We present a low-loss Er 3+ -doped silicate microsphere laser, exploring its temperature sensing characteristics. We measure the threshold power of the Er 3+ -doped silicate glass microsphere laser under 980 nm pumping, achieving an impressively low value of 3.14 mW. Subsequently, in order to study the effect of temperature on the laser, the microsphere laser is placed into a temperature controller, and high-temperature sensitivity of 17.56 pm/℃ is obtained in the experiment. The proposed microsphere is significant for applications in lasing and temperature sensing, offering substantial advantages in terms of lower threshold power and heightened temperature sensitivity.
We demonstrate a high-sensitivity curvature sensor based on the negative curvature hollow core fiber (NCHCF). The graded index fiber (GIF) is introduced between single mode fiber (SMF) and NCHCF for the sensor of cascaded structure of SMF-GIF-NCHCF-GIF-SMF. The coupling efficiency can be improved by cascading the GIF. The experimental results show that there are two coexisted mechanisms in the cascaded structure, where multi-mode interference (MMI) is sensitive to curvature change and anti-resonance (AR) is insensitive to curvature change. The obtained curvature sensitivity based on MMI is up to -4.97 nm/m-1 . With advantages of compactness, flexibility, high sensitivity and so on, the curvature sensor shows prospects in structural health monitoring, medical applications, energy exploration and other fields.
A novel parallel Fabry-Perot interferometer (FPI) assisted by a concave cavity structure and an external reflector, which can be employed for large-range displacement and temperature sensing, is proposed and experimentally demonstrated. Therein, the concave cavity consists of a single mode fiber (SMF), a graded index fiber (GIF) and a hollow core fiber (HCF), which are fusion spliced to realize flat and concave surfaces of SMF-GIF and GIF-HCF, respectively. The certain length of GIF is utilized to serve as an collimator, facilitating the reduction of the divergence angle and the expansion of the mode field radius of the propagating beam. Thus the propagating beam can split into the concave cavity structure’s sidewall and inner air area, when the concave cavity size is smaller than the mode field diameter of the beam from GIF. The external Fabry- Perot interferometer (EFPI), formed by GIF endface and the external reflector, is utilized to detect displacement. Meanwhile, the intrinsic Fabry-Perot interferometer (IFPI), formed by the endfaces of GIF and HCF, serves as a temperature sensor. The length of the silica cavity changes with temperature due to the thermal expansion and thermo-optical effect of silica. In consequence, the corresponding wavelength shift can be accurately observed in response to temperature variations. The experimental results indicate the displacement sensing range of EFPI is up to 30 mm, which is greatly increased compared to other FPI displacement sensors. Moreover, the proposed sensor has a temperature sensitivity of 11.52 pm/◦C in the range of 30◦C 100 ◦C.
This paper summarizes our recent progress on using 3D printing and laser micromachining methods to fabricate optical microsensors for various applications. Optical grade glasses are printed by 3D extrusion and laser sintering. High-precision and high surface quality optical structures of arbitrary shapes are obtained by ultrafast laser micromachining and CO2 laser resurfacing. Combining these advanced manufacturing methods, various optical structures and components can be made with flexible shape and desired accuracy. With unique advantages such as compact size, high thermal stability, and integrated optical functions, these 3D printed structures can be used as sensors for many applications.
In this paper, we report our recent research progresses on the design, fabrication and characterization of photonic sensors for harsh environment applications, with the help of novel Integrated Additive and Subtractive Manufacturing (IASM) system. Glass 3D printing with direct laser melting process in this IASM system presents the dimension accuracy on the order of tens or hundreds of microns. The addition of laser micromachining allows the fabrication of structures with micron dimension accuracy, showing the unique advantage of IASM system in high dimensional accuracy compared with traditional 3D printing process. A number of photonic sensors and devices will be summarized and presented, including (1) 3D printed all-glass fiber-optic pressure sensor for high temperature applications, (2) Information integrated glass module fabricated by IASM and (3) IASM for microfluidic pressure sensor fabrication.
We report a prototype reflection-mode fiber optic probe based on quantum dots filled micro-cavity. The probe was fabricated by sealing quantum dots liquid or coating inside a glass capillary pigtailed with a multimode optical fiber. And the probe was tested for in situ measurement of temperature change. By analyzing the back-reflected fluorescence signals generated from the quantum dots, the localized temperature of the microcavity structure could be correlated. The sensitivities based on fluorescence peak wavelength and full-width at half-maximum (FWHM) were calculated for both sensors in the biologically meaningful temperature range of 33.0-42.0C. This proposed reflection-mode trumpet-shape micro-cavity probe is attractive for chemical and biological sensing because it is cost-effective, simple to fabricate, mechanically robust and miniaturized in size.
In this paper, we summarize our recent research progresses on the understanding, design, fabrication, characterization of various photonic sensors for energy, defense, environmental, biomedical and industry applications. Femtosecond laser processing/ablation of various glass materials (fused silica, doped silica, sapphire, etc.) will be discussed towards the goal of one-step fabrication of novel photonic sensors and new enabling photonic devices. A number of new photonic devices and sensors will be presented.
Optofluid system has been more and more attractive in optical sensing applications such as chemical and biological analysis as it incorporates the unique features from both integrated optics and microfluidics. In recent years, various optofluid based structures have been investigated in/on an optical fiber platform which is referred to as “lab in/on a fiber”. Among those integrated structures, femto-second laser micromaching technique plays an important role due to its high precision fabrication, flexible design, 3D capability, and compatible with other methods. Here we present a ferrofluid based optical fiber magnetic field sensor fabricated by femtosecond (fs) laser irradiation .With the help of fs laser micromaching technique, a micro-reservoir made by capillary tube assembled in a single mode optical fiber could be fabricated. The micro-reservoir functions as a fiber inline Fabry-Perot (FP) cavity which is filled by ferrofluid liquid. The refractive index of the ferrofluid varies as the surrounding magnetic field strength changes, which can be optically probed by the FP interferometer. A fringe visibility of up to 30 dB can be achieved with a detection limit of around 0.4 Gausses. Due to the fabrication, micro-reservoirs can be assembled with optical fiber and distinguished through a microwave-photonic interrogation system. A quasi-distributed magnetic field sensing application has been demonstrated with a high spatial resolution of around 10 cm.
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