We investigated the spectral response of complex fiber micro-knots. We found reach spectral response for both transmitted and reflected light from these complex micro-knots. We analyzed these complex micro-knots and found good agreement between the calculated and the measured results.
Optical methods for extracting properties of tissues are commonly used. These methods are non-invasive, cause no harm to the patient and are characterized by high speed. The human tissue is a turbid media hence it poses a challenge for different optical methods. In addition the analysis of the emitted light requires calibration for achieving accuracy information. Most of the methods analyze the reflected light based on their phase and amplitude or the transmitted light. We suggest a new optical method for extracting optical properties of cylindrical tissues based on their full scattering profile (FSP), which means the angular distribution of the reemitted light. The FSP of cylindrical tissues is relevant for biomedical measurement of fingers, earlobes or pinched tissues. We found the iso-pathlength (IPL) point, a point on the surface of the cylinder medium where the light intensity remains constant and does not depend on the reduced scattering coefficient of the medium, but rather depends on the spatial structure and the cylindrical geometry. However, a similar behavior was also previously reported in reflection from a semi-infinite medium. Moreover, we presented a linear dependency between the radius of the tissue and the point's location. This point can be used as a self-calibration point and thus improve the accuracy of optical tissue measurements. This natural phenomenon has not been investigated before. We show this phenomenon theoretically, based on the diffusion theory, which is supported by our simulation results using Monte Carlo simulation.
We developed the concept of temporal depth imaging and defined non-flat signals as signals with different dispersion values as a function of time. We demonstrated how shifting the timing of a time lens makes it possible to retrieve the dispersion value of each point in the signal, which is equivalent to a 3D imaging system. Finally, we demonstrated how a time lens array can retrieve these values with a single measurement by comparing the different images obtained by the time lens array.
We developed temporal super-resolution technique by adopting super-resolution techniques from space to time. Similar to spatial optics, where knowledge about the basic building blocks of the image can lead to better resolution, as demonstrated by localization microscopy techniques. We are utilizing our knowledge on the shape and duration of the pulses to retrieve a super-resolution image in the time domain of an input signal. The resolution of our time-lens is much lower than the needed resolution to obtain the signal but never-the-less we obtain a temporal image with high resolution.
Light reflectance and transmission from soft tissue has been utilized in noninvasive clinical measurement devices such as the photoplethysmograph (PPG) and reflectance pulse oximeter. Most methods of near infrared (NIR) spectroscopy focus on the volume reflectance from a semi-infinite sample, while very few measure transmission. However, since PPG and pulse oximetry are usually measured on tissue such as earlobe, fingertip, lip and pinched tissue, we propose examining the full scattering profile (FSP), which is the angular distribution of exiting photons. The FSP provides more comprehensive information when measuring from a cylindrical tissue. In our work we discovered a unique point, that we named the iso-pathlength (IPL) point, which is not dependent on changes in the reduced scattering coefficient (µs’). This IPL point was observed both in Monte Carlo (MC) simulation and in experimental tissue mimicking phantoms. The angle corresponding to this IPL point depends only on the tissue geometry. In the case of cylindrical tissues this point linearly depends on the tissue diameter. Since the target tissues for clinically physiological measuring are not a perfect cylinder, in this work we will examine how the change in the tissue cross section geometry influences the FSP and the IPL point. We used a MC simulation to compare a circular to an elliptic tissue cross section. The IPL point can serve as a self-calibration point for optical tissue measurements such as NIR spectroscopy, PPG and pulse oximetery.
Extracting optical parameters of turbid medium (e.g. tissue) by light reflectance signals is of great interest and has many applications in the medical world, life science, material analysis and biomedical optics. The reemitted light from an irradiated tissue is affected by the light's interaction with the tissue components and contains the information about the tissue structure and physiological state. In this research we present a novel noninvasive nanophotonics technique, i.e., iterative multi-plane optical property extraction (IMOPE) based on reflectance measurements. The reflectance based IMOPE was applied for tissue viability examination, detection of gold nanorods (GNRs) within the blood circulation as well as blood flow detection using the GNRs presence within the blood vessels. The basics of the IMOPE combine a simple experimental setup for recording light intensity images with an iterative Gerchberg–Saxton (G-S) algorithm for reconstructing the reflected light phase and computing its standard deviation (STD). Changes in tissue composition affect its optical properties which results in changes in the light phase that can be measured by its STD. This work presents reflectance based IMOPE tissue viability examination, producing a decrease in the computed STD for older tissues, as well as investigating their organic material absorption capability. Finally, differentiation of the femoral vein from adjacent tissues using GNRs and the detection of their presence within blood circulation and tissues are also presented with high sensitivity (better than computed tomography) to low quantities of GNRs (<3 mg).
