- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2019
- 2018
- 2017
- 2016
- Optical pattern
- Phase diagram
- Surfactants
- Optical properties
- TB-MBJ
- FP-LAPW
- Electronic structure
- GGA
- DFT
- Infrared Radiation
- Optoelectronic Information Science and Engineering
- Chemistry
- Materials Science and Engineering
- University of Texas at Arlington
- Macquarie University
- Universiti Malaysia Terengganu
- Devi Ahilya University
- National Institute of Information and Communications Technologies (NICT)
- Povolzhskiy State University of Telecommunications and Informatics (PSUTI)
- University of Sa?da Dr Tahar Moulay
- University of Djillali Liabes
- Assumption University
- National Institute of Advanced Industrial Science and Technology
-
Process control and quality assurance in remote laser beam welding by optical coherence tomography
摘要： Remote laser beam welding significantly outperforms conventional joining techniques in terms of flexibility and productivity. This process benefits in particular from a highly focused laser radiation and thus from a well-defined heat input. The small spot sizes of high brilliance laser beam sources, however, require a highly dynamic and precise positioning of the beam. Also, the laser intensities typically applied in this context result in high process dynamics and in demand for a method to ensure a sufficient weld quality. A novel sensor concept for remote laser processing based on optical coherence tomography (OCT) was used for both quality assurance and edge tracking. The OCT sensor was integrated into a 3D scanner head equipped with an additional internal scanner to deflect the measuring beam independently of the processing beam. With this system, the surface topography of the process zone as well as the surrounding area can be recorded. Fundamental investigations on aluminum, copper, and galvanized steel were carried out. Initially, the influence of the material, the angle of incidence, the welding position within the scanning field, and the temperature on the OCT measuring signal were evaluated. Based on this, measuring strategies for edge tracking were developed and validated. It was shown that orthogonal measuring lines in the advance of the process zone can reliably track the edge of a fillet weld. By recording the topography in the trailing area of the process zone, it was possible to assess the weld seam quality. Comparing the results to microscopic measurements, it was shown that the system is capable of clearly identifying characteristic features of the weld seam. Also, it was possible to observe an influence of the welding process on the surface properties in the heat-affected zone, based on the quality of the measuring signal.
关键词： inline quality assurance,optical coherence tomography,remote laser beam welding,process control
更新于2025-11-28 14:24:20
-
Inline weld depth measurement for high brilliance laser beam sources using optical coherence tomography
摘要： As a result of the rapidly growing importance of applications in electro mobility that require a precisely defined laser weld depth, the demand for inline process monitoring and control is increasing. To overcome the challenges in process data acquisition, this paper proposes the application of a novel sensor concept for deep penetration laser beam welding with high brilliance laser sources. The experiments show that optical coherence tomography (OCT) can be used to measure the weld depth by comparing the distance to the material surface with the distance to the keyhole bottom measured by the sensor. Within the presented work, the measuring principle was used for the first time to observe a welding process with a highly focused laser beam source. First, a preliminary experimental study was carried out to evaluate the influence of the angle of incidence, the material, and the weld joint geometry on the quality of the sensor signal. When using a multimode fiber laser with a focus diameter of 320 μm, the measurements showed a distinct behavior for aluminum and copper. The findings about the measurement signal properties were then applied to laser beam welding with a single-mode fiber laser with a spot diameter of only 55 μm. The spot diameter of the OCT measuring beam was about 50 μm and thus only slightly smaller than that of the single-mode processing beam. A wide variety of tests were carried out to determine the limits of the measurement procedure. The results show that the application of OCT allows inline monitoring of the weld depth using both a multimode and a highly focused single-mode laser beam. In addition, various influences on the signal were identified, e.g., the material-specific melt pool dynamics as well as several characteristic reflection and absorption properties.
关键词： high brilliance laser beam sources,weld depth measurement,optical coherence tomography,laser beam welding
更新于2025-11-28 14:24:20
-
Helical Long-Period Gratings Inscribed in Polarization-Maintaining Fibers by CO2-Laser
摘要： We demonstrate fabrication of helical long-period gratings (HLPGs) in a polarization-maintaining fiber using CO2-laser. The maximum polarization dependent loss (PDL) of the grating was measured to be more than 30 dB at the resonance wavelength. The HLPG was found to have a high index sensitivity of -7248.6 nm/RIU when the surrounding refractive index changes in the range of 1.4470-1.4600, temperature sensitivity of 158.8 pm/°C, and strain sensitivity of 3.17 pm/με. The twist sensitivities based on intensity variation were measured to be 5.98 dB/ (rad/m) (co-directional twist) and -5.97 dB/ (rad/m) (contra-directional twist), respectively. The demonstrated grating devices have promising applications as high-sensitivity fiber sensors, PDL compensator etc.
