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Coherent ranging, also known as frequency-modulated continuous-wave (FMCW) laser-based light detection and ranging (lidar).sup.1 is used for long-range three-dimensional distance and velocimetry in autonomous driving.sup.2,3. FMCW lidar maps distance to frequency.sup.4,5 using frequency-chirped waveforms and simultaneously measures the Doppler shift of the reflected laser light, similar to sonar or radar.sup.6,7 and coherent detection prevents interference from sunlight and other lidar systems. However, coherent ranging has a lower acquisition speed and requires precisely chirped.sup.8 and highly coherent.sup.5 laser sources, hindering widespread use of the lidar system and impeding parallelization, compared to modern time-of-flight ranging systems that use arrays of individual lasers. Here we demonstrate a massively parallel coherent lidar scheme using an ultra-low-loss photonic chip-based soliton microcomb.sup.9. By fast chirping of the pump laser in the soliton existence range.sup.10 of a microcomb with amplitudes of up to several gigahertz and a sweep rate of up to ten megahertz, a rapid frequency change occurs in the underlying carrier waveform of the soliton pulse stream, but the pulse-to-pulse repetition rate of the soliton pulse stream is retained. As a result, the chirp from a single narrow-linewidth pump laser is transferred to all spectral comb teeth of the soliton at once, thus enabling parallelism in the FMCW lidar. Using this approach we generate 30 distinct channels, demonstrating both parallel distance and velocity measurements at an equivalent rate of three megapixels per second, with the potential to improve sampling rates beyond 150 megapixels per second and to increase the image refresh rate of the FMCW lidar by up to two orders of magnitude without deterioration of eye safety. This approach, when combined with photonic phase arrays.sup.11 based on nanophotonic gratings.sup.12, provides a technological basis for compact, massively parallel and ultrahigh-frame-rate coherent lidar systems. A massively parallel coherent light detection and ranging (lidar) scheme using a soliton microcomb--a light source that emits a wide spectrum of sharp lines with equally spaced frequencies--is described., Author(s): Johann Riemensberger [sup.1] , Anton Lukashchuk [sup.1] , Maxim Karpov [sup.1] , Wenle Weng [sup.1] , Erwan Lucas [sup.1] , Junqiu Liu [sup.1] , Tobias J. Kippenberg [sup.1] Author [...]

The fluorescence quenching of coumarin derivative, 6-methoxy-4-p-tolyloxymethyl-chromen-2-one by aniline is carried out in different solvent mixtures of benzene and acetonitrile at room temperature. The quenching is found to be appreciable and a positive deviation from linearity is observed in the Stern-Volmer plot in all the solvent mixtures. Various rate constants for fluorescence quenching processes have been estimated using a sphere of action static quenching model and a finite sink approximation model. From the positive deviation of linear Stern-Volmer plots and dependence of rate constants on the polarity of the solvents, it has been inferred that the quenching process is diffusion-limited, and static as well as dynamic quenching processes are responsible for the observed positive deviation in the Stern-Volmer plot. Further, both models have been found to agree well with transient state also in pure acetonitrile and benzene solvents. Key words: coumarin, finite sink approximation model, fluorescence quenching, sphere of action static quenching model, Stern-Volmer plot. A l'aide d'aniline, nous provoquons l'attenuation de la fluorescence dans un derive de coumarine, 6-methoxy-4-p-tolyloxymethyle-chromene-2-un, dans differents melanges de benzene et d'acetonitrile et a la temperature de la piece. L'attenuation est appreciable et nous observons une deviation de linearite dans le graphique de Stern-Volmer (S-V) pour tous les melanges de solvant. Nous evaluons differentes constantes de taux pour le processus d'attenuation de fluorescence en utilisant un modele de la sphere d'attenuation statique et une approximation de puits fini. A partir de la deviation positive de la linearite du graphique de S-V et de la dependance des constantes de taux sur la polarite des solvants, nous concluons que le mecanisme d'attenuation est statique et limite a la diffusion, alors meme que les mecanismes dynamiques d'attenuation peuvent aussi etre responsables de la deviation observee de linearite. De plus, les deux modeles sont en bon accord sur l'etat transitoire dans les solvants d'acetronitrile et de benzene purs. [Traduit par la Redaction] Mots-cles: coumarine, approximation du puits fini, attenuation de fluorescence, modele de la sphere d'attenuation statique, graphique de Stern-Volmer., 1. Introduction Coumarins are well-known oxygen heterocycles, which have been extensively explored as fluorescence probes [1, 2], optical brighteners [3], and as emitter layers in organic light emitting diodes (OLEDs) [...]

