ABSTRACT
We present experimental evidence for the different mechanisms driving the fluctuations of the local density of states (LDOS) in disordered photonic systems. We establish a clear link between the microscopic structure of the material and the frequency correlation function of LDOS accessed by a near-field hyperspectral imaging technique. We show, in particular, that short- and long-range frequency correlations of LDOS are controlled by different physical processes (multiple or single scattering processes, respectively) that can be-to some extent-manipulated independently. We also demonstrate that the single scattering contribution to LDOS fluctuations is sensitive to subwavelength features of the material and, in particular, to the correlation length of its dielectric function. Our work paves a way towards complete control of statistical properties of disordered photonic systems, allowing for designing materials with predefined correlations of LDOS.
ABSTRACT
As materials functionality becomes more dependent on local physical and electronic properties, the importance of optically probing matter with true nanoscale spatial resolution has increased. In this work, we mapped the influence of local trap states within individual nanowires on carrier recombination with deeply subwavelength resolution. This is achieved using multidimensional nanospectroscopic imaging based on a nano-optical device. Placed at the end of a scan probe, the device delivers optimal near-field properties, including highly efficient far-field to near-field coupling, ultralarge field enhancement, nearly background-free imaging, independence from sample requirements, and broadband operation. We performed ~40-nanometer-resolution hyperspectral imaging of indium phosphide nanowires via excitation and collection through the probes, revealing optoelectronic structure along individual nanowires that is not accessible with other methods.
ABSTRACT
Personal identification is based on the comparison between ante mortem and post mortem data which can be considered unique for each individual: palatal rugae represent a useful element for such a comparison, thanks to their apparent low variability with time and unique patterns. Literature however is scarce. This pilot study aims at assessing the reliability of palatal rugae in time and at developing an identification method based on their comparison. Two casts from the upper dental arch of 39 subjects were obtained in different periods of time; at their first cast, 85.2% of patients were less than 16 years old. The second cast was performed after a period of time which varied between 4 and 65 months later than the first cast. The first cast can be taken to simulate ante mortem information, the second post mortem information. Every cast was then digitised with a scanner. In the digital images the palatal rugae were highlighted by using Adobe® Photoshop® 7.0 software; each image was coded and a comparison between "simulated" ante mortem and post mortem data was performed. In all cases ante mortem and post mortem data from the same individual were correctly matched. The study seems to indicate that this technique is highly reliable and user friendly, even on subadults, where growth processes seem not to affect the specific morphology of palatal rugae.
Subject(s)
Forensic Dentistry , Palate, Hard/anatomy & histology , Female , Humans , Image Processing, Computer-Assisted , Male , Models, Dental , Pilot Projects , Reproducibility of ResultsABSTRACT
A revisited realization of the Young's double slit experiment is introduced to directly probe the photonic mode symmetry by photoluminescence experiments. We experimentally measure the far field angular emission pattern of quantum dots embedded in photonic molecules. The experimental data well agree with predictions from Young's interference and numerical simulations. Moreover, the vectorial nature of photonic eigenmodes results in a rather complicated parity property for different polarizations, a feature which has no counterpart in quantum mechanics.
ABSTRACT
We report on the observation of Anderson localization of near-visible light in two-dimensional systems. Our structures consist of planar waveguides in which disorder is introduced by randomly placing pores with controlled diameter and density. We show how to design structures in which localization can be observed and describe both the realization of the materials and the actual observation of Anderson localized modes by near-field scanning microscopy.
ABSTRACT
We investigate the photonic properties of one dimensional photonic crystals realized on Silicon On Insulator channel slot-waveguide to engineer slow light effects. Various geometries of the photonic pattern have been characterized and their photonic band-gap structure analyzed. The optimal geometry has been further used to realize a coupled resonator optical waveguide (CROW). A first optimization of these CROW devices shows a group velocity of more than c/10 at 1.55 mum. Full three dimensional calculations based on the planar wave expansion method have been used to compute the band diagram while full three dimensional calculations based on finite difference time domain methods have been used to study light propagation.
ABSTRACT
We produce a quantum degenerate mixture composed by two Bose-Einstein condensates of different atomic species, 41K and 87Rb. We study the dynamics of the superfluid system in an elongated magnetic trap, where off-axis collisions between the two interacting condensates induce scissorlike oscillations.
ABSTRACT
We report on the achievement of simultaneous quantum degeneracy in a mixed gas of fermionic 40K and bosonic 87Rb. Potassium is cooled to 0.3 times the Fermi temperature by means of an efficient thermalization with evaporatively cooled rubidium. Direct measurement of the collisional cross-section confirms a large interspecies attraction. This interaction is shown to affect the expansion of the Bose-Einstein condensate released from the magnetic trap, where it is immersed in the Fermi sea.
