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990 nm High-power High-beam-quality DFB Laser With Narrow Linewidth Controlled By Gain-coupled Effect
摘要： High-power single-longitudinal-mode regrowth-free gain-coupled distributed feedback laser diode based on ridge waveguide with periodic current injection is achieved at 990 nm. Our device is fabricated only by standard i-line lithography with micron-scale precision, obtains an excellent performance at high injection current. A continuous-wave power of over 0.681 W is achieved at 3 A. The maximum continuous-wave power at single-longitudinal-mode operation is up to 0.303 W at 1.4 A. Narrow linewidth emission has been reached with a 3 dB spectrum width less than 1.41 pm. The high side mode suppression ratio is over 35 dB. The lateral far field divergence angle is only 15.05 °, the beam quality factor M 2 is 1.245, achieving a laterally near-diffraction-limit emission. It is more beneficial for single mode fiber coupling as pumping sources and other applications which require high beam quality at high power with easy fabrication technique.
关键词： narrow linewidth,Single-longitudinal mode,Gain-coupled DFB,Semiconductor lasers
更新于2025-11-28 14:24:03
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Direct oscillation at 640-nm in single longitudinal mode with a diode-pumped Pr:YLF solid-state laser
摘要： A diode-pumped solid-state laser directly emitting continuous-wave (cw), single-longitudinal mode (SLM) output at 640-nm with a c-cut praseodymium-doped yttrium lithium fluoride (Pr:YLF) crystal was demonstrated for the first time, to the best of our knowledge. Combining two quarter-wave plates (QWPs) and one Brewster plate to form a twisted-mode cavity, this SLM solid-state laser achieved a maximum cw output power of 403 mW with a threshold of 600 mW and a slope efficiency of 26.8%. The emission spectrum had a linewidth of 150 MHz. The single-mode beam quality (M2) was 1.10 and 1.07 along the x and y direction, respectively.
关键词： Single-longitudinal-mode,Diode-pumped solid-state lasers,Visible lasers
更新于2025-11-28 14:23:57
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Comparison of Clinical Outcomes between Torsional and Longitudinal Phacoemulsification
摘要： Purpose: To compare the clinical outcomes during phacoemulsification when using recently improved longitudinal (Stellaris?, Bausch & Lomb, Rochester, NY, USA) and torsional (Infiniti Ozil?, Alcon, Fort Worth, TX, USA) ultrasound. Methods: The present study included 74 eyes of 59 patients undergoing cataract surgery. Operated eyes with mild cataract (nuclear sclerosis grade 1 and 2), moderate cataract (nuclear sclerosis grade 3) and hard cataract (nuclear sclerosis grade 4 and 5) were compared in terms of the total phacoemulsification (phaco) time, average phaco power, total phaco energy and amount of fluid used during cataract surgery between the 2 modalities. Endothelial cell density, corneal edema, central corneal thickness (CCT), surgically induced astigmatism (SIA) and best-corrected visual acuity (BCVA) were also evaluated preoperatively and up to 3 month postoperatively. Results: In mild cataracts, the operative parameters and corneal changes were similar between the 2 modalities. In moderate cataracts, the total phaco time was significantly higher in the torsional group than the longitudinal group, but the average phaco power, total phaco energy, and amount of fluid were not significantly different. In patients with hard cataract, the torsional group showed higher total phaco time (27.50 ± 17.77 sec vs. 97.08 ± 12.67 sec), average phaco power, total phaco energy, persistent corneal edema at 1 week postoperatively and more endothelial cell loss at 3 month postoperatively (16.33 ± 15.50% vs. 38.71 ± 26.49%). Postoperative CCT, SIA and BCVA were not significantly different in hard cataracts between the 2 modalities. Conclusions: In mild and moderate cataracts, the efficiency of phaco and corneal changes were similar between the 2 modalities. However, recently improved longitudinal phaco showed superior efficiency for hard cataracts and induced less endothelial cell loss than torsional phaco.
