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Convolutional neural networks (CNNs) have shown great performance in computer vision tasks, from image classification to pattern recognition. However, CNNs′${\rm CNNs}^{\prime }$ superior performance arises at the expense of high computational costs, which restricts their employment in real‐time decision‐making applications. Computationally intensive convolutions can be offloaded to optical metasurfaces, enabling sub‐picosecond latency and nearly zero energy consumption, but the currently reported approaches require additional bulk optics and can only process polarized light, which limits their practical usages in integrated lightweight systems. To solve these challenges, a novel design of the metasurface‐based optical convolutional accelerator is experimentally demonstrated, offering an ultra‐compact volume of 0.016 mm3${\rm mm}^{3}$, a low cross‐talk of ‐20 dB, polarization insensitivity, and is capable of implementing multiple convolution operations and extracting simultaneously various features from light‐encoded images. The ultra‐compact metasurface‐based optical accelerator can be compactly integrated with a digital imaging system to constitute an optical‐electronic hybrid CNN, which experimentally achieves a consistent accuracy of 96 % in arbitrarily polarized MNIST digits classification. The proposed ultra‐compact metasurface‐based optical convolutional accelerator paves the way for power‐efficient edge‐computing platforms for a range of machine vision applications. [ABSTRACT FROM AUTHOR]

A study was conducted to analyze wavelength-tunable switching among various channels using the self-injection seeding mechanism. The spacing between various wavelengths was tuned by adjustments in the electrical modulation frequency and the length of the dispersive fiber cavity. No optical bandpass filter was needed to separate two wavelengths. Results indicated the feasibility of switching in the gigahertz frequency range.

An external-cavity configuration for a 1.5-mum InGaAsP semiconductor laser, generating tunable dual-wavelength optical output across a wavelength range of 60.8 nm, is proposed and experimentally demonstrated. The Fabry-Perot (FP) grating-lens external cavity comprised an FP filter, converging lens, totally reflecting mirror and a diffraction grating. The relative intensity variation between the two wavelengths was smaller than 1.2dB and no mode hopping was observed.

The concurrent self-injection seeding of a gain-switched Fabry-Perot laser diode at two wavelengths generates dual-wavelength picosecond optical pulses. The scheme, which uses a fiber mirror to provide optical feedback, allows the electrical modulation frequency and dispersion-shifted fiber length to be modified for tuning the output wavelengths and their spacing, respectively, So far, it has generated single-mode pulses at alternate wavelengths around 1.3 micrometer.