Propagation Of Optical Pulses Research Articles

Nonlinear filtering of an optical pulse train using dissipative Kerr solitons

The capability to store light for extended periods of time enables optical cavities to act as narrowband optical filters, whose linewidth corresponds to the cavity’s inverse energy storage time. Here, we report on nonlinear filtering of an optical pulse train based on temporal dissipative Kerr solitons in microresonators. Our experimental results in combination with analytical and numerical modeling show that soliton dynamics enables information storage about the system’s physical state longer than the cavity’s energy storage time, thereby giving rise to a filter width that can be more than an order of magnitude below the cavity’s intrinsic linewidth. Such nonlinear optical filtering can find immediate applications in optical metrology, and low-timing jitter ultrashort optical pulse generation and potentially opens new avenues for microwave photonics.

Riemann‐Hilbert approach for multisoliton solutions of generalized coupled fourth‐order nonlinear Schrödinger equations

The main purpose of this work is to develop Riemann‐Hilbert approach to obtain the soliton solutions for generalized coupled fourth‐order nonlinear Schrödinger equations, which describe the simultaneous propagation of optical pulses in an inhomogeneous optical fiber. Starting from the spectral analysis of the Lax pair, a Riemann‐Hilbert problem is set up. After solving the obtained Riemann‐Hilbert problem with reflectionless case, we systematically derive multisoliton solutions for the generalized coupled fourth‐order nonlinear Schrödinger equations. In addition, the localized structures and dynamic behaviors of one‐ and two‐soliton solutions are shown by some graphic analysis.

Broadband mid-infrared pulse via intra-pulse difference frequency generation based on supercontinuum from multiple thin plates**Project supported by the National Key R&D Program of China (Grant No. 2017YFB0405202), the Major Program of the National Natural Science Foundation of China (Grant No. 61690221), the Key Program of the National Natural Science Foundation of China (Grant No. 11434016), and the National Natural Science

We report on the generation of optical pulses with a nearly one octave-spanning spectrum ranging from 1300 nm to 2500 nm at 1 kHz repetition rate, which are based on intra-pulse difference frequency generation (DFG) in β-barium borate crystal (β-BBO) and passively carrier-envelope-phase (CEP) stabilized. The DFG is induced by few-cycle pulses initiated from spectral broadening in multiple thin plates driven by a Ti: sapphire chirped-pulse amplifier. Furthermore, a numerical simulation is developed to estimate the conversion efficiency and output spectrum of the DFG. Our results show that the pulses from the DFG have the potential for seeding intense mid-infrared (MIR) laser generation and amplification to study strong-field physics and attosecond science.

Laser Frequency Combs: Graphene‐Coupled Terahertz Semiconductor Lasers for Enhanced Passive Frequency Comb Operation (Adv. Sci. 20/2019)

In article number 1900460, Hua Li, Juncheng Cao, Kai Zhang, Heping Zeng, and co-workers report a graphene-based approach for enhanced passive frequency comb operation and pulse generation in terahertz semiconductor lasers. The saturable absorption and group velocity dispersion compensation provided by a multi-layer graphene sample result in a laser frequency comb operation with highly stabilized frequency lines and optical pulse generation (16 ps) in the terahertz regime.

Vector breathers for the coupled fourth-order nonlinear Schrödinger system in a birefringent optical fiber

Abstract Optical fiber communication is widely applied in the information transmission and capacity handling of information. In this paper, coupled fourth-order nonlinear Schrodinger system, which describes the propagation of ultrashort optical pulses in a birefringent optical fiber, is studied. The Nth-order Darboux transformation and corresponding vector breather solutions are constructed, where N is a positive integer. Based on such solutions, we graphically show four different types of breathers: (1) the one with the one component containing the anti-eye-shaped breather and the other component containing the eye-shaped breather; (2) the one with each component containing the four-petaled breather; (3) the one with each component containing the eye-shaped breather; (4) the one with each component containing the Y-shaped breather. Moreover, we find that the range of the breather along the time axis decreases, and the angle between the breather and the time axis increases as the value of |γ| decreases, where γ represents the strength of higher-order linear and nonlinear effects.

Numerical study on nonlinear and chaotic effects in standard fibre using RK4IP method

In this paper, we carry out a numerical study on nonlinear and chaotic effects produced by the propagation of hyperbolic secant optical pulse in standard fibre. We use the fourth-order Runge–Kutta in the interaction picture (RK4IP) method to analyse the pulse interaction in the fibre medium, this method was employed due to its potential to reduce the numerical error while simultaneously allow increasing the step size. During the study, the input peak power was varied up hundreds of kW trough 1 km of standard single-mode fibre (SMF-28); as a consequence, it was possible to observe the generation of nonlinear and chaotic effects on the final spectrum. These numerical results show the spectral and temporal evolution of energy in a 3D rendering, here, it was possible to demonstrated break frequencies and fragmentation of packets of energy by changing the pump power. Finally, we show that this analysis can be used in subsequent studies employing complex dynamic pulses (noise-like pulses, NLPs).

