Deep subwavelength plasmonic whispering-gallery-mode cavity

Optics Express (Impact Factor: 3.53). 10/2012; 20(22):24918-24. DOI: 10.1364/OE.20.024918
Source: PubMed

ABSTRACT We propose a plasmonic whispering-gallery-mode cavity comprising of a dielectric disk with sub-hundred nanometer thickness sandwiched by two silver disks. By reducing radius and thickness carefully based on the investigated resonant wavelength dependencies, the surface-plasmon-polariton cavity mode with a resonant wavelength of 1550 nm can be confined in a disk with a radius of 88 nm and a thickness of 10 nm, where the physical size of the cavity is 0.000064 λ0 30: free space wavelength). The cavity mode has a deep subwavelength mode volume of 0.010 (λ/2n)3 and a high quality factor of 1900 at 40K, consequently, a large Purcell factor of 1.1 x 105.

1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We propose a mechanism of ultrahigh-Q metallic nanocavity resonances that involves an efficient loss-compensation scheme favorable for room-temperature operation. We theoretically show that surface plasmon-polaritons excited on the entrance and exit interfaces of a metallic nanocavity array efficiently transfer external optical gain to the cavity modes by inducing resonantly-amplified intracavity feedback. Surprisingly, the modal gain in the nanocavity with the externally amplified feedback is inversely proportional to the cavity length as opposed to conventional optical cavity amplifiers requiring longer cavities for higher optical gain. Utilizing this effect, we numerically demonstrate room-temperature nanocavity resonance Q-factor exceeding 10(4) in a 25-nm-wide silver nanoslit array. The proposed mechanism provides a highly efficient plasmonic amplification process particularly for subwavelength plasmonic cavities which are essential components in active nanoplasmonic devices.
    Scientific Reports 11/2014; 4:7124. DOI:10.1038/srep07124 · 5.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The optical response of a plasmonic gap-antenna is mainly determined by the Coulomb interaction of the two constituent arms of the antenna. Using rigorous calculations supported by simple analytical models, we observe how the morphology of a nanometric gap separating two metallic rods dramatically modifies the plasmonic response. In the case of rounded terminations at the gap, a conventional set of bonding modes is found that red-shifts strongly with decreasing separation. However, in the case of flat surfaces, a distinctly different situation is found with the appearance of two sets of modes: (i) strongly radiating longitudinal antenna plasmons (LAPs), which exhibit a red-shift that saturates for very narrow gaps, and (ii) transverse cavity plasmons (TCPs) confined to the gap, which are weakly radiative and strongly dependent on the separation distance between the two arms. The two sets of modes can be independently tuned, providing detailed control of both the near- and far-field response of the antenna. We illustrate these properties also with an application to larger infrared gap-antennas made of polar materials such as SiC. Finally we use the quantum corrected model (QCM) to show that the morphology of the gap has a dramatic influence on the plasmonic response also for subnanometer gaps. This effect can be crucial for the correct interpretation of charge transfer processes in metallic cavities where quantum effects such as electron tunneling are important.Keywords: optical antennas; plasmonic gaps; cavity modes; antenna modes; quantum effects; quantum corrected model; plasmonic resonances; phononic resonances
    01/2015; 2(2):150115153318000. DOI:10.1021/ph5004016
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Plasmonic nanoantennas, the properties of which are essentially determined by their resonance modes, are of interest both fundamentally and for various applications. Antennas with various shapes, geometries and compositions have been demonstrated, each possessing unique properties and potential applications. Here, we propose the use of a sidewall coating as an additional degree of freedom to manipulate plasmonic gap cavity modes in strongly coupled metallic nanodisks. It is demonstrated that for a dielectric middle layer with a thickness of a few tens of nanometers and a sidewall plasmonic coating of more than ten nanometers, the usual optical magnetic resonance modes are eliminated, and only magnetic toroid-like modes are sustainable in the infrared and visible regime. All of these deep-subwavelength modes can be interpreted as an interference effect from the gap surface plasmon polaritons. Our results will be useful in nanoantenna design, high-Q cavity sensing, structured light-beam generation, and photon emission engineering.
    12/2014; 2(1). DOI:10.1021/ph500229p


1 Download
Available from