We present a hybrid device based on graphene-coupled silicon (Si) photonic crystal (PhC) cavities, featuring triple light detection, modulation, and switching. Through depositing single-layer graphene onto the PhC cavity, the light-graphene interaction can be enhanced greatly, which enables significant detection and modulation of the resonant wavelength. The device is designed to generate a photocurrent directly by the photovoltaic effect and has an external responsivity of ∼14 mA/W at 1530.8 nm (on resonance), which is about 10 times higher than that off-resonance. Based on the thermo-optical effect of silicon and graphene, the device is also demonstrated in electro-optical and all-optical modulation. Also, due to the high-quality (Q) factor of the resonate cavity, the device can implement low threshold optical bistable switching, and it promises a fast response speed, with a rise (fall) time of ∼0.4 μs (∼0.5 μs) in the all-optical switch and a rise (fall) time of ∼0.5 μs (∼0.5 μs) in the electro-optical hybrid switch. The multifunctional photodetector, modulator, and optical bistable switch are achieved in a single device, which greatly reduces the photonic overhead and provides potential applications for future integrated optoelectronics.
A sensing enhancement sensor based on hybrid film fiber has been proposed to detect ammonia. The hybrid film coated on the MMF-SMF-MMF (Multimode Fiber–Single-mode Fiber–Multimode Fiber) structure is composed of single-walled carbon nanotubes with carboxylic acid groups (SWCNTs-COOH) self-assembled film and the silver film that was used to excite surface plasmon polariton (SPP) which contribute to enhancing the sensitive for refractive index (RI). The presence of free carboxylic acid functional groups and large surface area on the SWCNTs-COOH leads to high adsorption and selectivity toward amine compounds. The sensor works under a wavelength modulation scheme. And the resonance wavelength showed a red shift with an increase of the effective RI of the SWCNTs-COOH self-assembled film affected by ammonia concentration. The experimental results show that the sensor coated with hybrid film has high sensitivity and selectivity to ammonia gas. The proposed sensor is linearly responsive to ammonia concentration in the range 0 - 30 ppm, with a maximum sensitivity of 0.8 nm/ppm, the resolution 0.375 ppm, and the measured response 30 s, respectively. Finally, the sensor also has the advantages of simple structure and compact size, excellent stability, and low cost.
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