We propose a metalens structure based on graphene ribbons that can achieve the regulation function in terahertz bands. The metalens structure based on multilayer graphene we proposed in this paper can achieve focus at the different locations through the regulation of the Fermi level of graphene. The structure can be focused separately at 300μm(state1) or at 100μm(state2) or at 200μm(state3). And we can accurately regulate the focusing position of the reflected light by regulating the switch of states 1,2 and 3. This function can not only realize the switch control of metalens, but also realize the precise positioning function of subwavelength. We believe that our findings can provides a new method for wavefront manipulation of metalens and are beneficial in designing new function controlling devices.
We proposed a metalens structure based on graphene in the Terahertz (THz) regime by using the finite-difference timedomain method. The structure consists of two layers of graphene arrays, polymer dielectric spacer and a gold mirror film. The proposed metalens can realize two functions. The first function is to control x-polarized incidence and y-polarized incidence respectively by two layers of graphene, that is, to regulate x-polarized incidence when the working voltage is applied to the lower graphene and 0 voltage is applied to the upper graphene. When the working voltage is applied to the upper graphene and the 0 voltage is applied to the lower graphene, y-polarized incidence is regulated. The second function is to apply 0 voltage to the lower graphene, and regulate both x-and y-polarized incidence by changing the Fermi level of the upper graphene. The simulation results of FDTD show that the metalens structure can not only achieve different functions, but also the focusing effect is in good agreement with the design value. This work provides a new method for wavefront manipulation of metalens.
The relative intensity noise (RIN) is a main factor that limits the detection accuracy of the high precision fiber optic gyroscope (FOG). The RIN spectrum is determined by the normalized autocorrelation of the optical spectrum of the broadband source and is intrinsically different from other fundamental noises. In this paper, we propose an all-optical technique to suppress the RIN. With the power addition of the optical waves from the signal optical path and the reference optical path, the RIN is effectively eliminated at the eigen frequency of the FOG, which is also the demodulation window for the rotation rate signal. Compared with the traditional optical configuration of the FOG, there is only one additional optical component. Experimental results show that, with this method, we can achieve a nearly 3-fold improvement in the angular random walk coefficient. The improved optical configuration for RIN suppression is simple to realize and suitable for engineering application.
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