2D graphene has attracted extensive attention as a promising candidate for high‐performance photodetectors because of its superior optoelectronic properties. However, the realization of high‐sensitivity broadband graphene photodetectors remains a challenge. Lithium niobate (LiNbO3) has the advantages of spontaneous polarization, high dielectric constant, and high voltage electric coefficient, and it can improve the photoelectric detection characteristics of graphene by polarized doping. In this work, n‐ and p‐doping of graphene is demonstrated at the same time with the help of local ferroelectric polarization of x‐cut LiNbO3. This high‐sensitivity and broadband p–n junction photodetector shows a wide detection range of 405 to 2000 nm, a responsivity of ≈2.92 × 106 A W−1 at an incident power of 24 pW (λ = 1064 nm), and a high detectivity of ≈8.65 × 1014 Jones. In particular, a fast rise/decay time of ≈23 ms/≈23 ms is achieved. The graphene‐based LiNbO3 (bulk) photodetector shows higher responsivity​, and the graphene‐based LiNbO3 (film) photodetector a faster response time. This work not only deepens and expands the basic research on 2D materials and ferroelectric materials, but also demonstrates the great potential of doped graphene materials for high‐performance photodetection.

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The tungsten diselenide (WSe2) has attracted considerable interest owing to their versatile applications, such as p-n junctions, transistors, fiber lasers, spintronics, and conversion of solar energy into electricity. We demonstrate all-optical tuning of light in WSe2-coated microfiber (MF) using WSe2’s broad absorption bandwidth and thermo-optic effect. The transmitted optical power (TOP) can be tuned using external incidence pump lasers (405, 532, and 660 nm). The sensitivity under 405-nm pump light excitation is 0.30 dB/mW. A rise/fall time of ~ 15.3/16.9 ms is achieved under 532-nm pump light excitation. Theoretical simulations are performed to investigate the tuning mechanism of TOP. The advantages of this device are easy fabrication, all-optical control, high sensitivity, and fast response. The proposed all-optical tunable device has potential applications in all-optical circuitry, all-optical modulator, and multi-dimensionally tunable optical devices, etc.

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