Laser Pulse Heating of Spherical Metal Particles

We consider a general problem of laser pulse heating of spherical metal particles with the sizes ranging from nanometers to millimeters. We employ the exact Mie solutions of the diffraction problem and solve heat-transfer equations to determine the maximum temperature at the particle surface as a function of optical and thermometric parameters of the problem. The main attention is paid to the case when the thermometric conductivity of the particle is much larger than that of the environment, as it is in the case of metal particles in fluids. We show that in this case at any given finite duration of the laser pulse the maximum temperature rise as a function of the particle size reaches an absolute maximum at a certain finite size of the particle, and we suggest simple approximate analytical expressions for this dependence which covers the entire range of variations of the problem parameters and agree well with direct numerical simulations.Comment: 7 pages, 6 figure

Ultrahigh-capacity non-periodic photon sieves operating in visible light

Miniaturization of optical structures makes it possible to control light at the nanoscale, but on the other hand it imposes a challenge of accurately handling numerous unit elements in a miniaturized device with aperiodic and random arrangements. Here, we report both the new analytical model and experimental demonstration of the photon sieves with ultrahigh-capacity of subwavelength holes (over 34 thousands) arranged in two different structural orders of randomness and aperiodicity. The random photon sieve produces a uniform optical hologram with high diffraction efficiency and free from twin images that are usually seen in conventional holography, while the aperiodic photon sieve manifests sub-diffraction-limit focusing in air. A hybrid approach is developed to make the design of random and aperiodic photon sieve viable for high-accuracy control of the amplitude, phase and polarization of visible light. The polarization independence of the photon sieve will also greatly benefit its applications in optical imaging and spectroscopyThis research is supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Competitive Research Program (CRP Award No. NRF-CRP10-2012-04). The work is partially supported by the Institute of Materials Research and Engineering and the Agency for Science, Technology and Research (A*STAR) under Grant 1021740172. We also thank S. Goswami for editing our manuscript. F.J.G.-V. acknowledges the financial support from the Spanish Government under grant MAT2011-28581-C02-0

Probing magnetic and electric optical responses of silicon nanoparticles

We study experimentally both magnetic and electric optically induced resonances of silicon nanoparticles by combining polarization-resolved dark-field spectroscopy and near-field scanning optical microscopy measurements. We reveal that the scattering spectra exhibit strong sensitivity of electric dipole response to the probing beam polarization and attribute the characteristic asymmetry of measured near-field patterns to the excitation of a magnetic dipole mode. The proposed experimental approach can serve as a powerful tool for the study of photonic nanostructures possessing both electric and magnetic optical responses.This work was financially supported by Government of Russian Federation (Project Nos. 14.584.21.0009 10 and GOSZADANIE 2014/190, Zadanie No. 3.561.2014/K, 074- U01), Russian Foundation for Basic Research and the Australian Research Council

Roadmap on label-free super-resolution imaging

Label-free super-resolution (LFSR) imaging relies on light-scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super-resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state-of-the-art in this field, and to discuss the resolution boundaries and hurdles that need to be overcome to break the classical diffraction limit of the label-free imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction-limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super-resolution capability that are based on understanding resolution as an information science problem, on using novel structured illumination, near-field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere-assisted approaches. To this end, this Roadmap brings under the same umbrella researchers from the physics and biomedical optics communities in which such studies have often been developing separately. The ultimate intent of this paper is to create a vision for the current and future developments of LFSR imaging based on its physical mechanisms and to create a great opening for the series of articles in this field

Roadmap on Label-Free Super-resolution Imaging

Label-free super-resolution (LFSR) imaging relies on light-scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super-resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state-of-the-art in this field, and to discuss the resolution boundaries and hurdles that need to be overcome to break the classical diffraction limit of the label-free imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction-limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super-resolution capability that are based on understanding resolution as an information science problem, on using novel structured illumination, near-field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere-assisted approaches. To this end, this Roadmap brings under the same umbrella researchers from the physics and biomedical optics communities in which such studies have often been developing separately. The ultimate intent of this paper is to create a vision for the current and future developments of LFSR imaging based on its physical mechanisms and to create a great opening for the series of articles in this field.Peer reviewe

The Effect of pulse shape on 3D modelling of laser cleaning fluences

Prior research in the field of laser cleaning has suggested that shorter pulses are preferable to achieve low laser cleaning threshold fluences. These predictions were based mainly on exponential pulse shapes In the present work the three-dimensional model of laser cleaning developed by Boris Luk'yanchuk (B. S Luk'yanchuk et al., Appl Phys A, 77,2,209) which accounts for near-field focussing, has been used to calculate the laser cleaning threshold fluence for three different pulse shapes These were rectangular, sinusoidal and exponential For each pulse shape, the threshold fluence was determined as a function of pulse width (1- 200 ns) and height (1-15 GW/cm²). It was found that the threshold fluence is strongly dependent on the laser pulse shape, particularly for pulses greater than 100 ns in width. The threshold fluence of the rectangular pulse oscillated with a period equal to that of the period of oscillation of the particle on the substrate. In contrast, for both the exponential and sinusoidal pulses, the threshold fluence increases monotonically with pulse length

The Effect of Pulse Shape on 3D Modelling of Laser Cleaning Fluences

Prior research in the field of laser cleaning has suggested that shorter pulses are preferable to achieve low laser cleaning threshold fluences. These predictions were based mainly on exponential pulse shapes. In the present work the three-dimensional model of laser cleaning developed by Boris Luk'yanchuk (B. S. Luk'yanchuk et al., Appl Phys A, 77, 2, 209) which accounts for near-field focussing, has been used to calculate the laser cleaning threshold fluence for three different pulse shapes. These were rectangular, sinusoidal and exponential. For each pulse shape, the threshold fluence was determined as a function of pulse width (1- 200 ns) and height (1-15 GW/cm2). It was found that the threshold fluence is strongly dependent on the laser pulse shape, particularly for pulses greater than 100 ns in width. The threshold fluence of the rectangular pulse oscillated with a period equal to that of the period of oscillation of the particle on the substrate. In contrast, for both the exponential and sinusoidal pulses, the threshold fluence decreases initially then increases monotonically with pulse length.4 page(s

Manipulating the light intensity by magnetophotonic metasurfaces

We study numerically the possibility of controlling light properties by means of an external magnetic field. Considerable changes in the shape, value, and spectral position of the magneto-optical response are demonstrated in Voigt geometry for the transmitted light depending on the parameters of the magnetophotonic metasurface made up of nickel/silicon nanoparticles. The spectral overlapping of the fundamental magnetic and electric dipole Mie resonances leads to interference with a strong modification of phase relations, which manifests itself through an enhanced magneto-optical signal