Description: The Naval Research Laboratory (NRL) has developed a novel microfabrication process for creating highly precise, geometrically round tunnels in all-metal, photolithographically-formed structures for the purpose of transporting electron beams through vacuum electro-magnetic slow-wave circuits in the millimeter wave (mmW) and sub-mmW frequency ranges (approx. 90 GHz to over 1 THz). This patent-pending technique uses polymer monofilaments embedded in the photoresist to hold the shape of a beam tunnel during the UV-LIGA photolithographic process. The resulting quasi-3D structures are easily electro-formed with low-loss, high thermal conductivity metals, such as copper, to create both precise electromagnetic circuits and electron beam tunnels in a single process step. This technique can similarly create multiple beam tunnels of arbitrary cross sectional shape, waveguides, passive electromagnetic structures (e.g. filters), or a wide range of microfluidic devices.

Advantages/Features Include:

  • Overcomes fabrication process issues in the mmW and sub-mmW range with high yield
  • Enables fabrication of amplifier and oscillator circuits in a single step using a low-cost, UV flood source
  • Offers the capability for tunnel length-to-diameter aspect ratios of >500

Applications Include:

  • High power mmW and sub-mmW vacuum electron sources for radar, imaging, communications, and biomedical applications
  • High power passive electromagnetic component such as filters, wave-guides, couplers
  • Microfluidic devices


  • "Microfabrication of Fine Electron Beam Tunnels using UV-LIGA and Embedded Polymer Monofilaments for Vacuum Electron Devices," Journal of Micromechanics and Microengineering, 22 (2012): 015010.
  • "3D UV-LIGA Microfabricated Circuits for Wideband 50W G-band Serpentine Waveguide Amplifier," 36th Infared, Millimeter and Terahertz Waves (IRMMW-THz) Conference, Houston, TX, Paper Tu4A.1, Oct. 2011.

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