We investigated ultrafast rogue waves in fiber lasers and found three different patterns of rogue waves: single- peaks, twin-peaks, and triple-peaks. The statistics of the different patterns as a function of the pump power of the laser reveals that the probability for all rogue waves patterns increase close to the laser threshold. We developed a numerical model which prove that the ultrafast rogue waves patterns result from both the polarization mode dispersion in the fiber and the non-instantaneous nature of the saturable absorber. This discovery reveals that there are three different types of rogue waves in fiber lasers: slow, fast, and ultrafast, which relate to three different time-scales and are governed by three different sets of equations: the laser rate equations, the nonlinear Schrodinger equation, and the saturable absorber equations, accordingly. This discovery is highly important for analyzing rogue waves and other extreme events in fiber lasers and can lead to realizing types of rogue waves which were not possible so far such as triangular rogue waves.
Modern networks implement multi-layer encryption architecture to increase network security, stability, and robustness. We developed a new paradigm for optical encryption based on the strengths of optics over electronics and according to temporal optics principles. We developed a highly efficient all-optical encryption scheme for modern networks. Our temporal encryption scheme exploits the strength of optics over electronics. Specifically, we utilize dispersion together with nonlinear interaction for mixing neighboring bits with a private key. Our system encrypts the entire network traffic without any latency, encrypt the signal itself, exploit only one non- linear interaction, it is energetically efficient with low ecologic footprint, and can be added to current networks without replacing the hardware such as the lasers, the transmitters, the routers, the amplifiers or the receivers. Our method can replace current slow encryption methods or can be added to increase the security of existing systems. In this paper, we elaborate on the theoretical models of the system and how we evaluate the encryption strength with this numerical tools.
Light reflectance and transmission from soft tissue has been utilized in noninvasive clinical measurement devices such as the photoplethysmograph (PPG) and reflectance pulse oximeter. Most methods of near infrared (NIR) spectroscopy focus on the volume reflectance from a semi-infinite sample, while very few measure transmission. We have previously shown that examining the full scattering profile (FSP), which is the angular distribution of exiting photons, provides more comprehensive information when measuring from a cylindrical tissue, such as earlobe, fingertip and pinched tissue. Our hypothesis is that the change in blood vessel diameter is more significant than the change in optical properties. The findings of this work demonstrate a realistic model for optical tissue measurements such as NIR spectroscopy, PPG and pulse oximetery.
Human tissue is one of the most complex optical media since it is turbid and nonhomogeneous. In our poster, we suggest a new type of skin phantom and an optical method for sensing physiological tissue condition, basing on the collection of the ejected light at all exit angles, to receive the full scattering profile. Conducted experiments were carried out on an unique set-up for noninvasive encircled measurement. Set-up consisted of a laser, a photodetector and new tissues-like phantoms made with a polyvinyl chloride-plastisol (PVCP), silicone elastomer polydimethylsiloxane (PDMS) and PDMS with glycerol mixture. Our method reveals an isobaric point, which is independent of the optical properties. Furthermore, we present the angular distribution of cylindrical phantoms, in order to sense physiological tissue state.
Various techniques for recovering optical parameters were developed over the years. However each has its limitations, constraints and disadvantages (e.g. accuracy, computational speed, sample assembly, distinguishing between the different parameters, etc.). This research suggests an optical technique for extracting the reduced scattering coefficient (μs') of substances by examining the light transmission through or reflection from them. It uses the multiple planes Gerchberg- Saxton (G-S) algorithm to reconstruct the light phase created by the substance. At the end of the algorithm, μs' can be estimated from the standard deviation (STD) of the retrieved phase of the reemitted light. We will use the theory to compute the phase’s STD that directly correlated to the optical properties of different substances. Two possible applications for this technique, out of many others, are nanoparticles (NPs) penetration depth determination, for promoting topical medications, and detection of milk components quantitative signature as <i>en route </i>to milk content monitoring tool. For the former application, three materials were fabricated into NPs and all presented an activity enhancement with their size reduction. Then the NPs were applied on tissues and detected by our technique. For the latter, different milk content concentrations were examined resulting with different STD values suggesting it can be used as indicator for the milk component concentrations.
