Single-shot analysis of amplified correlated light.

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.

Polarization dynamics of ultrafast solitons.

We study the polarization dynamics of ultrafast solitons in mode-locked fiber lasers. We find that when a stable soliton is generated, its 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.

Cross-phase modulation aberrations in time lenses.

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.

Phase retrieval by an array of overlapping time-lenses.

Temporal imaging of both the intensity and the phase is important for investigating ultra-short events such as rogue waves or mode-locked laser dynamics in a record high resolution. We developed a temporal phase retrieval scheme based on several overlapping time-lenses, where all the time-lenses use the same fibers and detectors leading to high stability and low noise levels. We show that our phase retrieval technique converges faster than techniques that resort to a single time-lens, together with the Fourier transform of the signal.

Full-Stokes temporal imaging.

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.

Bidirectional Soliton Rain Dynamics Induced by Casimir-Like Interactions in a Graphene Mode-Locked Fiber Laser.

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 bidirectional 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.

Polarization dependence of asymmetric off-resonance long period fiber gratings: erratum.

Correction of Fig. 3 which was taken with different conditions than stated in the text. The figure presented here is the correct version with improved resolution.

Long period fiber gratings with off-resonance spectral response based on mechanical oscillations.

We present long period fiber gratings with off-resonance spectral response. Our long period fiber gratings are created by the periodic structure of large perturbations in the fiber diameter. These perturbations result in unique spectral response, even in off-resonance frequencies. Writing these long period fiber gratings is based on utilizing the mechanical vibrations of tapered fibers during the tapering process. This writing method is simple and robust; it has high efficiency, high reproducibility, and low polarization dependency; and it enables real-time tunability of the periodicity, efficiency, and length of the grating. We also demonstrate a complex grating by writing multiple gratings one on top of the other. Finally, we utilize the formation of the gratings in different fiber diameters to investigate the Young's modulus of tapered fibers.

Temporal superresolution based on a localization microscopy algorithm.

We investigate the resolution limits of time lenses based on a four-wave mixing process and present a superresolution technique in the time domain based on a localization microscopy algorithm. Our temporal superresolution technique retrieves features shorter by a factor of 2 than the resolution limit of the system. We present both measured and calculated results of the superresolution scheme and present calculated superresolution of input signals with higher complexity.

Polarization dependence of asymmetric off-resonance long period fiber gratings.

We present the polarization dependence of strong asymmetric long period fiber gratings written on tapered fibers. We found that for off-resonance conditions the spectral response and the output mode strongly depend on the input state of polarization. We utilize this dependence to obtain a mode selective device and demonstrate radially polarized and azimuthally polarized fiber lasers based on these asymmetric long period fiber gratings.

Fused fiber micro-knots.

We present fusing of a fiber micro-knot by a CO2 laser beam. We demonstrate tuning of the coupling strength and tuning of the spectral resonance of the micro-knot by the fusing process. The experimental results reveal that fusing the fiber micro-knots increases the coupling efficiency and improves the robustness and the stability of the micro-knots.