High performance on-chip polarization beam splitter at visible wavelengths based on a silicon nitride small-sized ridge waveguide.

Due to sensitive scaling of the wavelength and the visible-light absorption properties with the device dimension, traditional passive silicon photonic devices with asymmetric waveguide structures cannot achieve polarization control at the visible wavelengths. In this work, a simple and small polarization beam splitter (PBS) for a broad visible-light band, using a tailored silicon nitride (Si3N4) ridge waveguide, is presented, which is based on the distinct optical distribution of two fundamental orthogonal polarized modes in the ridge waveguide. The bending loss for different bending radii and the optical coupling properties of the fundamental modes for different Si3N4 ridge waveguide configurations are analyzed. A PBS composed of a bending ridge waveguide structure and a triple-waveguide directional coupler was fabricated on the Si3N4 thin film. The TM excitation of the device based on a bending ridge waveguide structure shows a polarization extinction ratio (PER) of ≥ 20 dB with 33 nm bandwidth (624-657 nm) and insertion loss (IL) ≤ 1 dB at the through port. The TE excitation of the device, based on a triple-waveguide directional coupler with coupling efficiency distinction between the TE0 and TM0 modes, shows a PER of ≥ 18 dB with 50 nm bandwidth (580-630 nm) and insertion loss (IL) ≤ 1 dB at the cross port. The on-chip Si3N4 PBS device is found to possess the highest known PER at a visible broadband range and small (43 µm) footprint. It should be useful for novel photonic circuit designs and further exploration of Si3N4 PBSs.

Polarization Splitting at Visible Wavelengths with the Rutile TiO2 Ridge Waveguide.

On-chip polarization control is in high demand for novel integrated photonic applications such as polarization division multiplexing and quantum communications. However, due to the sensitive scaling of the device dimension with wavelength and the visible-light absorption properties, traditional passive silicon photonic devices with asymmetric waveguide structures cannot achieve polarization control at visible wavelengths. In this paper, a new polarization-splitting mechanism based on energy distributions of the fundamental polarized modes in the r-TiO2 ridge waveguide is investigated. The bending loss for different bending radii and the optical coupling properties of the fundamental modes in different r-TiO2 ridge waveguide configurations are analyzed. In particular, a polarization splitter with a high extinction ratio operating at visible wavelengths based on directional couplers (DCs) in the r-TiO2 ridge waveguide is proposed. Polarization-selective filters based on micro-ring resonators (MRRs) with resonances of only TE or TM polarizations are designed and operated. Our results show that polarization-splitters for visible wavelengths with a high extinction ratio in DC or MRR configurations can be achieved with a simple r-TiO2 ridge waveguide structure.

Evaluation of BD Vacutainer SST™ II plus tubes for special proteins testing.

In the past few years, because of providing a closed system that allowed for collection, transport, processing, sampling, and storage of specimens, serum separator tubes gained widespread acceptance gradually in China. However, some limitations associated with gel tubes had been observed, for example, gel and analyte stability. In order to circumvent these problems, a new tube (BD Vacutainer(®) SST™ II Plus (BD SST™ II Plus)) containing a new gel was released by BD with respect to analyte and gel stability. We investigated the performance of BD SST™ II Plus tubes for special proteins testing using BD Vacutainer(®) Serum Glass Tubes (BD Serum Glass) as controls.Equivalence between these two types of tubes was demonstrated for all analytes at initial time, and data for all analytes except complement 3 (C3) and complement 4 (C4) indicated comparable stability over time in these two types of tubes. Concentration of C3 and C4 tended to increase with preservation time up to 72 hr in BD Serum Glass tubes. The stability of C3 and C4 was better in BD SST™ II Plus, which was demonstrated at timepoints up to 48 hr. We conclude that BD SST™ II Plus was suitable for collection and storage of samples for special proteins testing.