method is demonstrated on a variety of Raman modes with effective suppressing of backgrounds including non-resonant cross phase modulation and electronic background from two-photon absorption or pump-probe process. As such, our method is promising to be adopted by the SRS microscopy community for background-free chemical imaging.

Stimulated Raman scattering (SRS) is a powerful optical technique for probing the vibrational states of molecules in biological tissues and provides greater signal intensities than when using spontaneous Raman scattering. In this study, we examined the use of continuous wave (cw) and picosecond (ps) laser excitations to generate SRS signals in pure methanol, a carotene–methanol solution, acetone, and brain tissue samples. The cw-SRS system, which utilized two cw lasers, produced better signal-to-noise (S/N) than the conventional ps-SRS system, suggesting that the cw-SRS system is an efficient and cost-effective approach for studying SRS in complex systems like the brain. The cw-SRS approach will reduce the size of the SRS system, allowing for stimulated Raman gain/loss microscopy. In addition, we showed that there exists a resonance SRS (RSRS) effect from the carotene–methanol solution and brain tissue samples using cw laser excitations. The RSRS effect will further improve the signal-to-noise and may be utilized as an enhanced, label-free SRS microscopic tool for the study of biological tissues.

Resonance Raman and fluorescence spectroscopy were used to assess increased kynurenine pathway activity in brain samples from Alzheimer’s patients and age-matched controls. Increased activity was seen in areas of the brain involved in Alzheimer’s disease.

Light transmission of Laguerre-Gaussian vector vortex beams in different local regions in mouse brain tissue is investigated. Transmittance is measured in the ballistic and diffusive regions with various polarizations states and orbital angular momentums (OAM). The transmission change observed with structured light other than linear polarization is attributed to chiroptical phenomena from the chiral brain media and the handedness of the light. For instance, classically entangled beams showed higher transmittance and constant value dependency on OAM modes than linear modes did. Also, circular polarization beam transmittance showed strong increase with topical charge OAM ( l), which could be attributed to chiroptical effect.

Under stress conditions, pro-inflammatory cytokines, such as tumor necrosis factor-alpha, interleukin-1 beta, interleukin 6 and interferon gamma are released. It is known that these cytokines stimulate indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO), which increase tryptophan metabolism through the kynurenine pathway, and that this can cause increased production of neurotoxic compounds. Brain tissues from Alzheimer’s disease patients and agematched controls were investigated using label-free fluorescence spectroscopy. Tryptophan (exc. 280/ em. 340 nm) and its metabolites (N-formyl-L-kynurenine (exc. 325/em. 434 nm), kynurenine (exc. 365/em. 480 nm) and kynurenic acid (exc. 330/em. 390 nm)) have distinct spectral profiles. Preliminary results show a difference in the optical signatures in three important areas of the brain (hippocampus, BA 9, BA 17) between patients with Alzheimer’s disease and agedmatched controls (normal), and a marked relative increase in tryptophan in the Alzheimer’s patients. Thus determinations of tryptophan to tryptophan metabolite ratios could potentially be used to measure IDO and TDO activity and the degree of inflammation in the brain. This label-free optical technique may be useful in the study of Alzheimer’s and other neurodegenerative diseases.

Light transmission of Laguerre-Gaussian (LG) vortex beams in different local regions in mouse brain tissue is investigated. Transmittance is measured in ballistic region with various polarizations states and orbital angular momentums (OAM).

Brain samples from Alzheimer's patients and aged-matched controls were studied using label-free fluorescence. Increased tryptophan metabolite to tryptophan ratios were seen in the hippocampus and Brodmann's area 9 in Alzheimer's patients as compared to normal.

Resonance Raman spectroscopy using 532nm excitation was used to distinguish normal brain tissue from different grades of glioma tissues. Principal component analysis was used to analyze the spectral data and achieved high accuracy.

