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August 3, 2026 September 9, 2026

Mirror-Image-Induced Magnetic Modes - Notes

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Journal article

Elisabet Xifré-Pérez, Lei Shi, Umut Tuzer, Roberto Fenollosa, Fernando Ramiro-Manzano, Romain Quidant and Francisco Meseguer

ACS Nano

Volume 7

Issue 1

Pages 664-668

2013

DOI · 10.1021/nn304855t View article at ACS ACS Nano journal

Published abstract

Reflection in a mirror changes the handedness of the real world, and right-handed objects turn left-handed and vice versa. Also, we learn from electromagnetism textbooks that a flat metallic mirror transforms an electric charge into a virtual opposite charge. Consequently, the mirror image of a magnet is another parallel virtual magnet as the mirror image changes both the charge sign and the curl handedness. Here we report the dramatic modification in the optical response of a silicon nanocavity induced by the interaction with its image through a flat metallic mirror. The system of real and virtual dipoles can be interpreted as an effective magnetic dipole responsible for a strong enhancement of the cavity scattering cross section.

Figures

Schematic of the mirror image method for an electric charge and a magnetic dipole
Figure 1. Mirror image method for an electric charge and a magnetic dipole.
Transmission spectrum of a 505 nanometre silicon sphere on glass
Figure 2. Transmission spectrum of a polycrystalline silicon sphere on glass, comparing experiment and simulation.
Reflection spectra for silicon spheres of different diameters on a gold substrate
Figure 3. Reflection spectra of silicon spheres on a gold substrate.
Scattering cross section and simulated silicon sphere mirror configurations
Figure 4. Calculated scattering cross section and configurations used to model the mirror-image interaction.
Electric and magnetic field distributions and induced magnetic dipole scattering pattern
Figure 5. Field distributions, induced magnetic dipole and scattering pattern.

Figures reproduced for non-commercial use on the author’s personal website from E. Xifré-Pérez et al., ACS Nano 7, 664-668 (2013), DOI: 10.1021/nn304855t. Copyright © 2012 American Chemical Society. ACS sharing policy

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Article access and reuse

Copyright © 2012 American Chemical Society. The Version of Record was published in ACS Nano. The figures shown here are used non-commercially on an author’s personal website with full citation and remain subject to ACS copyright, sharing and permissions policies.

Related publications

Connections within F. Ramiro-Manzano's publication record, selected from shared research topics and evidence reviewed in the source papers.

Original embedded field-emission scanning electron micrograph of a typical hydrogenated amorphous silicon microsphere with a one micrometre scale bar
Journal article
Int. J. Therm. Sci. 213, 109829 (2025)
Thermal emission of hydrogenated amorphous silicon microspheres in the mid-infrared
R. Fenollosa and F. Ramiro-Manzano

What the related paper adds

This later paper extends the research direction developed in Mirror-Image-Induced Magnetic Modes. This paper distinguishes a new mid-infrared emission mechanism in hydrogenated amorphous silicon spheres. Vibrations of silicon-hydrogen bonds create a pronounced phononic band that can couple to the sphere resonances, while controlled laser heating reveals bond reconfiguration and the onset of transformation towards polycrystalline silicon.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Thermal emission of hydrogenated amorphous silicon microspheres in the mid-infrared. This paper shows that a silicon nanocavity can acquire a strongly enhanced magnetic-like optical response through interaction with its own image in a metallic mirror. The real particle and its virtual counterpart form an effective magnetic dipole, providing a route to amplify scattering without assembling two perfectly matched physical particles.

SEM image showing a side view of as-synthesized polycrystalline silicon microspheres.
Journal article
Adv. Opt. Mater. 11(15), 2300135 (2023)
Silicon Microspheres for Super-Planckian Light Sources in the Mid Infrared
R. Fenollosa, F. Ramiro-Manzano, M. Garín and F. Meseguer

What the related paper adds

This later paper extends the research direction developed in Mirror-Image-Induced Magnetic Modes. This work carries resonant thermal emission into the mid infrared, where the lowest-order modes of two-to-three-micrometre silicon spheres are widely separated and approach the absorption-emission matching condition. Several peaks exceed the calculated black-body limit, establishing the spheres as compact, spectrally selective mid-infrared sources.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Silicon Microspheres for Super-Planckian Light Sources in the Mid Infrared. This paper shows that a silicon nanocavity can acquire a strongly enhanced magnetic-like optical response through interaction with its own image in a metallic mirror. The real particle and its virtual counterpart form an effective magnetic dipole, providing a route to amplify scattering without assembling two perfectly matched physical particles.

