THz Filters Made by Laser Ablation of Stainless Steel and Kapton Film

Abstract

THz band-pass filters were fabricated by femtosecond-laser ablation of 25-μm-thick micro-foils of stainless steel and Kapton film, which were subsequently metal coated with a ∼70 nm film, closely matching the skin depth at the used THz spectral window. Their spectral performance was tested in transmission and reflection modes at the Australian Synchrotron’s THz beamline. A 25-μm-thick Kapton film performed as a Fabry–Pérot etalon with a free spectral range (FSR) of 119 cm−1, high finesse Fc≈17, and was tuneable over ∼10μm (at ∼5 THz band) with β=30∘ tilt. The structure of the THz beam focal region as extracted by the first mirror (slit) showed a complex dependence of polarisation, wavelength and position across the beam. This is important for polarisation-sensitive measurements (in both transmission and reflection) and requires normalisation at each orientation of linear polarisation.

Structure and Optical Anisotropy of Spider Scales and Silk: The Use of Chromaticity and Azimuth Colors to Optically Characterize Complex Biological Structures

“…The transmission and reflection coefficients of the FP etalon are dependent on the reflectivity R of the FP film (chitin in the case scales) interfaces; both interfaces are assumed to have the same reflectivity. The FP transmittance and reflectance spectra are given by: and complimentary reflectance (without absorbance ): respectively (widely used from visible to far-IR wavelengths [ 22 ]). The FP etalon imparts its reflectance/transmittance spectrum.…”

“…respectively (widely used from visible to far-IR wavelengths [22]). The FP etalon imparts its reflectance/transmittance spectrum.…”

Laser-Patterned Alumina Mask and Mask-Less Dry Etch of Si for Light Trapping with Photonic Crystal Structures

“…The plane approximating the sample’s surface was calculated using the three-point P method [ 21 ], where the coordinates of the focal point placed on the sample’s surface are determined. The plane through the point P (also P and P ) is given by with the normal coefficients determined experimentally.…”

Laser Patterned Alumina Mask and Mask-less Dry Etch of Si for Light Trapping

“…The plane approximating sample's surface was calculated using three points P 1,2,3 method [21] where the coordinates of the focal point placed on the sample's surface are determined. The plane through the point P 1 (also P 2 and P 3 ) is given by a n (x − x 1 ) + b n (y − y 1 ) + c n (z − z 1 ) = 0 with the normal coefficients (a n , b n , c n ) determined experimentally.…”