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Photoreceptor assessment in focal laser-treated central serous chorioretinopathy using adaptive optics and fundus autofluorescence
摘要： This study analyzed cone density, cone mosaic, and fundus autofluorescence (FAF) images in patients with focal laser-treated central serous chorioretinopathy (CSC). Observational case series. Forty-two eyes of 21 patients with unilateral treated CSC and bilateral best-corrected visual acuity of 1.0 (decimal fraction) were included. FAF and cone mosaic images were obtained in all patients with an adaptive optics fundus camera. Densities were recorded at 20 points throughout the macula, and choroidal thicknesses were measured. Mean choroidal thicknesses were 419.95 ± 110.33 mm in normal eyes, 459.09 ± 90.07 mm in eyes with active CSC, and 438.61 ± 107.57 mm in treated eyes. The highest density of cones in healthy eyes was 38146 cones/mm2, with a 5.66-mm intercellular space (IS), at 700 mm temporal to the center. In eyes with treated CSC, the highest density was 32749 cones/mm2, with a 6.13-mm IS, at 500 mm nasal to the center. In all quadrants, median values of maximum cone density were significantly higher in healthy eyes (P = .02, P = .003, P = .0001, and P = .001). Three types of lesions were identified on FAF and were correlated with those on cone mosaic images. Strong correlations were detected between the presence of hypoautofluorescent lesions on the first FAF image and a greater difference between maximum values of photoreceptor density (r2 = 0.46, P = .03), as well as between the presence of hypoautofluorescent lesions and the duration of pathology (r2 = 0.68, P < .001). The presence of hypoautofluorescent lesions and the duration of pathology were negative prognostic factors in CSC. Laser treatment could prevent photoreceptor loss.
关键词： photoreceptor density,cone mosaic,fundus autofluorescence,laser-treated central serous chorioretinopathy,adaptive optics
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Spatial inhomogeneity of the absorption and re-emission properties of an optically active medium in a resonator
摘要： The spatial inhomogeneity of absorption coefficient of the space between mirrors, filled by an optically active gas, is analyzed in quantum optical terms. It was theoretically shown, that the quantization of electromagnetic field in a cavity (optical resonator) can reveal the spatial inhomogeneity of absorption or re-emission ability of the optically active medium. It appears from the analytical calculations, the inhomogeneity is caused by the Doppler frequency shifts (including recoil effects) during the atom-photon collisions and the non-zero initial frequency width of the scanning signal. The proposed analytical representation of the absorption coefficient through the additive quantum optical terms gives deeper insight into intrinsic processes in the interacting with light matter.
关键词： absorption coefficient,many-body system,inhomogeneity,quantum optics
更新于2025-09-23 15:19:57
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Laser Beam Shaping Applications || Laser Beam Shaping in Array-Type Laser Printing Systems
摘要： In a variety of applications, including longitudinal solid-state laser pumping,1–4 fiber coupling for fiber lasers, and line printers,5–12 laser diode arrays have proven to be very effective light sources when combined with the appropriate beam shaping optics. As laser arrays can be designed in numerous ways, such as with phase-coupled single-mode emitters, uncoupled single-mode emitters, or uncoupled multimode emitters, the output properties of both the individual beams and the ensemble of beams vary dramatically. Inherently, many beam properties, including the output power level, beam profiles and beam propagation properties, beam coherence effects, and the overall device layout, are dependent upon the emitter structure. The optical systems that have been designed to work with these highly nontraditional light sources, which are anamorphic in both physical layout and beam properties, are themselves nontraditional, and typically employ a variety of modern micro-optical components. Within that context, a variety of unique systems13–15 have been developed for high-power, high-throughput printing applications, where the laser light is transformed into a linear arrangement of individually modulated beams and imaged onto a light-sensitive media. These systems typically combine the design and analysis techniques from classical imaging optics, illumination optics, and Gaussian beam optics into integral wholes. Certainly, many of the design concepts that have evolved to support the laser thermal printing application are applicable to other endeavors, of which laser projection is an example.
