Dynamics of frequency-modulated soliton-like pulses in a longitudinally inhomogeneous active optical waveguide

Conditions of the formation and amplification of frequency-modulated soliton-like pulses in longitudinally inhomogeneous active optical waveguides with anomalous dispersion of group velocities are studied. Group velocity dispersion profiles that are necessary for existence and amplification for active and passive optical waveguides are determined, and the dependences on the distance passed along the waveguide, duration, and chirp of the pulse are established.     

Generation of a sequence of frequency-modulated pulses in longitudinally inhomogeneous optical waveguides

The conditions for the generation and efficient amplification of frequency-modulated soliton-like wave packets in longitudinally inhomogeneous active optical waveguides have been studied. The possibility of forming a sequence of pico- and subpicosecond pulses from quasi-continuous radiation in active and passive optical waveguides with the group-velocity dispersion (GVD) changing over the waveguide length is considered. The behavior of a wave packet in the well-developed phase of modulation instability with a change in the waveguide inhomogeneity parameters has been investigated based on the numerical analysis.     

Amplification of chirped pulses in inhomogeneous three-level active optical fibers

The possibility of efficient amplification of self-similar frequency-modulated wave packets in amplifiers inhomogeneous along their length is investigated. Special features of the amplification dynamics in erbium fiber amplifiers that operate according to the three-level scheme are analyzed. It is shown that active optical fibers with a specially designed profile of the normal group-velocity dispersion allow amplifying subpicosecond pulses with high efficiency.     

基于等效衰减矢方法的非均匀光波导色散方程

利用转换矩阵理论和等效衰减矢的概念，以此为根据分析了任意折射率分布平板波导的模式传输特性，导出了意义明确的非均匀平板波导的色散方程的严格的解析解，并指出了ＷＫＢ法的局限性，数值计算的结果表明本文所得公式的结果和严格的数值解非常接近，表明本文所得的公式是严格的。     

Dispersion and nonlinear management for femtosecond optical solitons

We consider the concept of femtosecond propagation for optical solitons in a dispersion management fiber and study the optimal amplification of optical solitons through dispersion wells and barriers and also for the dispersion tailored profile case. For the former, we observed periodic soliton trapping for the in-phase injection case when their respective velocities were equal and opposite with their amplitudes being unequal and no soliton trapping for the off-phase injection case when the two pulses are having a phase difference of π. For the latter, we observed an enormous amplification of the soliton pulses which is one of our main results in this Letter.     

Divided-pulse amplification of ultrashort pulses

We propose and demonstrate a new approach, to the best of our knowledge, for avoiding nonlinear effects in the amplification of ultrashort optical pulses. The initial pulse is divided longitudinally into a sequence of lower-energy pulses that are otherwise identical to the original, except for the polarization. The low-intensity pulses are amplified and then recombined to create a final intense pulse. This divided-pulse amplification complements techniques based on dispersion management.     

Method of integral equation in the theory of weak-guiding inhomogeneous optical waveguides

A method of integral equation is stated and applied in the analysis of the characteristic and noncharacteristic modes in 3D weak-guiding inhomogeneous optical waveguides. The dispersion curves for the modes of diffused channel waveguides are studied near the critical conditions in absorbing media. The accuracy of recovering the permittivity profile in a channel waveguide from the far-field radiation of the fundamental mode is estimated.     

Generation of stable self-similar wave packets in inhomogeneous optical waveguides with a traveling refractive index wave

The specific features of the dynamics of wave packets in inhomogeneous optical waveguides with a traveling refractive index wave and a parabolic dependence of the refractive index on the transverse coordinates of the waveguide have been investigated. It has been shown that stable self-similar pulses of short (picoand subpicosecond) duration with a high total pulse energy and a large mode area can be generated in the corresponding waveguides. It has also been demonstrated that the self-similar regime of propagation of durationpreserving wave packets can be achieved, in particular, with the normal dispersion of the active optical waveguide used in the work.     

