On-chip terahertz amplitude modulator unit in series configuration design

Abstract

—Terahertz modulators play a pivotal role in the high-speed terahertz communication system. The development of a single modulation unit featuring simple structure and high modulation depth caters to the trend towards the miniaturization, integration, and multi-functionality of on-chip terahertz modulators. In this work, we propose a terahertz modulation unit in the form of a split-ring resonator integrated in series with microstrip lines for amplitude modulation. The modulator unit features an insertion loss of less than 1 dB under the On state, and a maximum modulation depth exceeding 30 dB under the Off state with an operational bandwidth greater than 15 GHz at 140 GHz. Subsequently, both the series-coupled and the dual-arm configuration of such a unit design for dual-band modulation were demonstrated. Series-coupled configuration featuring seamless connected units allows simultaneous modulation of terahertz carrier waves within multiple bands. Whilst dual-arm configuration consisting of a single split ring resonator unit having compact structure, but with challenges in multi-band modulation. Finally, we propose a characterization methodology of terahertz on-chip modulators involving a non-ideally conforming waveguide-finline-microstrip transition. Such conversion circumvents the challenges associated with conventional chip testing methods, and is highly practical in revealing the performance of stand-alone components. We believe that the proposed terahertz modulator unit design holds strong potential to provide compact and integrated solutions for analog signal processing in the upcoming Terahertz communications.