All Optical Fiber Optofluidic or Ferrofluidic Microsensors Fabricated by Femtosecond Laser Micromachining

Abstract

Research and development in photonic micro-/nanostructures functioned as sensors have experienced significant growth in recent years, fueled by their broad applications in the fields of physical, chemical, and biological quantities. Compared with conventional sensors with bulky assemblies, recent progress in femtosecond (fs) laser three-dimensional (3D) micromachining technique has been proven an effective way for one-step fabrication of assembly-free microstructures in various transparent materials (i.e., fused silica).When used for fabrication, fs laser has many unique characteristics, such as negligible cracks, minimal heat-affected zone, low recast, high precision, and the capability of embedded 3D fabrication, compared with conventional long pulse lasers (i.e., ns laser). The merits of this advanced manufacturing technique enable the unique opportunity to fabricate integrated sensors with improved robustness, enriched functionality, enhanced intelligence, and unprecedented performance. Recently, fiber-optic sensors have been widely used in many application areas, such as aeronautics and astronautics, petrochemical industry, chemical detection, biomedical science, homeland security, etc. In addition to the well-known advantages of miniaturized in size, high sensitivity, immunity to electromagnetic interference (EMI), and resistance to corrosion, fiber-optic sensors are becoming more and more desirable when designed with characteristics of assembly-free and operation in the reflection configuration. Additionally, such sensors are also needed in optofluidic/ferrofluidic systems for chemical/biomedical sensing applications. In this chapter, liquid-assisted laser micromachining techniques were investigated for the fabrication of assembly-free, all-optical fiber sensor probes. All-in-fiber optofluidic sensor and fiber in-line ferrofluidic sensor were presented as examples with respect to these laser processing techniques.