Tuning light-matter interaction of near-infrared nanoplasmonic scintillators

Abstract: Nanoplasmonic modification of scintillation has so far been explored mainly in the weak-coupling regime, where changes in the local density of optical states enhance radiative recombination via Purcell-type rate engineering. By contrast, strong light-matter coupling generates hybrid states that modify emission dynamics beyond simple decay-rate acceleration, but its implications for scintillator nanocrystals (NCs) under ionizing radiation remain poorly understood. All of these effects are beneficial for near-infrared scintillators, which are typically slow and have low brightness. Here, we present a quantum-optical framework to investigate how near-infrared scintillator NCs coupled to nanoplasmonic antennas evolve from weak coupling toward strong light-matter coupling. We compare broad- and narrow-antenna platforms with single and periodic Au nanorods and benchmark them against conductive plasmonic antennas based on indium tin oxide and graphene. As representative emitters, we consider wide-band PbS NCs and narrow-band cubic Lu2O3:Er3+ scintillators. The calculations show that the onset of strong-coupling signatures is jointly governed by emitter dephasing and the antenna linewidth, with narrow-band emitters coupled to spectrally narrow antennas providing the most favorable conditions. Among the platforms considered, graphene gives the lowest threshold (g = 4 meV) for observable coherent exchange owing to its ultranarrow antenna linewidth (\k{appa} = 3.5 meV). These results identify near-infrared conductive nanoantennas, particularly graphene-based ones, as promising platforms for accessing hybrid scintillation regimes relevant to radiation detection.

• The paper establishes a quantum-optical framework using a driven-dissipative Jaynes-Cummings model to capture the transition from Purcell-enhanced emission to strong coupling in NIR scintillators.
• The study shows that matching antenna and emitter linewidths, especially with graphene antennas, significantly lowers the coupling threshold required for observing coherent hybridization and Rabi splitting.
• The findings provide explicit design principles for enhancing radiation detectors and photonic devices by engineering light-matter interactions in nanocrystal systems.

Quantum-Optical Modulation in Near-Infrared Nanoplasmonic Scintillators

Overview

The paper "Tuning light-matter interaction of near-infrared nanoplasmonic scintillators" (2604.13775) develops a rigorous quantum-optical framework for investigating the crossover from weak to strong light-matter coupling in near-infrared (NIR) scintillator nanocrystals (NCs) embedded in nanoplasmonic environments. The focus is on elucidating how the interplay between emitter properties and antenna characteristics governs emission modification, especially under ionizing excitation relevant to radiation detection. The theoretical study leverages open quantum system modeling, benchmarking both wide-band and narrow-band NCs interfaced with gold, indium tin oxide (ITO), and graphene nanoantennas, and identifies conditions under which coherent hybridization and Rabi splitting manifest in scintillation.

Model and Methodology

The emitter-antenna system is treated with a driven-dissipative Jaynes-Cummings model in the open quantum systems formalism. The central parameters include light-matter coupling strength $g$, spectral detuning $\Delta = \omega_c - \omega_e$, antenna linewidth $K$, and emitter dephasing rate $\gamma_0$. Dissipative channels—antenna losses, emitter spontaneous emission, pure dephasing, and incoherent pumping—are incorporated via Lindblad superoperators. Simulations employ experimentally calibrated values for PbS (wide-band, $\gamma_0 = 75$ meV) and Lu$_2$O$_3$:Er$^{3+}$ (narrow-band, $\gamma_0 = 10$ meV) NCs as representative emitters, with antennas realized as single Au nanorods, periodic Au nanorod arrays, ITO spheres, and graphene flakes.

Temporal dynamics are assessed through the first-order field correlation function, while spectra are constructed from two-time correlation functions for both antenna and emitter emission channels. Spectral and temporal observables are mapped as functions of coupling strength and detuning, providing an explicit characterization of the transition from rate enhancement (Purcell effect) to strong coupling (Rabi splitting and coherent oscillations).

