Large angle beam splitter grating is an important optical element but the current design methods are mostly based on the scalar diffraction theory based on Thin Element Approximation approximation, which is difficult to evaluate and calculate well when large angle beam splitting is involved. In this work, a method combining finite difference time domain method with adjoint optimization is proposed. Each iteration only needs two electromagnetic simulations to obtain the gradient distribution of the grating structure region. Using this method, a 1×5 beam splitting grating with a splitting angle of 10 degrees is designed. The final uniformity error is 3.7%, and the total diffraction efficiency is 86.6%. For the two-dimensional splitter , a 3×5 beam splitting grating with a diffraction full angle of 82.4×14 degrees is designed. Under the condition of large angle beam splitting, good uniformity error can still be maintained, and the final uniformity error reaches 23.1%.
A gold nanoparticle enhanced microwave modulation with 1.55 μm light in graphene-based antenna has been studied in this paper. The modulation of antenna radiation is achieved by the conductivity tunable characteristic of graphene, and the conductivity of graphene is controlled by light. With the introduction of the gold nanoparticles for exciting optical wave localized enhancement, the interaction between the graphene and the light is enhanced. And then the Fermi level is enlarged, leading to the enhancement of the conductivity turning rage of graphene. At last, the modulation of microwave radiation is enhanced. In the simulation, as the Fermi level of graphene increases from 0.1 eV to 0.4 eV, the S11 coefficient of resonant point of antenna changes by 8 dB. In the experiment, the 0-29.4 mw 1550 nm light is used, the S11 coefficient of graphene antenna with gold nanoparticles changes by 1 dB, which is 2 times higher than that of graphene antenna without gold nanoparticles. The result demonstrates that the microwave modulation by light in graphene-based antenna could be enhanced by gold nanostructures with the localized surface plasmons.
An investigation on hybrid graphene-metal structure patch antenna has been carried out in the presented paper. The microwave radiation performance of the antenna is controlled by the optical tuning characteristic of graphene. The surface conductivity of graphene is changed, when variation of chemical potential is happened which can be regulated by an exterior light field. With simulations, the S11 coefficient of antenna is changed with a maximum of 32.2 dB when the chemical potential of graphene varies from 0 eV to 1 eV. The effect of different structure parameters, such as metal radiating patch sizes and graphene film widths, on the S11 coefficient in the graphene based antenna is further analyzed by simulations. With experiments, the measured S11 coefficient decreases gradually with optical intensity increases when using communication light with the wavelength of 1550 nm as modulation light. When the optical intensity of the communication light varieties from 0 mW to 25 mW, the S11 coefficient of the microwave is changed from -18.7 dB to -19 dB and the modulation depth is 0.3 dB. The results demonstrate the proposed method is a good candidate for modulating microwave directly by communication light.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.