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On-fiber micro-structures are favorable platforms for sensing in aqueous environments. Durable in-liquid operation with NIR light transmitted through fused optical microknot fibers defined on adiabatic tapers is presented in straight versus folded configurations. We suggest and demonstrate two schemes for OMF deployment: folded configuration which is intended for remote sensing, and straight configuration on either hydrophilic or hydrophobic substrate, the latter of which is useful in packaged geometries. We study experimentally the OMF preparation methods in folded, straight on glass surface and straight on PDMS surfaces. The persistent detection of NIR light transmission resonances in the presence of volatile liquid capabilities are experimentally demonstrated in the various configurations.

We suggest a time-lens array with a filling factor of 200% and increased resolution of 60% without decreasing the number of lenses in the array. This time-lens array is based on a series of orthogonally polarized time-lenses. We investigate the different nonlinear interactions and show that when the pump waves of two adjacent time-lenses have orthogonal states of polarization, it is possible to overlap by 50% without unwanted nonlinear interactions.

We study the polarization dynamics of ultrafast solitons in mode-locked fiber lasers. We find that when a stable soliton is generated, it's state-of-polarization shifts toward a stable state and when the soliton is generated with excess power levels it experiences relaxation oscillations in its intensity and timing. On the other hand, when a soliton is generated in an unstable state-of-polarization, it either decays in intensity until it disappears, or its temporal width decreases until it explodes into several solitons and then it disappears. We also found that when two solitons are simultaneously generated close to each other, they attract each other until they collide and merge into a single soliton. Although, these two solitons are generated with different states-of-polarization, they shift their state-of-polarization closer to each other until the polarization coincides when they collide. We support our findings by numerical calculations of a non-Lagrangian approach by simulating the Ginzburg-Landau equation governing the dynamics of solitons in a laser cavity. Our model also predicts the relaxation oscillations of stable solitons and the two types of unstable solitons observed in the experimental measurements., 10 pages, 6 figures, submitted to Opt. Exp

In this paper we present a new technique for a fiber-based temporal super resolving system allowing to improve the resolution of a temporal imaging system. The proposed super resolving concept is based upon translating the field of view multiplexing method that is used to increase resolution in spatial imaging systems from the spatial domain to the temporal domain. In this paper, an optical realization of our proposed system is presented, using optical fibers and electro-optic modulators. In addition, we show how one can apply this method using low-rate electronics for the required modulation. We also show simulation results that demonstrate the high resolution accepted in our method compares to the basic temporal imaging system. Experimental results which demonstrate resolution improvement by a factor of 1.5 based on the proposed method are presented together with an additional experiment that shows the ability to generate the desired modulation with low rate electronics.

Time-lenses in general proved to be useful for many applications and specifically when utilizing them for temporal imaging schemes where they can image ultrafast signals that cannot be detected by any electronic based device. Over the last few years, we demonstrated that when joining together several time-lenses into a single time-lens array, it is possible to gain more information on the input signal. Such as measuring temporal depth imaging, the state of polarization of the input signal as a function of time, and retrieving the phase dynamics. However, when designing an array of time-lenses, there is a trade-off between joining large number of small time-lenses, so each signal will interact with many time-lenses but each one has low resolution, and joining small number of large time-lenses, so each has better temporal resolution but on the expanse of interacting with smaller number of time-lenses in the array. We showed that one way to overcome this drawback is to overlap adjacent timelenses. Thus it is possible to both have large number of time-lenses without compromising on the size of each time-lens and obtaining high temporal resolution. In this proceeding, we overlap two time-lenses and measure the spectrum of the idler. We compare the numerical simulations of the frequency domain of the idler to the measured spectrum of the idler.

We investigated the vectorial nature of ultrafast rogue waves in fiber lasers. In this proceeding, we present the analytical evolution of the nonlinear Schroedinger equation in vector field and show that when considering two Solitons with different state of polarization, they do not stay static which indicates that such Solitons are not a solution of the system.

Time-lenses were developed rapidly over the last year. They enable measurements of ultrafast signals which were not measured before with limited electronics detectors. Time-lens enable to image ultrafast signals from sub picosecond time-scales to nanosecond time-scale while preserving the intensity, phase and state of polarization. However, most time-lenses are focus only on the time-domain and ignore the spatial domain. This hinder many ultrafast phenomena which combine the dynamics in time and space together. In this proceeding, we demonstrate the measured results of the mode splitter which is a crucial device for achieving a time-lens which combines time and space.