Photon emitters placed in an optical cavity experience an environment that changes how they are coupled to the surrounding light field. In the weak-coupling regime, the extraction of light from the emitter is enhanced. But more profound effects emerge when single-emitter strong coupling occurs: mixed states are produced that are part light, part matter (1,2), forming building blocks for quantum information systems and for ultralow-power switches and lasers (3-6). Such cavity quantum electrodynamics has until now been the preserve of low temperatures and complicated fabrication methods, compromising its use (5,7,8). Here, by scaling the cavity volume to less than 40 cubic nanometres and using host-guest chemistry to align one to ten protectively isolated methylene-blue molecules, we reach the strong-coupling regime at room temperature and in ambient conditions. Dispersion curves from more than 50 such plasmonic nanocavities display characteristic light-matter mixing, with Rabi frequencies of 300 millielectronvolts for ten methylene-blue molecules, decreasing to 90 millielectronvolts for single molecules--matching quantitative models. Statistical analysis of vibrational spectroscopy time series and dark-field scattering spectra provides evidence of single-molecule strong coupling. This dressing of molecules with light can modify photochemistry, opening up the exploration of complex natural processes such as photosynthesis (9) and the possibility of manipulating chemical bonds (10)., Creating strongly coupled mixed states from visible light and individual emitters is severely compromised by the hundred-fold difference in their spatial localization. To overcome this, high-quality cavities are used to [...]

Shape it, squeeze it, energize it or tie it into knots. Scientists are taking light to new extremes., Author(s): Elizabeth Gibney [sup.1] Author Affiliations: (1) Elizabeth Gibney is a reporter for Nature in London., SHAPING LIGHT Miles Padgett twists light in unexpected ways. The Photographic Unit/Univ. Glasgow Physicist [...]

The propagation and transport of electrons in crystals is a fundamental process pertaining to the functioning of most electronic devices. Microscopic theories describe this phenomenon as being based on the [...]

K shell X-rays of barium and thallium following internal conversion decay in [Cs.sup.137]and [Hg.sup.203], respectively, were detected using a Si(Li) X-ray detector coupled to PC-based 8k multichannel analyser employing the method suggested earlier by our group. The K shell X-ray intensity ratios and vacancy transfer probabilities for thallium and barium were calculated. The obtained results are compared with theoretical, semiempirical, and others' experimental results obtained via photoionization as well as decay processes. The effects of beta decay and internal conversion on X-ray emission probabilities are discussed. PACS Nos.: 32.30.Rj, 32.80.Fb. Employant une methode anterieurement proposee par notre equipe, nous utilisons un detecteur a rayon X de Si(Li), couple a un analyseur multicanaux (MCA) fiche dans un PC, afin de detecter les rayons X de la couche K du baryum et du Thallium, a la suite de la convention interne de [Cs.sup.137] et de [Hg.sup.203]. Nous calculons les rapports d'intensite des rayons X de la couche K et les probabilites de transfert de lacune dans le thallium et le baryum. Les resultats obtenus sont compares a d'autres, theoriques, semi-empiriques et experimentaux obtenus par photo-ionisation aussi bien que par des mecanismes de desintegration. Nous analysons les effets de la desintegration beta et de la conversion interne sur les probabilites d'emission X. [Traduit par la Redaction], 1. Introduction The precise values of K shell X-ray intensity ratios of elements find applications in several areas, such as atomic physics, nuclear physics, and material science. This information is [...]

