Efficient Batch Fabrication of High-Quality Microfiber Bragg Grating Sensors Using Alkaline Corrosion

Fabrication method plays a crucial role in fabricating high-quality microfiber Bragg grating (MFBG) sensors. The chemical etching method, especially with hydrofluoric acid (HF), is commonly used but has security concerns. This study introduces and evaluates a novel method using an alkaline (NaOH) solution under hydrothermal conditions as an alternative. Key parameters are assessed and include cost, safety, etch rate, microfiber surface roughness, diameter uniformity, mechanical strength, and sensing performance. The results reveal that while the HF etching method shows a faster corrosion rate, the NaOH etching method produces microfibers with ultralow surface roughness (<25 nm) and high-precision diameter uniformity, attributed to constant temperature and uniform vapor pressure. Surface roughness is reduced by 20 times compared to HF etching. Additionally, ten microfiber sensors with diameters of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5~\mu $ </tex-math></inline-formula>m and a diameter error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 0.15~\mu $ </tex-math></inline-formula>m were successfully fabricated using the NaOH etching method, demonstrating its capacity for batch production. Conversely, HF etching creates surface pits, negatively impacting tensile strength and spectral quality of microfibers. Collectively, these findings provide a new perspective on the fabrication of high-quality microfiber sensors.