Temporal imaging system have enabled imaging of ultrafast phenomena with high temporal resolution different ultrafast phenomena. Specifically, time-lenses which are based on nonlinear interaction of four-wave mixing have a wide field of view together with high F-number. These offers temporal imaging system with large magnifications in the time-domain. However, when considering a time-lens based on four-wave mixing interaction, the input signal must be synchronized to the pump wave which makes it challenging for measuring any ultrafast phenomena with unknown time-of-arrival. Therefore, we developed a temporal imaging system which does not require this synchronization between a signal and a pump wave. This is done by generating time-lenses with high repetition-rate. Therefore, any input signal will interact with one of the time-lenses and it will be imaged in time with high probability. In this proceeding, we demonstrate how our temporal scheme is able to measure with high temporal resolution the start-up dynamics of pulsation in a fiber laser.

A time-lens can image signals in time and map ultrafast signals from frequency to time. The concept of time-lens is based on the duality between the diffraction of light in space and the dispersion of pulses in time, which arises from the similarity between the equations describing these two phenomena. In this paper we explain how to use time-lenses in order to perform high-resolution temporal imaging on non-classical ultrafast signals. Such a scheme can be used e.g. for diagnosing quantum cryptography schemes on optical fiber networks or assessing the performance of photonic quantum computers and simulators.

We developed a unique temporal imaging scheme which is able to detect all the properties of an optical signal in a sub picosecond resolution. This includes imaging of the intensity, the phase, and the state of polarization as a function of time. We are aiming to utilize this advance temporal imaging scheme for studying ultrafast phenomena which were not investigated until now. In this proceeding we describe in details the experimental setup with all its components and parts beyond what we showed and explained in the paper.

Correlated beams are important in classical and quantum communication as well as other technologies. However, classical amplifiers, which are essential for long transmission of correlated beams, degrade the correlation due to noise and due to the amplifier spectral response. We measure, with a novel high resolution single-shot measurement system, the impact of amplifiers on correlated beams. We develop a new method for analyzing the correlation between the signal and idler beams by choosing peaks in the pulses according to their power levels. We demonstrate how to tailor the correlation after the amplifier to obtain either higher or lower correlation. Our research may influence the future use of amplifiers in non-classical communication systems as well as the transmission of quantum information over long distances.

Modern networks implement multilayer encryption architecture to increase network security, stability, and robustness. Encryption on the lower layers is essential for the safety of the entire network traffic. However, at the lower layers, the data rate is at its highest, and any latency affects the network bandwidth and reduces performance. The best solution to prevent latency is to resort to optical devices that operate at the optical transfer rate, which can revolutionize the field. We developed a new paradigm for optical encryption based on the strengths of optics over electronics and according to temporal optics principles and demonstrated a highly efficient all-optical encryption scheme for modern networks. Specifically, we utilize dispersion together with nonlinear interaction for mixing neighboring bits with a private key. The security of the system is not based on encryption algorithms but on the physical properties of photodetectors that are not able to read long ultrafast signals. Our system encrypts the entire network traffic with low latency, encrypts the signal itself, exploits only one nonlinear interaction, 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.

We study the aberrations of four-wave mixing based time lenses resulting from the cross-phase modulations of the pump wave. These temporal aberrations have no spatial equivalent and are important when imaging weak signals with strong pump waves. We show that as the pump power increases, the cross-phase modulations of the pump are responsible for shifting, defocusing, and imposing temporal coma aberrations on the image. We present experimental results of these aberrations with high agreement to analytical and numerical calculations.

We present highly efficient time-lenses for orthogonal polarized signal waves with a specific state of polarization. Our four-wave mixing based time-lenses exploit polarization mode dispersion to compensate for chromatic dispersion. The results reveal that the efficiency of the time-lens is increased fivefold for both states of polarization. We also compensate for any polarization-dependent losses in the system by tailoring the pump state of polarization. Our time-lenses can be implemented in current telecommunication systems together with polarization division multiplexing in order to reach higher bandwidth.

We developed novel fiber microknots which are designed for high order mode beams traveling in the fiber. The device is based on long period fiber gratings which excite high order modes in tapered fiber and a microknot which is fabricated on the tapered fiber. Thus, the light that resonates in the microknot is propagating in the tapered fiber in high order modes which have higher coupling to the environment. The light which exits the microknot and continue to propagate in the fiber is then exited back to the Gaussian mode by another long period fiber grating before the fiber returns to be a single mode fiber. We found that the spectral response of these microknots have deeper resonances and improved Q-factor.

