We study experimentally a fine structure of the optical Laue diffraction from two-dimensional periodic photonic lattices. The periodic photonic lattices with the C4v square symmetry, orthogonal C2v symmetry, and hexagonal C6v symmetry are composed of submicron dielectric elements fabricated by the direct laser writing technique. We observe surprisingly strong optical diffraction from a finite number of elements that provides an excellent tool to determine not only the symmetry but also exact number of particles in the finite-length structure and the sample shape. Using different samples with orthogonal C2v symmetry and varying the lattice spacing, we observe experimentally a transition between the regime of multi-order diffraction, being typical for photonic crystals to the regime where only the zero-order diffraction can be observed, being is a clear fingerprint of dielectric metasurfaces characterized by effective parameters.
We study, theoretically and experimentally, optical properties of different types of honeycomb photonic structures, known also as 'photonic graphene'. First, we employ the two-photon polymerization method to fabricate the honeycomb structures. In experiment, we observe a strong diffraction from a finite number of elements, thus providing a unique tool to define the exact number of scattering elements in the structure by a naked eye. Then, we study theoretically the transmission spectra of both honeycomb single layer and 2D structures of parallel dielectric circular rods. When the dielectric constant of the rod materials ε is increasing, we reveal that a twodimensional photonic graphene structure transforms into a metamaterial when the lowest TE01 Mie gap opens up below the lowest Bragg bandgap. We also observe two Dirac points in the band structure of 2D photonic graphene at the K point of the Brillouin zone and demonstrate a manifestation of the Dirac lensing for the TM polarization. The performance of the Dirac lens is that the 2D photonic graphene layer converts a wave from point source into a beam with flat phase surfaces at the Dirac frequency for the TM polarization.
Nano‐mechanical oscillator (NMO) based on amorphous carbon nanowhisker (CNW) with nanotraps for resonant weighting of nanoparticles in range of mass (10−14–10−15) g is presented. NMO with nanotraps is fabricated on the top of tungsten tip using focused electron beam technique. For resonant weighting the gold nanospheres are captured under the exposure of an electron beam by nanotraps locate on the top of CNW. Jump of gold nanoparticle to the nanotrap and oscillations of CNW are visualized using scanning electron microscope (SEM). The NMO amplitude‐frequency characteristics are calculated via automated numerical analysis of the sequence of SEM images obtained during the oscillations frequency sweeping. In order to calibrate the resonance mass detector based on CNW with nanotrap the gold nanosphere with diameter of (170 ± 5) nm and mass of (49.6 ± 9.2) × 10−15 g is weighed in vacuum.
Nanomechanical oscillators based on amorphous carbon whiskers, localized on the top of tungsten tip were fabricated and investigated. The whiskers were grown in the scanning electron microscope chamber using focused electron beam technique. Oscillation trajectories and amplitude-frequency characteristic of the oscillator were visualized at low and ambient pressure using a scanning electron microscope and a confocal laser-scanning microscope, respectively. We experimentally show that at ambient pressure, the resonant frequency decreases significantly but the Q-factor of the oscillator unexpectedly increases with respect to experimental data acquired at low pressure. The explanation was provided taking into account the role of thin water layer absorbed on the whisker from atmosphere. The model of the coupled oscillators is considered.
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