Symmetric silicon microring resonator optical crossbar array for accelerated inference and training in deep learning

Photonic integrated circuits are emerging as a promising platform for accelerating matrix multiplications in deep learning,leveraging the inherent parallel nature of light.Although various schemes have been proposed and demonstrated to realize such photonic matrix accelerators,the in situ training of artificial neural networks using photonic accelerators remains challenging due to the difficulty of direct on-chip backpropagation on a photonic chip.In this work,we propose a silicon microring resonator(MRR)optical crossbar array with a symmetric structure that allows for simple on-chip backpropagation,potentially enabling the acceleration of both the inference and training phases of deep learning.We demonstrate a 4×4 circuit on a Si-on-insulator platform and use it to perform inference tasks of a simple neural network for classifying iris flowers,achieving a classification accuracy of 93.3%.Subsequently,we train the neural network using simulated on-chip backpropagation and achieve an accuracy of 91.1%in the same inference task after training.Furthermore,we simulate a convolutional neural network for handwritten digit recognition,using a 9×9 MRR crossbar array to perform the convolution operations.This work contributes to the realization of compact and energy-efficient photonic accelerators for deep learning.

Multichannel and high-density hybrid integrated light source with a laser diode array on a silicon optical waveguide platform for interchip optical interconnection

A hybrid integrated light source was developed with a configuration in which a laser diode(LD)array was mounted on a silicon optical waveguide platform for interchip optical interconnection.This integrated light source is composed of 13-channel stripes with a pitch of 20 or 30μm.The output power of each LD in the 400 or 600-μm long LD array was over 40 mW at room temperature without cooling.An output power uniformity was 1.3 dB including an LD array power uniformity.The use of a SiON waveguide with a spot size converter resulted in an optical coupling loss of 1 dB between an LD and SiON waveguide.The integrated light source including 52 output ports demonstrated a reduction in the footprint per channel.We also demonstrated a light source with over 100 output ports in which the number of output ports is increased by using a waveguide splitter and multichip bonding.These integrated light sources are practical candidates for use with photonic integrated circuits for high-density optical interconnection.

Strip-loaded waveguide-based optical phase shifter for high-efficiency silicon optical modulators

We propose a novel silicon optical phase shifter structure based on heterogeneous strip-loaded waveguides on a photonic silicon on insulator(SOI) platform. The features of an etchless SOI layer and loaded strip would enhance the performance and uniformity of silicon optical modulators on a large-scale wafer. We implemented the phase shifter by loading an amorphous silicon strip onto an SOI layer with a vertical PN diode structure. Compared to the conventional lateral PN phase shifter based on half-etched rib waveguides, this phase shifter shows a >1.5 times enhancement of modulation efficiency and provides >20 GHz high-speed operation.