Near-infrared (NIR) radiation has been employed using one- and two-photon excitation of fluorescence imaging at wavelengths 650-950nm (optical window I) for deep brain imaging; however, longer wavelengths in NIR have been overlooked due to a lack of suitable NIR-low band gap semiconductor imaging detectors and/or femtosecond laser sources. This research introduces three new optical windows in NIR and demonstrates their potential for deep brain tissue imaging. The transmittances are measured in rat brain tissue in the second (II, 1,100-1,350nm), third (III, 1,600-1,870nm), and fourth (IV, centered at 2,200nm) NIR optical tissue windows. The relationship between transmission and tissue thickness is measured and compared with the theory. Due to a reduction in scattering and minimal absorption, window III is shown to be the best for deep brain imaging, and windows II and IV show similar but better potential for deep imaging than window I.

A cavity design that makes it possible to directly generate Laguerre–Gaussian modes on demand looks set to benefit applications in microscopy and data communications.

In this study, label-free fluorescence spectroscopy was used for the first time to determine spectral profiles of tryptophan, reduced nicotinamide adenine dinucleotide (NADH), and flavin denine dinucleotide (FAD) in fresh brain samples of a mouse model of Alzheimer’s disease (AD). Our results showed that the emission spectral profile levels of tryptophan and NADH were higher in AD samples than normal samples. The intensity ratio of tryptophan to NADH and the change rate of fluorescence intensity with respect to wavelength also increased in AD brain. These results yield an optical method for detecting early stage of AD by comparing spectral profiles of biomolecules.

Time resolved spectroscopic measurements with single-photon and multi-photon excitation of native molecules were performed ex vivo on brain tissues from an Alzheimer’s disease (AD) and a wild type (WT) mouse model using a streak camera. The fluorescence decay times of native NADH and FAD show a longer relaxation time in AD than in WT tissue, suggesting less non-radiative processes in AD. The longer emission time of AD may be attributed to the coupling of the key native building block molecules to the amyloid-tau and/or to the caging of the native fluorophores by the deposition of amyloid-beta or tau plaques and neurofibrillary tangles that affect the local non-radiative interactions.

Transmittance of Laguerre-Gaussian (LG) vortex beams in mouse brain tissue is measured with different orbital angular momentums (OAM). The transition point from ballistic to diffusive region for the mouse brain tissue is determined at about 480 μm. The observed transmittances of the LG beams show independence on OAM modes in both ballistic and diffusive regions, which may be attributed to the interference effects from brain tissue.

Light transmission of Gaussian (G) and Laguerre-Gaussian (LG) vortex beams in mouse brain tissue is investigated. Transmittance is measured with different orbital angular momentums (OAM) at various tissue thicknesses. In both ballistic and diffusive regions, transmittances of G and LG beams show no significant difference. The transition point from ballistic to diffusive region for the mouse brain tissue is determined at about 480 μm. The observed transmittances of the G and LG beams show independence on OAM modes, which may be attributed to poorly understood interference effects from brain tissue.

A supercontinuum (SC) light microscope is proposed for linear and nonlinear optical resonance and non-resonance processes in medical and biological applications. The SC can span from 300nm to 2500nm and may be used for a variety of applications for diagnosis of cancer, wound healing, fusing tissues, stimulation of nerves for therapeutic and treatment of disease. These will be discussed.

In this paper, a dual-view holographic three-dimensional (3D) display using a single spatial light modulator (SLM) and a directional light-guide plate (DLGP) is proposed and implemented. The SLM is used to load the phase-only hologram calculated from two different 3D scenes for optical holographic reconstruction, and the DLGP composed of pixelated gratings with different periods and orientation angles is employed to guide the reconstructed images into two completely separated viewing zones, where different reconstructed perspectives in each viewing zone will form a stereoscopic 3D image. Furthermore, an experimental verification system for the proposed dual-view holographic 3D display is constructed, and the experimental results demonstrate that the proposed system can successfully present different 3D images in the left and right viewing zones simultaneously, verifying the feasibility of the proposed dual-view holographic 3D display.

