Trench Type Fiber Optic Biosensor

in National workshop (full text oral presentation), 國內研討會(全文口頭發表)
標題Trench Type Fiber Optic Biosensor
AuthorsWei Te Wu(Benny), 吳瑋特
出版日期Oct 21 2011 12:0

Due to the flourishing development of the optical communication in recent years, people enjoy more convenient and faster data transferring speed. At optical communication industry, optic fibers are a part of the passive hardware components. Because the optical fiber has more benefits compared with traditional cable in data communication, such as low loss and more suitable for long-distance transmission. Just as the name implies, optic fibers play the core component in the fiber optics sensors.
Optical fiber needs to modify the structure in sensing application areas. There are several kinds of structure to achieve sensing requirements, such as fiber grating sensors, interferometer and trench type fiber optic sensors. We proposed the concept of trench type fiber optic sensors, in fact, it is the simplest structure. We remove some parts of fiber cladding layer in order to interaction with environment under the basic attenuated total reflection (ATR) principle. Moreover, we can modify functional materials on the exposed fiber core, such as nanoscale gold film and noble metal nanoparticles. Functional materials make fiber optic sensors different sensing scheme; nanoscale gold film inducing surface plasmon resonance (SPR) [1] and noble metal nanoparticles inducing particle plasmon resonance (PPR) [2-3].
In order to fabricate the proposed trench type fiber sensors, we introduce the femtosecond laser machining technique. The most prominent features of the femtosecond laser over conventional long-pulsed laser are ultra short pulse duration and very strong peak power intensity, which can photo-induce the non-linear multi-photon absorption of the material during irradiation interaction. The material vaporizes immediately after absorbing ultra high transient pulse energy from the ultra short pulse of femtosecond laser. It can be used to engrave on transparent, hard and brittle materials very precisely, such as silica-based optical fibers, without inducing any micro cracks and heat affected zone. We just use this mechanism to create one or more exposed structure.
Trench type fiber optic sensors which we had manufactured including U-shaped optical fiber which is shown in figure 1(a) [4]. It is a pity that tiny space of the U-shaped trench hard for air escaping and introduces the micro-loading effect. Therefore, we redesigned and scale-up the trench as D-shaped optical fiber for solving the above problem. D-shaped optical fibers are shown in figure 1(b) [5]. Moreover, in order to reach the synchronization multitargets sensing, we proposed the concept of multitrench sensors and multiphase sensors for enhancing the mixing in low Re situation. Multiphase sensor is shown in figure 1(c) [6].
In order to estimate the performance of fiber-optic sensors, we establish a refractive index sensing experimental, shown in figure 2 is an illustration of the experimental setup for refractive index sensing measurements The fiber-optic sensing system was used to measure the transmission power of the sensor was consisted of a function generator, a LED light source, a sensing fiber, a microfluidic chip, a photodiode, a lock-in amplifier and a computer for data acquisition. The refractive index and concentration for sucrose solution in the range of 1.333 to 1.403 [6]. We modify gold nanoparticles in the 6 mm sensing length of the fiber optic sensor, and the sensing scheme changes from ATR to the PPR scheme. We summarize the related sensing capabilities of all kinds of trench type fiber optic sensors fabricated by us are shown in table 1.

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