A resolution-enhanced photothermal microscopy technique, termed Modulated Difference Photothermal Microscopy (MD-PTM), is presented in this letter. The technique employs Gaussian and doughnut-shaped heating beams, modulated in unison but with contrasting phases, to create the photothermal signal. Moreover, the inverse phase properties of photothermal signals are harnessed to extract the required profile from the PTM magnitude, ultimately improving the PTM's lateral resolution. The difference coefficient characterizing the contrast between Gaussian and doughnut heating beams plays a crucial role in lateral resolution; an increase in this coefficient results in a broader sidelobe of the MD-PTM amplitude, a characteristic that readily results in an artifact. In order to segment phase images of MD-PTM, a pulse-coupled neural network (PCNN) is employed. The experimental micro-imaging of gold nanoclusters and crossed nanotubes, utilizing MD-PTM, exhibits the utility of MD-PTM in improving lateral resolution.
Optical transmission paths in two-dimensional fractal topologies, characterized by self-similar scaling, densely packed Bragg diffraction peaks, and inherent rotational symmetry, demonstrate remarkable robustness against structural damage and noise immunity, surpassing the capabilities of regular grid-matrix geometries. Experimental and numerical results in this work demonstrate phase holograms generated by fractal plane-divisions. Capitalizing on the symmetries of fractal topology, we develop numerical procedures for the creation of fractal holograms. This algorithm addresses the shortcomings of the conventional iterative Fourier transform algorithm (IFTA), enabling the optimized adjustment of millions of parameters within optical elements. Fractal holograms demonstrate, through experimental data, a notable reduction in alias and replica noise within the image plane, positioning them favorably for applications demanding both high accuracy and compact designs.
Optical fibers, renowned for their superior light conduction and transmission capabilities, have found extensive application in long-distance fiber optic communication and sensing systems. Due to the dielectric properties intrinsic to the fiber core and cladding materials, the transmitted light's spot size displays dispersion, leading to a considerable limitation on the utilization of optical fiber. The development of metalenses, incorporating artificial periodic micro-nanostructures, is opening exciting avenues for fiber innovation. An ultracompact fiber optic device for beam focusing is shown, utilizing a composite design integrating a single-mode fiber (SMF), a multimode fiber (MMF), and a metalens constructed from periodic micro-nano silicon columns. The MMF end face's metalens creates convergent beams with numerical apertures (NAs) of up to 0.64 in air and a focal length of 636 meters. Optical imaging, particle capture and manipulation, sensing, and fiber lasers could potentially benefit from the metalens-based fiber-optic beam-focusing device's capabilities.
Plasmonic coloration is a consequence of visible light resonating with metallic nanostructures, resulting in wavelength-dependent absorption or scattering. Fructose price Variations in surface roughness, impacting resonant interactions, can affect the sensitivity of this effect, causing the observed coloration to differ from the coloration predicted by simulations. Using electrodynamic simulations and physically based rendering (PBR), we detail a computational visualization strategy to probe the influence of nanoscale roughness on structural coloration in thin, planar silver films decorated with nanohole arrays. Nanoscale surface roughness is mathematically represented using a surface correlation function, with parameters describing roughness perpendicular or parallel to the film plane. Our findings showcase a photorealistic representation of how nanoscale roughness affects the coloration of silver nanohole arrays in both reflection and transmission. The impact on the color is much greater when the roughness is out of the plane, than when it is within the plane. This work's introduced methodology proves helpful in modeling artificial coloration phenomena.
Employing femtosecond laser writing, we demonstrate the construction of a PrLiLuF4 visible waveguide laser, pumped by a diode in this letter. In this study, the waveguide under investigation featured a depressed-index cladding, meticulously designed and fabricated to minimize propagation losses. At wavelengths of 604 nm and 721 nm, laser emission was observed, producing output powers of 86 mW and 60 mW, respectively, accompanied by slope efficiencies of 16% and 14%. For the first time, a praseodymium-based waveguide laser exhibited stable continuous-wave operation at 698 nanometers. The resulting output is 3 milliwatts, with a slope efficiency of 0.46%, perfectly corresponding to the wavelength requirement of the strontium-based atomic clock's transition. Laser emission from the waveguide at this wavelength is largely confined to the fundamental mode, which has the largest propagation constant, and exhibits a near-Gaussian intensity pattern.
