Decreasing Dispersion Profile Research Articles

Optical Pulse Compression in Fibre

Optical pulse compression using similariton propagation in an optical fibre with decreasing dispersion has been demonstrated for the first time. This compression scheme is a practical application of the sech-similariton solution to the generalized nonlinear schrodinger equation(NLSE) with distributed coefficients recently found using the self similarity technique. The fibre with a decreasing dispersion profile is constructed using the comb-profile approximation technique and different variations of the technique have been developed to improve the accuracy of the approximation.

Self-similar picosecond pulse compression for supercontinuum generation at mid-infrared wavelength in silicon strip waveguides

Self-similar pulse compression has important application in highly coherent supercontinuum (SC) generation. In this paper, we numerically present the mid-infrared self-similar picosecond pulse compression in a tapered suspended silicon strip waveguide, which is designed with exponentially decreasing dispersion profile along the direction of propagation. When the variation of the Kerr nonlinear coefficient γ(z), linear and nonlinear losses, higher-order nonlinearity, and higher-order dispersion are taken into consideration, the simulation result shows that a 1 ps input pulse centered at wavelength 2.8μm could be self-similarly compressed to 47.06 fs in a 3.9-cm waveguide taper, along with a compression factor Fc of 21.25, quality factor Qc of 0.78, and negligible pedestal. After that, the compressed pulse is launched into a uniform silicon strip waveguide, which is used for the generation of SC. We numerically demonstrate that the coherence of the generated SC by the compressed pulse can be significantly improved when compared to that generated directly by the picosecond pulse. The simulation results can be used to realize on-chip mid-infrared femtosecond light source and highly coherent supercontinuum, which can promote the development of on-chip nonlinear optics.

Mid-infrared self-similar compression of picosecond pulse in an inversely tapered silicon ridge waveguide

On chip high quality and high degree pulse compression is desirable in the realization of integrated ultrashort pulse sources, which are important for nonlinear photonics and spectroscopy. In this paper, we design a simple inversely tapered silicon ridge waveguide with exponentially decreasing dispersion profile along the propagation direction, and numerically investigate self-similar pulse compression of the fundamental soliton within the mid-infrared spectral region. When higher-order dispersion (HOD), higher-order nonlinearity (HON), losses (α), and variation of the Kerr nonlinear coefficient γ(z) are considered in the extended nonlinear Schrodinger equation, a 1 ps input pulse at the wavelength of 2490 nm is successfully compressed to 57.29 fs in only 5.1-cm of propagation, along with a compression factor Fc of 17.46. We demonstrated that the impacts of HOD and HON are minor on the pulse compression process, compared with that of α and variation of γ(z). Our research results provide a promising solution to realize integrated mid-infrared ultrashort pulse sources.

High Degree Picosecond Pulse Compression in Chalcogenide-Silicon Slot Waveguide Taper

In this paper, we propose and design a chalcogenide (As2S3)-based slot waveguide taper with exponentially decreasing dispersion profile to realize high-degree pulse compression of low-power chirped solitons. Based on the waveguide taper designed, pulse compression of fundamental solitons, and chirped 2-soliton breather are both investigated numerically. With self-similar pulse compression scheme, a 1 ps input pulse is compressed to 81.5 fs in 6 cm propagation. By using 2-soliton breather pulses, a 1 ps chirped pulse is compressed to 80.3 fs in just 2.54 cm. This is the first demonstration of the feasibility of high-degree nonlinear pulse compression in As2S3-based slot waveguide taper.

Soliton-like solutions of a derivative nonlinear Schrödinger equation with variable coefficients in inhomogeneous optical fibers

Under investigation in this paper is a derivative nonlinear Schrodinger equation with variable coefficients, which governs the propagation of the subpicosecond soliton pulses in inhomogeneous optical fibers. Through the nonisospectral Kaup–Newell scheme, the Lax pair is constructed with some constraints on the variable coefficients. Under the integrable conditions, bright one- and multi-soliton-like solutions are derived via the Hirota method. By suitably choosing the dispersion coefficient function, several types of inhomogeneous solitons are obtained in, respectively: (1) exponentially decreasing dispersion profile, (2) linearly decreasing dispersion profile, (3) exponentially increasing dispersion profile, and (4) periodically fluctuating dispersion profile. The intensity of the inhomogeneous soliton can be controlled by means of modifying the loss/gain term. Asymptotic analysis of the two-soliton-like solution is performed, which shows that the changes of the widths, amplitudes, and energies before and after the collision are completely caused by the variable coefficients, but have nothing to do with the collision between two soliton-like envelopes. Through suitable choices of variable coefficients, figures are plotted to illustrate the collision behavior between two inhomogeneous solitons, which has some potential applications in the real optical communication systems.

Stationary rescaled pulse in dispersion-decreasing fiber for pedestal-free pulse compression

By using the concept of a stationary rescaled pulse (SRP), we analyze an adiabatic soliton compression system based on dispersion-decreasing fiber (DDF). We show that a SRP can exist in a DDF with a linearly decreasing dispersion profile and that the SRP resembles a linearly chirped sech2 pulse. According to the analysis, we show numerically that pedestal-free pulse compression is possible by using the SRP.

Optical mixing effect and modulation instability in a dispersion decreasing fibre operating with picosecond light pulses

A numerical investigation into the propagation of ultrashort light pulses in the region of 1.55 µm was conducted and the conversion efficiency (CE) in four-wave mixing (FWM) generation of ordinary and dispersion decreasing fibres for use in wavelength division multiplexing (WDM) systems was investigated. The simulation studied six different profiles: linear, hyperbolic, Gaussian, logarithm, exponential and constant. For all the studied profiles there was a decrease in conversion efficiency with an increase in channel separation. The CE for the hyperbolic profile is around 103 times larger in magnitude compared with the constant, logarithm and linear profiles at 0.2 nm. Modulation instability was observed during the FWM signal propagation. Typically, a frequency of modulation Δ fMAX≃8 GHz at the beginning of the propagation of the mixing signal (15 km) was obtained. For the Gaussian profile, where the modulation instability (MI) is more efficient, and for a long propagation, the MI is growing and more frequency satellites are present. It is concluded that with the use of decreasing dispersion profile (DDF) fibres, control of the CE and the compression factor of FWM generation in WDM systems can be achieved.

Analysis of the four wave mixing effect (FWM) in a dispersion decreasing fiber (DDF) for a WDM system

We did a numerical investigation of the propagation of short light pulses in the region of 1.55 μm and the conversion efficiency (CE) for the four wave mixing generation (FWM) of ordinary and dispersion decreasing fibers for use in wavelength division multiplexing (WDM) systems. Our simulations studies three different profiles, linear, hyperbolic, and constant. One conclude that for all the profiles there is decrease of the conversion efficiency with the increase in the channel separation. The hyperbolic profile present a higher efficiency of around 1000 above in magnitude compared with the others profiles at 0.2 nm of channel separation. We calculate the conversion efficiency versus the fiber length for the three profiles. The conversion efficiency for the hyperbolic profile is higher when compared to the constant and linear profiles. The other interesting point of the hyperbolic profile is that the increase of the CE in the beginning of the fiber does not show any oscillation in the CE value ( log η ), which was observed for the constant and linear profiles. For all the profiles there is an increase of the conversion efficiency with the increase of the pump power. The compression factor C i for the generated FWM signal at ω 3 was measured along the DDF's and the constant profile fibers. One can conclude that with the use of decreasing dispersion profile (DDF) fibers one can have a control of the (CE) conversion efficiency and the compression factor of the four wave mixing (FWM) generation in WDM systems.