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In this paper, for the first time, tuned near-zero-index materials are used in a structure for the long-distance projection of very closely spaced objects with subwavelength separation. Near-zero-index materials have never been used for subwavelength projection/imaging. The proposed novel structure is composed of a two-layer slab that can project two slits with a subwavelength separation distance to a long distance without diverged/converged interference of the two imaged waves. The two-layer slab consists of a thin double-near-zero (DNZ) slab with an obtained tuned index of 0.05 and thickness of 0.04λ0 coupled with a high-index dielectric slab with specific thicknesses. Through a parametric study, the non-zero index of the DNZ layer is tuned to create a clear image when it is coupled with the high-index dielectric layer. The minimum size for the aperture of the proposed two-layer slab is 2λ0 to provide a clear projection of the two slits. The space between the slits is λ0/8, which is five times beyond the diffraction limit. It is shown that, through the conventional methods (e.g., only with high-index dielectric slabs, uncoupled with a DNZ layer), it is impossible to clearly project slits at a large distance (~λ0) due to the diffraction limit. An analytical analysis, as well as numerical results in a finite-element-based simulator, confirm the function of the proposed structure.

Measurements of Raman backscattering spectra between -15 C-omicron and 22 C-omicron in liquid water (including its supercooled state) and in polycrystalline ice (-35 C-omicron to 0 C-omicron) at two excitation wavelengths (407 and 532 nm) are presented. It is found that the spectrum-integrated backscattering cross-section of the 3400 cm(-1) band is about 1.2 times larger for ice in comparison to liquid water. The excitation-wavelength dependence of the cross-section in ice is very close to that in water. A discontinuous change of the spectrum is observed upon phase transition at 0 C-omicron. The results are applicable to preliminary calibration of lidar systems designed for water content surveys in the atmosphere. (C) 2017 Elsevier Ltd. All rights reserved.

Nanoscale thermometry is paramount to study primary processes of heat transfer in solids and is a subject of hot debate in cell biology. Here we report ultrafast temperature sensing using all-optical thermometry, exploiting synthetic nanodiamonds with silicon-vacancy (SiV) centers embedded at a high concentration. Using multiparametric analysis of photoluminescence (PL) of these centers, we have experimentally achieved an intrinsic noise floor of about 13 mK Hz , which is a 1000-fold increase in the readout speed in comparison to the current record values demonstrated with all-optical methods of comparable spatial-resolution and precision. Our thermometers are smaller than 250 nm across but can detect a 0.4 °C change of temperature in a measurement taking only 0.001 s. The exceptional sensitivity and simplicity of these thermometers enable a wide range of applications such as temperature monitoring and mapping within intracellular regions and in state-of-the-art solid-state electronic nanodevices.

Modern image detectors with exceptionally low readout noise of about one electron ( e − ) per pixel allow for applications with ultra-low levels of light intensity. In this Letter, we report a property of scientific CMOS detectors that makes accurate spectroscopy at ultra-low levels of illumination depending on a thorough calibration procedure. Our results reveal that pixel sensitivity to light may have significant nonlinearity at accumulation levels smaller than 50 e − per pixel. The sensitivity decreases by a factor of ∼ 0.7 at an accumulation level of ∼ 1 e − per pixel and photon detection rate of about 170 Hz. We demonstrate that the nature of this nonlinearity might be quite complicated: the photoelectric response of a pixel depends on both the number of accumulated electrons and the detection count rate (at rates larger than 250 Hz).

The negatively-charged nitrogen-vacancy (NV) center in diamond is at the frontier of quantum nano-metrology and bio-sensing. Recent attention has focused on the application of high-sensitivity thermometry using the spin resonances of NV centers in nano-diamond to sub-cellular biological and biomedical research. Here, we report a comprehensive investigation of the thermal properties of the center's spin resonances and demonstrate an alternate all-optical NV thermometry technique that exploits the temperature dependence of the center's optical Debye-Waller factor., 22 pages, 5 figures

We propose a new methodology for probing transport of just one electron, a process of great importance both in nature and in artificial devices. Our idea for locating a single electron is analogues to the conventional GPS where signals from several satellites are used to locate a macro object. Using fluorescent molecules as tiny sensors, it is possible to determine 3D displacement vector of an electron.

