Lixue Chen

A bistable switching of two-dimensional photonic crystal with Kerr point defect

Bistable switching behavior in a two-dimensional nonlinear photonic crystal with a Kerr point defect is researched by numerical simulation of finite-difference time-domain method. Optical bistable switching by whole localized defect-mode is observed in the component.

Excited state optical nonlinearity of cubane-like shaped clusters

Abstract Nonlinear absorption and refraction of novel cubane-like shaped metal clusters WOS 3 Cu 3 I(2-Mepy) 3 (I) and MoOS 3 Cu 3 I(2-Mepy) 3 (II) in DMF solution are studied by using Z -scan measurement technique with laser pulses of 10 ns pulse-width at the wavelength of 532 nm. The compound (I) possesses a self-focusing property, while compound (II) exhibits a self-defocusing property. The refractive nonlinearity of the cluster can be attributed to the excited-state nonlinear refraction effect. A theoretical model of the excited-state refraction is presented to analyze the experimental results. The theoretical results are in good agreement with the experimental data. The condition of the sign change of nonlinear refraction is also studied.

Optical limiting properties and nonlinearity of a novel pentanuclear cluster

Abstract Optical limiting (OL) properties of a new pentanuclear cluster [MoS4Cu4Br2(py)6] were studied by using ns laser pulses. The comparison of the OL performance of this compound [MoS4Cu4Br2(py)6] with that of C60 fullerene shows that the cluster is superior to the C60 fullerene. Pump–probe results show that the OL behavior of the cluster can be attributed to the excited-state absorption.

Strong optical limiting properties of novel planar clusters

Abstract The optical nonlinearity performance and optical limiting (OL) properties of the new pentanuclear clusters [WS 4 Cu 4 Br 2 (py) 6 ] [I] and [MoS 4 Cu 4 Br 2 (py) 6 ] [II] were studied by using nanosecond laser pulsed at 532 nm wavelength. The cluster (I) exhibits strong OL effects. It is the best among the same kind of clusters. The OL performance of compound [I] was demonstrated to be superior than that of compound [II], and that of the compound [II] was superior than the C 60 fullerene. The excited-state absorption has been studied by using Z-scan technique at the same time.

Supermodes of photonic crystal CCWs and multimode bistable switchings with uniform thresholds

Photonic crystal (PC) coupled cavity waveguides (CCWs) with completely separated eigenfrequencies (or supermodes) are investigated. Using a coupled mode theory (CMT), the properties of the supermodes, such as the eigenfrequencies (including the central frequencies and corresponding linewidths), the quality factors (Qs) and the electric field profiles, are expressed in very simple formulas, and these results agree well with those derived from transfer matrix method (TMM). We discuss the great differences between the supermodes and continuous modes, which are described by tight binding (TB) theory. Then, the potential application of supermodes as a multi-channel (covering the whole C-band) bistable switching is investigated. Using the results of CMT, we predict that the thresholds of all the channels are uniform, and verify this prediction using nonlinear transfer matrix method.