The new study generates massively parallel on-chip optical chaotic random number signals

On July 31, Professor Wang Xingjun of the School of Electronics of Peking University, and researchers Chang Lin and Shu Haowen jointly published an article online in the journal Nature Communication. This paper verifies the large-scale parallel chaotic signal generation scheme based on chaotic microcavity light comb, solves the bottleneck problem of the lack of high-speed parallel chaos source in traditional chaotic systems, combines with silicon-based optoelectronic functional chips for the first time, jointly realizes the on-chip ultra-large capacity parallel true random number generation, and demonstrates and verifies in optical decision-making application scenarios, which is expected to provide a new information processing toolbox based on parallel chaos for the next generation of integrated optoelectronic information systems.

On-chip information system based on chaotic microcavity light comb. (Photo courtesy of Shen Bitao)

“The realization of this technology is of key significance for the leapfrog development of high-speed and secure communication.” Wang Xingjun, one of the corresponding authors, told China Science News.

Chaotic characteristics describe the sensitivity of nonlinear dynamic systems to initial values, which is an important basic scientific problem in nonlinear disciplines, and at the same time, chaotic systems have many important applications in the field of modern information, such as in the field of communication, by building a synchronous chaotic system at both ends of transmission and reception, the chaotic signal output by the chaotic system can be used to generate keys or masks to achieve confidential communication.

In the field of computing, using the initial value sensitivity characteristics of chaotic systems, chaotic signals can be used as entropy sources to extract random numbers for computing tasks such as Monte Carlo simulation and reinforcement learning. Chaotic signals also have important application value in sensing and other fields, such as super-resolution imaging technology, multiple-input, multiple-output (MIMO) radar, and random modulation (RMCW) lidar based on chaotic laser.

At present, it is possible to use electrical or optical schemes to generate high-quality chaotic signals, but they are limited by the system architecture in terms of rate and parallelism, respectively, and it is difficult to meet the high throughput requirements of future systems.

High-speed parallelization is an inevitable trend in the development of information systems, and chaotic systems based on optical chaos can use the ultra-large bandwidth of optical systems to achieve high-speed chaos signal generation, but the optical chaos of traditional schemes is difficult to achieve low-cost parallel chaos signal generation. Chaos laser is currently the most widely used optical chaos signal generation scheme, but the parallel chaotic laser output needs to use at least one laser at each signal transmitter, and the excitation of the chaotic state requires the construction of a feedback loop, and the device and deployment cost limit the parallelization space of the chaotic laser.

Chaotic systems based on space optics can use space division multiplexing technology to generate multiple chaotic signal outputs, but the overall system needs to use large-volume space optical components, which is difficult to integrate, and cannot rely on the integration platform to achieve low-cost, large-scale parallel chaotic signal generation. Therefore, chaos-based application systems urgently need chaotic signal generation systems that can achieve large-scale integration and parallelization.

In this work, the research team verified the feasibility of chaotic microcavity combs as massively parallel chaos sources. Chaotic microcavity comb is a special state of microcavity comb, which can be generated by pumping the optical microcavity with a continuous optical laser, which appears as an equal-spaced frequency comb in the optical frequency domain or wavelength domain, and each comb tooth is loaded with a chaotic signal.

By utilizing the ultra-high nonlinear effects in a silicon-based integrated aluminum gallium arsenic photonic stage, the chaos bandwidth of the chaotic signal generated by each comb at 100 milliwatts of pumped optical power is comparable to that of a single chaos laser. The research team measured the correlation between the chaotic signals of each channel and proved that the channel-to-channel correlation of the chaotic light comb can be less than 0.04, which is a very excellent parallel chaos source. The research team further used the chaotic microcavity comb to demonstrate and verify the application in high-speed parallel true random number generation and optical decision system.

This work provides a new development direction for integrated chaotic information systems, and is expected to open up new technologies in the fields of confidential communication, sensing, and computing based on optical chaos. (Source: Cui Xueqin, China Science News)

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