Electron-multiplying charge coupled devices promise to revolutionize ultrasensitive optical imaging. The authors present a simple methodology allowing reliable measurement of camera characteristics and statistics of single-electron events, compare the measurements to a simple theoretical model, and report camera performance in a truly photon-counting regime that eliminates the excess noise related to fluctuations of the multiplication gain.

Absorption of single molecules is considered as a special case of an interference effect. Different schemes of interference measurements, which are more suitable for single molecules, are described. Advantages and disadvantages of absorption detection relative to emission (luminescence) detection are analyzed. A great attention is paid to a comparison of signal-to-noise ratios for the two types of measurements.

Detailed analysis is done for the case of a single pseudo local phonon interacting with an electronic molecular transition and a phonon bath. Both the sudden-jump model and the master equation formalism predict a complex optical line shape for a single-molecule embedded in a solid matrix. In addition to the conventional Lorentzian, the line consists of a dispersive component in the core region and a side band. The sudden jump model is applicable only if the vibration-phonon coupling is independent of the electronic wave functions. However if the line wings are neglected, the sudden jump model can fit experimental data even when the condition of its applicability is not fulfilled. An interesting property of the complex line was found at strong excitation. In this case the line behaves in a fashion intermediate to the homogeneously and inhomogeneously broadened spectra.

Despite a long history, the Raman scattering coefficient of water has so far only been measured with 10% uncertainty using a 95% confidence interval. In this paper, we present an experiment where we have achieved 1.5% uncertainty by using a low concentration of Rhodamine 6G in ethanol as a reference along with accurate consideration of polarization-related effects and the geometry of the experimental setup. We have found that the photon-to-photon Raman scattering coefficient of the OH stretching band of liquid water is (1.84±0.03)×10(-4) m(-1) when integrated over the spectral frequency range from 620 to 700 nm while the exciting laser operates at 532 nm. We have also accurately measured the depolarization ratio across this band.

The luminescence saturation behavior of a single molecule whose resonance frequency is affected by a spectral diffusion has been analyzed. On the basis of the analysis a simple way of the separate determination of the diffusive spectral line broadening and a “homogeneous” linewidth (due to fast dephasing processes) of a single molecule has been proposed.

We consider the collection efficiency for photons emitted by a single molecule in a solid excited by monochromatic light at low temperature, which depends upon the dipole radiation pattern, the orientation of the emission dipole, total internal reflection, and the numerical aperture of the collecting optics. By using the complete expression for the collection efficiency and varying the collection angle, we have determined the orientation of the dipole of a single terrylene molecule in hexadecane to be almost perpendicular to the substrate. By using saturation data we find that the angle between the optical axis of the collection paraboloid and the emission dipole moment is 16±6°. We estimate that the true saturation intensity of terrylene (for dipole moment parallel to the electric field of the light) is about (80±30) mW/cm 2 and that the ratio of the intersystem crossing rate to the total decay rate of the triplet state is about 3.3±1.2.

Using fluorescence excitation spectroscopy single pentacence molecules were studied under a microscope at a temperature of 1.8 K. The microscope has a resolution of 3 μm and allows the location of a single emitting molecule with an accuracy of 0.5 μm, in a total viewing field of 235 μm×175 μm. 133 images have been recorded by increasing the excitation frequency of the light at 592.344 nm in steps of 2 MHz. Each single molecule has a Lorentzian absorption profile with a width of about 14 MHz and can be observed in 10 consecutive images. The “position” of the single molecule is characterized by the x- and y-coordinates in the spatial domain and by its absorption frequency in the spectral domain.