关键词： optical fiber sensors,Fiber gratings,polarization-maintaining fibers,helical long-period gratings
更新于2025-11-28 14:24:03
-
High Sensitivity Polarimetric Optical Fiber Pressure Sensor Based on Tapered Polarization-Maintaining and Fiber Bragg Grating
摘要： In this paper, we propose a high sensitivity polarimetric optical fiber pressure sensor (OFPS) using a polarization-diversity loop composed of a polarization beam splitter, polarization controllers, and a sensor head. The sensor head consists of 8-cm-long tapered panda-type polarization-maintaining fiber (PMF) and a fiber Bragg grating (FBG) directly spliced with PMF, and the sensor head is located inside a pressure chamber. A pressure-induced birefringence change due to the photoelastic effect can be greatly enhanced at the tapered section of PMF, thereby increasing the pressure sensitivity of the sensor head. The tapered PMF was fabricated using a fusion splicer, and the tapered length and center waist diameter of the tapered PMF segment were ～350 and ～56.82 μm, respectively. At the polarization-diversity loop, PMF is used as a birefringent element to create an interference spectrum due to polarization interference. A pressure-induced birefringence change of PMF results in a wavelength shift of the interference spectrum. Because the PMF birefringence also has a cross sensitivity to temperature, the FBG is utilized for the compensation of the temperature effect on it. The resonance wavelength of the FBG is sensitive to ambient temperature changes but insensitive to changes in pressure. This spectral response of the FBG can be used to compensate additional ambient temperature changes occurred at the sensor head. The pressure sensitivity of our sensor was measured as approximately ?27.70 nm/MPa, and an adjusted R2 value representing the sensor linearity was measured as ～0.9903 in a measurement range of 0–0.5 MPa. Our fabricated sensor exhibits the highest pressure sensitivity among previously reported polarimetric OFPS.
关键词： Polarization-Maintain Fiber,Optical Fiber Sensor,Sagnac Interferometer,Pressure
更新于2025-11-28 14:24:03
-
Carboxyl graphene oxide solution saturable absorber for femtosecond mode-locked erbium-doped fiber laser
摘要： The carboxyl-functionalized graphene oxide (GO-COOH) is a kind of unique two-dimensional (2D) material and possesses excellent nonlinear saturable absorption property and high water-solubility. In this paper, we prepare saturable absorber (SA) device by depositing GO-COOH nanosheets aqueous solution on a D-shaped ?ber. The modulation depth (MD) and saturable intensity of the SA are measured to be 9.6% and 19 MW/cm2, respectively. By inserting the SA into the erbium-doped ?ber (EDF) laser, a passively mode-locked EDF laser has been achieved with the spectrum center wavelength of 1562.76 nm. The pulse duration, repetition rate, and the signal-to-noise ratio (SNR) are 500 fs, 14.79 MHz, and 80 dB, respectively. The maximum average output power is measured to be 3.85 mW. These results indicate that the GO-COOH nanosheets SA can be used as a promising mode locker for the generation of ultrashort pulses.
关键词： nonlinear optical materials,mode-locked pulse,?ber lasers,carboxyl graphene oxide
更新于2025-11-28 14:24:03
-
[IEEE 2018 European Conference on Optical Communication (ECOC) - Rome, Italy (2018.9.23-2018.9.27)] 2018 European Conference on Optical Communication (ECOC) - Ultra-Short Wavelength Operation of Thulium-Doped Fibre Amplifier in the 1628–1655nm Waveband
摘要： We present a silica-based thulium-doped fibre amplifier in the 1628-1655nm waveband based on Tm/Ge co-doped fibre. Up to 19dB external small signal gain and a noise figure of 4.4dB are achieved at 1655nm.
