A new publication from
Opto-Electronic Sciences;
DOI 10.29026/oes.2025.240021 , discusses enhanced amplified spontaneous emission via strong coupling in large-area plasmonic cone lattices.
At the nanoscale, intriguing phenomena such as strong light-matter coupling, polaritons, single-photon emission, nonlinear, and non-Hermitian optical effects emerge constantly, greatly advancing the field of information photonics. With the introduction of plasmonic resonant cavities, electromagnetic fields can be strongly localized below the diffraction limit, significantly enhancing the Purcell effect and yielding high Q/V (quality factor/mode volume) resonant modes, thereby accelerating progress in micro-nano lasers.
A major challenge lies in further shrinking the mode volume of microcavities, exploring physical extremes, and precisely controlling spatial distributions. Moreover, by introducing a periodic potential into the system and balancing gain and loss, it is possible to reduce the lasing threshold and overcome the limitations of traditional plasmonic lasers in mode selection, beam directionality, and polarization control—thus paving the way for truly sub-diffraction-limit nanolaser applications.
A team led by Professor Wenxin Wang at Harbin Engineering University, in collaboration with Professor Yong Lei from TU Ilmenau (Germany demonstrated that the fabrication of centimeter-scale plasmonic cone arrays via anodic aluminum oxide (AAO) templates, realizing cone-shaped units with extreme mode volumes. By triggering strong coupling along the Γ-X high-symmetry path, they achieved amplified spontaneous emission (ASE) in quantum emitters.
To explore the ultimate mode distribution in plasmonic microcavities, the team pioneered a non-etching fabrication process using AAO templates to construct metallic nanocones, guiding the localized electromagnetic field to focus at the plasmonic cone tip. By tuning the anodization voltage, they adjusted the aspect ratio of the nanocones, thus modifying the tip angle and investigating the spatial distribution of localized modes. This process also permits large-area periodic arrangement (centimeter scale) of the nanocones in either square or hexagonal lattices. The introduction of a periodic potential not only facilitates Bloch surface waves for compensating radiative loss—forming narrow-linewidth resonance modes—but also achieves high local density of states at high-symmetry points. Under such conditions, degenerate modes can be flexibly manipulated in terms of radiation mode, emission angle, and polarization.
In their experiments, the team observed that when the nanocone aspect ratio was set to 0.33, interactions between the localized mode at the cone tip and the propagating mode at the cone base entered the strong coupling regime along the Γ-X path, exhibiting a Rabi splitting as large as 258 meV. Subsequently, by aligning the flat-band mode on the upper branch of the split states with the emission energy of Nile Red quantum emitters—and under 638 nm excitation—they successfully enhanced the spontaneous emission rate of Nile Red and boosted the emission intensity by approximately 13.5 times. Meanwhile, the splitting phenomena emerging from the periodic potential also effectively controlled the emission direction and polarization of the spontaneous emission, offering new insights into the interaction between metallic periodic structures and quantum emitters, and opening avenues for research into polariton condensation and lasing at the nanoscale.
In summary, the proposed nanocone arrays provide an exemplary platform for investigating light-matter interactions under extreme mode distributions. They also lay an important foundation for exploring novel optical phenomena (such as surface-emitting nanolasers, strong coupling, and topological lasing) based on nanocone arrays.
Keywords: strong coupling / nanocone array / surface plasmon polariton / localized surface plasmon / amplified spontaneous emission
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Wenxin Wang received his Ph.D. from TU Ilmenau, Germany, in 2018. That same year, he established the Photonic Materials Group (PMG) at Harbin Engineering University, serving as the group leader. His research focuses on nano-lasing based on surface lattice resonances, strong coupling, and PCSEL (Photonic Crystal Surface Emitting Lasers). Since its founding, the group has published over 30 SCI papers (including ACS Nano, Nano Letters, Laser & Photonics Reviews, and Small), with an H-index of 29 and more than 3000 total citations. Dr. Wang also serves as Vice President of the Heilongjiang Western Returned Scholars Association, Advisor for OSA/SPIE Student Chapters. Several of his students have received the China Scholarship Council (CSC) National Scholarship, the National Scholarship for graduate students, and awards in national innovation competitions. The first authors of this paper, Jiazhi Yuan and Jiang Hu, are 2024 class graduates.
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Opto-Electronic Advances (OEA, IF=15.3). OES is dedicated to providing a professional platform to promote academic exchange and accelerate innovation. OES publishes articles, reviews, and letters of the fundamental breakthroughs in basic science of optics and optoelectronics.
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Yuan JZ, Hu J, Zheng Y et al. Enhanced amplified spontaneous emission via splitted strong coupling mode in large-area plasmonic cone lattices.
Opto-Electron Sci 4, 240021 (2025). doi:
10.29026/oes.2025.240021