Researchers have unveiled the concept of polaritonic Fourier crystals, which represent an innovative advancement over conventional photonic crystals. These structures leverage harmonic modulation of polariton momentum, allowing for enhanced light-matter interactions and effective nanolight guiding.
Polaritons arise from the coupling of light with the collective oscillations of charges, enabling extreme field confinement. For this study, the research team, led by Sergey G. Menabde, employed hexagonal boron nitride (hBN), which is known for its unique properties as it retains polaritonic behavior even under significant losses. Through near-field imaging techniques combined with full-wave numerical simulations, the team probed the behavior of phonon-polaritons within their newly engineered crystal.
“This work provides an alternative paradigm for polaritonic crystals, allowing greater control and interaction with light,” wrote the authors. The novel approach utilized holographic inscription to create structures where the polariton momentum could be modulated, addressing the long-standing issues of scattering loss associated with conventional polaritonic crystals. The previously observed severe losses at material edges were significantly reduced due to the smooth and continuous features of the engineered surfaces.
The team fabricated single-harmonic Fourier surfaces using azopolymeric films, achieving periods as fine as 485 nm. This fabrication method allowed for detailed band structure observation of the generated polartitonic Fourier crystals. The resultant structures were imaged using the scanning near-field optical microscopy (s-SNOM), confirming the successful implementation of wave phenomena within engineered polaritons.
Initial findings suggest the fundamental Bloch mode possesses a polaritonic bandgap even within naturally lossy hBN crystals. Using this discovery, the authors aim to establish how these polaritonic crystals could be applied for enhanced light manipulation at previously unattainable scales. “A polaritonic Fourier crystal enables precise engineering of dispersions, paving the way for new applications across device technologies,” the author emphasized.
The study broadens the horizon for polaritonics – facilitating the development of improved hyperbolic polaritonic nanostructures and could lead to significant impacts within the photonic circuitry used across various technologies, especially those requiring precision manipulation of light.
A bi-harmonic design was also introduced, which facilitates simultaneous bandgaps for both fundamental and higher-order modes, increasing the potential utility of these materials. Such advancements may hold the key to low-loss hyperbolic polaritonic crystals used for efficient information processing and transmission, especially pertinent as demand for strong and effective optics continues to grow.
Researchers assert these polaritonic Fourier crystals will not only contribute to the field of nanotechnology but will also inspire future studies aimed at integrating polaritonic systems with existing photonic technology. This pivotal advancement demonstrates the ability to reconcile fundamental research with practical applications.