Broadband terahertz guided-mode resonance filter using cyclic olefin copolymer.

Area of Science:

• Optics and Photonics
• Materials Science
• Terahertz Technology

Background:

• Guided-mode resonance filters (GMRFs) are crucial optical components.
• Operating GMRFs in the high-frequency terahertz (THz) region presents fabrication challenges.
• Material properties like low refractive index, low absorption, and high tensile strength are critical for THz GMRFs.

Purpose of the Study:

• To propose and fabricate an all-dielectric single-layer GMRF for high-frequency THz applications.
• To investigate the suitability of cyclic olefin copolymer (COC) films for THz GMRF fabrication.
• To demonstrate GMRF operation at significantly higher THz frequencies than previously achieved.

Main Methods:

• Material characterization of COC films, comparing them to polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE).
• Fabrication of single-layer COC-based GMRFs with varying grating periods (500 to 100 µm).
• Experimental measurement of resonance frequencies and comparison with rigorous coupled-wave analysis (RCWA) simulations.

Main Results:

• COC films exhibit favorable properties (low refractive index, low absorption, high tensile strength) for THz GMRF fabrication.
• Fabricated COC GMRFs showed resonance frequencies shifting to higher THz values with shorter grating periods.
• A GMRF with a 100-µm grating period achieved operation up to 2.759 THz, a significant advancement from the previous 0.7 THz limit.

Conclusions:

• Cyclic olefin copolymer (COC) is a suitable material for fabricating high-frequency THz guided-mode resonance filters.
• The proposed all-dielectric single-layer GMRF design enables operation at unprecedented THz frequencies.
• This work paves the way for advanced THz devices utilizing novel materials and fabrication techniques.