A novel method to generate cylindrical vector beams is presented based on a cat-eye cavity laser and a Mach-Zehnder interferometric arrangement. Some transverse modes can be generated by the cat- eye cavity laser and then superimposed by the Mach-Zehnder interferometric arrangement to form different kinds of cylindrical vector beams. First, simulations of four kinds of cylindrical vector beams based on four kinds of combinations of transverse modes are made and other situations are also discussed when the two beams are in-phase, 180° out-of-phase and with other phase difference. Then, an experimental set-up based on a cat-eye cavity laser and a Mach-Zehnder interferometric arrangement is built, and four forms of cylindrical vector beams generated by the experiment system. The experimental results agree well with the simulative results.
New light-emitting diodes (LED) structure constituted by the photonic crystal (PhC) is presented, and
the effects of structure parameters are investigated. Relying on the results of investigation, the structure
parameters of photonic crystal LED are optimized. By Using the FDTD algorithm, the enhancement
factor of photonic crystal LED is calculated efficiently, and the optimum values of structure parameters
are obtained after numerical optimization. With the optimum photonic crystal structure, the output
efficiency of LED is enhanced.
An ultracompact gas-sensor based on the two-dimensional photonic crystal microcavity is presented. The sensor is
formed by a point-defect resonant cavity. The transmission spectrums of the sensor with different ambient refractive
indices ranging from 1.0 <i>n</i> = to 1.01 <i>n</i> = are calculated. The calculation results show that a change in ambient refractive
index of Δ<i>n</i>=1×10<sup>-4</sup>is apparent, the sensitivity of the sensor (Δλ/Δ<i>n</i>) is achieved with 433nm/RIU(when lattice
constant 520 <i>a</i>=520<i>nm</i>), where RIU means refractive index unit . The properties of the sensor are analyzed and calculated
using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method.
Using the fabry-Perot cavity mode, the performances of the refractive index sensor are analyzed theoretically. The sensor
is optimized using the photonic crystal waveguide structure and simulated using the FDTD method. As the small sensing
area (~10μm<sup>2</sup>) of the device would require only ~1<i>fL</i> sample analyte, these ultracompact gas sensors would be widely
used in little sample analyte in gas measurement.