Abstract
Microwave performance extraction of optically-controlled squared frequency-selective surface (FSS) structures printed on highly resistive (HR) silicon substrate are presented, from a innovative bistatic microwave photonic characterization technique operating in the 40 to 60 GHz frequency range, commonly used for radar cross section (RCS) measurements. According to typical physical photon absorption phenomenon occurring in photoconductive materials, these structures demonstrate experimentally a bandpass filtering frequency response cancellation through reflection coefficient measurements, under specific incident collective illumination in the Near-infrared region (NIR). This behaviour is attributed to their microwave surface impedance modification accordingly to the incident optical power, allowing ultrafast reconfigurability of such devices by optics
Highlights
Metasurfaces (MTS) can act today as a new generation of frequency-selective surface (FSS)which have significantly contributed to advanced modern communication systems enhancements.Applications of MTSs at microwaves encompass those of FSS, namely, phase shifting elements for reflector antennas [1,2,3,4,5,6], filtering interfaces in radomes to reduce radar cross section (RCS) levels in military platforms [7], as well as new generation of antennas [8,9,10]
For the first time, this paper describes the development of a novel accurate free space experimental set-up dedicated to microwave reflection/transmission Fresnel coefficients measurements
Microwave Teflon lenses placed between antennas and the material under test (MUT), under a small signal incidence angle of 28◦ with the respect to the normal of the MUT, are added for the guarantee of microwave signal focus in a foot print at order of MUT surface dimensions and microwave signal wavelength value
Summary
Metasurfaces (MTS) can act today as a new generation of frequency-selective surface (FSS). A complementary frequency and phase agility in MTS design is expected in future industrial systems, as in 5G communications where a dynamic frequency allocation at end user level is required In this area, main research works have been largely devoted to electronic solutions suggestion, such as by local electrical switching [11] from planar active devices (diodes) networks, or by substrate material permittivity change under specific electrical bias, using phase change materials. Optical control becomes a disruptive alternative providing many advantages such as ultrafast activation speed, and EMI-protected external control In this context, for the first time, this paper describes the development of a novel accurate free space experimental set-up dedicated to microwave reflection/transmission Fresnel coefficients measurements. Through light/matter interaction, the photon energy absorption produces a material conductance change ∆σ (2) , which is strongly dependent on carriers dynamics such as lifetime τ and mobility μn,p , in association with the incident photon flux Φ(t), quantum efficiency η and effective volume of the light/matter interaction area wA [17]
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