We demonstrate a novel silicon-on-insulator dual-microring resonator for sensing application. Numerical analysis shows that the Q factor of dual-microring resonator is three orders of magnitude higher than that of conventional single-ring resonator with lossless waveguide and thereby as a sensor, the resolution and minimum level of detection is enhanced greatly. For the resonance peak of inner ring, a Q value of 1.07 × 10⁷ is achieved theoretically in weak coupling conditions while the sensing area is kept below 50 × 50 μm². Detection limit of refractive index change of 3.85 × 10^-6 can be achieved for bulk refractive index sensing. Moreover, by enlarging bending radius of the outer ring, Q factor can be further improved. The analytical description of output spectrum response is derived. In addition, for low propagation loss waveguide, critical coupling condition of two rings and bus waveguides is obtained and it's essential for sensor device optimization.

In this article, the lineshape of Fano-like resonance of graphene plasmonic oligomers is investigated as a function of the parameters of the nanostructures, such as disk size, chemical potential and electron momentum relaxation time in mid-infrared frequencies. Also, the mechanism of the optimization is discussed. Furthermore, the environmental index sensing effect of the proposed structure is revealed, and a figure of merit of 25.58 is achieved with the optimized graphene oligomer. The proposed nanostructure could find applications in the fields of chemical or biochemical sensing.

The SiO ₂ /SiN _x dielectric film stacks deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) are employed on the top of the oxide-confined vertical-cavity surface-emitting lasers (VCSELs). The reflecting mirror characteristics of the dielectric films are measured with varying numbers of pairs from 4 to 12. The prepared devices have low threshold current of 0.3 mA, single-mode peak power of 1.4 mW at room temperature. The thermal resistance of the device depending on ambient temperature is estimated according to the relationship of wavelength shift and dissipated power, allowing us to extract the actual temperature in active region and the temperature dependence of the output characteristics of the VCSEL. The beam property of the device is characterized by the far field pattern (FFP). Depending on the drive current, the average divergence angles of the output beam estimated from the full-width-half-maximum (FWHM) of the FFP varies between 20.4° and 21.2°. Furthermore, polarization-controlled single mode emission is achieved by introducing a built-in grating into the VCSEL with orthogonal polarization suppression ratio (OPSR) around 19 dB.

The output characteristics of vertical cavity surface emitting lasers (VCSELs) arrays are largely influenced by temperature. We systematically studied thermal properties in 20-element oxide-confined VCSEL arrays via both theory and experiment. The output power, conversion efficiency, and threshold current dependent on ambient temperatures were measured. According to the relationship of wavelength shift and dissipated power, the device thermal resistance dependent on ambient temperature was obtained. The actual temperature in active region was successfully extracted. A 3-D heat diffusion model was established to simulate temperature distribution accurately.