Figure 1: experimental setup and temperature
Journal article
ACS Photonics 6(12), 3174-3179 (2019)
Thermal Emission of Silicon at Near-Infrared Frequencies Mediated by Mie Resonances
R. Fenollosa, F. Ramiro-Manzano, M. Garín and R. Alcubilla

What the related paper adds

This later paper extends the research direction developed in Mirror-Image-Induced Magnetic Modes. This study turns a single silicon microsphere into a resonant thermal emitter in the near infrared. Heating produces discrete Mie peaks instead of a smooth black-body spectrum, with quality factors around 400 and a predicted microsecond response, and points towards emission above the Planck limit in selected spectral intervals.

What this paper adds to the related work

This paper provides an earlier basis for the later development reported in Thermal Emission of Silicon at Near-Infrared Frequencies Mediated by Mie Resonances. This paper shows that a silicon nanocavity can acquire a strongly enhanced magnetic-like optical response through interaction with its own image in a metallic mirror. The real particle and its virtual counterpart form an effective magnetic dipole, providing a route to amplify scattering without assembling two perfectly matched physical particles.

Protocol Exchange
Protocol
Protocol Exchange (2013)
Processing and Characterization of Monodisperse Silicon Colloids
L. Shi, X. Lu, R. Fenollosa, I. Rodriguez, J. T. Harris, F. Ramiro-Manzano, B. A. Korgel and F. Meseguer

What the related paper adds

This paper complements Mirror-Image-Induced Magnetic Modes within the same research line. This protocol makes the silicon-colloid platform reproducible at smaller and more uniform sizes. It describes how to fabricate monodisperse spheres in the 300 to 500 nanometre range and how to characterize individual particles with a purpose-built confocal microscope, linking controlled processing to well-resolved electric and magnetic Mie modes.

What this paper adds to the related work

Alongside Processing and Characterization of Monodisperse Silicon Colloids, this paper develops a complementary part of the problem. This paper shows that a silicon nanocavity can acquire a strongly enhanced magnetic-like optical response through interaction with its own image in a metallic mirror. The real particle and its virtual counterpart form an effective magnetic dipole, providing a route to amplify scattering without assembling two perfectly matched physical particles.

Complete original Figure 2 composition extracted directly from the article PDF
Journal article
J. Appl. Phys. 109, 102424 (2011)
Silicon colloids: A new enabling nanomaterial
F. Meseguer, R. Fenollosa, I. Rodriguez, E. Xifre-Perez, F. Ramiro-Manzano, M. Garin and M. Tymczenko

What the related paper adds

This earlier paper establishes a scientific basis for Mirror-Image-Induced Magnetic Modes. This paper defines silicon colloids as a material platform rather than a single device. It surveys polycrystalline, amorphous and porous spherical particles, explains their strong low-order Mie resonances and infrared light confinement, and opens applications ranging from optical filtering to light-controlled forces between particles.

What this paper adds to the related work

Building on the earlier contribution Silicon colloids: A new enabling nanomaterial, this paper advances the research line. This paper shows that a silicon nanocavity can acquire a strongly enhanced magnetic-like optical response through interaction with its own image in a metallic mirror. The real particle and its virtual counterpart form an effective magnetic dipole, providing a route to amplify scattering without assembling two perfectly matched physical particles.

Research fields

Bottom-up

A polycrystalline silicon microsphere provides a high-index dielectric nanocavity whose resonances are set by particle size. Placing the same type of cavity on glass or near a metallic mirror changes its environment without redesigning the particle itself.

Simulations & fits

Three-dimensional FDTD calculations compare the real sphere-mirror system with an image-dipole construction. Electric- and magnetic-field maps show how the mirror suppresses or reinforces specific Mie multipoles and produces the observed magnetic response.

Characterization

Fourier-transform infrared reflection and transmission spectra are recorded for individual spheres on gold and glass. Mode assignments and microscope-based diameter estimates allow the spectral changes to be attributed to interaction with the virtual image rather than to particle-size variation.

RESEARCH TOPICS

CouplingA 505 nm polycrystalline-silicon sphere is first characterised on glass and then transferred onto a gold-coated substrate. The metal does not behave like a second identical resonator: its reflected field has the opposite phase, so the sphere couples to an electromagnetic image rather than producing the usual symmetric/antisymmetric mode splitting of two real cavities.InterferenceThe decisive field is formed by the electric dipole of the silicon sphere and its phase-inverted mirror image. Their antisymmetric combination suppresses the ordinary electric-dipole picture and produces a circulating displacement-current pattern.MagnetismThe mirror converts the sphere's a₁₁ electric mode into a magnetic-like resonance with a scattering cross-section larger than the other cavity modes. Unlike metallic magnetic resonators, this response lies in silicon's transparency region, so it avoids much of the absorption normally associated with plasmonic structures.MaterialsThe colloids are annealed for one hour at 800 °C in vacuum to transform amorphous silicon into polycrystalline silicon. Using one physical sphere in both environments isolates the substrate-induced change from particle-to-particle variability.ResonatorsMie theory identifies the electric and magnetic multipoles supported by the isolated silicon nanocavity. The experiment therefore treats the mirror spacing and phase relation as part of the resonator design, not merely as a reflective substrate.
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