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Cascaded Mach-Zehnder interferometers with Vernier effect for gas pressure sensing
摘要： We propose a compact ultrasensitive gas pressure fiber sensor based on cascaded Mach-Zehnder interferometers (MZI) with Vernier effect. Each MZI is composed of a hollow core fiber (HCF) sandwiched in between two short multimode fibers (MMF). The lengths of the HCFs in the two MZIs are set a little different in order to generate an envelope in the transmission spectrum of the cascaded structure for Vernier effect sensing. The HCF in one MZI is opened to make the air hole connect to the external environment and act as sensing element. The HCF in the other MZI is kept closed serving as reference element. The two MZIs have quite different responses to changes in gas pressure, but have almost the same response to temperature variation. Therefore, the Vernier effect occurs when the gas pressure changes, but not when the temperature varies. As a result, the proposed structure has an ultra-high gas pressure sensitivity with a quite low temperature cross-sensitivity. Experimental results show that the gas pressure sensitivity referring to the envelope of the proposed sensor is -73.32 nm/MPa in the range of 0 - 0.8 MPa, with a temperature cross-sensitivity of only 0.72 kPa/°C.
关键词： Vernier effect,gas pressure,Hollow core fiber,Mach-Zehnder interferometer
更新于2025-11-28 14:23:57
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Laser Cutting Parameters Effect on 316L Stainless Steel Surface
摘要： Laser cutting is a cutting technology that enables fast processing in high precision. This technology utilizes high temperatures generated by engine to perform the cutting process. Selection of cutting parameters becomes the main factor to determine the cutting surface quality. Cutting parameters in the form of cutting speed and gas pressure are varied between 60 mm/minute - 100 mm/minute and 17 bar - 21 bar to examine the effect on surface character. The character of the laser-cutting surface on 316L series stainless steel material was observed related to the roughness, hardness and microstructure. The results showed that the parameters of cutting speed and gas pressure had an effect on the cutting surface. Changes in cutting speed has more effect on surface roughness while gas pressure has more effect on cutting surface hardness. Observations on the surface also illustrated that there were differences in cutting quality along with the deeper penetration performed by the laser.
关键词： gas pressure,hardness,cutting speed,surface roughness
更新于2025-09-23 15:19:57
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS WITH HIERARCHICAL STRUCTURE FOR NEW TECHNOLOGIES AND RELIABLE STRUCTURES 2019 - Tomsk, Russia (1–5 October 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS WITH HIERARCHICAL STRUCTURE FOR NEW TECHNOLOGIES AND RELIABLE STRUCTURES 2019 - Cutting of aluminum alloys with a Q-switched repetitively pulsed CO2 laser under conditions of intense material evaporation
摘要： The results of an experimental study of laser cutting of aluminum-lithium alloys using a repetitively pulsed CO2 laser with Q-switching under conditions of intense material evaporation are presented. The dependence of cut quality on the assisted gas pressure is determined. It is shown that a high-quality cut with a sheet thickness of 1.5 mm can be obtained at a gas pressure of 0.5–0.6 bar, which is significantly less compared to cutting with a continuous laser power. This makes it possible to reduce the assisted gas consumption. The dependence of cut surface roughness on the pulse repetition rate is measured.
关键词： laser cutting,aluminum-lithium alloys,material evaporation,Q-switched CO2 laser,cut quality,pulse repetition rate,gas pressure
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Cascaded Fabry–Pérot Interferometers with Vernier Effect for Gas Pressure Measurement
摘要： A sensitivity enhanced gas pressure sensor with Vernier effect is proposed in this paper. The sensor is a cascade configuration which two Fabry–Pérot interferometers (FPIs) with different free spectrum range (FSR). Each Fabry–Pérot interferometer is fabricated by inserting a piece of hollow core fiber (HCF) in between two sections of single mode fiber (SMF). Femtosecond laser is applied for drilling an opening on the HCF of sensing FPI to make the air hole interact with outside environment, while the air hole of the reference FPI is kept closed. Gas pressure response is measured by monitoring the wavelength shift of the envelope extracted from the superimposed spectrum of the cascaded FPIs. Experimental results show that the sensitivity of the cascade configuration can attain -65.482nm/MPa, which is -13 times of single sensing FPI.
关键词： Vernier effect,Fabry–Pérot interferometer,gas pressure
更新于2025-09-16 10:30:52
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An Experimental and Theoretical Comparison of Plasmonic Properties of Metallic Nano-Particles Have Different Morphological Properties
摘要： In this study, we have grown some plasmonic metal-nanoparticles have different morphological properties on the microscope slide and silicon wafer as substrates depending on an ambient background gas pressure and number of laser pulses by using Pulse Laser Deposition (PLD) technique in connection with a nanosecond Nd:YAG laser system. The morphology of these nanoparticles thin film was investigated by Atomic Force Microscopy. UV-vis spectra have shown that plasmonic metal- nanoparticles present a Localised Surface Plasmon Resonance band in visible and near-infrared (NIR) regions depending on the morphologic structure of the nanoparticles thin film. The LSPR of the plasmonic metal nanoparticles was calculated theoretically using Boundary Element Method simulation programme. The reliability of experimental results was verified by comparing the theoretical results with their experimental counterparts produced by using PLD, both were obtained in this work. Both theoretical and experimental results and their comparison have been presented and discussed in this study, and a conclusion has been made that the theoretical and experimental results for Cu were in all good agreement.
关键词： LSPR,BEM,nanoparticle,gas pressure,PLD
更新于2025-09-12 10:27:22
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Effects of a cathode output aperture on the hollow cathode glow discharge
摘要： Glow discharge with a cylindrical hollow cathode mounted on a process vacuum chamber has been studied in a wide range of gas pressures from 0.01 to 10 Pa. The chamber serves as the discharge anode. A diaphragm is fastened on the cathode end to protect the discharge plasma inside the chamber from contamination with the sputtered cathode material. The discharge characteristics depend on area So of the diaphragm ori?ce. A double layer appears at the ori?ce when So < S* ≈ (2 m/M)1/2S, where m is the electron mass, M is the ion mass, and S is the cathode surface area. Electrons accelerated in the double layer effectively ionize the gas and can produce, inside the chamber, a plasma with the same density as inside the cathode. At the gas pressure less than ～0.3 Pa, the low-voltage double layer can be replaced with a high-voltage accelerating gap between the plasma inside the cathode and the plasma produced inside the chamber by a beam-plasma discharge.
关键词： double layer,hollow cathode,glow discharge,gas pressure,plasma
更新于2025-09-09 09:28:46