T. Luehder, J. Plentz, J. Kobelke, K. Wondraczek, and M.A. Schmidt, "All-Fiber Integrated In-Line Semiconductor Photoconductor," J. Lightwave Technol. 37, 3244 (2019).
Here, we present a fully fiber-integrated semiconductor wire based photoconductor for the photodetection of light at visible and near-infrared wavelengths. The device consisting of an electrically connected micrometer sized germanium wire running parallel to a single-mode core of a gradient index fiber shows features such as temporal responses shorter than 20 ns and a linear response between 10 nW and 20 μW in the wavelength domain between 600 nm and 1300 nm, while light powers up to 2 mW can be measured. A sophisticated polarization dependency has been revealed, showing a non-intuitive dependence on wavelength and light power that has been explained by a developed model. Due to its design flexibility our electrically connected semiconductor enhanced fiber concept principally allows to detect a defined fraction of light, while the remaining part is still available for further diagnostics, thus defining a novel type of detection scheme for all-in-fiber optoelectronic light detection.