Abstract
We demonstrate a simple and effective strategy for implementing a polarizing beamsplitter for the terahertz spectral region, based on an artificial dielectric medium that is scalable to a range of desired frequencies. The artificial dielectric medium consists of a uniformly spaced stack of metal plates, which is electromagnetically equivalent to a stacked array of parallel-plate waveguides. The operation of the device relies on both the lowest-order, transverse-electric and transverse-magnetic modes of the parallel-plate waveguide. This is in contrast to previous work that relied solely on the transverse-electric mode. The fabricated polarizing beamsplitter exhibits extinction ratios as high as 42 dB along with insertion losses as low as 0.18 dB. Building on the same idea, we also demonstrate an isolator with non-reciprocal transmission, providing high isolation and low insertion loss at a select design frequency. The performance of our isolator far exceeds that of other experimentally demonstrated terahertz isolators, and indeed, even rivals that of commercially available isolators for optical wavelengths. Because these waveguide-based artificial dielectrics are low loss, inexpensive, and easy to fabricate, this approach offers a promising new route for polarization control of free-space terahertz beams.
Highlights
We have experimentally demonstrated a highly efficient and versatile PBS for the THz spectral region based on artificial dielectrics
The device geometry is exceedingly simple compared to all previous PBS attempts for this spectral region
Since the devices are made from stacked metallic plates, as opposed to dielectric materials, they uniquely possess extremely high power handling capabilities, limited only by the breakdown of air within the plates
Summary
The artificial dielectric medium consists of a uniformly spaced stack of identical, rectangular metal plates. The detected time-domain signals are given in the inset, and as before, along with the amplitude spectra, prove the highly efficient and non-dispersive broad-band operation of the device in transmission This observation is not surprising since the TEM mode of the PPWG is a very low-loss and dispersion-less propagating mode[14]. These agree very well with the theoretical power dependences of cos4θ and cos2θ sin2θ given by the solid curves for the reflection and transmission arms, respectively These results confirm that we can achieve any power division by rotating the input polarization axis, a versatile PBS. A suitable arrangement that may provide continuous control of the plate spacing would allow dynamic tunability of the isolation-peak, adding versatility to the isolator
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