关键词： beam shaping,laser thermal printing,Gaussian beam optics,micro-optical components,laser diode arrays
更新于2025-09-23 15:19:57
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Double-pulse speckle contrast correlations with near Fourier transform limited free-electron laser light using hard X-ray split-and-delay
摘要： the ability to deliver two coherent X-ray pulses with precise time-delays ranging from a few femtoseconds to nanoseconds enables critical capabilities of probing ultra-fast phenomena in condensed matter systems at X-ray free electron laser (feL) sources. Recent progress made in the hard X-ray split-and-delay optics developments now brings a very promising prospect for resolving atomic-scale motions that were not accessible by previous time-resolved techniques. Here, we report on characterizing the spatial and temporal coherence properties of the hard X-ray feL beam after propagating through split-and-delay optics. Speckle contrast analysis of small-angle scattering measurements from nanoparticles reveals well-preserved transverse coherence of the beam. Measuring intensity fluctuations from successive X-ray pulses also reveals that only single or double temporal modes remain in the transmitted beam, corresponding to nearly fourier transform limited pulses.
关键词： spatial coherence,split-and-delay optics,speckle contrast,temporal coherence,X-ray Free Electron Lasers
更新于2025-09-23 15:19:57
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Ghost imaging at an XUV free-electron laser
摘要： Here we present the results of a classical ghost imaging experiment accomplished at an XUV free-electron laser (FEL). To perform such experiment at an FEL source each x-ray pulse was transmitted through a moving diffuser, which created a noncorrelated speckled beam. This beam was then split in two identical branches by introducing a beam splitter in the form of a transmission grating. In one of these branches the sample was positioned. We demonstrate the possibility of image formation, a double bar in our case, in the beam that has never interacted with the sample. With this experiment we extend the quantum optics methodology to the FEL community.
关键词： XUV free-electron laser,speckle pattern,quantum optics,ghost imaging,transmission grating
更新于2025-09-23 15:19:57
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Widea??Bandgap Organic Crystals: Enhanced Opticala??toa??Terahertz Nonlinear Frequency Conversion at Neara??Infrared Pumping
摘要： Enhanced terahertz (THz) wave generation is demonstrated in nonlinear organic crystals through refractive index engineering, which improves phase matching characteristics substantially. Unlike conventional low-bandgap nonlinear organic crystals, the newly designed benzimidazolium-based HMI (2-(4-hydroxy-3-methoxystyryl)-1,3-dimethyl-1H-benzoimidazol-3-ium) chromophore possesses a relatively wide bandgap. This reduces the optical group index in the near-infrared, allowing better phase matching with the generated THz waves, and leads to high optical-to-THz conversion. A unique feature of the HMI-based crystals, compared to conventional wide-bandgap aniline-based crystals, is their remarkably larger macroscopic optical nonlinearity, a one order of magnitude higher diagonal component in macroscopic nonlinear susceptibility than NPP ((1-(4-nitrophenyl)pyrrolidin-2-yl)methanol) crystals. The HMI-based crystals also exhibit much higher thermal stability, with a melting temperature Tm above 250 °C, versus aniline-based crystals (116 °C for NPP). With pumping at the technologically important wavelength of 800 nm, the proposed HMI-based crystals boost high optical-to-THz conversion efficiency, comparable to benchmark low-bandgap quinolinium crystals with state-of-the-art macroscopic nonlinearity. This performance is due to the excellent phase matching enabled by decreasing optical group indices in the near-infrared through wide-bandgap chromophores. The proposed wide-bandgap design is a promising way to control the refractive index of various nonlinear organic materials for enhanced frequency conversion processes.
