  Mechanical tuning of a 3D-printed, polymer-based one-dimensional photonic
crystal was demonstrated in the terahertz spectral range. The investigated
photonic crystal consists of 13 alternating compact and low-density layers and
was fabricated through single-step stereolithography. While the compact layers
are entirely polymethacrylate without any intentional internal structures, the
low-density layers contain sub-wavelength sized slanted columnar inclusions to
allow the mechanical compression in a direction normal to the layer interfaces
of the photonic crystal. Terahertz transmission spectroscopy of the photonic
crystal was performed in a spectral range from 83 to 124 GHz as a function of
the compressive strain. The as-fabricated photonic crystal showed a distinct
photonic bandgap centered at 109 GHz, which blue shifted under compressive
stress. A maximum shift of 12 GHz in the bandgap center frequency was
experimentally demonstrated. Stratified optical models incorporating simple
homogeneous and inhomogeneous compression approximations were used to analyze
the transmission data. A good agreement between the experimental and
model-calculated transmission spectra was found.

Applied Physics;Optics