Modulators for mid-infrared and terahertz light

The rise of mid-infrared and terahertz wave technology over the past two decades has led to incredible insights and potential applications for next-generation optoelectronics. Modulators, which control amplitude, phase, and/or polarization of incident light, are widely used in communications, imaging, and sensing and are crucial for further development of technology functioning in the mid-infrared and terahertz frequency regimes. The lack of natural materials with optical responses in these frequency regimes has led to a surge in engineering efforts to create novel devices and architectures for achieving control over the properties of mid-infrared and terahertz radiation. Major efforts in the field have been devoted to studying carrier concentration modulation, liquid crystals, phase-change materials, and micro-electromechanical systems for controlling the light-matter interaction. Although there has been considerable progress in realizing mid-infrared and terahertz modulators, novel approaches are seeking higher modulation speed, more functionality, and miniaturized size. In this perspective, we review the recent advancements of modulators for mid-infrared and terahertz wavelengths. We discuss various modulation mechanisms, along with their relative performance, and consider future architectures to improve upon the current technology for mid-infrared and terahertz modulation.