Human tissue is one of the most complex optical media since it is turbid and nonhomogeneous. We suggest a new optical method for sensing physiological tissue state, based on the collection of the ejected light at all exit angles, to receive the full scattering profile. We built a unique set-up for noninvasive encircled measurement. We use a laser, a photodetector and tissues-like phantoms presenting different diameters and different reduced scattering coefficients. Our method reveals an isobaric point, which is independent of the optical properties and linearly depends on the exact tissue geometry. Furthermore, we present the angular distribution of cylindrical silicon based phantoms containing blood vessels in different diameters, in order to sense physiological tissue state. We show, for the first time, by simulation and experiments, that the vessel diameter influences on the full scattering profile. In addition, we found higher reflection intensity for larger vessel diameters, in accordance to the shielding effect. These findings can be useful for biomedical applications such as non-invasive and simple diagnostic of the fingertip joint, ear lobe and pinched tissues.
Light reflectance and transmission from soft tissue has been utilized in noninvasive clinical measurement devices such as the photoplethysmograph (PPG) and reflectance pulse oximeter. Incident light on the skin travels into the underlying layers and is in part reflected back to the surface, in part transferred and in part absorbed. Most methods of near infrared (NIR) spectroscopy focus on the volume reflectance from a semi-infinite sample, while very few measure transmission. We have previously shown that examining the full scattering profile (angular distribution of exiting photons) provides more comprehensive information when measuring from a cylindrical tissue. Furthermore, an isobaric point was found which is not dependent on changes in the reduced scattering coefficient. The angle corresponding to this isobaric point depends on the tissue diameter. We investigated the role of multiple scattering and absorption on the full scattering profile of a cylindrical tissue. First, we define the range in which multiple scattering occurs for different tissue diameters. Next, we examine the role of the absorption coefficient in the attenuation of the full scattering profile. We demonstrate that the absorption linearly influences the intensity at each angle of the full scattering profile and, more importantly, the absorption does not change the position of the isobaric point. The findings of this work demonstrate a realistic model for optical tissue measurements such as NIR spectroscopy, PPG, and pulse oximetery.
We irradiated neuroblastoma SH-SY5Y cell line with low-level light-emitting diode (LED) illumination at a visible wavelength of 520 nm (green) and intensity of 100 mW/cm2. We captured and analyzed the cell morphology before LED treatment, immediately after, and 12 and 24 h after treatment. Our study demonstrated that LED illumination increases the amount of sprouting dendrites in comparison to the control untreated cells. This treatment also resulted in more elongated cells after treatment in comparison to the control cells and higher levels of expression of a differentiation related gene. This result is a good indication that the proposed method could serve in phototherapy treatment for increasing sprouting and enhancing neural network formation.
Most methods for measuring light-tissue interaction focus on volume reflectance, while very few measure light transmission. In a previous work, we suggested investigating the influence of blood vessel diameter on photons exiting the tissue at all exit angles to receive the full scattering profile. By this method, we have shown that there is a central angle, i.e., the isobaric point, independent of blood vessel diameter. The vessel diameter changes the effective reduced scattering coefficient. However, both the scattering profile and the value of the isobaric point strongly depend on optical properties and the exact geometry of the tissue. In this study, we investigate the dependency of the isobaric point on tissue diameter and scattering coefficient in both two-dimensional and three-dimensional simulations. We show that the value of this point linearly depends on tissue diameter. The findings of this work solve the dilemma of whether to measure transmission or reflection since the isobaric point reduces by half the total amount of exiting photons. Furthermore, the full scattering profile is sensitive to changes in the scattering properties, but a single isobaric point to these changes is expected. If this point is not found, it is a diagnostic indication of an unexpected change in the tissue.
Most methods for measuring light–tissue interactions focus on the volume reflectance while very few measure the transmission. We investigate both diffusion reflection and diffuse transmission at all exit angles to receive the full scattering profile. We also investigate the influence of blood vessel diameter on the scattering profile of a circular tissue. The photon propagation path at a wavelength of 850 nm is calculated from the absorption and scattering constants via Monte Carlo simulation. Several simulations are performed where a different vessel diameter and location were chosen but the blood volume was kept constant. The fraction of photons exiting the tissue at several central angles is presented for each vessel diameter. The main result is that there is a central angle that below which the photon transmission decreased for lower vessel diameters while above this angle the opposite occurred. We find this central angle to be 135 deg for a two-dimensional 10-mm diameter circular tissue cross-section containing blood vessels. These findings can be useful for monitoring blood perfusion and oxygen delivery in the ear lobe and pinched tissues.
Gerchberg-Saxton is a well known iterative approach for computing the phase-only element producing the desired output
intensity distribution. However, the converged phase is a continuous distribution while for fabrication a discrete
(quantized) distribution is required.
In this paper we present a novel and improved method for designing a quantized phase-only beam shaping mask.
The proposed approach performs well even for binary phase-only mask and even when a gray level output distribution is