Wei Li Zhang

Chaos Synchronization and Communication in Mutually Coupled Semiconductor Lasers Driven by a Third Laser

We numerically investigate the chaos synchronization and message transmission between two mutual coupling semiconductor lasers (MCSLs) subject to identical unidirectional injections (UIs) from an external cavity semiconductor laser (ECSL). The synchronization between the MCSLs is realized through injection locking in conjunction with symmetric operation. The simulation results show that stable isochronal synchronization between the MCSLs can be achieved under proper driving injections. This type of synchronization is robust to parameter mismatch up to tens of percentage and frequency detuning of several tens of gigahertz, which is much better than those of the MCSLs systems with self-feedback. Moreover, the investigations on the mutual chaos pass filtering effects and the message transmission indicate that the isochronal synchronization allows mutual message exchange with a bit rate higher than 10 Gb/s, when the chaos modulation technology is adopted. In addition, the MCSLs can synchronize with the ECSL for proper UI and MC, which provides an opportunity for array chaos synchronization and chaos communication networks. Finally, leader/laggard synchronization can also be achieved in the proposed system.

Chaos synchronization communication using extremely unsymmetrical bidirectional injections

Chaos synchronization and message transmission between two semiconductor lasers with extremely unsymmetrical bidirectional injections (EUBIs) are discussed. By using EUBIs, synchronization is realized through injection locking. Numerical results show that if the laser subjected to strong injection serves as the receiver, chaos pass filtering (CPF) of the system is similar to that of unidirectional coupled systems. Moreover, if the other laser serves as the receiver, a stronger CPF can be obtained. Finally, we demonstrate that messages can be extracted successfully from either of the two transmission directions of the system.

Polarization Switching and Hysteresis of VCSELs With Time-Varying Optical Injection

We study the influence of time-varying orthogonal optical injection on polarization switching (PS) of vertical-cavity surface-emitting lasers (VCSELs). Three cases are considered: scanning injection strength, and scanning frequency detuning in two different reference ranges. In all the three cases, fast sweep rates make PSs happen at higher (lower) values for upward (downward) scans, and thus enlarge the hysteresis region. Furthermore, types of PS and the emission states of the laser can be controlled, if the scanning parameter and scanning range are chosen properly. Statistical analysis indicates PS for the third case is not so stable as that for the first two cases.

One-to-Many and Many-to-One Optical Chaos Communications Using Semiconductor Lasers

A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications.

Periodically chirped sampled fiber Bragg gratings for multichannel comb filters

Periodically chirped sampled fiber Bragg gratings (PC-SFBGs) are proposed as multichannel comb filters. A PC-SFBG consists of many chirp periods corresponding to the periodic chirp effect. With the same chirp coefficient released for a linearly chirped SFBG (LC-SFBG), the spectral self-imaging phenomenon is also observed in the PC-SFBG. Compared with a uniform SFBG, the PC-SFBG exhibits a narrower channel spacing and a similar group-delay characteristic in the reflection bands. Meanwhile, the PC-SFBG ensures a more accurate phase-shift condition (or a better tolerance on the chirp coefficient) and higher peak reflectivities than the LC-SFBG

A pseudo-planar metasurface for a polarization rotator

New demonstrations of effective interaction between light and artificially electromagnetic interface, or the metasurface, have stimulated intensive research interests on control of light to realize applications in beam steering, optical imaging and light focusing, etc. Here we reported a new type of planar metasurface of which every individual metamolecule is single metallic layer with stereo structure and the metasurface is name as Pseudo-Planar Metasurface (PPM). The metamolecule of the PPM is a chiral structure and therefore derives significant optical activity.

Accurate analytical expression for reflection-peak wavelengths of sampled Bragg grating

An analytical expression for calculating the reflection-peak wavelengths of sampled Bragg grating (SBG) is achieved for the first time. The index modulation distribution of SBG is expanded into Fourier series; then the equivalent index modulation and local Bragg period are obtained to derive the expression. Consequently, the introduction of duty cycle and sampling period ensures the accuracy of expression. The phase-matching condition is well explained by the constant phase shift technique. Under this condition, the calculated results based on expression are in good agreement with the numerical reflection spectra obtained by the piecewise uniform method

Vectorial polariton solitons in semiconductor microcavities

This paper presents numerical studies of vectorial polariton solitons in semiconductor microcavities. In the simulation, polarization degree of freedom of the polariton fields is taken into consideration. In the bistable regime, bright and/or dark solitons are found to bifurcate from the homogonous solutions of the two circular polarization modes. The combinations of solitons in the two polarization directions can be bright-dark, dark-bright, bright-bright, and dark-dark.

Theoretical study on polarization dynamics of VCSELs with negative optoelectronic feedback

We investigate theoretically the polarization dynamics of vertical-cavity surface-emitting lasers (VCSELs) subjected to negative optoelectronic feedback. As we vary the feedback delay and strength, the VCSEL exhibits interesting nonlinear dynamics in the two-linear polarized directions. The output instability and negative current modulation induced by delayed feedback can also cause polarization switching (PS) to happen. In addition, we investigate the case when the free-running VCSEL emits in the modulated-elliptical state and find that the laser experiences in succession the elliptical polarization, the x-mode polarization, and the mixed-mode polarization states with an increasing feedback strength.

Optical Flip-Flop Using Bistable Vertical-Cavity Semiconductor Optical Amplifiers With Anti-Resonant Reflecting Optical Waveguide

Flip-flop operations of anti-resonant reflecting-optical-waveguide (ARROW) vertical-cavity semiconductor optical amplifiers (VCSOAs) under the influence of undesired high-order injection modes are investigated theoretically. Three types of flip-flop operations, namely: (1) flip-flop triggered by optical injection, (2) inverse flip-flop triggered by optical injection, and (3) flip-flop triggered by injection current, are to be considered in the studies. It is found that with the presence of ARROW, all three types of optical flip-flop are insensitive to high-order injection modes, and stable single-mode flip-flop can be maintained in the operation.