The signal-to-noise ratio achieved via the double Michelson approach is similar to previously reported methods, but with the added flexibility of arbitrarily adjusting the pump-probe delay time.
The groundwork for the development and characterization of cutting-edge chirped volume Bragg gratings (CVBGs) using femtosecond laser inscription was established. The phase mask inscription technique allowed us to realize CVBGs in fused silica, featuring a 33mm² aperture and a length of approximately 12mm, with a chirp rate of 190 ps/nm centered around a wavelength of 10305nm. The radiation's polarization and phase were severely distorted by the strong mechanical stresses. We posit a potential resolution to this predicament. The local modification of fused silica, while affecting the linear absorption coefficient, does so to a degree that is inconsequential, thereby enabling these gratings for use in high average-power laser systems.
In the field of electronics, the dependable unidirectional flow of electrons within a conventional diode has been essential. The quest for a consistent one-way light path has presented a long-standing difficulty. While a number of novel concepts have been proposed in recent times, the creation of a unidirectional light stream in a bi-directional port system (like a waveguide) presents a demanding challenge. This study introduces what we believe to be a revolutionary method for breaking the reciprocal nature of light, leading to a one-directional light flow. We show, through the example of a nanoplasmonic waveguide, that time-dependent interband optical transitions in systems with backward wave propagation can lead to the transmission of light exclusively in one direction. Lipopolysaccharides The energy flow, within our design, is strictly unidirectional; light is entirely reflected in a single direction of propagation, and not disturbed in the other. From communications to smart windows, thermal radiation management, and solar energy harvesting, this concept has a wide array of potential applications.
This paper introduces a modified Hufnagel-Andrews-Phillips (HAP) Refractive Index Structure Parameter model, better matching experimental data through the utilization of turbulent intensity (the ratio of wind speed variance to the square of average wind speed) and Korean Refractive Index Parameter yearly statistics. The modified model is then compared to the CLEAR 1 profile model and various data sets. Evaluated against the CLEAR 1 model, these comparisons suggest that this new model furnishes a more consistent presentation of the averaged experimental data profiles. Moreover, comparing this model to the experimental datasets detailed in published literature reveals a good fit between the model and average data, and a generally acceptable match to non-averaged datasets. This enhanced model is anticipated to be of value in both system link budget estimations and atmospheric research.
Employing laser-induced breakdown spectroscopy (LIBS), the optical measurement of gas composition was conducted on randomly distributed, fast-moving bubbles. To induce plasmas, crucial for LIBS measurements, laser pulses were focused on a point situated within a flow of bubbles. The depth, or distance between the laser focal point and the liquid-gas interface, significantly influences the plasma emission spectrum in two-phase fluid systems. Despite this, the 'depth' effect has not been considered in past research. In a calibration experiment near a calm and flat liquid-gas interface, we examined the 'depth' effect using proper orthogonal decomposition. This was followed by training a support vector regression model to extract the gas composition from the spectra, uninfluenced by the intervening liquid. Real-world two-phase fluid scenarios were used to perform a precise measurement of the mole fraction of oxygen in the bubbles.
The precalibrated, encoded information utilized by the computational spectrometer results in spectra reconstruction. Over the past ten years, a low-cost, integrated paradigm has arisen, exhibiting tremendous application potential, particularly within portable and handheld spectral analysis instruments. Feature spaces are used by conventional methods employing a local-weighted strategy. The inherent limitations of these methods arise from their disregard for the potential for exaggerated coefficients in significant features, preventing a precise representation of variations in a more detailed feature space. A novel method, local feature-weighted spectral reconstruction (LFWSR), is detailed herein, enabling the creation of a highly accurate computational spectrometer. Departing from previous methodologies, the presented method learns a spectral dictionary through L4-norm maximization for representing spectral curve attributes, and takes into account the statistical importance ranking of features. In accordance with the ranking, weight features and update coefficients are leveraged to ascertain similarity. Moreover, the inverse distance-weighted technique is used for choosing samples and assigning importance to a locally-focused training set. Ultimately, the concluding spectrum is rebuilt using the locally trained data and the acquired measurements. The experiments performed corroborate that the reported method's dual weighting systems consistently produce the highest attainable accuracy.
