Antenna design harnesses intense terahertz waves by controlling polarization at the source
Antenna design harnesses intense terahertz waves by controlling polarization at the source lead image
Although several optics applications exist for controlling polarization in UV, visible and near-infrared wavelengths, there are still few options available for broadband pulses at terahertz wavelengths. Metamaterial wave plates have been proposed as a solution with sufficient flexibility and bandwidths, but are difficult to create and suffer from low transmission. New work explores precluding the need for optics by tuning THz waves at the source.
Ropagnol et al. designed an interdigitated large aperture photoconductive antenna (ILAPCAs) for the generation of intense THz waves with on demand control of the polarization. Employing horizontal and vertical electrodes to tune the polarization, the device emits two THz pulses with crossed polarization, delayed in time with respect to one another.
Developing devices for transmitting THz radiation has posed challenges for the field. The low transmission prevents working with intense THz waves, which would be needed to generate higher field amplitudes. In addition, intense THz pulses can cause nonlinear effects inside metamaterials themselves, which would induce some time variation in the electric field.
The group’s device allows for peak fields beyond 80 kV/cm, a leap forward in intensity given the amount of control. The polarizations of the generated intense THz pulses range from linear to quasi-circular over a quarter of the THz cycle. Emitting the two pulses from the same location allows the pulses to be paired throughout their entire propagation distance.
Ropagnol hopes the work brings nonlinear, non-resonant THz applications to fruition where polarization control is needed.
Source: “Generation of intense sub-cycle terahertz pulses with variable elliptical polarization,” by X. Ropagnol, E. Isgandarov, X. Chai, S. M. Raeis-Zadeh, S. Safavi-Naeini, M. Reid, F. Blanchard, and T. Ozaki, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0086309 .
