Interference filters for temperature sensing, liquid detection and mode-locked laser applications / Yang Yaoxian

Yang , Yaoxian (2024) Interference filters for temperature sensing, liquid detection and mode-locked laser applications / Yang Yaoxian. Masters thesis, Universiti Malaya.

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Abstract

Interference filter, also known as a thin film filter or dielectric filter, is an optical device that selectively transmits or reflects specific wavelengths of light according to the principle of interference. As an advanced optical transmission and sensing technology, optical fiber technology plays a key role in communication, sensing, medical, industrial and scientific fields. This paper aims to discuss the principles and diversified applications of some of these technologies. One of the most widely utilised approaches in substance detection is optical sensor detection. Through the interaction of the sample on the wave characteristics of light, the absorption spectrum, scattering spectrum and transmission spectrum are analyzed to determine the properties of the material composition. This detection method is not only simple to operate, but also has the advantages of high accuracy, non-contact, fast detection speed and high sensitivity. The researchers found that based on the fiber conduction characteristics and the interaction between light and matter, the light signal results can be analyzed to determine the material composition and other properties of the test sample. In this paper, the sensitivity of microfiber sensing technology and Singlemode-Multimode-Singlemode (SMS) fiber structure based on step large-core multimode fiber in temperature and refractive index sensing is discussed. The microfiber ring resonator (MRR) structure based on flame heating conical stretching technology has great research potential in the field of sensing. In this paper, a MRR sensor with a ring diameter of about 400μm and an optical fiber diameter of about 2μm has been successfully prepared. At the same time, the standard single-mode fiber (SMF-28) and the advanced multimode fiber (MMF-S105/125-22A) are fused together, and the SP- DSMSFR sensor is fabricated by side-grinding D-shape grinding in the centre of the multi-mode fiber. The experiments of temperature change, different solution and glycerin solution were carried out on the two sensors respectively. Compared with the experimental results, both sensors have good detection performance and have the potential to be used as solution detectors. In addition, SMS fiber is integrated into the ring cavity of an erbium-doped fiber laser (EDFL) as a saturable absorber (SA). A stable mode-locked pulse laser is obtained.

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