Optical Near-Field Microscopy of Light Focusing through a Photonic Crystal Flat Lens

Abstract

We report here the direct observation by using a scanning near-field microscopy technique of the light focusing through a photonic crystal flat lens designed and fabricated to operate at optical frequencies. The lens is fabricated using a III-V semiconductor slab, and we directly visualize the propagation of the electromagnetic waves by using a scanning near-field optical microscope. We directly evidence spatially, as well as spectrally, the focusing operating regime of the lens. At last, in light of the experimental scanning near-field optical microscope pictures, we discuss the lens ability to focus light at a subwavelength scale.

Formation of collimated beams behind the woodpile photonic crystal

“…In particular, if the wave front of the beam acquires positive curvature (due to propagation in a material with negative or anomalous diffraction), then the beams can be focalized behind the modulated media [17]. The effect is related to superlensing (see [18] for theory and [19] for experiments in 2D PhCs, resulting in imaging of point sources by a PhC slice). In this way, the issues of the light propagation effects behind the PhCs deserve careful and consistent study, both to understand the physics of the waves and beam propagation in and behind the modulated materials as well as for the applications where the shaping of the beams is required.…”

Diffraction-managed superlensing using metallodielectric heterostructures

“…12 More sophisticated devices following the above primitive idea has been presented recently. 13 However the spot size of the image field is clearly diffraction limited.…”

Photonic crystal carpet: Manipulating wave fronts in the near field at 1.55μm

“…6 the concept is verified using SNOM in collection mode [21]. Thanks to the configuration of both devices and experimental set up, a phase imaging is performed by a unique near field intensity measure without optical heterodyne detection [19].…”

“…We start from an InP-based heterostructure (InP-200 nm/InGaAsP-500 nm/InP-1300 nm) grown by molecular beam epitaxy to confine light (at 1.55 µm) in the vertical direction. To create the two-dimensional patterning, we take benefit of the one-mask process primarily developed for photonic crystal based flat lenses [21]. In brief, we employ a negative resist (HSQ) mask used for the electron beam lithography step to define simultaneously the matrix of the reflector, the pillars of the cloaking area as well as the injection guide constituted here of a monomode ridge waveguide progressively enlarged to form the quasi-plane wave requested to illuminate the device.…”