Real-time imaging of electromagnetic fields

Abstract

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.

High-Efficiency Diagnosis of Antenna Radiation Characteristics Based on Scanning Optic-Induced Plasma Scattering Technology

“…SOPS technology was invented as a basic technology for fast imaging of electromagnetic fields [28]. The core idea of the technology is to use a massless scattering "probe" to measure the electromagnetic field, replacing the probe transport mechanism with an ultra-fast scanning laser.…”

“…The resolution of the imaging is affected by the arrangement of the plasma, which mainly depends on the diameter of the laser beam [34] and can be significantly smaller than the aperture of a conventional probe. In microwave bands, super resolution and ultra-fast imaging speed can be realized at the same time [28].…”

“…The data processing procedure of imaging electromagnetic field from the scattered signals can refer to the modulated scattering technique [35]- [40]. According to the reciprocity principle, the electromagnetic field to be measured, recorded as EAUT, is proportional to the square of the variation of the backscattered signal ΔS11 [28]:…”

“…The SOPS technology provides a real-time technology to image electromagnetic fields, combining various advantages [28]. Applying this technique to antenna diagnosis is so attractive, but it still faces a few issues.…”

“…Based on our previous work [28], we invented scanning optic-induced plasma scattering (SOPS) technology to realize the near real-time imaging of the electromagnetic field. Due to the photoconductive effect, the semiconductor material is excited out of the electron-hole pairs and forms a plasma region [29]- [33] under the irradiation of a near-infrared laser.…”