- 标题
- 摘要
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- 实验方案
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Generation and pulsating behaviors of loosely bound solitons in a passively mode-locked fiber laser
摘要： We demonstrate the experimental observation of loosely bound solitons and pulsations in a passively mode-locked ?ber laser. The soliton amount inside one soliton bunch typically increases with the increment of pump power, while the average pulse-to-pulse separation in the regime of hundreds of picoseconds decreases in principle accordingly. Besides, by employing the real-time measurement based on the dispersive Fourier-transform technique, we ?nd that some solitons in a single bunch are experiencing a simultaneous pulsating process with a period corresponding to 100 times longer than the cavity round-trip time. The experimental results can be bene?cial for better understanding the formation of multiple solitons and pulsating solitons and enriching the nonlinear phenomena in complex soliton systems.
关键词： dispersive Fourier-transform technique,pulsating solitons,loosely bound solitons,passively mode-locked ?ber laser
更新于2025-09-19 17:13:59
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Laser-Induced Optoacoustic Spectroscopy Studies of Inorganic Functionalized Metallic Nanorods
摘要： Plasmonic nanoparticles can be used in photothermal therapy thanks to their ability to generate local heat. The light-to-heat conversion efficiency is crucial for therapeutic and diagnostic applications. The photothermal properties of gold nanorods functionalized with silica layers of controllable thickness were characterized using both theoretical and experimental approaches. The time-resolved laser-induced optoacoustic spectroscopy (LIOAS) was used to determine the amount of absorbed energy changed promptly into heat. The heat generation efficiencies were simulated by the means of finite integration technique. The obtained parameters were correlated with silica thickness. Experimental results are consistent with theoretical predictions, thus LIOAS is a unique reliable method for studying photothermal effect in gold nanoparticles.
关键词： noble metal nanoparticles,finite integration technique,laser-induced optoacoustic spectroscopy,surface plasmon resonance,photothermal effect
更新于2025-09-19 17:13:59
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Suppression of amplitude fluctuation in Brillouin optical fiber reflectometry employing polarization beam splitter and pre-amplification technique
摘要： We propose and validate the suppression effect on amplitude fluctuation in Brillouin optical time domain reflectometry sensing system with a polarization beam splitter and pre-amplification technique. The p- and s-components of local oscillator interfere respectively with two halves of Brillouin scattering amplified by a Erbium doped fiber amplifier. Theoretical analysis indicates that the polarization influence on the beat amplitude is eliminated with the proposed scheme; and experimental results show that the amplitude variation along the sensing fiber could be extracted accurately, and the temperature sensing error is about 5%. The proposed method is helpful to improve the measurement accuracy of the BOTDR sensing system.
关键词： Pre-amplification technique,Polarization beam splitter,Brillouin optical time domain reflectometry,Amplitude fluctuation suppression,sensing system
更新于2025-09-19 17:13:59
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Fiber Laser || Laser Surface Modification — A Focus on the Wear Degradation of Titanium Alloy
摘要： Over the years, engineering materials are being developed due to the need for better service performance. Wear, a common phenomenon in applications requiring surface interaction, leads to catastrophic failure of materials in the industry. Hence, preventing this form of degradation requires the selection of an appropriate surface modification technique. Laser surface modification techniques have been established by researchers to improve mechanical and tribological properties of materials. In this chapter, adequate knowledge about laser surface cladding and its processing parameters coupled with the oxidation, wear and corrosion performances of laser-modified titanium has been reviewed.
关键词： Titanium,Laser surface cladding,Wear,Surface modification technique
更新于2025-09-19 17:13:59
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Coherence of a Driven Electron Spin Qubit Actively Decoupled from Quasistatic Noise
摘要： The coherence of electron spin qubits in semiconductor quantum dots suffers mostly from low-frequency noise. During the past decade, efforts have been devoted to mitigate such noise by material engineering, leading to substantial enhancement of the spin dephasing time for an idling qubit. However, the role of the environmental noise during spin manipulation, which determines the control fidelity, is less understood. We demonstrate an electron spin qubit whose coherence in the driven evolution is limited by high-frequency charge noise rather than the quasistatic noise inherent to any semiconductor device. We employ a feedback-control technique to actively suppress the latter, demonstrating a π-flip gate fidelity as high as 99.04 (cid:1) 0.23% in a gallium arsenide quantum dot. We show that the driven-evolution coherence is limited by the longitudinal noise at the Rabi frequency, whose spectrum resembles the 1=f noise observed in isotopically purified silicon qubits.
关键词： gallium arsenide quantum dot,low-frequency noise,Rabi frequency,1=f noise,semiconductor quantum dots,π-flip gate fidelity,isotopically purified silicon qubits,feedback-control technique,high-frequency charge noise,electron spin qubits
更新于2025-09-19 17:13:59
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Estimation of temperature-dependent yield strength and modulus of elasticity during laser bending
摘要： In this work, an inverse method is developed to estimate the temperature-dependent value of yield strength (Y) and modulus of elasticity (E) of the material during a laser bending process. The method requires measurement of bend angle of the laser scanned workpiece. The inverse model uses the bend angle computed by a direct model. The temperature-dependent Y and E are inversely estimated by minimizing the difference between actual and direct model predicted bend angles. The validation of the proposed method is demonstrated with the help of two examples. For this purpose, inversely estimated values of E and Y are used to predict bend angles for various processing conditions and predicted values are compared with actual values. In examples, actual data has been obtained from a detailed FEM simulation in lieu of shop floor experiments. Later on, the proposed method is also validated by performing shop floor experiments for AH36 steel.