关键词： Longitudinal,Cataract surgery,Phacoemulsification,Nuclear density,Torsional
更新于2025-09-23 15:22:29
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Development of a Visual Field Simulation Model of Longitudinal Point-Wise Sensitivity Changes From a Clinical Glaucoma Cohort
摘要： Purpose: To develop a new visual field simulation model that can recreate real-world longitudinal results at a point-wise level from a clinical glaucoma cohort. Methods: A cohort of 367 glaucoma eyes from 265 participants seen over 10.1 ± 2.5 years were included to obtain estimates of "true" longitudinal visual field point-wise sensitivity and estimates of measurement variability. These two components were then combined to reconstruct visual field results in a manner that accounted for correlated measurement error. To determine how accurately the simulated results reflected the clinical cohort, longitudinal variability estimates of mean deviation (MD) were determined by calculating the SD of the residuals from linear regression models fitted to the MD values over time for each eye in the simulated and clinical cohorts. The new model was compared to a previous model that does not account for spatially correlated errors. Results: The SD of all the residuals for the clinical and simulated cohorts was 1.1 dB (95% confidence interval [CI]: 1.1–1.2 dB) and 1.1 dB (95% CI: 1.1–1.1 dB), respectively, whereas it was 0.4 dB (95% CI: 0.4–0.4 dB) using the previous simulation model that did not account for correlated errors. Conclusions: A new simulation model accounting for correlated measurement errors between visual field locations performed better than a previous model in estimating visual field variability in glaucoma. Translational Relevance: This model can provide a powerful framework to better understand use of visual field testing in clinical practice and trials and to evaluate new methods for detecting progression.
关键词： visual field,glaucoma,simulations,longitudinal
更新于2025-09-23 15:22:29
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Longitudinal analysis of molecular alteration in serum samples of dextran sodium sulfate-induced colitis mice by using infrared spectroscopy
摘要： Established diagnostic regimens for in?ammatory bowel diseases, such as colonoscopy, sigmoidoscopy, and small bowel follow-through have high sensitivity, but adherence rates of the eligible population for the disease screening is poor due to associated expenses, the risk of complications, time, and comfort issues. Thus, it is critical to develop an A?ordable, Sensitive, Speci?c, User-friendly, Rapid, Equipment-free, and Deliverable (ASSURED) screening test that could increase the participation rate of the eligible group. In this study, we present infrared spectroscopy of serum accompanied with data analysis to monitor longitudinal analysis of molecular alteration in colitis mouse samples. Dextran Sodium Sulfate-induced colitis mouse model sera were used to understand the disease aggravation by testing of the alteration of carbohydrates and the protein secondary structures re?ected in the spectra. Samples derived from mouse models at days 0, 3, and 7 of chemical administration were used for spectral measurements. Spectral data at Biomarker peaks show there is not any speci?c alteration of serum sample composition at day 3 of the chemical feeding, but a signi?cant alteration on the marker can be seen at day 7. The results of this study will thus pave the way for the development of an ASSURED prototype that can have clinical application.
关键词： Colitis,Longitudinal analysis,Serum,Infrared ATR spectroscopy,Mouse models
更新于2025-09-23 15:22:29
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Exploiting Evanescent Field Polarization for Giant Chiroptical Modulation from Achiral Gold Half-Rings
摘要： For applications seeking to realize on-chip polarization discriminating nanoantennas, efficient energy conversion from surface waves to far-field radiation is desirable. However, the response of individual nanoantennas to the particular polarization states achievable in surface waves, such as evanescent fields, has not yet been thoroughly investigated. Here, we report giant modulation of visible light scattering from achiral gold half-rings when switching between evanescent surface wave excitation produced from total internal reflection of left-handed and right-handed circularly polarized light. The effect is driven by a differing relative phase between the in-plane transverse and longitudinal field oscillations of the evanescent wave depending on the incident light handedness. As longitudinal field oscillations are not found in free-space excitation, this presents a fundamentally different mechanism for chiroptical responses as traditional mechanisms for circular dichroism only account for purely transversal field oscillations. Although the half-ring scattering modulation is dependent on the wave vector orientation, an orientation invariant response is also realized in planar chiral nanoantennas composed of eight half-rings in a rotationally symmetric arrangement, with up to 50% scattering modulation observed at 725 nm. Though both structures are found to produce scattering modulation when switching the handedness of free-space light, the distinct polarization properties of evanescent fields are shown to be strictly required to observe giant scattering modulation. These results ultimately deepen our understanding of the range of possible chiroptical effects in light-matter interactions.