A dual-mode adaptive singular value decomposition ghost imaging technique, designated as A-SVD GI, is proposed, facilitating an easy transition between imaging and edge detection modes. Receiving medical therapy Through a threshold selection method, foreground pixels are localized adaptively. Through the application of singular value decomposition (SVD) – based patterns, the foreground region is the sole area illuminated, ultimately yielding high-quality images with less sampling. By manipulating the range of pixels chosen as foreground, the A-SVD GI system can be reconfigured for edge detection, directly displaying the edges of objects without necessity for the initial image. Numerical simulations and experiments are both employed to assess the efficacy of these two operating modes. In contrast to traditional methods of separately analyzing positive and negative patterns, we've developed a single-round approach to reduce experimental measurements by half. Data acquisition is accelerated by modulating binarized SVD patterns, produced by the spatial dithering technique, using a digital micromirror device (DMD). The dual-mode A-SVD GI's applications are extensive, encompassing remote sensing and target recognition; furthermore, it has potential for further use in multi-modality functional imaging/detection.
Ptychography of EUV, characterized by high speed and wide field, is presented at 135nm wavelength, using a table-top high-order harmonic source. A scientifically designed complementary metal-oxide-semiconductor (sCMOS) detector, coupled with an optimally configured multilayer mirror, has led to a substantial reduction in total measurement time, potentially diminishing it by up to five times compared to previous measurements. A 100 m by 100 m field of view is achievable through the sCMOS detector's fast frame rate, capturing images at a speed of 46 megapixels per hour. The EUV wavefront is characterized promptly, employing a combination of an sCMOS detector and orthogonal probe relaxation techniques.
Within nanophotonics, the chiral properties of plasmonic metasurfaces, particularly the differential absorption of left and right circularly polarized light causing circular dichroism (CD), are a highly active area of research. In the context of different chiral metasurfaces, there's frequently a requirement to fathom the physical origins of CD, and to establish design rules for optimizing structures with robustness. Our numerical analysis examines CD at normal incidence for square arrays of elliptic nanoholes etched in thin metallic layers (silver, gold, or aluminum) on a glass substrate, which are tilted in relation to their symmetry axes. The wavelength region where extraordinary optical transmission is observed coincides with the appearance of circular dichroism (CD) in absorption spectra, signifying highly resonant light-surface plasmon polariton coupling at the metal/glass and metal/air interfaces. Trained immunity We illuminate the physical origin of absorption CD through a thorough contrast of optical spectra under differing polarization conditions (linear and circular), aided by static and dynamic simulations of electric field magnification at the local level. Moreover, the CD's optimization hinges on the ellipse's parameters—diameters and tilt—alongside the metallic layer's thickness and the lattice constant. The use of silver and gold metasurfaces is optimal for circular dichroism (CD) resonances exceeding 600 nanometers, while aluminum metasurfaces are beneficial for producing strong CD resonances in the short-wavelength visible and near-ultraviolet ranges. The chiral optical effects observed at normal incidence in this straightforward nanohole array, as revealed by the results, suggest potential applications for sensing chiral biomolecules within such plasmonic structures.
A new technique for the creation of beams exhibiting rapidly adjustable orbital angular momentum (OAM) is introduced. This method leverages a single-axis scanning galvanometer mirror to introduce a phase tilt onto an elliptical Gaussian beam, which is then configured as a ring using optics that perform a log-polar transformation. The kHz-range mode switching capability of this system allows for relatively high-power operation with impressive efficiency. The HOBBIT scanning mirror system, utilizing the photoacoustic effect for light/matter interaction, achieved a 10dB amplification in the generated acoustics at the interface between glass and water.
Nano-scale laser lithography's throughput capacity is insufficient to enable substantial industrial application. Enhancing lithography speed using multiple laser foci is an effective and straightforward method. However, conventional multi-focus approaches are frequently marred by non-uniform laser intensity distributions across the multiple foci, hindering their ability to exert individual control over each focal point, thus compromising the critical need for nanoscale precision.