Photon entanglement, the cornerstone of quantum correlations, provides a level of coherence that is not present in classical correlations. Harnessing it by study of its passage through organic matter may offer new possibilities for medical diagnosis technique. In this work, we study the preservation of photon entanglement in polarization, created by spontaneous parametric down-conversion, after one entangled photon propagates through multiphoton-scattering brain tissue slices with different thickness. The Tangle-Entropy (TS) plots show the strong preservation of entanglement of photons propagating in brain tissue. By spatially filtering the ballistic scattering of an entangled photon, we find that its polarization entanglement is preserved and non-locally correlated with its twin in the TS plots. The degree of entanglement correlates better with structure and water content than with sample thickness.

Atherosclerosis is characterized by the growth of fibrous plaques due to the retention of cholesterol and lipids within the artery wall, which can lead to vessel occlusion and cardiac events. One way to evaluate arterial disease is to quantify the amount of lipid present in these plaques, since a higher disease burden is characterized by a higher concentration of lipid. Although therapeutic stimulation of reverse cholesterol transport to reduce cholesterol deposits in plaque has not produced significant results, this may be due to current image analysis methods which use averaging techniques to calculate the total amount of lipid in the plaque without regard to spatial distribution, thereby discarding information that may have significance in marking response to therapy. Here we use Directional Fourier Spatial Frequency (DFSF) analysis to generate a characteristic spatial frequency spectrum for atherosclerotic plaques from C57 Black 6 mice both treated and untreated with a cholesterol scavenging nanoparticle. We then use the Cauchy product of these spectra to classify the images with a support vector machine (SVM). Our results indicate that treated plaque can be distinguished from untreated plaque using this method, where no difference is seen using the spatial averaging method. This work has the potential to increase the effectiveness of current in-vivo methods of plaque detection that also use averaging methods, such as laser speckle imaging and Raman spectroscopy.

Light transmission of Laguerre Gaussian (LG) vortex beams with different orbital angular momentum (OAM) values (L) in scattering beads and mouse brain tissue media were experimentally investigated for the first time in comparison with Gaussian (G) beams. The LG beams with different OAM were generated using a spatial light modulator (SLM) in reflection mode. The scattering beads media consist of various sizes and concentrations of latex beads in water solutions. The transmissions of LG and G beams through scattering beads and brain tissue media were measured with different ratios of sample thicknesses (z) to scattering mean free path (l s ) of the turbid media, z/l s . The results indicate that within the ballistic region where z/l s is small, the LG and G beams show no significant difference, while in the diffusive region where z/l s is higher, the vortex beams show higher transmission than G beams. In the diffusive region, the LG beams with higher L values show higher transmission than the beams with lower L values due to the eigen channels in the media. The transition points from the ballistic to diffusive regions for different scattering beads and brain tissue media were studied.

Resonance Raman (RR) spectroscopic technique has a high potential for label-free and in-situ detection of biomedical lesions in vivo. This study evaluates the ability of RR spectroscopy method as an optical histopathology tool to detect the atherosclerotic plaque states of abdominal aorta in vitro. This part demonstrates the RR spectral molecular fingerprint features from different sites of the atherosclerotic abdominal aortic wall tissues. Total 57 sites of five pieces aortic samples in intimal and adventitial wall from an autopsy specimen were examined using confocal micro Raman system of WITec 300R with excitation wavelength of 532nm. The preliminary RR spectral biomarkers of molecular fingerprints indicated that typical calcified atherosclerotic plaque (RR peak at 964cm-1) tissue; fibrolipid plaque (RR peaks at 1007, 1161, 1517 and 2888cm-1) tissue, lipid pool with the fatty precipitation cholesterol) with collagen type I (RR peaks at 864, 1452, 1658, 2888 and 2948cm-1) in the soft tissue were observed and investigated.

