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Abstract We report a novel approach for dynamically tuning and reconfiguring microwave bandpass filters (BPFs) based on optically controlled switching elements using photoconductivity modulation in semiconductors. For a prototype demonstration, a BPF circuit featuring a second‐order design using two closely coupled split‐ring resonators embedded with multiple silicon chips (as switching elements) was designed, fabricated, and characterized. The silicon chips were optically linked to fiber‐coupled laser diodes (808 nm light) for switching/modulation, enabling dynamic tuning and reconfiguring of the BPF without any complex biasing circuits. By turning on and off the two laser diodes simultaneously, the BPF response can be dynamically reconfigured between bandpass and broadband suppression. Moreover, the attenuation level of the passband can be continuously adjusted (from 0.7 to 22 dB at the center frequency of 3.03 GHz) by varying the light intensity from 0 to 40 W/cm². The tuning/reconfiguring 3‐dB bandwidth is estimated to be ~200 kHz. In addition, the potential and limitations of the proposed approach using photoconductivity modulation are discussed. With the strong tuning/reconfiguring capability demonstrated and the great potential for high‐frequency operation, this approach holds promise for the development of more advanced tunable filters and other adaptive circuits for next‐generation sensing, imaging, and communication systems. 

We report the design, simulation, and analysis of a THz phased array, using lens-coupled annular-slot antennas (ASAs) for potential beyond 5G or 6G wireless communications. For a prototype demonstration, the ASA employed was designed on a high resistivity Si substrate with a radius of 106 μm, and a gap width of 6 um for operation at 200 GHz. In order to achieve higher antenna gain and efficiency, an extended hemispherical silicon lens was also used. To investigate the effect of the silicon lens on the ASA phased array, a 1 × 3 array and 1 × 5 array (the element distance is 0.55λ) were implemented with a silicon lens using different extension lengths. The simulation shows that for a 1 × 3 array, a ±17° scanning angle with an about −10 dB sidelobe level and 11.82 dB gain improvement (compared to the array without lens) can be achieved using a lens radius of 5000 μm and an extension length of 1000 μm. A larger scanning angle of ±31° can also be realized by a 1 × 5 array (using a shorter extension length of 250 μm). The approach of designing a 200 GHz lens-coupled phased array reported here is informative and valuable for the future development of wireless communication technologies. 

We present a photoinduced reconfigurable metasurface to enable high spatial resolution terahertz (THz) wave modulation. Conventional photoinduced THz wave modulation uses optically induced conductive patterns on a semiconductor substrate to create programmable passive THz devices. The technique, albeit versatile and straightforward, suffers from limited performance resulting from the severe lateral diffusion of the photogenerated carriers that undermines the spatial resolution and conductivity contrast of the photoinduced conductive patterns. The proposed metasurface overcomes the limitation using a metal-jointed silicon mesa array with subwavelength-scaled dimensions on an insulator substrate. The structure physically restrains the lateral diffusion of the photogenerated carriers while ensuring the electrical conductivity between the silicon mesas , which is essential for THz wave modulation. The metasurface creates high-definition photoconductive patterns with dimensions smaller than the diffusion length of photogenerated carriers. The metasurface provides a modulation depth of −20 to −10 dB for the THz waves between 0.2 to 1.2 THz and supports a THz bandpass filter with a tunable central frequency. The new, to the best of our knowledge, design concept will benefit the implementation of reconfigurable THz devices.