Characterization of nanoporous Al₂O₃ films at terahertz frequencies

Terahertz birefringence in nanoporous Al₂O₃ films grown on Al substrates is characterized nondestructively by polarization-resolved terahertz spectroscopy. Sparse deconvolution is used to find the film thicknesses from the data, showing good agreement with the values measured directly by destructive cross-sectional field-emission scanning electron microscopy.