Subwavelength imaging of light confinement in high-Q/small-V photonic crystal nanocavity

Abstract

International audienceThe optical near field of a high-Q and ultrasmall volume photonic crystal nanocavity is visualized with a subwavelength resolution by using a scanning near-field optical microscope (SNOM) operating at the same time in collection-scanning mode and in interaction-scanning mode. It is shown that the nanocavity resonant mode is selectively visualized by using the SNOM interaction-scanning mode while the whole electromagnetic field surrounding the nanocavity is probed using the SNOM collection-scanning mode. The different optical near-field images are compared in light of a three-dimensional numerical analysis and we demonstrate an unexpected mode coupling at the cavity resonance

Influence of dimensional fluctuations on the optical coupling between nanobeam twin cavities

“…The resolution of these pictures is-to the best of our knowledge-one of the best obtained on such nanophotonic structures (<0.2λ 0 ). 27,32 Although we noticed earlier that the splitting given by our model is qualitative at this gap width, the theoretical intensity maps remain in good agreement with those obtained experimentally with the SNOM. It allows us to determine the field pattern of a structure with a given disorder, much more rapidly than using 3D-FDTD, although it fails to describe precisely the field enhancement in the slot for two identical cavities.…”

Influence of dimensional fluctuations on the optical coupling between nanobeam twin cavities

“…The resolution of these pictures is-to the best of our knowledge-one of the best obtained on such nanophotonic structures (<0.2λ 0 ). 27,32 Although we noticed earlier that the splitting given by our model is qualitative at this gap width, the theoretical intensity maps remain in good agreement with those obtained experimentally with the SNOM. It allows us to determine the field pattern of a structure with a given disorder, much more rapidly than using 3D-FDTD, although it fails to describe precisely the field enhancement in the slot for two identical cavities.…”

Mode Mapping Photonic Crystal Nanocavities with Q>5×105 Using Free-Carrier Absorption

“…Mujumdar et al successfully show NSOM mode mappings of a Q = 55 000 cavity while noting that the imaging profoundly influences the spectral characteristics of the mode [16]. They measure a Q-factor degradation close to a factor of 2, which is in line with the experiment of Lalouat et al [23]. A perturbation of this order in the field of a Q ∼ 10 5 cavity would mean the probe tip becomes the vastly dominating loss mechanism of the cavity, defeating the first-order perturbation principle.…”

Optofluidic Near-Field Optical Microscopy: Near-Field Mapping of a Silicon Nanocavity Using Trapped Microbeads

“…More particularly, it has been found that the nanopatterns of the nanocavity resonant mode clearly appear in the trapping potential map of a 500 nm diameter bead. Those results bring us to envisage optofluidic near-field optical microscopy as an original thermally driven near-field optical microscopy technique, much simpler to implement than conventional scanning probe microscopy techniques, , aiming at revealing the optical near-field of nanostructures.…”

Influence of dimensional fluctuations on the optical coupling between nanobeam twin cavities

“…The resolution of these pictures is-to the best of our knowledge-one of the best obtained on such nanophotonic structures (<0.2λ 0 ). 27,32 Although we noticed earlier that the splitting given by our model is qualitative at this gap width, the theoretical intensity maps remain in good agreement with those obtained experimentally with the SNOM. It allows us to determine the field pattern of a structure with a given disorder, much more rapidly than using 3D-FDTD, although it fails to describe precisely the field enhancement in the slot for two identical cavities.…”

Mode Mapping Photonic Crystal Nanocavities with Q>5×105 Using Free-Carrier Absorption

“…Mujumdar et al successfully show NSOM mode mappings of a Q = 55 000 cavity while noting that the imaging profoundly influences the spectral characteristics of the mode [16]. They measure a Q-factor degradation close to a factor of 2, which is in line with the experiment of Lalouat et al [23]. A perturbation of this order in the field of a Q ∼ 10 5 cavity would mean the probe tip becomes the vastly dominating loss mechanism of the cavity, defeating the first-order perturbation principle.…”

Optofluidic Near-Field Optical Microscopy: Near-Field Mapping of a Silicon Nanocavity Using Trapped Microbeads

“…More particularly, it has been found that the nanopatterns of the nanocavity resonant mode clearly appear in the trapping potential map of a 500 nm diameter bead. Those results bring us to envisage optofluidic near-field optical microscopy as an original thermally driven near-field optical microscopy technique, much simpler to implement than conventional scanning probe microscopy techniques, , aiming at revealing the optical near-field of nanostructures.…”

Influence of dimensional fluctuations on the optical coupling between nanobeam twin cavities

“…The resolution of these pictures is-to the best of our knowledge-one of the best obtained on such nanophotonic structures (<0.2λ 0 ). 27,32 Although we noticed earlier that the splitting given by our model is qualitative at this gap width, the theoretical intensity maps remain in good agreement with those obtained experimentally with the SNOM. It allows us to determine the field pattern of a structure with a given disorder, much more rapidly than using 3D-FDTD, although it fails to describe precisely the field enhancement in the slot for two identical cavities.…”

Mode Mapping Photonic Crystal Nanocavities with Q>5×105 Using Free-Carrier Absorption

“…Mujumdar et al successfully show NSOM mode mappings of a Q = 55 000 cavity while noting that the imaging profoundly influences the spectral characteristics of the mode [16]. They measure a Q-factor degradation close to a factor of 2, which is in line with the experiment of Lalouat et al [23]. A perturbation of this order in the field of a Q ∼ 10 5 cavity would mean the probe tip becomes the vastly dominating loss mechanism of the cavity, defeating the first-order perturbation principle.…”

Optofluidic Near-Field Optical Microscopy: Near-Field Mapping of a Silicon Nanocavity Using Trapped Microbeads

“…More particularly, it has been found that the nanopatterns of the nanocavity resonant mode clearly appear in the trapping potential map of a 500 nm diameter bead. Those results bring us to envisage optofluidic near-field optical microscopy as an original thermally driven near-field optical microscopy technique, much simpler to implement than conventional scanning probe microscopy techniques, , aiming at revealing the optical near-field of nanostructures.…”