In this research we have studied the influence of λ = 0.532 µm laser light illumination on the formation and properties of surface relief gratings in amorphous [As.sub.2][S.sub.3] and [As.sub.40][Se.sub.15][Se.sub.45] films, as well as a bulk [As.sub.2][S.sub.3] sample. The surface relief grating formation was studied for a wide range of grating periods (~1 - ~80 µm) for the variable thicknesses of the samples. The examination of the relief depth, Δh, and its dependence on the grating period at constant exposures shows that the impact of sample thickness could manifest itself as a shift in the optimal grating period at holographic surface relief formation ([As.sub.2][S.sub.3]) and affect the process itself. PACS Nos.: 78.66.Jg, 42.70.Ln, 81.65.Cf. Nous etudions ici l'influence de l'illumination laser a λ = 0.532 µm sur la formation et les proprietes d'un reseau de surface en relief dans des films de a-[As.sub.2][S.sub.3] et a-[As.sub.40][S.sub.15][Se.sub.45], ainsi que sur un echantillon en volume de a-[As.sub.2][S.sub.3]. Nous etudions la formation du reseau de surface en relief pour un large domaine de pas du reseau, ~1 a ~80 µm, pour des epaisseurs variables des echantillons. L'examen de la dependance de la profondeur du relief Δh sur le pas du reseau pour la meme illumination montre que l'epaisseur de l'echantillon pourrait generer un deplacement dans le pas optimal du reseau a la formation du relief de surface holographique ([As.sub.2][S.sub.3]) et affecter le procede lui-meme. [Traduit par la Redaction], Introduction The presence of surface relief (SR) formations for As-, S-, and Se-containing chalcogenide films as explained by photostructural transformations is a subject of permanent interest [1-9]. The phenomenon causing [...]

Gamma-ray bursts (GRBs) are most probably powered by collimated relativistic outflows (jets) from accreting black holes at cosmological distances. Bright afterglows are produced when the outflow collides with the ambient medium. Afterglow polarization directly probes the magnetic properties of the jet when measured minutes after the burst, and it probes the geometric properties of the jet and the ambient medium when measured hours to days after the burst (1-5). High values of optical polarization detected minutes after the burst of GRB 120308A indicate the presence of large-scale ordered magnetic fields originating from the central engine (5) (the power source of the GRB). Theoretical models predict low degrees of linear polarization and no circular polarization at late times (6-8), when the energy in the original ejecta is quickly transferred to the ambient medium and propagates farther into the medium as a blast wave. Here we report the detection of circularly polarized light in the afterglow of GRB 121024A, measured 0.15 days after the burst. We show that the circular polarization is intrinsic to the afterglow and unlikely to be produced by dust scattering or plasma propagation effects. A possible explanation is to invoke anisotropic (rather than the commonly assumed isotropic) electron pitch-angle distributions, and we suggest that new models are required to produce the complex microphysics of realistic shocks in relativistic jets (9-11)., Magnetic fields play a crucial role in the physics of relativistic jets--for example, in their formation, acceleration and colliniation (1,12,13). On smaller spatial scales, there is a strong connection between [...]

An investigation of how ultracold molecules are broken apart by light reveals surprising, previously unobserved quantum effects. The work opens up avenues of research in quantum optics. See Letter p.122 [...]

The ability to confine light is important both scientifically and technologically. Many light confinement methods exist, but they all achieve confinement with materials or systems that forbid outgoing waves. These [...]