关键词： silica-based,Tm/Ge co-doped fibre,ultra-short wavelength operation,optical communications,thulium-doped fibre amplifier
更新于2025-11-28 14:24:03
-
Passively Q-switched and mode-locked Tm-Ho co-doped fiber laser using a WS2 saturable absorber fabricated by chemical vapor deposition
摘要： We demonstrate a passively Q-switched and mode-locked Tm-Ho co-doped fiber laser based on a WS2 saturable absorber (SA) fabricated by chemical vapor deposition method. When the pump power increases from 0.32 W to 0.38 W, the repetition rate of the Q-switched laser pulse increases 47.1 kHz to 90.1 kHz and the pulse width decreases from 6.2 μs to 1.7 μs. In addition, the mode-locking operation can also be observed by adjusting the polarization controller (PC) and mode-locked laser pulses at 1883.2 nm can be achieved at a high pump power between 0.5 W and 0.64 W. The pulse duration is 1.07 ns and repetition rate is 23.8 MHz and the pulse is the longest mode-locked pulse with WS2-SA ever reported.
关键词： Mode-locked lasers,Optical fiber lasers,Ultrafast optics
更新于2025-11-28 14:24:03
-
Polarization induced non-reciprocal phase controlled all-fiber loop mirror based inclinometer
摘要： An optical fiber inclinometer based on non-reciprocal phase change effect in a single-mode fiber loop mirror (FLM) is proposed. The phase of light waves in FLM is controlled by two-phase shifters (PSs). The relationship between the inclination angles and phase differences of the two-PSs, and transmitted light power was derived by Jones calculus. The signature of the birefringence obtained through simulation on the output light has been confirmed by experimentation. From the results, it was found that when the birefringence of the two-PSs are different, two measurement sensitivities (17.07 × 10?3 deg?1 and 21.37 × 10?3 deg?1) can be realized with one angle measurement system. We also report a method for changing measurable ranges, and measurement sensitivity. Since the angle can be directly measured from the transmitted light power, the results of this work contribute to the realization of simple and low-loss inclinometers using standard single-mode fiber.
关键词： Optical fiber inclinometer,Tilt measurement,Fiber optics,Sagnac interferometer,Fiber loop mirror
更新于2025-11-28 14:24:03
-
An All-Optical, Actively Q-Switched Fiber Laser by an Antimonene-Based Optical Modulator
摘要： Q-switched ?ber lasers are of great interest in industrial material processing, nonlinear frequency conversion, spectroscopy etc. However, passive Q-switching possesses drawbacks of degradation and failure of the saturable absorber and the di?culty in accurate modi?cation of the repetition rate. To overcome these issues, active Q-switching that can normally modulate the cavity quality-factor by an externally-driven Q-switcher is in high demand. Herein, an actively Q-switched laser with antimonene-based all-optical modulator is devised based on the high photo-thermal e?ciency (48%) and broadband response in antimonene. It is demonstrated that this actively modulated laser represents all-optically tunable output parameters (e.g., output repetition rate), environmental stability, and easy synchronization. It is anticipated that this actively antimonene-based all-optical modulator with advantages of large modulation depth, low energy consumption, and high conversion e?ciency has great potential in all-optical information processing and pulsed laser engineering.
关键词： actively Q-switching,antimonene,2D materials,all-optical modulators
更新于2025-11-28 14:24:03
-
A single-longitudinal-mode narrow-linewidth dual-wavelength fiber laser using a microfiber knot resonator
摘要： A stable narrow-linewidth dual-wavelength single-longitudinal-mode (SLM) erbium-doped fiber laser is demonstrated using a microfiber knot resonator (MKR). A MKR made by the microfiber knotting method exhibits the characteristics of flexibility, high quality factor and broad free spectral range and can be used as a comb-like ultra-narrow band pass filter. SLM operation of the fiber laser can be generated as a function of the Vernier effect by cascading a 650 μm diameter MKR in the ring cavity. In combination with a common fiber Bragg grating, narrow linewidths (0.016 nm and 0.019 nm) of dual wavelength are generated. Finally, a SLM ring laser with narrow linewidth and low-frequency noise is achieved. Simultaneous generation of first- and second-order optical vortex beams in the dual-wavelength fiber laser using different mode-selective couplers is demonstrated.
关键词： fiber lasers,fiber optics,optical communication
更新于2025-11-28 14:24:03