The terahertz (THz) absorption and index of refraction of brain tissues from a mouse model of Alzheimer’s disease (AD) and a control wild-type (normal) mouse were compared using THz time-domain spectroscopy (THz-TDS). Three dominating absorption peaks associated to torsional–vibrational modes were observed in AD tissue, at about 1.44, 1.8, and 2.114 THz, closer to the peaks of free tryptophan molecules than in normal tissue. A possible reason is that there is more free tryptophan in AD brain tissue, while in normal brain tissue more tryptophan is attached to other molecules. Our study suggests that THz-absorption modes may be used as an AD biomarker fingerprint in brain, and that THz-TDS is a promising technique for early diagnosis of AD.

The accurate identification of the human brain tumor boundary and the complete resection of the tumor are two essential factors for the removal of the glioma tumor in brain surgery. We present a visible resonance Raman (VRR) spectroscopy technique for differentiating the brain tumor margin and glioma grading. Eighty-seven VRR spectra from twenty-one human brain specimens of four types of brain tissues, including the control, glioma grade II, III, and IV tissues, were observed. This study focuses on observing the characteristics of new biomarkers and their changes in the four types of brain tissue. We found that two new RR peaks at 1129 cm−1 and 1338 cm−1 associated with molecular vibrational bonds in four types of brain tissues are significantly different in peak intensities of VRR spectra. These two resonance enhanced peaks may arise from lactic acid/phosphatidic acid and adenosine triphosphate (ATP)/nicotinamide adenine dinucleotide, respectively. We found that lactic acid and ATP concentrations vary with glioma gratings. The higher the grade of malignancy, the more the increase in lactic acid and ATP concentrations. These two RR peaks may be considered as new molecular biomarkers and used to evaluate glioma grades and identify the margin of gliomas from the control tissues. The metabolic process of lactic acid and ATP in glioma cells based on the VRR spectral changes may reveal the Warburg hypothesis.

In this paper, a binocular holographic three-dimensional (3D) display system combining a single spatial light modulator (SLM) and a grating is proposed and implemented. A synthetic phase-only hologram of the left and right 3D perspective images of an object is calculated by the layer-based Fresnel diffraction method according to the depth information, and uploaded onto the SLM for holographic 3D reconstruction with correct depth cues. The grating is designed and fabricated to guide the reconstructed left and right 3D perspective images to the corresponding eyes. Optical experiments demonstrate that the proposed system can successfully present binocular holographic 3D images with both the accommodation effect and binocular parallax, which enables observation free of the accommodation-vergence conflict and visual fatigue problem.

There are three short wavelength infrared (SWIR) optical windows outside the conventionally used first near-infrared (NIR) window (650 to 950 nm). They occur in the 1000- to 2500-nm range and may be considered second, third, and fourth NIR windows. The second (1100 to 1350 nm) and third windows (1600 to 1870 nm) are now being explored through label-free linear and multiphoton imaging. The fourth window (2100 to 2350 nm) has been mostly ignored because of water absorption and the absence of sensitive detectors and ultrafast lasers. With the advent of new technology, use of window IV is now possible. Absorption and scattering properties of light through breast and prostate cancer, bone, lipids, and intralipid solutions at these windows were investigated. We found that breast and prostate cancer and bone have longer total attenuation lengths at NIR windows III and IV, whereas fatty tissues and intralipid have longest lengths at windows II and III. Since collagen is the major chromophore at 2100 and 2350 nm, window IV could be especially valuable in evaluating cancers and boney tissues, whereas windows II and III may be more useful for tissues with high lipid content. SWIR windows may be utilized as additional optical tools for the evaluation of collagen in tissues.

Light scattering and transmission of Gaussian (G) and Laguerre-Gaussian (LG) vortex beams with different orbital angular momentum (L) in various turbid media were investigated. Transmittance was measured with varied ratios of sample thickness (z) to scattering mean free path (lsubs/sub) of turbid media, z/lsubs/sub. In the ballistic region, the LG and G beams were found to have no significant difference on transmittance, while in the diffusive region, the LG beams showed a higher received signal than the G beams, and the LG beams with higher L values showed a higher received signal than those with lower L values. The transition points from ballistic to diffusive regions for different scattering media were determined. This newly observed transmittance difference of LG and G beams may be used for deep target detection in turbid media through LG beam imaging.