提出了一种具有超薄有源层的谐振腔增强型石墨烯光电探测器的设计方法, 利用谐振腔结构可以将光场限制在腔内, 有效增强探测器的吸收. 通过研究谐振腔内光场谐振条件及谐振模式下探测器响应度增强的机理, 建立了驻波效应下谐振腔增强型石墨烯光电探测器光吸收模型, 仿真分析谐振腔反射镜反射率、谐振腔腔长对于腔内光场增强器件性能的影响. 理论分析表明, 谐振腔增强型石墨烯光电探测器在850 nm处响应度可达0.5 A/W, 相比无腔状态下提高了32倍; 半高全宽为10 nm. 采用谐振腔结构能够提高石墨烯光电探测器件的光电响应, 为解决光电探测器响应度与响应速度之间的相互制约关系提供了途径.

To decrease the considerable nonreciprocal phase drift caused by environmental magnetic fields in fiber-optic gyroscope (FOG), magnetic shields on optical fiber coil (OFC) are necessarily used in medium- and high-accuracy FOG protection. Cubic boxes and spherical shells without any gaps have been widely adopted for decades in shields, posing challenge for tradeoff between weight limitation of shields and its shielding demand yet. Here, an open-type magnetic shields (OMSs) with several coaxial permalloy foil tubes in few hundred micrometers thickness is proposed, overlaying on the winding process of fiber coil and finally combining with OFC as an integration module (OFC-OMS). The shielding effectiveness (SE) and longitudinal availability were adjustable by changing permalloy tubes' thickness, intervals between coaxial foil tubes, and extended length in endcaps. The optimized result showed that an OMS set with six coaxial permalloy foil tubes achieved a longitudinal availability of 82.6% for SE above 20dB in both axial and radial magnetic field and further revealed anisotropic shielding effect in axial magnetic field remarkably resulting in a 40-dB longitudinal availability of 70.1%. Total mass of OMS reduced by around 75% comparing with the conventional magnetic shields for OFC, which showed immense potentials on reduction of FOG size and processing cost.

Detection of the terahertz (THz) electromagnetic spectrum(wavelengths range 0.03-3 mm) is a promising technique for a large variety of strategic applications, such as biomedical diagnostics and process, quality control, homeland security, and environmental monitoring, etc. Graphene has been recognized internationally to have dominant advantages in photodetectors operating due to its high carrier mobility, gapless spectrum, and frequency-independent absorption coefficient. Graphene photodetector operating in the THz region has been extensively studied with great interests. A graphene microcavity photodetector with THz electromagnetic spectrum is demonstrated in this paper, and its responsivity and detectivity under THz electromagnetic spectrum are evaluated. In the designed device, we adopt a distributed bragger reflection (DBR) consisting of two semiconductor materials SiO2 and TiO2 to form an alternating cavity with high-finesse planar, sandwich the absorbing graphene layer between the cavitys top and bottom layers, and design the DBRs reflectivity by the optical transmission matrix method. The monolayer graphenes optical absorption mechanism of the THz radiation spectrum is studied by the conductivity matrix and Maxwells equations with the electromagnetic boundary conditions. Graphenes transfer matrix and absorption coefficient equation are further derived. It is found that at THz region, graphenes conductivity plays an important role in its absorptionand its absorption is 9-22 times enhanced compared with that at the visible region. An optical absorption model of microcavity-enhanced graphene photodetector at THz region is established. The photodetectors absorption rate and responsitivity are analyzed specifically. Theoretical analysis shows that absorption rate is symmetrical to the microcavitys center position and changes periodically, and the shift of the microcavity length influences the period numbers. The maximum rate of the photodetectors absorption reaches 0.965 at 0.12 THz, which increases 93% compared with its maximum absorption rate 0.5 with no cavity. The optimal structure parameters for the designed photodetector are as follows, the top and bottom mirrors reflectivity are 0.928 and 0.998 respectively, the microcavity length is 2.5 mm, the graphene is 0.035 mm away from the top mirror. Under the optimal structure, the photodetectors responsivity reaches 236.7 A/W, and its full width at half maximum reaches 0.035 THz. The designed graphene microcavity photodetector can exhibit high responsivity and detectivity in THz radiation spectrum.