关键词： nanoantenna,extrinsic chirality,evanescent fields,planar chirality,polarization discrimination,longitudinal field oscillations
更新于2025-09-23 15:21:21
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Terahertz electromagnetic waves radiated from coherent longitudinal optical (LO) phonons and LO-phonon plasmon coupled modes in (001)-, (110)-, and (111)-oriented semi-insulating GaAs single crystals
摘要： We report on terahertz electromagnetic waves from coherent longitudinal optical (LO) phonons and coherent LO-phonon plasmon coupled (LOPC) modes in (001)-, (110)-, and (111)-oriented semi-insulating GaAs single crystals. The coherent LO phonons and coherent LOPC modes are observed in the three samples. In contrast, coherent transverse optical (TO) phonons are not observed in the (110)- and (111)-oriented samples in spite of that the TO phonon is the Raman active mode. We conclude that only the coherent longitudinal oscillating polarization such as coherent LO phonons and coherent LOPC modes radiate the terahertz wave and that the Raman selection rule does not contribute to the terahertz-wave-radiation process. The photogenerated electron-density dependence of the frequencies of the coherent LOPC mode is almost the same in the three samples. This ?nding indicates that the coupling of the LO phonon with the plasmon is not in?uenced by the surface orientations of the three samples.
关键词： coherent LO-phonon plasmon coupled mode,coherent longitudinal optical (LO) phonon,terahertz time-domain spectroscopy,coherent transverse optical phonon,ultrafast phenomena,Raman scattering effect
更新于2025-09-23 15:21:01
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Study of Laser-Generated Longitudinal Waves Interacting with an Internal Spherical Cavity by Use of a Transmission Time Delay Method
摘要： In order to improve the detection sensitivity and stability of scanning laser ultrasound techniques, we propose a transmission time delay method, based on the time delay of transmitted longitudinal waves, for the evaluation of the size and position of an internal cavity. By studying the interacting process between the longitudinal wave and the internal cavity through theory and finite element method, the relationships among the time delay, cavity radius, and the detection distance were determined. The monotonicity of the relationship indicates that the time delay can be used to inverse the radius and the depth position of the internal cavity. The laser ultrasound experiments were performed on three aluminum samples with different internal cavities through the concentric transmission method. The C-scan results show that compared with using amplitude attenuation to detect the cavity, the time delay of transmitted waves can detect the internal cavities more stably and accurately. The experimental data are close to the theoretical and simulation results, and the inversion of cavity depth was achieved based on the measured parameters (the time delay, cavity radius, frequency, velocity). The results demonstrate that the transmission time delay method has a great application potential in the localization and quantification of the internal defects.
关键词： Laser ultrasonic,Time delay,Longitudinal wave,Internal cavity,Creeping wave
更新于2025-09-23 15:21:01
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Doubly Q-switched single longitudinal mode Nd:YAG laser with electro-optical modulator and Cr4???:YAG
摘要： An electro-optical modulator (EOM) and Cr4+:YAG saturable-absorber-based doubly Q-switched Nd:YAG laser at 1.06 μm with single-longitudinal-mode (SLM) output was demonstrated. The spatial-hole-burning suppression and cavity axial-mode selection were provided by a twisted-mode technique and resonant-reflector-mediated SLM operation. The Cr4+:YAG initial transmittance (??0) affected the pulse profile, pulse energy, and laser spectra, which were analyzed theoretically and experimentally. Consequently, the laser output obtained an SLM rate of 96.2% with a symmetry factor of 0.64 when ??0 was 6.2%. The results indicate that symmetric and SLM laser pulse can be obtained in a double Q-switched laser by adjusting the cavity loss according to ??0. Compared with a solely Q-switched laser, the double Q-switches of EOM and Cr4+:YAG provide a practical route toward the generation of a symmetric temporal profile and SLM operation.
关键词： Twisted-mode cavity,Symmetric pulses,Doubly Q-switched,Resonant reflector,Single-longitudinal-mode
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) - Formation of Space Charge Wave with Wide Frequency Spectrum in Helical Electron Beam of Two-Stream FEL Transit Section with Longitudinal Electric Field
摘要： The longitudinal electric field effect on the formation of a space charge wave (SCW) with wide frequency spectrum in the helical two-stream relativistic electron beam (REB), which moves in transit section of multiharmonic two-stream superheterodyne free-electron laser, is analyzed. In the framework of cubic nonlinear approximation, it is shown that the use of the accelerating electric field makes it possible to increase the multiharmonic SCW width of the frequency spectrum. It is shown that the retarding electric field causes the increase of the amplitude level SCW harmonics, as well as the decrease of its saturation length.
关键词： three-wave parametric resonance,helical electron beam,two-stream instability,two-stream superheterodyne free-electron laser,longitudinal electric field
更新于2025-09-23 15:19:57