Design of hollow core step-index antiresonant fiber with stepped refractive indices cladding

2023

Front. Optoelectron.

In-fiber whispering gallery mode (WGM) microsphere resonators have received remarkable attention due to the superiorities of compact structure, high stability and self-alignment. As an in-fiber structure, WGM microsphere resonators have been demonstrated in various applications, such as sensors, filters and lasers, which have significant impacts on modern optics. Herein, we review recent progress of in-fiber WGM microsphere resonators, which involve fibers of diverse structures and microspheres of different materials. First, a brief introduction is given to in-fiber WGM microsphere resonators, from structures to applications. Then, we focus on recent progresses in this field, including in-fiber couplers based on conventional fibers, capillaries and micro-structure hollow fibers, and passive/active microspheres. Finally, future developments of the in-fiber WGM microsphere resonators are envisioned. Graphical Abstract

Section: Discussionmentioning

confidence: 99%

Recent progress of in-fiber WGM microsphere resonator

Yang

2023

Front. Optoelectron.

“…Researchers have reported various sensing methods for these decomposed gases, such as gas chromatography, mass spectrometry, infrared spectroscopy, as well as detection tube and carbon nanotube gas sensing, and it is always challenging to achieve a balance between their accuracy and cost [7][8][9][10][11]. Recently, laser spectroscopy, such as Tunable Diode Laser Absorption Spectroscopy (TDLAS) and Photoacoustic Spectroscopy (PAS), has gradually become a hot spot in the field of optical gas sensing, and various techniques have been reported in the literature, such as special optical fibres that are potential gas chambers [12][13][14][15]. Chen et al developed an optical H 2 S sensor based on TDLAS with Wavelength Modulation Spectroscopy (WMS) and obtained the Minimum Detection Limit (MDL) of 20 ppm [16].…”

Section: Introductionmentioning

confidence: 99%

Optical gas sensing of sub‐ppm SO ₂ F ₂ and SOF ₂ from SF ₆ decomposition based on photoacoustic spectroscopy

Wang

et al. 2022

IET Optoelectronics

SF6 has been recognized worldwide as the main insulating gas for Gas‐Insulated Switchgear (GIS). It is often required to accurately and effectively detect typical SF6 decomposition. In this paper, a sub‐ppm‐level SO2F2 and SOF2 gas sensor based on photoacoustic spectroscopy (PAS) is proposed and demonstrated. The steel resonant photoacoustic cell with a resonant frequency of 1750 Hz was designed and fabricated. The harmonic detection technique in wavelength modulation spectroscopy was applied to improve the signal‐to‐noise ratio. A mercury‐cadmium‐telluride photodetector was added in the PAS system to monitor the input optical power, in order to compensate for the errors caused by power fluctuations. SO2F2 and SOF2 were measured by using distributed feedback quantum cascade lasers at 6648 and 7463 nm, respectively. The results show that the proposed sensor performed with favourable linearity within the dynamic range, and reached the minimum detection limit of 0.22 ppm for SO2F2 and 0.28 ppm for SOF2, which indicated its great potential for monitoring the decomposition process of SF6 in GIS.

“…Tunable diode laser absorption spectroscopy (TDLAS) has also been investigated for ultra-sensitive gas detection [ 4 ]. An extended optical gas chamber could be realized by hollow-core optical fibers to achieve ppb-level sensitivity in TDLAS [ 5 , 6 , 7 ].…”

Section: Introductionmentioning

confidence: 99%

Optical Gas-Cell Dynamic Adsorption in a Photoacoustic Spectroscopy-Based SOF2 and SO2F2 Gas Sensor

Wang

et al. 2022

Sensors

SO2F2 and SOF2 are the main components from the decomposition of insulation gas SF6. Photoacoustic spectroscopy (PAS) has been acknowledged as an accurate sensing technique. Polar material adsorption for SO2F2 and SOF2 in the photoacoustic gas cell of PAS may affect detection efficiency. In this paper, the optical gas-cell dynamic adsorptions of four different materials and the detection effects on SO2F2 and SOF2 are theoretically analyzed and experimentally demonstrated. The materials, including grade 304 stainless steel (SUS304), grade 6061 aluminum alloy (Al6061), polyvinylidene difluoride (PVDC), and polytetrafluoroethylene (PTFE), were applied inside the optical gas cell. The results show that, compared with metallic SUS304 and Al6061, plastic PVDC and PTFE would reduce the gas adsorption of SO2F2 and SOF2 by 10 to 20% and shorten the response time during gas exchange. The complete gas defusing period in the experiment was about 30 s. The maximum variations of the 90% rising time between the different adsorption materials were approximately 3 s for SO2F2 and 6 s for SOF2, while the generated photoacoustic magnitudes were identical. This paper explored the material selection for PAS-based gas sensing in practical applications.