Mode converters (MCs) play an essential role in mode‐division multiplexing (MDM) systems. Numerous schemes have been developed on the silicon‐on‐insulator (SOI) platform, yet most of them focus solely on the conversion of fundamental mode to one or two specific higher‐order modes. In this study, we introduce a hybrid shape optimization (HSO) method that combines particle swarm optimization (PSO) with adjoint methods to optimize the shape of the S‐bend waveguide, facilitating the design of arbitrary‐order MCs featuring compactness and high performance. Our approach was validated by designing a series of 13 μm‐long MCs, enabling efficient conversion between various TE modes, ranging from TE ₀ to TE ₃ . These devices can be fabricated in a single lithography step and exhibit robust fabrication tolerances. Experiment results indicate that these converters achieve low insertion losses under 1 dB and crosstalks below −15 dB across bandwidths of 80 nm (TE ₀ –TE ₁ ), 62 nm (TE ₀ –TE ₂ ), 70 nm (TE ₀ –TE ₃ ), 80 nm (TE ₁ –TE ₂ ), 55 nm (TE ₁ –TE ₃ ), and 75 nm (TE ₂ –TE ₃ ). This advancement paves the way for flexible mode conversion, significantly enhancing the versatility of on‐chip MDM technologies.

The combination of the integrated waveguide and phase-change materials (PCMs) provides a promising platform for reconfigurable and multifunctional photoelectric devices. Through plasmonic enhancement and the low loss propagation of the waveguide, the footprint and power consumption of the photoelectric device can be effectively improved. In this work, a metal double-ring structure embedded with phase change materials was proposed to utilize the plasmonic effect for enhancement of the light-matter interaction. In particular, the overall temperature difference in the PCM cell can be confined within 2 °C during the crystallization process, thus avoiding the interior heterogeneous crystallization. The insertion loss of the cell in amorphous and crystalline states at a wavelength of 1550 nm are 2.3 dB and 1.0 dB, respectively. A signal contrast ratio of 15.8% is achieved under the ultra-small footprint (50 × 90 nm²) at a wavelength of 1550 nm.

In this paper, the effect of Sb₂Se on the phase change characteristics of Ge₂Sb₂Te₅(GST) is systemically studied for applications in phase-change random access memory (PRAM).

The data shuttling between computing and memory dominates the power consumption and time delay in electronic computing systems due to the bottleneck of the von Neumann architecture. To increase computational efficiency and reduce power consumption, photonic in-memory computing architecture based on phase change material (PCM) is attracting increasing attention. However, the extinction ratio and insertion loss of the PCM-based photonic computing unit are imperative to be improved before its application in a large-scale optical computing network. Here, we propose a 1 × 2 racetrack resonator based on Ge₂Sb₂Se₄Te₁ (GSST)-slot for in-memory computing. It demonstrates high extinction ratios of 30.22 dB and 29.64 dB at the through port and drop port, respectively. The insertion loss is as low as around 0.16 dB at the drop port in the amorphous state and about 0.93 dB at the through port in the crystalline state. A high extinction ratio means a wider range of transmittance variation, resulting in more multilevel levels. During the transition between crystalline and amorphous states, the tuning range of the resonant wavelength is as high as 7.13 nm, which plays an important role in the realization of reconfigurable photonic integrated circuits. The proposed phase-change cell demonstrates scalar multiplication operations with high accuracy and energy efficiency due to a higher extinction ratio and lower insertion loss compared with other traditional optical computing devices. The recognition accuracy on the MNIST dataset is as high as 94.6% in the photonic neuromorphic network. The computational energy efficiency can reach 28 TOPS/W, and the computational density of 600 TOPS/mm². The superior performance is ascribed to the enhanced interaction between light and matter by filling the slot with GSST. Such a device enables an effective approach to power-efficient in-memory computing.