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We theoretically study the Casimir interaction between Weyl semimetals. When the distance a between semi-infinite Weyl semimetals is in the micrometer regime, the Casimir attraction can be enhanced by the chiral anomaly. The Casimir attraction depends sensitively on the relative orientations between the separations ( b 1, b 2) of Weyl nodes in the Brillouin zone and show anisotropic behavior for the relative orientation of these separations ( b 1, b 2) when they orient parallel to the interface. This anisotropy is quite larger than that in conventional birefringent materials. The Casimir force can be repulsive in the micrometer regime if the Weyl semimetal slabs are sufficiently thin and the direction of Weyl nodes separations ( b 1, b 2) is perpendicular to the interface. The Casimir attraction between Weyl semimetal slabs decays slower than 1/a 4 when the Weyl nodes separations b 1 and b 2 are both parallel to the interface.

We simultaneously compare the probe transmission, Four-Wave Mixing (FWM) and fluorescence signals with dressing effects in a four-level atomic system. The variation rules of three types of signals are exhibited by changing the frequency detuning and power of incident laser beams. The interplay between two ladder subsystems is investigated in the Y-type atomic system. In particular, the fluorescence signal with ultra-narrow linewidth is obtained due to being sheared twice by the electromagnetically induced transparency window. Such fluorescence with very high coherence and monochromaticity can be used for the quantum correlation and narrow linewidth laser.

A simple clock enhanced loop of cascaded electro-absorption modulators (EAMs) and 10 GHz clock recovery modules is presented. The intensity of harmonic of clock-frequency component is analyzed theoretically and verified experimentally in a 160 Gb/s OTDM 100 km transmission system. The 10 GHz clock component is enhanced obviously before launching into the clock recovery module and the recovered clock signal exhibits low rms jitter of < 400 fs. Moreover, completely error-free (10−12) transmission is observed for more than two hours without using forward error correction technology. The power penalty is about 3.6 dB. The proposed loop has merits of enhancing base clock component, simultaneously de-multiplexing and clock recovery, which make the performance of this loop more stable and high suppression of non-target channels.

The bifurcation of a periodic solution for a delay differential equation related to optical bistability has been discussed analytically. Using the theory of retarded functional differential equations, we have proved that it follows precisely the period-doubling route.

A sequence of three-letter words was constructed for the antisymmetric map Xn+1=F(Xn,A)=A*Xn+(1-A)*Xn, which contains all the information about the occurrence of periodic windows on the parameter axis.