Design and measurement of the TE25,10 mode generator.

The high-mode generator is a passive device operating at low power, which is helpful for the mode converter test. It has generally served as the input of the mode converter to evaluate the performance. Here, we realized the design of the TE25,10 mode generator. The multi-section coaxial resonator was designed to improve the TE25,10 mode purity. Two mirrors were used to excite the TE25,10 mode resonance based on the geometric optics. The construction of the TE25,10 mode generator was realized. The purity of the measured TE25,10 mode was 91%, which was in good agreement with the theory.

Time-resolved photoconductivity distribution measurement by a synchronized double-scanning method.

The lifetime and the distribution of photoconductivity generated in laser-illuminated semiconductors are critical to photoconductivity-based applications. We propose a synchronized double-scanning method to measure time-resolved diffusion in the form of an afterglow embedded in the distribution map. The method combines spatial scanning of a coaxial resonator with synchronized laser scanning to map the dynamically excited conductivity on a semiconductor wafer. Thus, the photoconductivity afterglow effects can be mapped and retrieved by images of dynamic photoconductivity distribution. The photoconductivity lifetimes of silicon wafers with different thicknesses and by different lasers were measured and evaluated, which were also validated by the microwave photoconductivity decay (µ-PCD) method. In addition, the behavior of photoconductivity diffusion around a structural defect was exhibited. The method is nondestructive and can be applied in the photoconductivity property diagnostic.

Real-time imaging of electromagnetic fields.

The measurement and diagnosis of electromagnetic fields are important foundations for various electronic and optical systems. This paper presents an innovative optically controlled plasma scattering technique for imaging electromagnetic fields. On a silicon wafer, the plasma induced by the photoconductive effect is exploited as an optically controlled scattering probe to image the amplitude and phase of electromagnetic fields. A prototype is built and realizes the imaging of electromagnetic fields radiated from antennas from 870MHz to 0.2 terahertz within one second. Measured results show good agreement with the simulations. It is demonstrated that this new technology improves the efficiency of electromagnetic imaging to a real-time level, while combining various advantages of ultrafast speed, super-resolution, ultra-wideband response, low-cost and vectorial wave mapping ability. This method may initiate a new avenue in the measurement and diagnosis of electromagnetic fields.