Abstract
This paper presents an on-chip device that can perform gigahertz-rate amplitude modulation and switching of broadband terahertz electromagnetic waves. The operation of the device is based on the interaction of confined THz waves in a novel slot waveguide with an electronically tunable two dimensional electron gas (2DEG) that controls the loss of the THz wave propagating through this waveguide. A prototype device is fabricated which shows THz intensity modulation of 96% at 0.25 THz carrier frequency with low insertion loss and device length as small as 100 microns. The demonstrated modulation cutoff frequency exceeds 14 GHz indicating potential for the high-speed modulation of terahertz waves. The entire device operates at room temperature with low drive voltage (<2 V) and zero DC power consumption. The device architecture has potential for realization of the next generation of on-chip modulators and switches at THz frequencies.
Highlights
IntroductionExisting solutions for terahertz modulation are limited to free space propagation of quasi-optical signals[14,16,17,20], which may be ideal for THz spectroscopy and imaging, but not really suitable for THz communication which requires modulators be integrated with other components such as amplifiers and detectors on a single chip to enable realization of integrated THz transmitter and receiver systems[5,6,21]
Terahertz (THz) electromagnetic waves are roughly defined over a frequency band of 0.1–10 × 1012 Hz which corresponds to wavelengths of 0.3–0.003 cm[1,2]
Existing solutions for terahertz modulation are limited to free space propagation of quasi-optical signals[14,16,17,20], which may be ideal for THz spectroscopy and imaging, but not really suitable for THz communication which requires modulators be integrated with other components such as amplifiers and detectors on a single chip to enable realization of integrated THz transmitter and receiver systems[5,6,21]
Summary
Existing solutions for terahertz modulation are limited to free space propagation of quasi-optical signals[14,16,17,20], which may be ideal for THz spectroscopy and imaging, but not really suitable for THz communication which requires modulators be integrated with other components such as amplifiers and detectors on a single chip to enable realization of integrated THz transmitter and receiver systems[5,6,21]. Due to higher carrier scattering in the 2DEG medium, the plasmonic wave propagation is over-damped imposing practical limitations for the realization of THz components www.nature.com/scientificreports/. Since 2DEG is physically confined to nanometer thickness, the interaction length of free space terahertz wave propagating normally through the 2DEG is quite small This results in the low modulation index in case of modulators. We propose such a device with experimental measurements showing gigahertz speed modulation of THz waves for the first time
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