Formation of parabolic pulses in inhomogeneous fiber optical amplifiers

The conditions for forming pulses with parabolic envelope asymptotics in inhomogeneous fiber optical amplifiers are investigated. The profile of normal group-velocity dispersion, which ensures formation of parabolic pulses with a reduced rate of frequency modulation, is determined. It is shown by numerical simulation that the presence of chirp in the input pulse may cause narrowing of the spectrum at a certain energy.     

Optical soliton with group delay in microring coupled-resonator optical waveguides

This paper derives the dispersion relation of microring coupled-resonator optical waveguides (CROWs) without any approximation by using the transfer matrix method. Based on the established dispersion relation of CROWs it obtains the slow group velocity and dispersion coefficient. It finds that the effect of dispersion on optical pulses can be adjusted to balance the effect of nonlinearity by changing coupling coefficient or loss, so optical soliton with group delay can be obtained in microring CROWs. The optical soliton with group delay is of great significance for applications of microring CROWs in delay lines and optical buffers of future all-optical communication systems.     

Optimized amplification of femtosecond optical pulses by dispersion management for octave-spanning optical frequency comb generation

We report a method for optimizing the amplification of femtosecond optical pulses by using dispersion management. The amount of dispersion provided to the seed optical pulse of an erbium-doped fiber (EBF) has an optimal region that enhances the output power of an amplifier. The power enhancement is accompanied by spectral broadening, which originates from adiabatic narrowing in the erbium-doped fiber. The amplified optical pulses can be used to generate an octave-spanning optical frequency comb (OFC) by employing a highly nonlinear fiber (HNLF).     

Chalcogenide glasses as a medium for controlling parameters of ultrashort IR pulses: II

The propagation of ultrashort optical pulses in planar chalcogenide glass waveguides with uniform or periodic claddings is considered. In comparison with silica waveguides a structure based on chalcogenide glass provides higher nonlinearity. This material has a high normal dispersion in the wavelength range of 1.5–3.5 μm. Periodic waveguide structures can be used to compensate for this dispersion. High-intensity laser pulses propagating in these structures undergo spectral broadening. The influence of the phase self-modulation of a pulse on its spectrum and width is analyzed using numerical simulations.     

光孤子脉冲在光纤放大器中的传播

本文建立了包括增益色散,受激喇曼散射,双光子吸收效应的理论模型,讨论了光孤子脉冲在光纤放大器中的传播.数值计算结果表明:在反常色散范围内,光孤子的放大是不稳定的.增益色散导致光脉冲对称分裂,而受激喇曼散射则导致不对称的分裂.在增益色散和受激喇曼散射的共同作用下可获得新的时域和频域特征.有限带宽的放大能抑制受激喇曼散射引起的自频移.本文对有啁啾的光孤子脉冲的放大也进行了分析.     

Dispersion characteristics of SOI-based slot optical waveguides

The invention of the slot waveguide had enabled a number of interesting novel linear or nonlinear optical applications by guiding light in nanometers-wide low index slots guarded by high-index slabs. As one of its key characteristics, the low modal index for this kind of waveguides has been demonstrated by many studies. However, their higher order dispersion properties have not been thoroughly investigated yet, while the growing size and complexity of these devices and their potential nonlinear optical applications involving short optical pulses demand further understanding in their dispersion behavior. We here carry out a numerical study on the higher order dispersion characteristics of the SOI-based slot structures around the 1550 nm wavelength. Our results show that they could have significantly different second order dispersion properties in contrast to the traditional channel SOI waveguides. Their potentially large normal dispersion could have an impact on various nonlinear or linear applications. The relationship between the dispersion performance and the waveguide design is also investigated, and the results could show further venues to optimize or control the dispersion properties of such waveguides.     

