Differential quartz-enhanced photoacoustic spectroscopy

To address the issues of low ratio of evanescent field (γ) and high reflectivity between waveguide cross‐section and gas for the mid‐infrared waveguide sensors, we propose a chalcogenide (ChG) suspended waveguide with Ge28Sb12Se60 as the core layer and silica (SiO2) as the buffer layer. The SiO2 beneath the waveguide core ridge structure is removed to create suspended structure. The waveguide sensing performance is obtained using a 10% methane (CH4) sample. The fabricated waveguide exhibits a γ of 112%, which is a 10% improvement compared to a free‐space optical sensor with the same optical path length. The good agreement between the theoretical and experimental results of γ confirms the reliability of our theoretical investigation approach. The influences of fabrication error, environmental temperature, and pressure on sensing performances are discussed. This work provides theoretical guidance for designing waveguide structures with large γ, contributing to the further enhancement of on‐chip sensor performance.

Section: Introductionmentioning

confidence: 99%

Theoretical and experimental investigation of chalcogenide suspended waveguide gas sensor

Huang,

Wang,

et al. 2023

“…At present, various salinity sensors have been designed and manufactured by researchers based on different optical fiber sensing principles. Various salinity sensors based on fiber gratings, [16][17][18] surface plasmon resonance, [19][20][21] fiber resonators, 22,23 and optical fiber interferometers, [24][25][26][27] and so forth have been proposed and designed. For instance, Zhang and colleagues proposed and optimized a salinity sensor combined with grating fiber in 2003, but its salinity sensitivity was only 10.4 pm/‰.…”

Section: Introductionmentioning

confidence: 99%

Parallel dual‐cavity fiber‐optic F‐P salinity sensor based on hollow core fiber and ceramic ferrule

Sun

Yang

et al. 2023

A parallel dual‐cavity fiber‐optic Fabry‐Perot (F‐P) salinity sensor based on hollow core fiber and a ceramic ferrule is proposed. The sensor is comprised of a F‐P reference cavity and a F‐P sensing cavity in parallel. The reference cavity is a closed cavity that is fusion spliced with a segment of single‐mode optical fiber (SMF) and a small piece of silica tube (ST). The sensing cavity is an open liquid cavity that is connected by a ferrule after inserting two single‐mode fibers into a ceramic core, facilitating the replacement of salt water. Variations in the salinity of salt water will affect the change in refractive index of optical path, and then change the output spectral structure. By precisely controlling the length of two cavities, the free spectral range (FSR) of the sensing cavity is approximately equal to the FSR of the reference cavity, resulting in the generation of the Vernier effect, which improves the sensitivity of the sensor to salinity greatly. From the experimental results, it can be seen that the sensor sensitivity to salinity reaches −0.78 nm/‰ (−3809.68 nm/RIU) in the salinity range from 35‰ to 20‰ at room temperature of 25°C, which is 10.8 times higher than the sensitivity of a single sensing cavity. The enhancement factor is generally consistent with theoretical analysis results.

“…The lasers operating at 2 μm spectral region have many attractive applications, such as sensing, [1][2][3][4] wind light detection and ranging, [5][6][7][8][9] medical processing, [10][11][12][13] analytical atomic and molecular spectroscopy, [14][15][16] and pumping for ZnGeP 2 optical parametric oscillator (ZGP OPO) to generate 3-5 μm mid-infrared (IR) laser 17,18 and 8-12 μm long-wave laser. 19 Rare-earth doped vanadate crystals exhibit excellent properties in 2 μm wave band.…”

Section: Introductionmentioning

confidence: 99%

A good beam quality Ho:GdVO₄ laser pumped by thulium‐doped fiber laser at 1940 nm

Yang,

Li,

Zheng

et al. 2023

We demonstrate a Ho:GdVO4 solid‐state laser pumped by a thulium (Tm)‐doped fiber laser at 1940nm. In continuous wave mode, a maximum output power of 6.1 W was obtained under the absorbed pump power of 31.9 W with the slope efficiency of 24.3% at the temperature of 18°C. The wavelength of output laser was 2048.53 nm with full width at half maximum of 0.2 nm. In Q‐switched mode, a maximum single pulse energy of 0.94 mJ was obtained with a minimum pulse duration of 7.3 ns at the pulse repetition frequency of 5 kHz, corresponding to a peak power of 129 kW and an average output power of 4.7 W. The beam quality factor of M2 was 1.01 under the maximum absorbed pump power. To the best of our knowledge, 0.94 mJ is the highest single pulse energy in single holmium (Ho) doped GdVO4 laser pumped by Tm‐doped fiber laser at 1940 nm, and 1.01 is the best beam quality factor of M2 in Ho:GdVO4 laser pumped by a Tm‐doped fiber laser.