Key Results

The simulations demonstrate that the onset of strong coupling signatures is controlled by both emitter linewidth (dominated by pure dephasing in the NCs studied) and antenna linewidth. Narrow-band emitters coupled to narrow-band antennas yield the lowest threshold for observable coherent exchange. For instance:

• Au Nanorod Antennas: Broad Au nanorods only achieve spectral splitting and Rabi oscillations at high $g$ ($\Delta = \omega_c - \omega_e$0 meV). Periodic Au arrays, which have reduced plasmonic linewidth due to collective lattice effects, manifest strong-coupling features—split polariton doublets and pronounced Rabi oscillations—at substantially lower $\Delta = \omega_c - \omega_e$1.
• Emitter–Antenna Linewidth Matching: Narrow-band Lu$\Delta = \omega_c - \omega_e$2O$\Delta = \omega_c - \omega_e$3:Er$\Delta = \omega_c - \omega_e$4 NCs with periodic Au antennas exhibit earlier and clearer emission splitting and oscillations than wide-band PbS NCs, emphasizing the role of emitter dephasing.
• Alternative Antenna Platforms: ITO antennas, with $\Delta = \omega_c - \omega_e$5 meV, require $\Delta = \omega_c - \omega_e$6 meV for the onset of spectral splitting. Graphene antennas, exhibiting ultranarrow linewidths ($\Delta = \omega_c - \omega_e$7 meV), enable observable strong coupling at $\Delta = \omega_c - \omega_e$8 meV and maintain coherent oscillations in emission out to $\Delta = \omega_c - \omega_e$92 ps, substantially exceeding metallic nanoantennas in achievable hybridization.

The peak Purcell enhancement factor is determined to be $K$0 in cavities maintained outside the strong-coupling regime up to highest $K$1, with qualitative differences between efficiency-driven emission acceleration in wide-band systems and rapid lifetime shortening in narrow-band, high-QE emitters.

Experimental Design Principles and Implications

The analysis provides explicit design rules: maximize the match between emitter and antenna spectral linewidths and minimize both to lower the strong-coupling threshold. Narrow-band NIR emitters coupled to ultranarrow antennas (particularly graphene-based) are optimal for realizing hybrid light-matter states under ionizing excitation. The framework generalizes beyond noble-metal plasmonics, showing that conductive platforms such as ITO and graphene are particularly attractive for NIR regimes due to low loss, high confinement, and narrow spectral resonances.

Practical implications include:

• Radiation Detection: Exploiting strong coupling to sculpt emission spectra and temporal profiles, potentially improving timing and energy resolution in NIR scintillation detectors.
• Remote Collection and Signal Structuring: NIR emission can be collected remotely using semiconductor layers, enabling advanced detector architectures.
• Hybrid Optical Signal Generation: The emission becomes temporally extended and structured, opening possibilities for applications in nuclear-powered batteries, spectrally encoded imaging, and persistent luminescence alternatives.

A particularly bold finding is the identification of graphene antennas as achieving observable strong coupling with the lowest $K$2 threshold seen in the study, due to the combination of ultranarrow linewidth and high mode confinement, suggesting a pathway for ultra-efficient, coherent NIR scintillation modulation.

Future Directions

The study suggests future exploration of alternative conductive plasmonic materials (e.g., TiN), dual-emission scintillators, and broader spectral engineering of nanoplasmonic hybrid architectures. Extension to ionizing-radiation-driven plasmonic concepts—where scintillation acts as a structured and temporally modulated signal—could foster new classes of functional nanoscale detectors and radiative energy conversion platforms. The framework developed here is directly applicable to any luminescent system where light-matter coupling engineering and spectral/temporal control under incoherent excitation are desired.

Conclusion

This work integrates quantum-optical theory and numerical simulation to delineate the crossover from Purcell-enhanced emission to strong-coupling induced hybrid light-matter dynamics in NIR scintillator NCs under ionizing excitation. The results demonstrate that ultranarrow antenna linewidths and minimal emitter dephasing are critical for accessing coherent hybrid states, especially in conductive nanoplasmonic architectures. The identification of graphene antennas as optimal platforms for strong coupling at extremely low $K$3 expands the design space for hybrid scintillation regimes with applicability to advanced radiation detection, photonic device engineering, and novel structured emission functionalities.