Scattering loss caused by roughness of waveguide sidewalls is a key problem for long circumference microring based applications, such as comb filters. This paper presents a Si microring resonator incorporated with the multimode waveguide and single-mode waveguide, which suppresses the unwanted resonance of high-order modes while allowing the fundamental mode resonance with low loss. Both numerical and experimental results proved that the proposed solution is capable to achieve ~88.5% scattering loss reduction which is promising for narrow channel spacing comb filters.

The high-efficiency binary blazed grating couplers with perfectly vertical and nearly vertical coupling are proposed. The efficiencies of them are much higher than those of other types of grating couplers without bottom mirrors under vertical and oblique incidence respectively. For perfectly vertical coupler with transverse-electric polarized incident light, the coupling efficiency, which is defined as the ratio between the power coupled to the fundamental mode of the chip waveguide and that carried by the fundamental mode of the input optical fiber, is 75%, while the nearly vertical coupler with the incident angle of 10.2° has a coupling efficiency of 84%. Rigorous coupled-wave diffraction analysis and a complete optimization method have been used to make the optimal design valid and unique.

This paper reports the efforts of suppressing Er ion’s second-order cooperative up-conversion (CUC). Er/Yb and Er/Y silicate glass waveguides were fabricated, which have same structure, similar Er concentration and peak emission cross-section. Under same 1480 nm pump power, Er/Yb silicate glass shows 4.7 times weaker visible up-conversion luminescence and four times stronger infrared luminescence than Er/Y silicate glass. Through analyzing the physical mechanism, we found that the energy back transfer from Er to Yb plays a significant role on the luminescence difference, which affects and further suppresses the second-order CUC process in Er/Yb co-doped materials.Highlights► Material composition, photoluminescence property and Er emission cross-section of Er/Y and Er/Yb silicates were studied. ► Suppression of second-order cooperative up-conversion (CUC) was studied. ► To analyze the origin of the suppressed CUC, a physical mechanism was given.

Polycrystalline ErxYb2−xSiO5 (x = 0, 0.2, 0.5, 1, 2) powders were fabricated by sol–gel method and crystallized by 1200 °C annealing. The crystal structure variation as a function of composition was revealed by X-ray diffraction measurement. Intense Er visible and infrared luminescence was observed using 974 nm and 650 nm laser excitation. Yb-participated strong Er up-conversions in the visible range show different Green to Red emission ratios for the different Er concentrations samples. The dilution of Er by Yb was responsible for the increase of the 1.53 μm photoluminescence lifetime. The potential applications of the ErYb silicate were predicted under different pumping wavelengths.Highlights► Polycrystalline ErYb silicate powders were fabricated and characterized. ► Yb-participated Er up-conversions induced strong visible emissions. ► Yb can enhance the Er up-conversions beyond dilution and sensitization effect.

We report the first observation of near-infrared electroluminescence (EL) in ErYb silicate based metal–insulator–semiconductor (MIS) light-emitting device. The ErYb silicate thin film and the device were fabricated on silicon substrate using the standard silicon technology. The EL spectrum at 1.53 μm was observed under a current density of 1.2 mA/cm2. The conduction mechanism of the device was Fowler–Nordheim tunneling and the EL mechanism was attributed to the direct impact excitation of Er ions by the hot electrons produced by the high electric field in the silicate layer.Highlights► ErYb silicate based metal–insulator–semiconductor device was studied. ► Near-infrared electroluminescence was obtained in ErYb silicate. ► The Er ions were directly impact excited by hot electrons in the ErYb silicate.

This study uses a dipole embedded in Al2O3 layer to excite a symmetric surface plasmon polariton (SPP) mode in Au/Al2O3/Au waveguide to investigate its profile properties by using finite-difference time-domain (FDTD) method. The excited dipole decay radiatively direct near-field coupling to SPP mode owing to thin Al2O3 layer of 100 nm. The effects of electric and magnetic field intensity profiles and decay length have been considered and characterized. It is found that dipole location is an important factor to influence the horizontal and vertical profile properties of symmetric SPP mode in Au/Al2O3/Au waveguide. The amplitudes of electric and magnetic field intensity and the wavelengths of metal-insulatormetal (MIM) SPP resonance mode can be tuned by varying dipole location. The horizontal and vertical decay lengths are 19 and 24 nm, respectively. It is expected that the Au/Al2O3/Au waveguide structure is very useful for the practical applications of designing a SPP source.

In this paper, a binary blazed grating-based polarization independent filter on silicon on insulator (SOI) under full conical incidence is presented. The properties of the grating filter are investigated by rigorous coupled-wave analysis. It’s shown that the filter demonstrates high reflectivity (R>99%) at its resonant wavelength, which stays the same under three different polarization states. It indicates that this grating filter is polarization-independent. The final data shows its polarization-dependent loss (PDL) is only 0.04 dB and the full width at half maximums (FWHMs) of the transverse electric (TE-) and transverse magnetic (TM-) polarized light are 0.24 and 0.46 nm, respectively.

The frequency bands for self-collimation at both TE and TM polarizations in square lattice annular photonic crystals are studied systematically by plane-wave expansion and finite difference time domain methods. By increasing the inner ring radius or reducing the outer ring radius, the self-collimation band will be moved to a lower frequency. Compared with the TM modes, TE ones have different frequency sensitivities to both the inner ring radius and outer ring radius tuning. Using these features, a polarization insensitive self-collimation waveguide in a high dielectric contrast system with bandwidth up to 102.9 nm is demonstrated as an example of the implementation of photonic integration circuits.