Optica Open
arXiv.svg (5.58 kB)

Apparatus for high-precision angle-resolved reflection spectroscopy in the mid-infrared region

Download (5.58 kB)
posted on 2023-11-30, 19:44 authored by Takashi Kuroda, Siti Chalimah, Yuanzhao Yao, Naoki Ikeda, Yoshimasa Sugimoto, Kazuaki Sakoda
Fourier transform (FT) spectroscopy is a versatile technique for studying the infrared (IR) optical response of solid-, liquid-, and gas-phase samples. In standard FT-IR spectrometers, a light beam passing through a Michelson interferometer is focused onto a sample with condenser optics. This design enables us to examine relatively small samples, but the large solid angle of the focused infrared beam makes it difficult to analyze angle-dependent characteristics. Here we design and construct a high-precision angle-resolved reflection setup compatible with a commercial FT-IR spectrometer. Our setup converts the focused beam into an achromatically collimated beam with an angle dispersion as high as 0.25$^\circ$. The setup also permits us to scan the incident angle over ~8$^\circ$ across zero (normal incidence). The beam diameter can be reduced to ~1 mm, which is limited by the sensitivity of an HgCdTe detector. The small-footprint apparatus is easily installed in an FT-IR sample chamber. As a demonstration of the capability of our reflection setup we measure the angle-dependent mid-infrared reflectance of two-dimensional photonic crystal slabs and determine the in-plane dispersion relation in the vicinity of the $\Gamma$ point in momentum space. We observe the formation of photonic Dirac cones, i.e., linear dispersions with an accidental degeneracy at $\Gamma$, in an ideally designed sample. Our apparatus is useful for characterizing various systems that have a strong in-plane anisotropy, including photonic crystal waveguides, plasmonic metasurfaces, and molecular crystalline films.



This arXiv metadata record was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv.

Usage metrics




    Ref. manager