关键词： organic crystals,terahertz,refractive index engineering,phase matching,nonlinear optics
更新于2025-09-23 15:19:57
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The TeraFERMI Electro-Optic Sampling Set-Up for Fluence-Dependent Spectroscopic Measurements
摘要： TeraFERMI is the THz beamline at the FERMI free-electron-laser facility in Trieste (Italy). It uses superradiant Coherent Transition Radiation emission to produce THz pulses of 10 to 100 μJ intensity over a spectral range which can extend up to 12 THz. TeraFERMI can be used to perform non-linear, ?uence-dependent THz spectroscopy and THz-pump/IR-probe measurements. We describe in this paper the optical set-up based on electro-optic-sampling, which is presently in use in our facility and discuss the properties of a representative THz electric ?eld pro?le measured from our source. The measured electric ?eld pro?le can be understood as the superimposed emission from two electron bunches of different length, as predicted by electron beam dynamics simulations.
关键词： THz spectroscopy,free-electron-lasers,nonlinear optics
更新于2025-09-23 15:19:57
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Development of a Thulium Fiber Laser for an Atomic Spectroscopy Experiment
摘要： A convenient thulium ?ber laser source is described with 3 W of output power operating at a wavelength of 2059 nm with a slope e?ciency of 49% with respect to input pump power and 60% with respect to absorbed pump power. The laser was applied in an atomic helium spectroscopy experiment to quench 3He (2058.63 nm) and 4He (2058.69 nm) meta-stable singlets (21S0), allowing for further investigation of the helium ?ne structure. The customized laser e?ectively eliminates the singlet counts to well below a background level (1%). A simpli?ed analysis describes the basic laser performance with ?tted constants in reasonable agreement with previous work.
关键词： fiber,thulium fiber laser,laser,spectroscopy,fiber laser,rare-earth elements,optics,thulium
更新于2025-09-23 15:19:57
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FibAR: Embedding Optical Fibers in 3D Printed Objects for Active Markers in Dynamic Projection Mapping
摘要： We experimentally investigate mutual information and generalized mutual information for coherent optical transmission systems. The impact of the assumed channel distribution on the achievable rate is investigated for distributions in up to four dimensions. Single channel and wavelength-division multiplexing (WDM) transmission over transmission links with and without inline dispersion compensation are studied. We show that for conventional WDM systems without inline dispersion compensation, a circularly symmetric complex Gaussian distribution is a good approximation of the channel. For other channels, such as with inline dispersion compensation, this is no longer true and gains in the achievable information rate are obtained by considering more sophisticated four-dimensional (4D) distributions. We also show that for nonlinear channels, gains in the achievable information rate can also be achieved by estimating the mean values of the received constellation in four dimensions. The highest gain for such channels is seen for a 4D correlated Gaussian distribution.
关键词： mutual Information,digital communication,fiber nonlinear optics,optical fiber communication,Channel models
更新于2025-09-23 15:19:57
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Spina??Controlled Nonlinear Harmonic Generations from Plasmonic Metasurfaces Coupled to Intersubband Transitions
摘要： Metasurfaces that generate nonlinear optical responses provide new degrees of freedom for applications such as nonlinear holography, wave mixing, and new frequencies generation. To extend the utility of flat nonlinear optics, metasurfaces providing both giant nonlinear response for efficient frequency mixing in subwavelength films and a single-beam output with a local wavefront control need to be developed. Metasurfaces with giant nonlinear response have recently been realized using the concept of intersubband polaritons. Separately, nonlinear metasurfaces providing a single-beam nonlinear output with a local wavefront control have been studied. However, a metasurface platform that possesses both of these properties has yet to be demonstrated. Herein, the first such platform is presented and its operation for three- and four-wave mixing processes is demonstrated. This approach is based on using Pancharatnam–Berry phase control of local nonlinear response and on employing meta-atoms with specific symmetries to enable generation of only a single nonlinear beam. Experimentally, 400 nm-thick metasurfaces with a wavefront-controlled single-beam output are demonstrated for second- and third-harmonic generation at pump wavelength of approximately 10 μm. Power conversion efficiencies of 7.6 × 10?4% and 3.6 × 10?4% are obtained for the two nonlinear processes, respectively, at peak pumping intensity of only 80 kW cm?2.
关键词： nonlinear beam-steering,nonlinear optics,spin angular momentum,metasurfaces,intersubband transitions
更新于2025-09-23 15:19:57