In the realm of physics, synthetic dimensions (SDs) have emerged as one of the frontiers of active research, offering a pathway to explore phenomena in higher-dimensional spaces, beyond our conventional 3D geometrical space. The concept has garnered significant attention, especially in topological photonics, due to its potential to unlock rich physics inaccessible in traditional dimensions. Researchers have proposed various theoretical frameworks to study and implement SDs, aiming at harnessing phenomena like synthetic gauge fields, quantum Hall physics, discrete solitons, and topological phase transitions in four dimensions or higher.
One of the primary challenges in conventional 3D space is the experimental realization of complex lattice structures with specific couplings. SDs offer a solution by providing a more accessible platform for creating intricate networks of resonators with anisotropic, long-range, or dissipative couplings. This capability has already led to groundbreaking demonstrations of non-Hermitian topological winding, parity-time symmetry, and other phenomena.
A key goal in this field is the construction of a “utopian” network of resonators where any pair of modes can be coupled in a controlled manner. Achieving this goal necessitates precise mode manipulation within photonic systems, offering avenues for enhancing data transmission, energy harvesting efficiency, and laser array radiance.
As reported in Advanced Photonics, an international team of researchers has created customizable arrays of waveguides to establish synthetic modal dimensions. This advance allows for effective control of light in a photonic system, without the need for complicated extra features like nonlinearity or non-Hermiticity. Professor Zhigang Chen of Nankai University notes, “The ability to adjust different modes of light within the system brings us a step closer to achieving ‘utopian’ networks, where all parameters of an experiment are perfectly controllable.”
In their work, the researchers modulate perturbations (“wiggling frequencies”) for propagations that match the differences between different modes of light. To do so, they employ artificial neural networks (ANNs) to design waveguide arrays in real space. The ANNs are trained to create waveguide setups that have exactly the desired mode patterns. These tests help reveal how light propagates and gets confined within the arrays.
The implication of this work is substantial. By fine-tuning waveguide distances and frequencies, the researchers aim to optimize the design and fabrication of integrated photonic devices. Beyond photonics, this work offers a glimpse into geometrically inaccessible physics with promise for applications ranging from mode lasing to quantum optics and data transmission. The interplay of topological photonics and synthetic dimension photonics empowered by ANNs opens new possibilities for discoveries that may lead to unprecedented materials and device applications.
The research in synthetic dimensions and topological photonics continues to push the boundaries of our understanding of physics, paving the way for exciting advancements in various fields. With continued innovation and collaboration, the potential for groundbreaking discoveries in higher-dimensional spaces remains vast.