Broadband and compact polarization beam splitter based on an asymmetrical directional coupler with extra optimizing designs.

In this paper, a novel, to the best of our knowledge, polarization beam splitter (PBS) based on an asymmetrical directional coupler (DC) was proposed, which consists of a strip waveguide (WG) and a ${{\rm Si}_3}{{\rm N}_4}$SiN loaded horizontal slot WG. By carefully adjusting the geometric parameters of the DC, the phase match condition between these two WGs can be satisfied for the transverse magnetic (TM) polarization, while the coupling efficiency of the transverse electric (TE) polarization is frustrated due to the large phase mismatch. The extra optimizing designs include adding filters to the output ports as well as introducing the tapered structure into the DC, which is settled by the particle swarm optimizing (PSO) algorithm so that the performance of the proposed PBS is improved over a broadband range.

Dual-layer waveguide grating antenna with high directionality for optical phased arrays.

Development of the waveguide grating antenna with high directionality is significantly important for the optical phased array. A SiN/Si dual-layer structure with the grating pattern on the SiN layer is proposed to improve the directionality of the waveguide grating antenna. High directionality of more than 89% can be achieved, and the length of the waveguide grating antenna is longer than 4 mm.

Two-Photon Photochemistry of CdSe Quantum Dots.

The two-photon photochemistry of CdSe quantum dots (QDs) has been systematically studied. We find that upon intense irradiation CdSe quantum dots that absorb two or more visible photons undergo photodarkening. The quantum yield for this process is on the order of 6% in chloroform and much smaller in nonpolar solvents, such as octane.

The flexibility of UV-inducible mutation in Deinococcus ficus as evidenced by the existence of the imuB-dnaE2 gene cassette and generation of superior feather degrading bacteria.

The lexA-imuB-dnaE2 gene cassette contributing to the TLS (translesion synthesis) polymerase activity and can easily cause mutation after DNA damage in many bacteria. But it was previously thought that TLS polymerase activity was unlikely to exist in the radio-resistant genus Deinococcus. In our preliminary studies, the lexA-imuB-dnaE2 gene cassette was found in a newly isolated feather-degrading Deinococcus ficus.