Abstract
We study the near-field probing of the slow Bloch laser mode of a photonic crystal by a bowtie nano-aperture (BNA) positioned at the end of a metal-coated fiber probe. We show that the BNA acts as a polarizing nanoprobe allowing us to extract information about the polarization of the near-field of the slow-light mode, without causing any significant perturbation of the lasing process. Near-field experiments reveal a spatial resolution better than λ/20 and a polarization ratio as strong as 110. We also demonstrate that the collection efficiency is two orders of magnitude larger for the BNA than for a 200 nm large circular aperture opened at the apex of the same metal-coated fiber tip. The BNA allows for overcoming one of the main limitations of SNOM linked to the well-known trade off between resolution and signal-to-noise ratio.
Highlights
For more than fifteen years, 2D photonic crystals (PCs) have been used to control optical fields down to the nanoscale [1]
We study the near-field probing of the slow Bloch laser mode of a photonic crystal by a bowtie nano-aperture (BNA) positioned at the end of a metal-coated fiber probe
The high sensitivity of the BNA to the electric field and its polarization filtering properties yield optical near-field probes with a high spatial resolution and an enhanced collection efficiency compared to conventional, metal coated optical fiber probers
Summary
For more than fifteen years, 2D photonic crystals (PCs) have been used to control optical fields down to the nanoscale [1]. The signal detected by conventional metalcoated aperture and apertureless probes is usually a “mixture” of electric and magnetic components In this case, the probe apex can be viewed as nanoscale optical antenna [13] with electric and magnetic dipole moments which convert both electric and magnetic near-field information into free space propagating modes, albeit with a rather low conversion efficiency [14,15,16,17,18,19]. It has been shown that the nature of the coupling between the probe and the slow Bloch mode (SBM) is very critical, in particular due to the large propagating component of the field which interferes with the evanescent contribution and swamps some of the finer details [8]
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