Computational analysis of novel high performance optically controlled RF switches for reconfigurable millimeterwave-to-THz circuits

Abstract

Optically controlled RF switches with a novel non-contact device architecture that achieves high performance in the millimeterwave-to-terahertz (mmW-THz) region are proposed and investigated through simulation. The significant change in conductivity in semiconductors caused by photogenerated carriers is used to develop RF switches having very high performance. By including a thin layer of insulator between the active semiconductor material and the metal contacts, the carrier concentration can be enhanced over that of conventional devices. For a prototype demonstration, G-band coplanar waveguide-based optical switches (using Si and Ge as active materials) with different contact geometries have been modeled and simulated. The proposed switches outperform both conventional solid-state switches and phase-change material-based switches in the switch figure-of-merit, and are promising for developing a novel class of tunable and reconfigurable mmW-THz circuits for advanced sensing, imaging, and communication.

Tunable and reconfigurable bandstop filters enabled by optically controlled switching elements

“…The BSF design was modelled using ANSYS HFSS full‐wave simulation combined with the physics‐based model for the Si chip conductivity from [7]. The on‐state silicon modelling and simulation was performed assuming a photoconductivity of 2000 S/m (corresponding to a moderate light intensity of 20 W/cm 2 , see Figure 2) for Si chip employed.…”

“…In addition, semiconductor thin films with longer carrier lifetime such as Ge can also be employed for higher photo‐induced carrier densities and thus higher achievable photoconductivities. Beyond that, integrated optically controlled switching elements with transfer‐printed micro‐LEDs [19] using advanced device architectures (with noncontact coupling configurations) could be developed and employed for superior performance and mmW‐THz operation [7].…”

“…To address the above issues and develop an alternative approach for designing and implementing high-performance tunable and reconfigurable circuits, a novel optical modulation technology based on photo-induced free carriers in semiconductors has been proposed and investigated [7] for realizing bias-free tuning/switching elements. To verify the effectiveness of this approach and simplify the experiment process, the concept of split-ring resonators (SRR) coupled to a microstrip transmission line was chosen for a prototype demonstration as shown in Figure 1 (an exemplary design) [8].…”

“…However, the potential of this concept for developing RF switching elements for reconfigurable microstrip filters has not yet been explored and demonstrated. Taking Si as an example, the photoconductivity as a function of light intensity and film thickness is calculated as shown in Figure 2, using the physics-based model in [7]. As can be seen, with increasing light intensity, the photoconductivity increases almost linearly first and then tends to saturate when the light intensity approaches 120 W/cm 2 .…”

Dynamically tuning and reconfiguring microwave bandpass filters using optical control of switching elements

“…To address these challenges and develop an alternative approach for achieving high‐performance multifunctional filter circuits required in next‐generation communication systems, a novel optical switching technology based on the modulation of semiconductor photoconductivities has been introduced and explored 11 . This switching technology, previously validated in both D‐band and G‐band (110–220 GHz) using silicon, 12 has been successfully employed to demonstrate a versatile and adaptable bandstop filter (BSF) using split‐ring resonators (SRRs) 13 in the absorption mode.…”