Three-dimensional few-cycle optical pulses of Gaussian and super-Gaussian cross-section inside the Bragg medium based on carbon nanotubes with dissipation

We have considered the problem of dynamic propagation of the three-dimensional few-cycle optical pulses of Gaussian and super-Gaussian cross-section inside the Bragg medium with carbon nanotubes. The system has dissipation and additional energy “pumping”. We have shown that the pulse propagation is stable inside the considered environment. The special aspect of the pulse evolution of different cross-sections has been determined.

Constructing a partially transparent computational boundary for UPPE using leaky modes

In this paper, we introduce a method for creating a transparent computational boundary for the simulation of unidirectional propagation of optical beams and pulses using leaky modes. The key element of the method is the introduction of an artificial-index material outside a chosen computational domain and utilization of the quasi-normal modes associated with such artificial structure. The method is tested on the free space propagation of TE electromagnetic waves. By choosing the material to have appropriate optical properties, one can greatly reduce the reflection at the computational boundary. In contrast to the well-known approach based on a perfectly matched layer, our method is especially well suited for spectral propagators.

The Physical Parameters of EDFA and SOA Optical Amplifiers and Bit Sequence Variations Based Optical Pulse Generators Impact on the Performance of Soliton Transmission Systems

Abstract This study has outlined the effects of physical parameters of erbium doped fiber amplifier (EDFA), semiconductor optical amplifier (SOA) on the performance of amplified soliton transmission systems. Injection current-based SOA, EDFA length is taken into account. It is observed that the optimum soliton power and signal per noise ratio are achieved with 5 m EDFA length and 900 mA injection current-based SOA. As well as the bit sequence variations based user defined bit sequence generator are employed in order to measure the soliton transmission system performance. The signal per noise ratio is enhanced with 4 bit sequence. Soliton peak power, output soliton power, and maximum Q-factor are optimized with 8 bit sequence for soliton propagation length of 150 km and possible transmission data rates of 160 Gb/s. Improvement percentage ratio in soliton peak power by using two amplification techniques a long propagation length is deeply stimulated with optiwave simulation program.

Optimal pulse propagation in an inhomogeneously gas-filled hollow-core fiber

We study optical pulse propagation through a hollow-core fiber filled with a radially inhomogeneous cloud of cold atoms. A co-propagating control field establishes electromagnetically induced transparency. In analogy to a graded index fiber, the pulse experiences micro-lensing and the transmission spectrum becomes distorted. Based on a two-layer model of the complex index of refraction, we can analytically understand the cause of the aberration, which is corroborated by numerical simulations for a radial Gaussian-shaped function. With these insights, we show that the spectral distortions can be rectified by choosing an optimal detuning from one-photon resonance.

Asymmetrical and self-similar structures of optical breathers for the Manakov system in photorefractive crystals and randomly birefringent fibers

In this paper, the main attention is focused on the optical breather structures of the Manakov system, which can be used to describe the optical pulse propagation in photorefractive crystals and randomly birefringent fibers. The breather solutions of the system are constructed by the Darboux transformation method. The asymmetrical and self-similar structures of optical breathers are observed for the first time.

587 nm nanosecond optical pulse generation by synchronously-driven gain-switched laser diodes with optical injection locking

We describe a novel optical pulse source that can generate yellow-orange optical pulses based on the synchronization of two gain-switched laser diodes under continuous-wave laser light injection. Sum frequency generation of amplified 1309 nm and 1064 nm optical pulses produced 587 nm pulses with 1 ns duration and 2 nJ pulse energy at a repetition rate of 5 MHz. The presented optical pulse source can also produce bursts of picosecond optical pulses inside nanosecond pulse envelopes. These optical pulses are applicable to stimulated emission depletion microscopy for super-resolution imaging of biomedical specimens with green- or yellow- fluorescent proteins labels.

Optical vector lattice breathers of a two-component Rabi-coupled Gross–Pitaevskii system with variable coefficients

A two-component Rabi-coupled Gross–Pitaevskii system with variable coefficients is under investigation. The system can be used to describe the optical vector pulse propagations in two complex electric fields in Bose–Einstein condensates. A rotation transformation and a similarity transformation are successively implemented to transform the system into the celebrated Manakov system. Via utilizing the vector breather solutions obtained of the Manakov system, and choosing several typical kinds of similarity transformation functions, novel vector lattice breathers are excited and observed. These breathers possess lattice background waves, and exhibit abundant patterns.

Width-tunable optical pulse generator based on the polarization-sensitive feature of LiNbO3 crystal in Mach–Zehnder modulator

A width-tunable optical pulses generation scheme by using a single Mach–Zehnder modulator (MZM) based on polarization-sensitive feature of LiNbO3 crystal is proposed and experimentally demonstrated. In the proposed system, a continuous-wave light is sent into MZM via a polarization controller (PC), and interference in a polarization beam splitter after passing through another PC. Experimental results show that the full-width at half-maximum of pulses (10 GHz) can be tuned continuously from 20.39 to 53 ps by adjusting the DC bias voltage of MZM and PCs. A 40 to 10 Gbit / s optical time division multiplexing (OTDM) signal demultiplexing experiment has been demonstrated using the time window provided by the proposed scheme. And the results show that the proposed width-tunable optical pulses generation scheme can be used in OTDM demultiplexing.

