All-fibre phase filters with 1-GHz resolution for high-speed passive optical logic processing

Linear optical wave energy redistribution methods for photonic signal processing

Manipulating the phase of an optical wave over time and frequency gives full control to the user to implement a wide variety of energy preserving transformations directly in the analogue optical domain. These can be achieved using widely available linear mechanisms, such as temporal phase modulation and spectral phase filtering. The techniques based on these linear optical wave energy redistribution (OWER) methods are inherently energy efficient and have significant speed and bandwidth advantages over digital signal processing. We describe several recent OWER methods for optical signal processing, including denoising passive amplification, real-time spectrogram analysis, passive logic computing, and more. These functionalities are relevant whenever the signal is found on a classical or quantum optical wave, or could be upconverted from radio frequencies or microwaves, and they are of interest for a wide range of applications in telecommunications, sensing, metrology, biomedical imaging, and astronomy. The energy preservation of these methods makes them particularly interesting for quantum optics applications. Furthermore, many of the individual components have been demonstrated on-chip, enabling miniaturization for applications where size and weight are a main constraint.

Optics-Enabled Highly Scalable Inverter for Multi-Valued Logic

The rapid advancements in machine learning have exacerbated the interconnect bottleneck inherent in binary logic-based computing architectures. An interesting approach to tackle this problem involves increasing the information density per interconnect, i.e., by switching from a two-valued to a multi-valued logic (MVL) architecture. However, current MVL implementations offer limited overall performance and face challenges in scaling to process data signals with radix (number of logic levels) even just above 3. In this work, a novel concept is introduced for implementation of a highly scalable and fully passive inverter based on the frequency-domain phase-only linear manipulation of the input MVL data signal, which is encoded in the amplitude variations of an electromagnetic wave along the time axis. As a key advantage, this solution is entirely independent of the input radix. The proposed design is implemented using an optical fibre Bragg grating device. Inversion of quaternary signals is experimentally demonstrated, as well as binary and ternary signals, at a remarkable operation speed of 32 GBaud, with an estimated energy consumption of ≈ 24 fJ/bit. The proposed method is universal and can be applied to any system that supports transmission and detection of coherent waves, such as microwave, plasmonic, mechanical, or quantum.

Metatronics-inspired high-selectivity metasurface filter

Metatronic circuits extend the concept of subwavelength-scaled lumped circuitry from electronics to optics and photonics, providing a distinctive design paradigm for versatile optical nanocircuits. Here, based on the design of optical nanocircuits using metatronics concept, we introduce a general approach for dispersion synthesis with metasurface to achieve high-selectivity filtering response. We theoretically and numerically demonstrate how to achieve basic circuit lumped elements in metatronics by tailoring the dispersion of metasurface at the frequency of interest. Then, following the Butterworth filter design method, the meticulously designed metasurface, acting as lumped elements, are properly stacked to achieve a near-rectangular filtering response. Compared to the conventional designs, the proposed approach can simultaneously combine high selectivity with the theoretically widest out-of-band rejection in a considerably simple and time-efficient manner of circuit assembly, similar to electronic circuits, without extensive numerical simulations and complex structures. This dispersion synthesis approach provides exciting possibilities for high-performance metasurface design and future integrated circuits and chips.

All-in-one, all-optical logic gates using liquid metal plasmon nonlinearity

Electronic processors are reaching the physical speed ceiling that heralds the era of optical processors. Multifunctional all-optical logic gates (AOLGs) of massively parallel processing are of great importance for large-scale integrated optical processors with speed far in excess of electronics, while are rather challenging due to limited operation bandwidth and multifunctional integration complexity. Here we for the first time experimentally demonstrate a reconfigurable all-in-one broadband AOLG that achieves nine fundamental Boolean logics in a single configuration, enabled by ultrabroadband (400-4000 nm) plasmon-enhanced thermo-optical nonlinearity (TONL) of liquid-metal Galinstan nanodroplet assemblies (GNAs). Due to the unique heterogeneity (broad-range geometry sizes, morphology, assembly profiles), the prepared GNAs exhibit broadband plasmonic opto-thermal effects (hybridization, local heating, energy transfer, etc.), resulting in a huge nonlinear refractive index under the order of 10-4-10-5 within visual-infrared range. Furthermore, a generalized control-signal light route is proposed for the dynamic TONL modulation of reversible spatial-phase shift, based on which nine logic functions are reconfigurable in one single AOLG configuration. Our work will provide a powerful strategy on large-bandwidth all-optical circuits for high-density data processing in the future.