Passive Optical Chips that Convert Light into Binary Signals Using Chaos

What is it about?

Optical switches and bifurcation effects usually rely on materials that change their properties at high light intensities (nonlinear materials). In this work, we show that a similar switching behavior can be achieved using only linear effects with nanostructure-induced scattering and chaotic states. We use a special type of tiny optical resonator that supports both chaotic light patterns and stable whispering gallery modes (WGMs), where light circulates around the edge. Normally, chaotic light modes spread energy across a wide range of wavelengths, but their fast, time-based behavior isn’t well understood. We added many small silicon nanocrystals onto the surface of the microresonator’s waveguide. This enhances the chaotic interactions. Surprisingly, the output signal from this device becomes “digitized”—instead of random values between 0 and 1, the signal jumps between levels very close to either 0 or 1. Light entering the system first interacts with chaotic modes, and then either fades away or transfers into a stable WGM. This creates a natural “yes or no” pathway that produces a clean digital output. Because the device is passive (requires no external power beyond the input light), it can convert a regular periodic light signal (like a clock pulse) into a binary (0 and 1) signal in real-time. We achieved strong signal contrasts (over 12.3 dB), fast data rates (over 100 million bits per second), and a wide range of signal levels (20 dB dynamic range).

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Photo by Luke Jones on Unsplash

Photo by Luke Jones on Unsplash

Why is it important?

In this study, we developed a new way to control chaotic light patterns inside tiny optical resonators by using silicon nanocrystals, avoiding the need for large and complex structures. Unlike previous designs, our chip-based device works on an integrated photonics platform and doesn’t require any electrical power to function. We explored how these chaotic light patterns behave over time and found that they can naturally produce a clean digital output of 0s and 1s. This passive approach to generating random digital signals offers a low-power alternative to traditional electronic systems for high-speed data processing.

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