Two-dimensional Materials Integration To Silica Optical Fiber For Optoelectronic Devices

The rise of two-dimensional(2D)materials and optical microfiber(MF)has led to fruitful achievements from fundamental physics to applications.Among 2D materials,graphene shows superior electrical,optical,thermal,mechanical and even chemical properties,and has attracted broad interest in physics and optoelectronic research.MF as a bridge between fiber optics and nanotechnology,can realize light-matter interactions in the microscale and even the nanoscale space,which is promising for sensors,nonlinear optics and quantum optics applications.The integration of 2D materials to MF platform might be an optional choice for realizing multifunctional,miniaturized optoelectronic devices,which is an impeding request for micro/nano-photonics.In this thesis,I mainly focus on optical microfiber/fiber hybridized with 2D materials for optoelectronics,i.e.optical fiber polarizer,single-mode single-polarization microresonator,optical modulator and photodetector.The summary of my research work is as follows:(1)Stereo graphene-microfiber(GMF)coil structure for multifunctional devices.The unique MF coil structure can enable arbitrary length of the light-graphene interactions,while retaining the miniaturization of devices.It was theoretically and experimentally demonstrated that GMF could serve as a broadband optical fiber polarizer,with polarization extinction ratio higher than 15 dB in the optical communication bandwidth.When the adjacent MF coils were self-coupled to each other,the GMF could realize single-mode single-polarization microresonators with extinction ratio higher than 11 dB.The possibility of GMF for the all-optical modulation applications was also explored,based on the Pauli blocking effects of the graphene interband transitions.It was found that the modulation depth of GMF could be as high as 7.5 dB with moderate pump power,and the modulation efficiency was 0.2 dB/mW.By further optimizations,the GMF structure will have practical applications in polarization control,filter and all-optical modulators.(2)Strain gauges MF integrated with monolayer graphene and tungsten disulfide(WS2).First,the MF-graphene waveguide structure was expolored for enhancing the strain effects on the graphene light absoprtion.It was found theoretically and experimentally that these parameters,i.e.,the MF geometric scale,probe light wavelength and strain,could significantly influence the modulation depth of the devices.The measured maximized modulation depth of the device induced by uniaxial strain was as large as 30%with moderate 5%strain magnitude,which was more than two orders of magnitude larger than previous results.As for the MF-WS2 hybrid waveguide,it was showed that the waveguide structure can greatly enhance the exciton absorption/emission intensity,and the second harmonic generations(SHGs)of the WS2 film.Further,the strain gauge could effectively control the exciton energy and SHG conversion efficiency of WS2.This work demonstrates the potentials of waveguide-coupled 2D-materials structures for high-performance tunable photonic devices.(3)Optical fiber endface integrates molybdenum disulfide(MoS2)or graphene-CsPbBr3 heterostructure for the sensitive photodetection.A set of technical processes were developed for realization of integrating metal electrodes and semiconductors onto optical fiber endface.It was experimentally demonstrated the photoresponsivity of MoS2 based photodetectors for detecting violet light(@400 nm)can reach 0.6 A/W.As for the graphene-CsPbBr3 heterostructure,it showed that the photoresponsivity can be as high as 2 ×104 A/W thanks to the photogating effects.This kind of devices can provide a new route to active,optical fiber based optoelectronic devices.