10.1021/acs.nanolett.7b03050.s001 Ruoming Peng Ruoming Peng Kaveh Khaliji Kaveh Khaliji Nathan Youngblood Nathan Youngblood Roberto Grassi Roberto Grassi Tony Low Tony Low Mo Li Mo Li Midinfrared Electro-optic Modulation in Few-Layer Black Phosphorus American Chemical Society 2017 electro-optic modulation mid-IR narrow-band compound semiconductors Few-Layer Black Phosphorus Black phosphorus material Midinfrared Electro-optic Modulation 2017-09-27 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Midinfrared_Electro-optic_Modulation_in_Few-Layer_Black_Phosphorus/5461033 Black phosphorus stands out from the family of two-dimensional materials as a semiconductor with a direct, layer-dependent bandgap spanning the visible to mid-infrared (mid-IR) spectral range. It is, therefore, a very promising material for various optoelectronic applications, particularly in the important mid-IR range. While mid-IR technology has been advancing rapidly, both photodetection and electro-optic modulation in the mid-IR rely on narrow-band compound semiconductors, which are difficult and expensive to integrate with the ubiquitous silicon photonics. For mid-IR photodetection, black phosphorus has already been proven to be a viable alternative. Here, we demonstrate electro-optic modulation of mid-IR absorption in few-layer black phosphorus. Our experimental and theoretical results find that, within the doping range obtainable in our samples, the quantum confined Franz–Keldysh effect is the dominant mechanism of electro-optic modulation. A spectroscopic study on samples with varying thicknesses reveals strong layer dependence in the interband transition between specific pairs of sub-bands. Our results show that black phosphorus is a very promising material to realizing efficient mid-IR modulators.