Phase retrieval is an important field in communication systems, since detectors are generally able to measure intensity while the phase is lost. One of the most common phase retrieval methods is the Gerchberg-Saxton (GS). This algorithm uses two intensity images, while imposing the amplitudes known from the intensities and keeping the phase, the algorithm iteratively reconstructs the lost phase. It was demonstrated that by adding more intensity images, one increase the probability to converge to the correct reconstruction. Space time duality states that since spatial diffraction and temporal dispersion are described by similar equations, the same methodologies developed in space are applicable in time. Following this principle, temporal lenses where developed. Since temporal imaging systems suffer from the same phase loss, phase retrieval methods were applied in this field as well. However, as in space, accurate phase retrieval requires multiple intensity images. In this work, we propose a temporal phase retrieval methods based on Gerchberg-Saxton, where the multiple planes are measured by a timelens array. The temporal lens array is achieved using four-wave mixing interaction between a signal and a chirped pump wave, resulting in high temporal magnification. The proposed iterative phase reconstruction algorithm takes advantage of the overlap between nearby lenses, which improves the convergence. We demonstrate how increasing the number of planes improves the reconstruction. Furthermore, the use of shifted lenses, as opposed to several defocused images, has a practical advantage in regards to additional errors in the system.

Over the last years, we developed advanced microfiber devices including fiber microknots and long period fiber gratings on tapered fibers. In this proceeding, we present our try out to create a twisted fiber for manipulating the state of polarization of the light and specifically to rotate the state of polarization. This attempt did not succeed due to the fact that we tapered the fiber during the twisting by heating it which relieved all the tension in the fiber and prevented from creating twisted birefringence.

In this proceeding, we describe in details our experimental setup and the free-space scheme which enable us to develop advanced time-lenses. We compare different methods for preparing the pump pulses and explain their pros and cons. Specifically, we show that when assembling the time-lens in free space, the system has lower losses which result in higher efficiency and thus less amplifiers. Since we do not need as many amplifiers, the noise level is lower and we can detect weaker signals.

On-fiber microstructures are favorable platforms for sensing in aqueous environments. We suggest and demonstrate two deployment schemes of microstructured fibers: folded configuration intended for remote sensing, and straight configuration on either hydrophilic or hydrophobic substrate, the latter of which is useful in packaged geometries. The persistent detection of NIR light transmission resonances in the presence of volatile liquid capabilities are experimentally demonstrated. We present numerical results on the photonic transmission in microknot resonators with different contact coupling area geometries and refractive index variations. A recipe for the experimental realization of a significant Q-factor increase in microknot resonators is also prescribed.

We demonstrate a temporal imaging system that can capture events with unknown time-of-arrival in the time domain without the need to synchronize the signal. The temporal imaging system is based on a time-lens that uses a high repetition-rate fiber laser for the pump wave together with a time-stretch scheme. After dispersion, the timing between adjacent pump pulses is smaller than the pulse width. Therefore, the signal interacts with one of the pump pulses with high probability, regardless of its arrival time. We discuss the intensity dependence and temporal aberrations of such an imaging system and demonstrate a direct temporal imaging of the buildup dynamics of solitons.

Fiber lasers are convenient for studying extreme and rare events, such as rogue waves, thanks to the lasers’ fast dynamics. Indeed, several types of rogue wave patterns were observed in fiber lasers at different time-scales: single peak, twin peak, and triple peak. We measured the statistics of these ultrafast rogue wave patterns with a time lens and developed a numerical model proving that the patterns of the ultrafast rogue waves were generated by the non-instantaneous relaxation of the saturable absorber together with the polarization mode dispersion of the cavity. Our results indicate that the dynamics of the saturable absorber is directly related to the dynamics of ultrafast extreme events in lasers.

We developed a full-Stokes temporal imaging system which measures the Stokes vector of ultrafast signals as a function of time. The system is based on a time-lens array where each time-lens in the array projects the signal on a different state of polarization.

Fiber micro-knots are a promising and a cheap solution for advanced fiber-based sensors. We investigated complex fiber micro-knots in theory and experiment. We compared the measured spectral response and present an analytical study of simple micro-knots with double twists, twin micro-knots, figure-eight micro-knots, and tangled micro-knots. This research brings the simple fabrication process and robustness of fiber micro-knots into the world of complex resonators which may lead to novel optical devices based on fiber micro-knots.

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.

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.

We study experimentally and theoretically the interactions among ultrashort optical pulses in the soliton rain multiple-pulse dynamics of a fiber laser. The laser is mode-locked by a graphene saturable absorber fabricated using the mechanical transfer technique. Dissipative optical solitons aggregate into pulse bunches that exhibit complex behavior, which includes acceleration and bi-directional motion in the moving reference frame. The drift speed and direction depend on the bunch size and relative location in the cavity, punctuated by abrupt changes under bunch collisions. We model the main effects using the recently proposed noise-mediated pulse interaction mechanism, and obtain a good agreement with experiments. This highlights the major role of long-range Casimir-like interactions over dynamical pattern formations within ultrafast lasers.

We investigated the resolution limits of time-lenses and developed a super-resolution technique in the time domain based on localization microscopy algorithm, demonstrating an improved resolution by a factor of two.