Highly linear wavelength-tunable microring-assisted Mach-Zehnder modulator.

This paper proposes a wavelength-tunable microring-assisted Mach-Zehnder modulator (MRAMZM) based on the graphene structure. The integrated graphene on the racetrack microring achieves the tunability of the working wavelength and introduces the one-cycle loss of the microring corresponding to the working wavelength. Through the analysis of the modulation characteristic curve with loss, it is determined to eliminate the second- and third-order nonlinearities. The graphene-embedded asymmetric coupling structure is used to control the coupling efficiency, and finally, the linearity of the device in the range of 2 nm (1.5543 to 1.5562 µm) is improved. The simulation result shows that when the working wavelength is in this range, the spurious-free dynamic range third-order intermodulation distortion of this modulator is about 114dB⋅Hz2/3.

Extended Risley scanning system with 30 × 360 coverage.

We propose a beam scanning system based on an extended Risley prism structure. This system uses a rotating mirror structure and expands the original construction of the balanced and stable Risley prism. There is much research on extended Risley prism structures, but the scanned angle of their extended systems is less than 180°. The proposed system in this paper can expand scanned angle to 360°, showing practical significance and application value in the field of beam scanning. This is achieved by using reflectors and multiple transmitter and receiver structures with optimized positions and transmission directions. Simulation results show that the scanning range is 360° and ±14∘ in the horizontal and vertical directions, respectively, at 110 m while the angular resolution is 0.2∘×2∘.

Graphene-Based Polarization-Independent Mid-Infrared Electro-Absorption Modulator Integrated in a Chalcogenide Glass Waveguide.

A polarization-insensitive graphene-based mid-infrared optical modulator is presented that comprised SiO2/ Ge23Sb7S70, in which two graphene layers are embedded with a semiellipse layout to support transverse magnetic (TM) and transverse electric (TE) polarizing modes with identical absorption. The key performance index for the polarization independent modulator is polarization-sensitivity loss (PSL). The waveguide of our device just supports basic TE and TM modes, and the PSL between two modes is of < 0.24 dB. The model can offer extinction ratio (ER) more than 16 dB and insertion loss less than 1 dB. The operation spectrum ranges from 2 to 2.4 µm with optical bandwidth of 400 nm. The 3 dB modulation bandwidth is as high as 136 GHz based on theoretical calculation.