Plastic waveguide for terahertz wave
The invention discloses a plastic waveguide for guiding terahertz (THz) wave with a wavelength ranging from 30 to 3000 μm. The plastic waveguide includes a core and a cladding layer. At least part of the core is made of a first plastic medium having a first refractive index, and the maximum length of a cross-section of the core is smaller than the wavelength of the guided terahertz wave. The cladding layer surrounds the core and has a second refractive index lower than the first refractive index. In the invention, only one wave mode is propagated in the plastic waveguide, and a first attenuation constant of the core for the guided terahertz wave is higher than a second attenuation constant of the cladding layer for the guided terahertz wave.
1. A plastic waveguide for guiding terahertz (THz) wave with a wavelength ranging from 30 to 3000 μm, the plastic waveguide comprising:
a core, at least part of the core made of a first plastic medium having a first refractive index, the maximum length of a cross-section of the core being smaller than the wavelength of the guided terahertz wave; and
a cladding layer surrounding the core and having a second refractive index lower than the first refractive index;
wherein only one wave mode is propagated in the plastic waveguide, and a first attenuation constant of the core for the guided terahertz wave is higher than a second attenuation constant of the cladding layer for the guided terahertz wave.
2. The plastic waveguide of claim 1 , wherein the maximum length of the cross-section of the core is 0.15 to 0.35 times the wavelength of the guided terahertz wave.
3. The plastic waveguide of claim 1 , wherein the cross-section of the core is circle, and the propagated wave mode is HE 11 mode.
4. The plastic waveguide of claim 1 , wherein the core includes a central portion and a peripheral portion surrounding the central portion, and the peripheral portion is made of the first plastic medium.
5. The plastic waveguide of claim 4 , wherein the central portion is made of a second plastic medium different from the first plastic medium.
6. The plastic waveguide of claim 4 , wherein the central portion is made of an air medium or vacuum.
7. The plastic waveguide of claim 6 , wherein the maximum length of the cross-section of the core is larger than or equal to 0.15 and smaller than 1 times the wavelength of the guided terahertz wave.
8. The plastic waveguide of claim 4 , wherein the central portion is made of the first plastic medium.
9. The plastic waveguide of claim 1 , a third attenuation constant of the plastic waveguide for the guided terahertz wave is between 0.001 cm −1 and 0.01 cm −1 .
10. The plastic waveguide of claim 1 , wherein the first plastic medium is polyethylene (PE).
11. The plastic waveguide of claim 1 , wherein the cladding layer is selected from the group consisting of air and vacuum.
12. The plastic waveguide of claim 1 , wherein the cladding layer is a polymeric material.