Tong Kun Lim

On-off intermittency in an experimental synchronization process

Abstract We have experimentally realized the on-off intermittency in a synchronization process between two unidirectionally coupled nonlinear oscillators. The exponent of the power law of the conditional probability of the laminar phase in our case is found to be −3 2 and we have found that the “on-off” intermittency is related to the fluctuation in the transverse Lyapunov exponents.

An experimental study of storing information in a controlled chaotic system with time-delayed feedback

Abstract The multistability of a time-delayed feedback system can be used as an alternative for storing information. In this case the information is stored in various temporal patterns by controlling a chaotic system. The capability of storing information can be enhanced since more complex wave forms can be stored, each of which can be used as a memory unit. We showed numerically and experimentally this possibility in a hybrid diode laser system. We also showed that this method is robust to possible errors in the process of coding information.

Absorption effect in the calculation of a second-order nonlinear coefficient from the data of a Maker fringe experiment

The effect of light absorption by sample in the analysis of Makerfringe data for estimating a second-order nonlinear coefficient hasbeen studied experimentally. Two theories, one by Jerphagnon andKurtz that neglects the absorption effect and one by Herman and Haydenthat takes into account the absorption effect, were compared with theexperimental results. It was found that Jerphagnon and Kurtzsformula was unable to predict correctly not only the magnitude but alsothe incident angle dependence or the sample thickness dependence of thesecond harmonic signal generated by the sample with strong absorption, whereas the theory by Herman and Hayden was able to make thosepredictions fairly well. It was also found that the error in theestimated nonlinear coefficient when one uses Jerphagnon and Kurtzsformula could be as large as 2-4 times the true value, depending onsample thickness.

Single-mode GaAs/AlGaAs W waveguides with a low propagation loss

We have designed a low-loss single-mode GaAs/AIGaAs optical waveguide with a symmetric five-layer heterostructure at the 1.31-µm wavelength by use of an effective-index method. Waveguides with a W-shaped refractive-index profile have been grown by use of a metallo-organic chemical vapor deposition technique and fabricated with a chemical wet-etching method. Propagation loss has been measured by use of the Fabry-Perot resonance method and a sequential-cleaving experiment. The measured loss is as low as 0.19 dB/cm for waveguides with 2.3-µm thickness and 4.3-µm width, which is comparable to the lowest-loss semiconductor waveguides yet reported. These waveguides could be used to make low-loss modulators for guided-wave devices.

Secure communication by small time continuous feedback

Abstract A secure communication through the synchronization of chaotic signals is experimentally demonstrated using the nonlinear driven oscillator circuit implement. In our experiment, we use the small time continuous feedback method for synchronization. This method does not require that the system under study should be divided into subsystems.

Synchronization via small continuous feedback

Abstract A recently proposed method [K. Pyragas, Phys. Lett. A 181 (1993) 203] of synchronizing outputs of two chaotic systems by small time continuous feedback perturbations is realized experimentally in a circuit implementation. The effect of the difference in the parameters between the two systems on synchronization has been investigated. The experimental results are interpreted in terms of calculated conditional Liapunov exponents.

On-off intermittency in a quasiperiodic driven nonlinear oscillator☆

Abstract We have experimentally realized the on-off intermittency in a quasiperiodic driven nonlinear oscillator. The perturbation to the system is not random or chaotic but quasiperiodic. The exponent of the power law of the conditional probability of the laminar phase in our case is found to be −3 2 . We have also checked the local transverse Lyapunov exponent distribution and found that the on-off intermittency is related to the loss of the transverse stability of the invariant manifold.

Nonchaotic attractor with a highly fluctuating finite-time Lyapunov exponent in a hybrid optical system

We discuss the birth of the strange nonchaotic attractor (SNA) when the system has large fluctuations of the finite-time Lyapunov exponents. We find that chaotic and periodic behaviors can be achieved, in turn, by a nearly sinusoidal perturbation. If the time interval of the chaotic divergence is long enough and the perturbations are always added, it will be enlarged by a positive finite Lyapunov exponent. The attractor created by a perturbation can be an SNA. Also, we prove the existence of a SNA by calculating the external phase sensitivity property and the local Lyapunov exponents.

Controlling spatio-temporal chaos in a nonlinear optical system by Fourier space filtering

We present an experimental and numerical study on the selection of unstable patterns embedded in a nonlinear optical system in weakly or strongly turbulent states by Fourier space filtering. This is implemented on a liquid crystal light valve showing abundant stationary and dynamic patterns. We drive the system into weak or strong turbulence and then control them into stationary or nonstationary patterns. The various target patterns can be easily achieved by the simple filter of pinhole type in the Fourier space.

Experimental study on the blowout bifurcation route to strange nonchaotic attractor

Based on the measurement on an analog nonlinear oscillator circuit, two distinct dynamical phenomena, a strange nonchaotic attractor(SNA) and on-off intermittency, have been investigated in a dissipative and nonlinear system driven by two periodic external forces whose frequencies are incommensurate. Our result shows that the blowout bifurcation that destabilizes the invariant subspace is closely related to the SNA and that the loss of the transverse stability of the torus can lead to the birth of the SNA because the on-off intermittency occurs in a quasiperiodically driven dynamical system, as numerically presented by Yalcinkaya and Lai [T. Yalcinkaya and Y. C. Lai, Phys. Rev. Lett. 77, 5039 (1996)].