A general conceptual problem of time-dependent single molecule spectra is discussed theoretically in the framework of recently developed intensity-time-frequency correlation spectroscopy. It is shown that the new method is closely related to a "gedanken" three-pulse photon echo experiment done on an ensemble of identical molecules interacting with statistically identical microscopic environments. The correlation function is an integral transform (under certain conditions a Fourier transform) of the echo amplitude as a function of the delay between the first and the second pulses. [S0163-1829(99)10907-X].

We demonstrate a temperature noise floor of 0.3 K Hz(-1/2) and a long-term stability better than 0.6 K (peak-to-peak value) using a single crystal of diamond smaller than 50 nm across and containing about 100 nitrogen-vacancy centres as a temperature sensor. We compare the achieved characteristics to other single-particle sensors and show that it is one of the best ratiometric all-optical nano-probes of temperature to date.

A rigorous numerical solution is presented for plane wave scattering by a photoreceptor cell. The calculated optical intensity distribution exhibits axial oscillations which are explained on the basis of substantial Bessel-wave type radiation mode excitation.

Typical disturbances of biological environment such as background scatter and refractive index variations have little effect on the size-dependent scattering property of highly refractive nanocrystals, which are potentially attractive optical labels. We report on what is to our knowledge the first investigation of these scattering optical labels, and their sizing, in particular, by imaging at subvideo frame rates and analyzing samples of diamond nanocrystals deposited on a glass substrate in air and in a matrix of weakly scattering polymer. The brightness of a diffraction-limited spot appears to serve as a reliable measure of the particle size in the Rayleigh scattering limit.

In a ring travelling-wave dye laser a parasitic structure in the intracavity absorption spectrum is fully eliminated and a detection limit as low as 10 -10 cm -1 is obtained. The sensitivity dependence of the intracavity laser spectrometer with travelling-wave cavity on the pumping level is also investigated.

To model the light-guiding properties of a hexagonal array of dielectric cylinders, we have numerically solved Maxwell's equations with the finite-difference time-domain technique. The sizes and refractive indices of the cylinders are representative of those of the outer segments of the cone photoreceptors in the human central retina. In the array, light propagates predominantly as a “slow” mode, with a noticeable contribution of a “fast” mode, with the optical field localized in the intra- and inter-cylinder spaces, respectively. Interference between these modes leads to substantial (up to approximately 60%) axial oscillations in optical power within the cylinders. Our numerical model offered approximate dependence of the optical intensity distribution within the cylinders on their radii and separations.

A new design of an optical resonator for generation of single-photon pulses is proposed. The resonator is made of a cylindrical or spherical piece of a polymer squeezed between two flat dielectric mirrors. The mode characteristics of this resonator are calculated numerically. The numerical analysis is backed by a physical explanation. The decay time and the mode volume of the fundamental mode are sufficient for achieving more than 96% probability of generating a single-photon in a single-mode. The corresponding requirement for the reflectivity of the mirrors (~99.9%) and the losses in the polymer (100 dB/m) are quite modest. The resonator is suitable for single-photon generation based on optical pumping of a single quantum system such as an organic molecule, a diamond nanocrystal, or a semiconductor quantum dot if they are imbedded in the polymer.

The dependence of the sensitivity of intra-cavity laser spectroscopy (ILS) at the transition stage of generation on the pumping power and spectral width has been investigated experimentally. The time interval of linear growth of the sensitivity is shown to be limited and determined by the excess of the pumping power over the threshold. The combination of physical parameters of the system which determines the value of the effect is found. Possible mechanisms of the phenomenon are discussed. Insufficiency of the generally accepted description of a multimode laser in ILS within the frames of rate equations and the necessity of the inclusion of parametric processes are pointed out.

We built an, interferometer where one of the two slits of a classical Young's setup is replaced by a single molecule embedded in a solid matrix. This enabled direct measurement of the first order coherence of the 0-0 single-molecule emission, which at high excitation powers proves to be split in coherent and incoherent parts. We demonstrate an order of magnitude higher precision in axial localization of single molecules in comparison with that of confocal microscopy. These experiments open a possibility for single-molecule holography. Detection of single molecules with low luminescence quantum yields could be another application of this technique.