Flexible alumina ceramic waveguides for terahertz applications

Abstract

The THz waveguides disclosed herein are used to transmit signals having a THz frequency in the range from 0.1 THz to 10 THz and include an alumina core surrounded by an optional cladding. The core may have a diameter (D1) in the range from 10 μm to 500 μm and may be comprised of a ceramic ribbon having a dielectric constant (Dk). The optional cladding may have a dielectric constant (Dk) less than the core. The THz waveguides can be formed using a continuous firing process and nano-perforation technology that enables access to a wide form factor range. In one example, rectangular waveguides, or ribbons, may be fabricated in the 10 μm to 200 μm thick range at widths in the range from sub-millimeters to several meters and lengths in the range from millimeters to several hundred meters.

What is claimed is: 
     
         1 . A method of forming long, thin ribbons of a ceramic material, comprising:
 providing a ceramic sheet material having a thickness of 500 μm or less and a length of at least 1 m,   wherein the ceramic sheet material has a first edge and a second edge, and   wherein the first and second edges extend along the length of the ceramic sheet material;   creating, via a laser, a damage track on the ceramic sheet material to form a first section and a second section,   wherein the damage track extends along the length of the ceramic sheet material,   wherein the damage track is 15 mm or less from the first edge in a direction toward the second edge of the ceramic sheet material,   wherein a first width of the first section is defined by the first edge and the damage track, and   wherein a second width of the second section is defined by the damage track and the second edge; and   separating the first section from the second section,   wherein the separated first section has a thickness of 500 μm or less, a length of at least 1 m, and the first width is 15 mm or less.   
     
     
         2 . The method according to  claim 1 , wherein the separating comprises applying mechanical and/or thermal stress along the damage track to cause separation of the first section from the second section. 
     
     
         3 . The method according to  claim 1 , wherein the separating of the first section from the second section occurs nearly coincidental to the creating of the damage track. 
     
     
         4 . The method according to  claim 3 , wherein the laser is a short-pulsed laser and wherein the laser is a high-frequency pulse rate laser. 
     
     
         5 . The method according to  claim 4 , wherein the ceramic sheet material has a thickness of 150 μm or less. 
     
     
         6 . The method according to  claim 5 , wherein the ceramic sheet material has a thickness of 10 μm to 100 μm. 
     
     
         7 . The method according to  claim 6 , wherein the ceramic sheet material has a length of at least 10 m. 
     
     
         8 . The method according to  claim 1 , further comprising moving the first section through a coating die. 
     
     
         9 . The method according to  claim 8 , further comprising coating the first section with a dielectric cladding material that has a dielectric constant lower than that of the ceramic sheet material. 
     
     
         10 . The method according to  claim 9 , wherein the dielectric cladding material is polymer. 
     
     
         11 . The method according to  claim 10 , wherein the polymer is selected from the group consisting of polytetrafluoroethylene, SU-8, fluoropolymers, polystyrene, polyimide, parylene-N, high-density polyethylene, and polypropylene. 
     
     
         12 . The method according to  claim 11 , wherein the ceramic sheet material is high purity alumina such that the alumina purity of at least 99%, and wherein the alumina has an average grain size of 5 μm or less. 
     
     
         13 . The method according to  claim 1 , further comprising applying a break resistance of 100 MPa or less to the damage track during the separating. 
     
     
         14 . The method according to  claim 1 , wherein the damage track comprises ablated regions. 
     
     
         15 . The method according to  claim 14 , wherein the ablated regions have a depth that is less than the thickness of the ceramic sheet material. 
     
     
         16 . The method according to  claim 15 , wherein the damage track includes a surface crack between at least some of the ablated regions. 
     
     
         17 . The method according to  claim 16 , wherein the damage track has a kerf of 1 μm or less.