关键词： Inverse technique,Finite element method,Yield strength,Laser bending,Modulus of elasticity
更新于2025-09-19 17:13:59
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Two-Stage Collapse of PNIPAM Brushes: Viscoelastic Changes Revealed by an Interferometric Laser Technique
摘要： Many temperature-responsive polymers exhibit a single-phase transition at the lower critical solution temperature (LCST). One exception is poly(N-isopropylacryamide) (PNIPAM). PNIPAM brush layers (51 ± 3 nm thick) that are end-grafted onto glass beads collapse in two stages. The viscoelastic changes of a PNIPAM brush layers were investigated with an interferometric laser method at different temperatures. This method is able to measure the two-stage collapse of beads coated with a polymer brush layer. When these beads are situated close to a hydrophilic glass surface, they exhibit Brownian motion. As this Brownian motion changes with temperature, it reveals the collapse of the polymer layer. The characteristic spectrum of the Brownian motion of beads are modelled by a damped harmonic oscillator, where the polymer layer acts as both spring and damping. The change of the Brownian motion spectrum with temperature indicates two transitions of the PNIPAM brush layer, one at 36 °C and one at 46 °C. We attribute the first transition to the LCST volume collapse of PNIPAM. Here, changes of the density and viscosity of the brush dominate. The second transition is dominated by a stiffening of the brush layer.
关键词： PNIPAM,viscoelastic changes,interferometric laser technique,brush layers,temperature-responsive polymers,two-stage collapse
更新于2025-09-19 17:13:59
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Optimization of welding parameters in laser welding of Ti6Al4V using VIKOR optimization method
摘要： Ti6Al4V alloys are widely preferred in the biomedical industries owing to its higher corrosion resistance in human body environment. Welding plays a critical role in the manufacture of complicated biomedical components. Hence, the necessity to identify suitable joining process for joining Ti6Al4V is very important. In this work, an attempt is made to study the CO2 laser welding of titanium sheets (Ti6Al4V) having dimensions of 100 (cid:1) 60 (cid:1) 3 mm. Laser welding was done based on L9 Taguchi array with welding speed (v), laser power(P), and shielding gas ?ow rate(f) as input parameters. The weld quality was analysed by measuring the depth of penetration (DOP), bead width (BW), and hardness values. Full penetration was observed only in two welding trials. The optimized parameters were identi?ed by using the VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) multi-objective optimization technique. Analytic Hierarchy Process (AHP) is used for determining the weights of the relative importance of the output factors. VIKOR method identi?ed that the 7th experimental run (power = 1.3 kW, speed = 0.3 m/min, shielding gas ?ow rate = 20 L/min) as the optimized parameter for getting the weld with full depth of penetration, lesser bead width, higher microhardness values in the fusion zone (FZ) and heat affected zone (HAZ). The metallurgical characterization of the optimized weld is also dicussed with the aid of microstructures taken from Scanning Electron Microscope (SEM).
关键词： CO2 laser welding,Hardness values,Bead geometry,VIKOR multi-objective optimization technique,Ti6Al4V
更新于2025-09-19 17:13:59
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[IEEE SoutheastCon 2019 - Huntsville, AL, USA (2019.4.11-2019.4.14)] 2019 SoutheastCon - Design and Construction of Automated Electroluminescent Imaging System for Solar Cell Series Resistance Analyses
摘要： The Electroluminescence technique (ELIT) is used to characterize the spatial uniformity of the series resistance of a solar cell. When current is applied across the metal contacts, a solar cell operates analogously to LED. The image of the illuminated solar cell is captured via a Pentax K100D camera and sent wirelessly using a Wi-Fi SD card to a local computer. The captured image is displayed on the computer terminal, then the image is used for the qualitative evaluation of the series resistance is then obtained by the image processing tools in MATLAB for it to be displayed on the GUI. The primary advantages of the system are its low cost, automation, and simplicity. This EL system aims to measure within 5 percent accuracy of an I-V testing device at a fraction of the cost.
关键词： solar cell,Electroluminescence technique,MATLAB,automation,series resistance
更新于2025-09-19 17:13:59
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[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Development of micro dye laser based on micro wire molding technique
摘要： Three dimensional microfluidic dye laser inside PDMS has been fabricated by microwire molding technique. Visible laser emission from micro-laser was achieved in a micro-laser of 1mM R6G dye dissolved in a mixture of ethanol and benzyl alcohol as the active medium. The laser output intensity profile and variation of the output with the pump power was studied and a threshold of 4.5 mW pump power was observed.
关键词： microwire molding technique,Micro dye laser,Microchannel,PDMS
更新于2025-09-19 17:13:59