The inaugural, to our knowledge, continuous-wave laser operation of a Tm³⁺,Ho³⁺-codoped calcium fluoride crystal at 21 micrometers is reported. Crystals of Tm,HoCaF2, prepared by the Bridgman method, were examined spectroscopically. For the 5I7 to 5I8 transition in Ho3+, the stimulated emission cross-section, measured at a wavelength of 2025 nanometers, equals 0.7210 × 10⁻²⁰ square centimeters, and the thermal equilibrium decay time is 110 milliseconds. At this 3, it's. Tm, a time of 03. A HoCaF2 laser, operating at 2062-2088 nm, produced an output power of 737mW, characterized by a slope efficiency of 280% and a laser threshold of 133mW. Continuous tuning of wavelengths was exhibited from 1985 nm to 2114 nm, a 129 nm range. combined remediation Ultrashort pulse generation at 2 meters is anticipated from Tm,HoCaF2 crystal structures.
Freeform lens design faces a complex problem in precisely managing the distribution of irradiance, notably when the objective is a non-uniform light distribution. The use of zero-etendue approximations for realistic sources is prevalent in simulations demanding detailed irradiance distributions, where all surfaces are assumed smooth. These activities may hinder the overall performance metrics of the developed designs. Employing the linear characteristics of our triangle mesh (TM) freeform surface, we devised an efficient Monte Carlo (MC) ray tracing proxy under extended light sources. In terms of irradiance control, our designs perform better than those found in the LightTools design feature. A lens, fabricated and evaluated within the experiment, demonstrated the expected performance.
The critical role of polarizing beam splitters (PBSs) extends to applications that demand sophisticated polarization control, particularly polarization multiplexing or high polarization purity. The considerable volume associated with conventional prism-based passive beam splitters often limits their applicability in ultra-compact integrated optical systems. A single-layer silicon metasurface PBS is demonstrated, allowing for the precise and on-demand deflection of two orthogonally polarized infrared light beams to distinct angles. The metasurface's architecture, employing silicon anisotropic microstructures, allows for diverse phase profiles for each orthogonal polarization state. Two metasurfaces, engineered with distinct deflection angles for x- and y-polarized light, demonstrate effective splitting capabilities at a 10-meter infrared wavelength in experimental settings. This thin, planar PBS is anticipated to be employed within various compact thermal infrared system designs.
The biomedical field is experiencing growing interest in photoacoustic microscopy (PAM), which combines light and sound with exceptional efficiency. Typically, the frequency range of a photoacoustic signal spans tens to hundreds of megahertz, necessitating a high-performance data acquisition card to ensure precise sampling and control. For depth-insensitive scenes, the photoacoustic maximum amplitude projection (MAP) imaging is frequently complex and costly to accomplish. Our low-cost MAP-PAM system, implemented with a custom-designed peak-holding circuit, identifies extreme values using Hz data sampling. The input signal's dynamic range is 0.01 volts to 25 volts, and the input signal's -6 dB bandwidth is potentially 45 MHz. Both in vitro and in vivo investigations have verified that the imaging performance of the system matches that of conventional PAM. Thanks to its compact size and incredibly low price (around $18), this device presents a groundbreaking performance model for PAM, opening up possibilities for optimal photoacoustic sensing and imaging solutions.
A novel deflectometry-based procedure for quantifying the spatial distribution of two-dimensional density fields is proposed. In this method, light rays are perturbed by the shock-wave flow field, as observed in the inverse Hartmann test, before arriving at the screen from the camera. Once the coordinates of the point source are found through phase analysis, calculating the light ray's deflection angle makes the determination of the density field's distribution possible. A detailed explanation of the density field measurement deflectometry (DFMD) principle is provided. bioreactor cultivation Within supersonic wind tunnels, an experiment was designed to measure density fields in wedge-shaped models with three varied wedge angles. A comparative analysis of the experimental data from the proposed technique with the theoretical outcomes unveiled a measurement error of roughly 27.61 x 10^-3 kg/m³. This method's strengths consist of rapid measurement, simple device construction, and low production costs. We believe this approach, to the best of our knowledge, is novel in measuring the density field of a shockwave flow field.
The task of achieving a high transmittance or reflectance Goos-Hanchen shift enhancement through resonance encounters a challenge due to the drop in the resonance zone.