Optical laser fields have been widely used to achieve quantum control over the motional and internal degrees of freedom of atoms and ions (1,2), molecules and atomic gases. A route to controlling the quantum states of macroscopic mechanical oscillators in a similar fashion is to exploit the parametric coupling between optical and mechanical degrees of freedom through radiation pressure in suitably engineered optical cavities (3-6). If the optomechanical coupling is 'quantum coherent'--that is, if the coherent coupling rate exceeds both the optical and the mechanical decoherence rate--quantum states are transferred from the optical field to the mechanical oscillator and vice versa. This transfer allows control of the mechanical oscillator state using the wide range of available quantum optical techniques. So far, however, quantum-coherent coupling of micromechanical oscillators has only been achieved using microwave fields at millikelvin temperatures (7,8). Optical experiments have not attained this regime owing to the large mechanical decoherence rates (9) and the difficulty of overcoming optical dissipation (10). Here we achieve quantum-coherent coupling between optical photons and a micromechanical oscillator. Simultaneously, coupling to the cold photon bath cools the mechanical oscillator to an average occupancy of 1.7 ± 0.1 motional quanta. Excitation with weak classical light pulses reveals the exchange of energy between the optical light field and the micromechanical oscillator in the time domain at the level of less than one quantum on average. This optomechanical system establishes an efficient quantum interface between mechanical oscillators and optical photons, which can provide decoherence-free transport of quantum states through optical fibres. Our results offer a route towards the use of mechanical oscillators as quantum transducers or in microwave-to-optical quantum links (11-15)., Mechanical oscillators are at the heart of many precision experiments and can exhibit exceptionally low dissipation. The possibility of controlling the quantum states of engineered micro- or nano-mechanical oscillators has [...]

Recent research has uncovered a remarkable ability to manipulate and control electromagnetic fields to produce effects such as perfect imaging and spatial cloaking (1,2). To achieve spatial cloaking, the index of refraction is manipulated to flow light from a probe around an object in such a way that a 'hole' in space is created, and the object remains hidden (3-14). Alternatively, it maybe desirable to cloak the occurrence of an event over a finite time period, and the idea of temporal cloaking has been proposed in which the dispersion of the material is manipulated in time, producing a 'time hole' in the probe beam to hide the occurrence of the event from the observer (15). This approach is based on accelerating the front part of a probe light beam and slowing down its rear part to create a well controlled temporal gap--inside which an event occurs--such that the probe beam is not modified in any way by the event. The probe beam is then restored to its original form by the reverse manipulation of the dispersion. Here we present an experimental demonstration of temporal cloaking in an optical fibre-based system by applying concepts from the space-time duality between diffraction and dispersive broadening16. We characterize the performance of our temporal cloak by detecting the spectral modification of a probe beam due to an optical interaction and show that the amplitude of the event (at the picosecond timescale) is reduced by more than an order of magnitude when the cloak is turned on. These results are a significant step towards the development of full spatio-temporal cloaking., The detection of an object or an event is often performed by measuring a change in the properties of a light probe that interacts with the object or with elements [...]

We have demonstrated the output characteristics of optical parametric amplification (OPA) seeded by a supercontinuum (SC) generated in deionized water excited by 1064 nm. The SC spectrum (from 426 to 943 nm) overlaps well with the tuning range of a 355 nm pumped OPA for both the signal and idler. The tunable range covers from 430 to 2035 nm, with a maximum overall energy conversion efficiency of 32% in the OPA stage. A FWHM bandwidth of 54 nm near the degeneracy point from 658 to 760 nm can be generated by using a collinear OPA. Chirping of the SC pulses is also investigated with the OPA technique. The time delay between the 430 nm component and the 567 nm component of the generated SC due to chirp is measured to be -10.72 ps, increasing almost linearly with the wavelength. [c] 2010 Optical Society of America OCIS codes: 190.4410, 320.6629, 320.0320, 010.7340.

