| Summary: | 碩士 === 國立中正大學 === 物理系 === 92 === This thesis utilizes a CO2 laser to fabricate the long period fiber gratings in a point-by-point technique, and study the changes of their resonance wavelengths with different temperature fields and ambient refractive index. The primary purpose is to make a compact and highly sensitive optical fiber sensor, and to study how to increase the sensitivity of such a sensor.
First of all, we study shifts on resonance wavelength and changes on transmission peak depth for the fabricated long period fiber grating under a variety of refractive index of different solution concentrations. Next, a chemical synthesis method was utilized to form gold nanospheres in water, and then those gold nanospheres were modified on the surface of a long period fiber grating for the study of its wavelength shift and peak depth change. Results showed that the slope of wavelength shifts increased from -17.9 (nm / RIU ) to -23.5 (nm / RIU ); while for changes of peak depth, its slope increased from 37.3 (dB / RIU) to 59.3 (dB / RIU ). We have learned that gold nanospheres modified on fiber grating surface can increase its sensitivity on detetcting solution concentrations. Finally, DNP and anti-DNP molecules are used for further investigation. For a fiber grating modified with gold nanospheres we applied the DNP coating on its surface and used it to detect the anti-DNP. The tight bonding of DNP and anti-DNP compounds have made this method not only can increase the sensitivity and accuracy, but also can boarden the application for chemical sensing.
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