Enhanced backscattering for infrared detection using photonic crystal based flat lens.

An n=-1 flat lens based on photonic crystal semiconductor technology is evaluated for infrared detection purposes. The idea consists in exploiting the backscattered waves of an incident plane wave impinging on a target placed in the focal region of a flat lens. It is shown that subwavelength detection of micronic dielectric targets can be obtained at 1.55 µm using the double focus of reflected waves induced by negative refraction. Complex relations among the intrinsic nature, the shape and size of the target, and detection efficiency are interpreted in terms of target eigenmode excitation. Reflectivity is modulated by the intrinsic mode nature, transverse, circular, or longitudinal, with an enhancement of the detection sensitivity in the case of whispering-gallery modes. It is believed that such a study paves the way to the definition of original noninvasive infrared sensors.

Image reconstruction using a photonic crystal based flat lens operating at 1.55 µm.

We used an optimized photonic crystal based flat lens for target detection and image reconstruction of micrometer sized objects for an operating wavelength of 1.55 µm. Using numerical retrieval procedures inspired from tomography, the ability to detect subwavelength sized targets and to image metallic objects of complex shapes is shown. The relation between the reconstructed image quality and lens resolution is investigated.

Optical near-field microscopy of light focusing through a photonic crystal flat lens.

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.

Photonic-crystal-based cloaking device at optical wavelengths.

We present a photonic crystal cloaking device at optical wavelengths based on the association of two lattices working in different regimes, namely, stop band and negative refraction. The idea is to reconstruct in phase an incident cut Gaussian modulated plane wave by using the photonic crystal dispersion properties to ensure that no light penetrates in the core of the device. It is believed that such a cloaking device could become a building block for future generations of 3D integrated optical circuits.