Polarizing beam splitter for THz radiation
A polarizing beam splitter includes thin electrically conductive metal sheets each having an edge and a thickness substantially less than the wavelength λ of a terahertz signal. The sheets are arranged in a stack or array to define wave propagation passages for energy of a terahertz beam directed at a face formed by edges of the sheets, and constitutes an artificial dielectric which operates below cutoff to allow selective transmission through the passages and/or reflection from said face, separating polarization states of the beam with defined power splitting. The artificial dielectric beam splitter can be configured to operate over a broad terahertz band. The sheets are flat, without micropatterned surface features, are robust and simple to manufacture, and form a broad band polarizing beam slitter for terahertz radiation. Complete separation of the transmitted and reflected beam is achieved below cutoff by rotating the polarization of the input beam.
1. A polarizing-beam-splitter comprising: thin electrically conductive metal sheets, each of the thin electrically conductive metal sheets having an edge and a thickness that is less than or equal to one-twentieth the wavelength Λ of a terahertz signal, the thin electrically conductive metal sheets arranged in a stack to define wave propagation passages for energy of a terahertz input beam directed at an angle to a face formed by edges of the sheets, which constitutes an artificial dielectric that operates below a frequency cutoff to enable selective transmission through the wave propagation passages and reflection from the face, wherein the terahertz beam separates into a first polarization component selectively transmitted along a transmission path in the wave propagation passages between successive thin electrically conductive metal sheets and a second polarization component reflected from the face, thus separating polarization states of the input beam along different reflection and transmission paths, wherein a separation to the two polarization states is carried out with an extinction ratio better than 20 dB.
2. The polarizing-beam-splitter of claim 1 wherein the thin electrically conductive metal sheets are flat.
3. The polarizing-beam-splitter of claim 2 wherein the thin electrically conductive metal sheets are without micropatterned surface features.
4. The polarizing-beam-splitter of claim 2 wherein the thin electrically conductive metal sheets are without dielectric material dielectric material sandwiched between sheets.
5. The polarizing-beam-splitter of claim 2 wherein the thin electrically conductive metal sheets are without plastic material sandwiched between sheets.
6. The polarizing-beam-splitter of claim 2 wherein the thin electrically conductive metal sheets are without polymer material sandwiched between sheets.
7. The polarizing-beam-splitter of claim 2 wherein the thin electrically conductive metal sheets are without insulator material sandwiched between sheets.
8. The polarizing-beam-splitter of claim 1 wherein the splitting of the input energy into the transmitted and reflected beams is controlled by rotating the polarization axis of the input beam.