Dielectric mirrors are widely used in optical setups for spectral regions such as UV, visible, as well as IR. Yet, for the rapidly growing field of terahertz spectroscopy dielectric multilayer optics are sparsely utilized. But with low-loss materials high quality THz optics can be obtained. We present two approaches for the realization of highly effective dielectric THz mirrors. First, four thin slices of high-resistivity silicon and five common polypropylene (PP) foils were alternately stacked together to obtain a broad reflection band. This stop-band blueshifts with increasing angles of incidence. But due to the high index step between Si and PP a band from 0.32 to 0.375 THz always remains the stopband for all incidence angles and both the s- and p-polarization. The measurement data obtained in reflection and transmission geometry are reproduced well by numerical simulations. With a minor change of the layer sequence a microresonator is obtained which reveals a sharp transmission peak at around 0.3 THz within the reflection band. The second material system consists of ceramic laminates of alumina (A) and alumina-zirconia (AZ). Measurements on 12.5 pairs of A/AZ layers yield a strong stop-band from 0.3 to 0.37 THz at normal incidence, which again match numerical simulations. The big advantage of the ceramic mirror is the rugged, quasimonolithic design of the sintered multilayer structure.

Date Published: 19 April 2006
PDF: 9 pages
Proc. SPIE 6194, Millimeter-Wave and Terahertz Photonics, 61940K (19 April 2006); doi: 10.1117/12.661610

Published in SPIE Proceedings Vol. 6194:
Millimeter-Wave and Terahertz Photonics
Dieter Jäger; Andreas Stöhr, Editor(s)