Pulse Compression by Filamentation in Argon with an Acoustic Optical Programmable Dispersive Filter for Predispersion Compensation

We have experimentally demonstrated pulses 0.4 mJ in duration smaller than 12 fs with an excellent spatial beam profile by self-guided propagation in argon. The original 52 fs pulses from the chirped pulsed amplification laser system are first precompressed to 32 fs by inserting an acoustic optical programmable dispersive filter instrument into the laser system for spectrum reshaping and dispersion compensation, and the pulse spectrum is subsequently broadened by filamentation in an argon cell. By using chirped mirrors for post-dispersion compensation, the pulses are successfully compressed to smaller than 12 fs.     

光脉冲在微环耦合谐振光波导中传输线性特性的数值仿真

利用传输矩阵法得到了微环耦合谐振光波导色散关系的一般表达式,并由色散关系出发讨论了光脉冲在微环耦合谐振光波导中传输时的线性特性,包括带宽、群速度、色散和线性相位变化,这些特性对微环耦合谐振光波导在光通信和光传感领域的应用有重要意义. 关键词： 微环光波导 光脉冲线性特性 传输矩阵法 数值仿真     

Bright and dark solitons in the normal dispersion regime of inhomogeneous optical fibers: Soliton interaction and soliton control

Symbolically investigated in this paper is a nonlinear Schrödinger equation with the varying dispersion and nonlinearity for the propagation of optical pulses in the normal dispersion regime of inhomogeneous optical fibers. With the aid of the Hirota method, analytic one- and two-soliton solutions are obtained. Relevant properties of physical and optical interest are illustrated. Different from the previous results, both the bright and dark solitons are hereby derived in the normal dispersion regime of the inhomogeneous optical fibers. Moreover, different dispersion profiles of the dispersion-decreasing fibers can be used to realize the soliton control. Finally, soliton interaction is discussed with the soliton control confirmed to have no influence on the interaction. The results might be of certain value for the study of the signal generator and soliton control.     

Broadening compensation for ultrashort pulses in photonic crystals

Extremely large group velocity dispersion of both signs can be achieved at the band edges of guided modes in photonic crystal waveguides. The selection of a proper value and sign of this parameter allows the design of short-length waveguides to compensate for pulse broadening. This pulse broadening can be caused, for instance, when a photonic crystal delay line is introduced. We present a theoretical study of the possibilities of using photonic crystal waveguides as intra-circuital dispersion compensation elements for ultrashort pulses, so the width of a transmitted pulse can be reduced. However, we also demonstrate that recovering the original pulse shape is not possible for these large-bandwidth pulses due to higher-order dispersion terms.     

Design considerations for a compact grism stretcher for non-collinear optical parametric chirped-pulse amplification

The dispersion management of a non-collinear optical parametric chirped-pulse amplifier is presented. A stretcher based on a combination of a grating and a prism pair (grism) is given and analyzed in detail. This combination can provide up to 300 nm acceptance bandwidth and is suitable for parametric amplification of few-cycle pulses. The amplified pulses can be compressed by the dispersion of optical glasses such as SF57 and the residual high-order dispersion may be compensated by adaptive optical filters and chirped mirrors.     

Soliton dynamics of megawatt ultrashort light pulses in a hollow photonic-crystal fiber: Effect of high-order dispersion and retarded nonlinearity

The properties of megawatt optical solitons in hollow photonic-crystal fibers (PCFs) are studied. We demonstrate regimes where high-power laser pulses can be compressed to a few cycles of light field and identify the main tendencies in the soliton dynamics of ultrashort laser pulses in hollow PCFs originating from dispersion properties and limited transmission band of such waveguides. The influence of retarded nonlinearity on the soliton dynamics of high-power laser pulses in a hollow PCF is analyzed. In a multisoliton regime, retarded nonlinearity and high-order dispersion are shown to result in the formation of high-power pulses displaying no oscillations of their temporal envelope, which would be typical of standard high-order solitons.