Zijian Zhu

Optimizing doping profiles has always been a key approach to enhance the performance of silicon modulators. Nevertheless, the pursuit of innovative profiles has encountered barriers in recent times. To tackle this issue, the idea of inverse design, widely adopted in passive photonic devices, can be employed in silicon active devices. As a result, we incorporate the inverse design method with the particle swarm optimization (PSO) algorithm and achieve a G-shaped doping profile for the modulator, exhibiting superior $V_{\pi } L$ of 0.68 V $\cdot$ cm and low loss of 9.3 dB/cm. The small-signal frequency response suggests a reliable operation range under reverse biases of 1 $\sim$ 3 V with the bandwidth over 26 GHz. The silicon modulator with a G-shaped design demonstrates remarkable efficiency in modulation and very low loss, suggesting its great potential for application in microwave front-end systems. The use of inverse design shows great potential in enhancing active silicon photonic devices, allowing for faster, higher-capacity, and more reliable data communication systems.

In silicon modulator design, implantation is always a key factor, significantly influencing the doping profile and carrier distribution. As waveguide doping is limited by the compact footprint of the modulator rib, three-dimensional complex optimization is a viable option to improve performance. This work proposes an X-intersected modulator based on two inversely slanted junctions using the effective 3D Monte Carlo method for junction generation. The optimized results show that the modulation efficiency of the design is 1.09 V·cm, while the loss is 18 dB/cm, and the 3 dB bandwidth reaches over 35 GHz owing to the decreased resistance and capacitance of the 3D junction. This work demonstrates the benefits of 3D doping design in silicon modulators, contributing to higher efficiency and avoiding additional PN overlap to introduce lower capacitance. The design of 3D doping profiles well balances the DC and AC performance, and provides novel modulator solutions for high-speed datacom.

We demonstrate a 3-dB power splitter optimized by an enhanced particle swarm optimization algorithm based on a curved directional coupler, with a set of silicon columns introduced into the coupling region. The proposed device exhibits compact size, low loss and low wavelength dependence in the O-band. We employ the particle swarm optimization algorithm to engineer the dispersion by designing the radius of the silicon columns automatically. The demonstrated 3-dB power splitter enabled by silicon columns in silicon-on-insulator can achieve multiple performance metrics simultaneously according to our simulation results, with a compact footprint as small as 11.9 µm, low excess loss as low as 0.04 dB and broad 3-dB operational bandwidth of 60 nm with transmission fluctuations within 0.05 in the wavelength range from 1270 to 1330 nm. This work pioneers the silicon columns in the coupling region and adopts an enhanced particle swarm optimization algorithm to optimize device properties, providing significant potential for application in large-scale PICs as well as offering a new degree of freedom in the design of power splitters.

We experimentally demonstrate a low-loss and low-crosstalk 16-channel 200 GHz-channel-spacing arrayed waveguide grating router (AWGR) with a size of 0.67 × 0.37 mm ² , targeting for C-band wavelength division multiplexing (WDM) interconnect routing applications. As a result, the AWGR features a channel spacing of 200±10 GHz, a free spectral range of 25.62 nm and a 3 dB channel bandwidth of 0.9 nm. Based on comprehensive optimal design, the measured characterization revealed 5.55 dB maximum channel loss non-uniformity with 1.13 dB best-case channel insertion loss. Besides, the fabricated device exhibits good cyclic-frequency operation for all 16 × 16 port combinations with channel crosstalk of –15.11 dB.

Wepropose and experimentally demonstrate the ultra-compact mode (de)multiplexers and polarization beam splitter (PBS) based on tapered bent asymmetric directional couplers. The strong coupling strength introduced by tapered bent waveguides significantly shortens the coupling length. As a result, high coupling and conversion efficiencies over a broad bandwidth can be obtained with small footprint. The coupling length of the fabricated PBS and mode (de)multiplexers are less than 4.9 μm and 8.7 μm, respectively. From 1534-1600 nm, the measured insertion loss (IL) is less than 1.4 and 1.55 dB for the TE ₁ -TE ₀ and TE ₂ -TE ₀ mode (de)multiplexers, respectively, and the crosstalk (CT) is less than −10 dB. The fabricated PBS shows low insertion loss of 0.55 dB and decent crosstalk of < −14 dB for both polarizations over an 85 nm wavelength range from 1505-1590 nm. Meanwhile, the larger fabrication tolerance ensures that the proposed devices can be readily fabricated with the standard complementary metal-oxide-semiconductor (CMOS) process.