We achieve a broadband and ultrahigh responsivity all-fiber photodetector by integrating hybrid CNT/graphene films on a side-polished fiber (SPF).

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In graphene-based optoelectronic devices, the ultraweak interaction between a light and monolayer graphene leads to low optical absorption and low responsivity for the photodetectors and relative high half-wave voltage for the phase modulator. Here, an integration of the monolayer graphene onto the side-polished optical fiber is demonstrated, which is capable of providing a cost-effective strategy to enhance the light–graphene interaction, allowing us to obtain a highly efficient optical absorption in graphene and achieve multifunctions: photodetection and optical phase modulation. As a photodetector, the device has ultrahigh responsivity ( 1.5 × 10 7    A / W ) and high external quantum efficiency ( > 1.2 × 10 9 % ). Additionally, the polybutadiene/polymethyl methacrylate (PMMA) film on the graphene can render the device an optical phase modulator through the large thermo-optic effect of the PMMA. As a phase modulator, the device has a relatively low half-wave voltage of 3 V with a 16 dB extinction ratio in Mach–Zehnder interferometer configuration.

Graphene has been widely used in photodetectors; however its photoresponsivity is limited due to the intrinsic low absorption of graphene. To enhance the graphene absorption, a waveguide structure with an extended interaction length and plasmonic resonance with light field enhancement are often employed. However, the operation bandwidth is narrowed when this happens. Here, a novel graphene-based all-fiber photodetector (AFPD) was demonstrated with ultrahigh responsivity over a full near-infrared band. The AFPD benefits from the gold-enhanced absorption when an interdigitated Au electrode is fabricated onto a Graphene-PMMA film covered over a side-polished fiber (SFP). Interestingly, the AFPD shows a photoresponsivity of >1 × 104 A/W and an external quantum efficiency of >4.6 × 106% over a broadband region of 980–1620 nm. The proposed device provides a simple, low-cost, efficient, and robust way to detect optical fiber signals with intriguing capabilities in terms of distributed photodetection and on-line power monitoring, which is highly desirable for a fiber-optic communication system.

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