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Refractive Index Measurement of Lithium Ion Battery Electrolyte with Etched Surface Cladding Waveguide Bragg Gratings and Cell Electrode State Monitoring by Optical Strain Sensors
摘要： In this scientific publication, a new sensor approach for status monitoring, such as state of charge and state of health, of lithium ion batteries by using special Bragg gratings inscribed into standard optical glass fibers is presented. In addition to well-known core gratings, embedded into the anode of 5 Ah lithium ion pouch cells as a strain monitoring unit, the manufacturing of a surface cladding waveguide Bragg grating sensor incorporated into the cell’s separator, that is sensitive to changes of the refractive index of the surrounding medium, is demonstrated. On the basis of the experiments carried out, characteristics of the cell behavior during standard cyclization and recognizable marks in subsequent post-mortem analyses of the cell components are shown. No negative influence on the cell performance due to the integrated sensors have been observed; however, the results show a clear correlation between fading cell capacity and changes of the interior optical signals. Additionally, with the novel photonic sensor, variations in the electrolyte characteristics are determinable as the refractive index of the solution changes at different molar compositions. Furthermore, with the manufactured battery cells, abuse tests by overcharging were conducted, and it was thereby demonstrated how internal battery sensors can derive additional information beyond conventional battery management systems to feasibly prevent catastrophic cell failures. The result of the research work is an early stage photonic sensor that combines chemical, mechanical and thermal information from inside the cell for an enhanced battery status analysis.
关键词： lithium ion,battery aging,cladding waveguide,battery electrolyte,optical sensors,battery safety,fiber Bragg grating,electrode active material,status monitoring
更新于2025-11-28 14:23:57
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Femtosecond Laser Written Depressed-Cladding Waveguide 2 × 2, 1 × 2 and 3 × 3 Directional Couplers in Tm3+:YAG Crystal
摘要： Ion-doped crystal-based compact devices capable of beam splitting and coupling are enthralling for a broad range of classical and quantum integrated photonics applications. In this work, we report on the fabrication of depressed-cladding waveguide 2D 2×2, 1×2 and 3D 3×3 directional couplers in Tm3+:YAG crystal by femtosecond laser writing. The performances of the couplers are characterized at 810 nm, showing single-mode guidance, polarization independence, ?nely matched splitting ratios. These results open up new opportunities in the bene?cial fabrication of 3D circuits and devices in crystals.
关键词： crystal,femtosecond laser writing,directional coupler,depressed-cladding waveguide,integrated photonics,yttrium aluminum garnet,quantum memory
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - An Increase in Refractive Index Contrast in a Waveguide Inscribed in Tellurite Glass by Means of Sub-Nanosecond Bursts of Femtosecond Pulses
摘要： Femtosecond laser direct writing (FLDW) of waveguides in dielectric glasses and crystals is well-recognized technique for manufacturing of compact laser sources, optical sensors, labs-on-a-chip and optical chips for quantum computing [1]. For this technology the main obstacle to compaction of optical circuits and an increase in the number of elements on an optical chip is constraint of the refractive index contrast Δn between the core and the cladding of a waveguide that is given by the nature of FLDW. Insufficient RIC also restricts application of the depressed cladding waveguides in mid-IR due to mode leakage [2]. The largest ever-obtained refractive index change is associated with ion migration in a phosphate glass under the thermal regime of laser writing, and it is as high as +0.03 [3]. Recently we found that simultaneous actions of rarefaction and electronic excitation lead to enhanced negative refractive index change in the laser modified spots in silica glass and sapphire [4], wherein the required conditions were produced by a sub-nanosecond burst of femtosecond laser pulses. Here we report on FLDW of a low loss waveguide with enhanced refractive index contrast in 70TeO2-22WO3-8Bi2O3 glass inscribed by bursts of pulses with exponentially decaying amplitudes in each burst and pulse separation of 10 ps. The depressed cladding waveguide composing of 14 parallel tracks with reduced refractive index was inscribed at wavelength of 1030 nm (Fig.1.(a)). The maximum refractive index change Δn produced by train of ordinary pulses in the investigated glass was as high as -0.002 [2]. Mapping of refractive index change in tracks inscribed by the bursts with different burst energies and pulse separation intervals is shown in Fig.1(c) The range of the parameters was found for which the burst produced smooth tracks of negative refractive index change, and its amplitude is increased by factor of 3 in comparison with tracks inscribed by ordinary pulses. The maximum index change Δn was obtained with pulse separation interval of 10 ps. Beside enhanced refractive index change the burst train inscribed tracks with reduced cross section. That is, the track height is less at least by a factor of 3 in comparison with one inscribed by ordinary pulses under the same energy for a burst and an ordinary pulse (Fig1(a),(b)). We consider that the enhanced index change and the reduced track height are inevitably accompanied by strong localization of energy deposition through a reduction in peak pulse intensity that allowed avoiding destructive Kerr self-focusing. We consider that the new technique of FLDW paves the way for better confinement of radiation in a depressed cladding waveguide writing waveguides with well deterministic architectures. The increase in the waveguide non-linearity and extension of operation range to mid-IR is inevitably expected.
关键词： sub-nanosecond bursts,tellurite glass,depressed cladding waveguide,refractive index contrast,Femtosecond laser direct writing
更新于2025-09-12 10:27:22