Discover how researchers are leveraging the unique properties of deformed Reuleaux-triangle resonators to achieve exceptional points, a phenomenon with far-reaching implications for sensors, optics, and beyond.
The Emergence of EPs
One of the most intriguing and bewildering phenomena of non-Hermitian systems is exceptional points (EPs): special points in parameter space at which corresponding eigenvalues and eigenvectors intersect when their real parts coalesce with their imaginary parts.
This intriguing phenomenon has recently drawn the interest of researchers as it provides a new route for various applications ranging from sensing, optics to wave manipulation. Many exciting phenomena for EPs have been demonstrated, including power oscillations12,13 and non-reciprocal light propagation14–16 as well as chiral modes17,18 and orbital angular momentum (OAM) lasers19.
In the past, a EP inside circle micro cavity requires at least two scatters to be introduced in order to form an EP and complicating the system. But a group of researchers, led by Prof. Xiaobei Zhang from Shanghai University (SHU) in China has come up with an elegant solution: deformed Reuleaux triangle resonators (RTRs), which break rotational symmetry and thus make the way to exceptional points straighter.
Streaking Rotational Symmetry to Enforce Easier EP Implementation
The researchers’ approach is based on the rippled Reuleaux-triangle resonator. In a circular microcavity, an EP is usually formed through two scatters: breaking the rotational symmetry of the microcavity—splitting into even modes and odd modes—and merging two eigenvalues (and related eigenvectors) together.
The denaturation step could be streamlined using a deformed Roll Through Random coil (RTR) form, which we describe further below. The RTR incorporates a deformed geometry, which inherently breaks the rotational symmetry and removes the need for the first scatter. This simplification allows an EP to directly form, where split WGMs can merge due to the second scatter.
We show that the far-field pattern of a high-chirality mode generated in such an EP by the deformed RTR is highly sensitive to external nanoparticles. As a result, this enhanced sensing would allow detection of single nanoparticles from the distance of 4,000 nanometers with deformed RTR.
Conclusion
Although there are many challenges that remain, the success of the SHU researchers is a testament to the strength of creative design and curiosity over non-Hermitian systems. They have exploited the specific properties of such “deformed” Reuleaux-triangle resonators to provide a shortcut to exceptional points and access new sensing, as well as optical possibilities. The field of non-Hermitian physics will no doubt lead to many more new, fascinating results which shape the landscape of our present-day knowledge and expand them for exciting prospects.
