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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.
Bibliographical noteFunding Information:
This work was supported by the Air Force Office of Scientific Research (award no. FA9550-14-1-0277; R.P., N.Y., M.L.) and the National Science Foundation (award no. ECCS-1351002 for R.P., N.Y., M.L.; University of Minnesota MRSEC under award no. DMR-1420013 for K.K.). Device fabrication was carried out at the University of Minnesota Nanofabrication Center, which receives partial support from the NSF through the National Nanotechnology Coordinated Infrastructure (NNCI) program. The authors also used resources at the Characterization Facility, which is a member of the NSF-funded Materials Research Facilities Network via the NSF MRSEC program.
- Black phosphorus
- electro-absorptive modulation
- electro-optic modulation
- quantum confined Franz-Keldysh effect
- transmission extinction measurement
How much support was provided by MRSEC?
Reporting period for MRSEC
- Period 4
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.