Suspended low-loss germanium waveguides for the longwave infrared.

Author(s) Osman, A.; Nedeljkovic, M.; Penades, S.; Wu, Y.; Qu, Z.; Khokhar, A.Z.; Debnath, K.; Mashanovich, G.Z.
Journal Opt Lett
Date Published 2018 Dec 15

Germanium is a material of high interest for mid-infrared (MIR) integrated photonics due to its complementary metal-oxide-semiconductor (CMOS) compatibility and its wide transparency window covering the 2-15 μm spectral region exceeding the 4 and 8 μm limit of the silicon-on-insulator platform and Si material, respectively. In this Letter, we report suspended germanium waveguides operating at a wavelength of 7.67 μm with a propagation loss of 2.6±0.3  dB/cm. To the best of our knowledge, this is the first demonstration of low-loss suspended germanium waveguides at such a long wavelength. Suspension of the waveguide is achieved by defining holes alongside the core providing access to the buried oxide layer and the underlying Si layer so that they can be wet etched using hydrofluoric acid and tetramethylammonium hydroxide, respectively. Our MIR waveguides create a new path toward long wavelength sensing in the fingerprint region.

DOI 10.1364/OL.43.005997
ISSN 1539-4794
Citation Osman A, Nedeljkovic M, J Penades S, Wu Y, Qu Z, Khokhar AZ, et al. Suspended low-loss germanium waveguides for the longwave infrared. Opt Lett. 2018;43(24):5997-6000.