Asymmetric propagation and limited wavelength translation of optical pulses through a linear dispersive time-dynamic system.

We study optical pulse propagation through a linear, dispersive, gain-loss-assisted bulk medium whose refractive index is time-varying. To analyze the dynamics, we have used a novel technique of time transformation that provides universal formulas of pulse propagation. Our analytical and numerical investigations reveal that optical pulses show asymmetric behavior while propagating in opposite direction through such a medium, in both the temporal and spectral domains. Moreover, the wavelength shift during this process is the most interesting outcome which is limited in range, but could be tuned by varying the refractive index with time. Phenomena that are observed in this Letter are novel and realizable in practical devices such as coupled waveguides where the refractive index is a function of time.

Rogue wave solutions for a coupled nonlinear Schrödinger equation in the birefringent optical fiber

In this paper, we investigate a fourth-order coupled nonlinear Schrödinger equation, which describes the propagation of ultrashort optical pulses in the birefringent optical fiber. Lax pair is constructed through the symbolic computation, along with the corresponding Darboux transformation (DT) which is different from that given in the existing literatures. Rogue wave solutions are obtained by virtue of the DT. Three different types of the rogue waves based on the solutions are exhibited, i.e., the anti-eye-shaped, eye-shaped four-petaled ones. Moreover, we find that the wave structure is affected by the relative background amplitudes and certain parameter in the solutions, and the range of the first-order rogue wave along the x axis increases with the increase of the fourth order term γ, while the range of the rogue wave along the t axis decreases.

Dipole and Combo Optical Solitons in Birefringent Fibers in the Presence of Four-Wave Mixing

The ultimate theme of this study is to develop dipole and combo optical solitons in birefringent fibers (BF) along with the effect of four-wave mixing (4WM). Two types of rough mediums are used which are Kerr law and parabolic law. Ansatz method of Choudhuri is applied to obtain dark in the bright (dipole) soliton solutions providing bright background for the propagation of optical dark pulse. Ansatz method of Li is applied to obtain combo soliton solutions providing bright solitary wave and dark solitary wave solutions. These results also exist to hold in non-Kerr media with higher order dispersion.

A robust numerical integrator for the short pulse equation near criticality

Abstract The short pulse equation was introduced by Schafer–Wayne (2004) for modeling the propagation of ultrashort optical pulses. While it can describe a wide range of solutions, its ultrashort pulse solutions with a few cycles, which the conventional nonlinear Schrodinger equation does not possess, have drawn much attention. In such a region, the solutions can become quite close to a singularity, and thus existing numerical methods cease to work stably, or even if they do, they require high computational cost. In this paper, we propose a robust numerical integration method which is obtained by combining a hodograph transformation and some structure-preserving methods. The resulting scheme successfully works even when the singularity occurs, and thus gives a highly robust method for resolving near singular solutions of interest. It is confirmed by numerical experiments, and some new insights about derivative blow-up are obtained.

Invite paper: Self-imaging in multimode graded-index fibers and its impact on the nonlinear phenomena

Abstract The phenomenon of periodic self-imaging of optical beams, occurring inside any graded-index (GRIN) medium, was studied during the decade of the 1970s and was exploited to commercialize the GRIN lens. It has been found in recent years that the periodic self-imaging also affects the nonlinear propagation of optical pulses inside multimode GRIN fibers. In this paper, we first present the theory of self-imaging in linear GRIN fibers using a modal expansion approach. It is shown that the optical field at any point inside the fiber can be written without any reference to the fiber modes as a two-dimensional integration over the input field using a propagation kernel that is similar to that found in diffraction theory. However, this kernel has a specific property that reproduces the input field precisely in a periodic fashion along the length of a GRIN fiber (self-imaging). We apply this kernel to study the propagation of a Gaussian beam and discuss how self-imaging is modified by self-focusing produced by the Kerr nonlinearity. We then consider propagation of the continuous and pulsed Gaussian beams inside a GRIN fiber and discuss how self-imaging affects the modulation instability, leads to the formation of GRIN solitons, and produces novel temporal and spectral features when short optical pulses are launched that are intense enough to form high-order solitons.

Combined solitary wave solution of higher-order nonlinear Schrödinger equation with non-Kerr terms in the heterogeneous optical fiber system

In this paper we present a new type of combined solitary wave solution for the variable coefficients higher-order nonlinear Schrödinger (HNLS) equation with non-Kerr nonlinearity, which governs the propagation of optical pulses in the heterogeneous optical fiber system under certain parametric conditions. Unlike those previously-reported solitary wave solutions for the classes HNLS, the expression of this solution in this paper is a composition of the summation of a hyperbolic secant function and a hyperbolic tangent function, and the solution can show the properties of bright and dark soliton respectively. Furthermore, we investigate the stability of the combined solitary wave solution under the small perturbation of noise, amplitude and phase position by using numerical simulation method.