In a deterministic figuring process, it is critical to guarantee high stability of the removal function as well as the accuracy of the dwell time solution, which directly influence the convergence of the figuring process. Hence, when figuring steep optics, the ion beam is required to keep a perpendicular incidence, and a five-axis figuring machine is typically utilized. In this paper, however, a method for high-precision figuring of high-slope optics is proposed with a linear three-axis machine, allowing for inclined beam incidence. First, the changing rule of the removal function and the normal removal rate with the incidence angle is analyzed according to the removal characteristics of ion beam figuring (IBF). Then, we propose to reduce the influence of varying removal function and projection distortion on the dwell time solution by means of figure error compensation. Consequently, the incident ion beam is allowed to keep parallel to the optical axis. Simulations and experiments are given to verify the removal analysis. Finally, a figuring experiment is conducted on a linear three-axis IBF machine, which proves the validity of the method for high-slope surfaces. It takes two iterations and about 9 min to successfully figure a fused silica sample, whose aperture is 21.3 mm and radius of curvature is 16 mm. The root-mean-square figure error of the convex surface is reduced from 13.13 to 5.86 nm. [c] 2010 Optical Society of America OCIS codes: 220.4610, 220.5450.

Three different sensing platforms for the analysis of telomerase activity in human cells are described. One sensing platform involves the label-free analysis of the telomerase activity by a field-effect-transistor (FET) device. The telomerase-induced extension of a primer associated with the gate of the FET device, in the presence of the nucleotide mixture dNTPs, alters the gate potential, and this allows the detection of telomerase extracted from 65 [+ or -] 10 293T (transformed human embryonic kidney) cells/[micro]L. The second sensing platform involves the optical detection of telomerase using CdSe/ZnS quantum dots (QDs). The telomerase-stimulated telomerization of the primer-functionalized QDs in the presence of the nucleotide mixture dNTPs results in the synthesis of the G-rich telomeres. The stacking of hemin on the self-organized G-quadruplexes found on the telomers results in the electron transfer quenching of the QDs, thus providing an optical readout signal. This method enables the detection of telomerase originating from 270 [+ or -] 20 293T cells/[micro]L. The third sensing method involves the amplified surface plasmon resonance (SPR) detection of telomerase activity. The telomerization of a primer associated with Au film-coated glass slides, in the presence of telomerase and the nucleotide mixture (dNTPs), results in the formation of telomeres on the surface, and these alter the dielectric properties of the surface resulting in a shift in the SPR spectrum. The hybridization of Au NPs functionalized with nucleic acids complementary to the telomere repeat units with the telomeres amplifies the SPR shifts due to the coupling between the local plasmon of the NPs and the surface plasmon wave. This method enables the detection of telomerase extracted from 18 [+ or -] 3 293T cells/[micro]L. 10.1021/ac101976t

We present a novel method for remote sensing of crosswind using a passive imaging device, such as a video recorder. The method is based on spatial and temporal correlations of the intensity fluctuations of a naturally illuminated scene induced by atmospheric turbulence. Adaptable spatial filtering, taking into account variations of the dominant spatial scales of the turbulence (due to changes in meteorological conditions, such as turbulence strength, or imaging device performance, such as frame rate or spatial resolution), is incorporated into this method. Experimental comparison with independent wind measurement using anemometers shows good agreement. OCIS codes: 010.0280, 010.1330, 010.3920, 110.0115, 280.4991.

A flip-flop (FF) is a kind of latch and the simplest form of memory device, which stores various values either temporarily or permanently. Optical FF memories form a fundamental building block for alloptical packet switches in next-generation communication networks. An all-optical clocked delay FF using a single terahertz optical asymmetric demultiplexer-based interferometric switch is proposed and described. Numerical simulation results are also reported. OCIS codes: 200.0200, 200.4660, 210.0210, 210.4680, 060.4510, 230.4320.

Optical design and tolerancing of aspheric or free-form surfaces require attention to surface form, structured surface errors, and nonstructured errors. We describe structured surface error profiles and effects on the image point-spread function using harmonic (Fourier) decomposition. Surface errors over the beam footprint map onto the pupil, where multiple structured surface frequencies mix to create sum and difference diffraction orders in the image plane at each field point. Difference frequencies widen the central lobe of the point-spread function and summation frequencies create ghost images. [c] 2010 Optical Society of America OCIS codes: 220.0220, 220.1920, 220.3620, 110.2990, 290.5838.