Terahertz (THz) waves, situated between the microwave and infrared regions of the electromagnetic spectrum, have drawn considerable attention over the past two decades. Researchers from the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences, in collaboration with researchers from the Nanjing University, have developed a novel method to modulate the polarization of THz waves, marking significant progress in optics and photonics. This study was published in Optica.
Polarization-the orientation of light waves-is a cornerstone of modern technology, critical in everything from next-generation wireless communications to biomedical imaging. However, manipulating the polarization of THz waves has long been a formidable challenge.
The difficulty with THz waves from two main features: their mesoscale wavelength, which is three orders of magnitude larger than visible light, leading to inefficient light-matter interactions, and their broad bandwidth of 0.1 to 10 THz, which requires highly achromatic responses that are challenging to achieve.
To address these challenges, the researchers has developed an innovative device called the phase-compensated mirror-total internal reflection (PCMT) device. By adjusting two key parameters-mirror-prism distance and liquid crystal birefringence-the researchers achieved achromatic phase control, enabling precise manipulation of polarization states across a wide and tunable bandwidth with minimal intensity change.
This device has demonstrated the ability to generate and actively switch between orthogonal linear polarizations and left- or right-handed circular polarizations over a broad frequency range of 1.6 to 3.4 THz. It achieves exceptional degrees of polarization, with both degrees of linear/circular polarization (DoLP/DoCP) values exceeding 0.996. Furthermore, it enables the realization of arbitrary polarization states at any center frequency, with relative bandwidths surpassing 90%.
"Our work demonstrates that THz waves, often considered unruly, can now be tamed and orchestrated with precision," said Prof. CHEN Xuequan from AIR. "This breakthrough opens the door to a multitude of applications, making THz technologies more accessible and versatile than ever before."
This innovation has the potential to transform industries reliant on polarization-sensitive technologies, offering a versatile and efficient solution for communication, sensing, material characterization, and more.
The proposed THz polarization controlling device. (a) schematic of the device and (b) measured polarization outputs. (Image by AIR)
