We demonstrate the 4-stage traveling wave photodetector (TWPD) with monolithically integrated bias circuitry network based on a silicon photonics process. A bias circuitry network comprised of inductors is integrated at the input terminal to provide the bias voltage for device while prevent the leak of the RF signal into the voltage circuitry. Experimentally, the maximum RF powers of load terminal are 8 dB higher than input end at high frequencies, validated the effectiveness of RF-choke.
Silicon nitride photonic integrated circuits with ultra-low loss are widely used in applications such as telecommunications and optical sensing. However, the radiation loss increases rapidly as the radius is reduced, resulting in large-sized silicon nitride photonic integrated circuits. The weak thermo-optical effect limits the high-efficiency, low-power consumption applications. In this paper, a stepped index waveguide structure is studied to reduce the bending loss by enhancing the mode confinement. A bend with a radius of 30μm is designed using Ansys MODE. Polymer with a high thermo-optic coefficient is used as the cladding of the silicon nitride waveguide to improve the tuning performance of the phase shifter. The grooves around the waveguide also acts as an adiabatic trench to increase the efficiency of the thermal electrode. A π phase shift under thermal tuned power of 7.5mW is achieved with a 300μm long silicon nitride waveguide. Finally, a cascaded silicon nitride micro-ring resonator with radius of 50μm is designed to achieve an efficient filter with a wide tuning range of 116nm. This scheme provides a novel approach for high-density, wide-tunable and miniaturized devices in silicon nitride photonic integrated circuits.
We demonstrate a single chip silicon-based optical single sideband (OSSB) modulator which is composed of a branch line coupler (BLC) and a silicon dual-parallel Mach-Zehnder modulator (DP-MZM). Benefit from the powerful tool of optical domain compensation we propose, the constrains such as power imbalance and phase offset of BLC are eliminated. As a result, we realize a fully functional OSSB chip to implement full carrier OSSB (FC-OSSB) and suppressed carrier OSSB (SC-OSSB) modulations. The maximum sideband suppression ratio (SSR) of 35 dB is derived at 21 GHz.
We demonstrate 32-channel dispersive optical phased arrays on a Si3N4-on-SOI integration platform. The phase difference is introduced by the arrayed waveguide. Beam steering in phased-array direction with an aliasing-free range of 22.4° and free spectrum ranges of ∼ 60 nm and ∼ 6 nm is achieved. Meanwhile, the main lobe is deflected simultaneously by 19.67° in the other direction by tuning the wavelength from 1500 nm to 1630 nm. Measurement results show that the dispersive optical phased array provides a compact, low-power and massively parallel solution for LiDAR applications.
We demonstrate a hybrid solid-state beam scanner based on 32-channel silicon nitride optical switch with the assistance of transmission blazed grating. The optical switch exhibits rather low power consumption of 7.2 mW/π. Besides, end-fire antennas offer high optical efficiency with less reflection. Non-mechanical two-dimensional beam steering with range of 14.32° × 9.94° and beam divergence of <0.1° is achieved by wavelength tuning and onchip optical path switching. The proposed system eliminates complex control and time-consuming array phase calibration, providing a flexible, scalable and effective solution for all solid-state coaxial light detection and ranging (LiDAR) technology.
We demonstrate the 4-stage and 8-stage silicon traveling-wave photodetectors (TWPDs) with inductive gain peaking technique. Compared with un-peaked TWPDs, the bandwidths of 4-stage and 8-stage TWPDs integrated with inductors are improved from 32 GHz to 44 GHz, and from 16GHz to 24 GHz, respectively. It is experimentally validated that gain peaking is an effective technology to improve bandwidths for multiple-stage TWPDs.
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