Nano-mechanical tuning and imaging of a photonic crystal micro-cavity resonance

Abstract

Abstract:We show that nano-mechanical interaction using atomic force microscopy (AFM) can be used to map out mode-patterns of an optical micro-resonator with high spatial accuracy. Furthermore we demonstrate how the Q-factor and center wavelength of such resonances can be sensitively modified by both horizontal and vertical displacement of an AFM tip consisting of either Si 3 N 4 or Si material. With a silicon tip we are able to tune the resonance wavelength by 2.3 nm, and to set Q between values of 615 and zero, by expedient positioning of the AFM tip. We find full on/off switching for less than 100 nm vertical, and for 500 nm lateral displacement at the strongest resonance antinode locations.

Near-field interactions between a subwavelength tip and a small-volume photonic-crystal nanocavity

“…1͑d͒, the maximum redshift is measured to be 0.9 nm. Remarkably and in contrast to the previous works that use an AFM probe, 8,9 we never observed any degradation of the cavity Q factor or of its peak transmittance, even in the case of the strongest recorded interaction. This result confirms the theoretical prediction of Koenderink et al We believe that our nanometric-size tip operates in a weaker interaction than the AFM probes, allowing us to achieve the cavity tuning without Q-factor and peak-transmittance degradation.…”

“…8, which relies on 2D computational results and considered an undefined "optical field," all the components of the electric field and of the magnetic fields are taken into account in this work in order to allow a quantitative comparison with the experimental near-field interaction maps. As a matter of fact, if for a TE polarization of light in a 3D asymmetric waveguide, the x components of the electric field are predominant, calculations have clearly shown that the other components are clearly non-negligible: It is found here that ͉E x ͉ 2 is only 2.5 times larger than ͉E y ͉ 2 and ͉E z ͉ 2 .…”

“…Thus far, except for the theoretical predictions by Koenderink et al, such a result has never been achieved experimentally: A drastic degradation of the resonator quality factor ͑Q͒ has been systematically reported as the tip was penetrating the cavity near-field. 8,9 In this work, we experimentally demonstrate that a subwavelength sized metallic tip permits one to tune the resonance of an ultralow volume photonic crystal nanocavity without sacrificing its Q factor. We also present an innovative mapping method, which allows us to track, at the subwavelength scale, the near-field interactions between the tip and the nanocavity.…”

“…5,6 In all these previous works, the probe was not supposed to modify the observed system. However, it has been recently observed [7][8][9] that the nanometric tip could also be a means to change the microcavity optical properties. If, in such cases, the interaction between the near-field probe and the microcavity prevents one from a direct visualization of the electromagnetic field, it also opens the way to an exciting challenge: Using near-field probes to manipulate the light in solid-state resonators.…”

Influence of the tip in near-field imaging of nanoparticle plasmonic modes: Weak and strong coupling regimes

“…[20][21][22][23][24] However, the antenna optical response is extremely sensitive to environmental changes, 5,8,9 thus the process of measurement of its near field may result in the modification of the antenna modes, similar to probe-induced modifications in other nanophotonic systems. [25][26][27][28] In this work we address this issue, presenting a basic understanding of the near-field coupling between s-SNOM probes and plasmonic nanoantennas ͑here gold nanodisks͒. We find that weak dielectric probes allow for plasmon mode mapping, whereas metallic probes introduce substantial modification of the antenna modes due to strong probe-antenna coupling.…”