TY - GEN
T1 - Investigation of a micro-optical species concentration sensor concept based on whispering galley mode resonators
AU - Das, Nirod
AU - Ioppolo, Tindaro
AU - Volkan Otugen, M.
PY - 2007
Y1 - 2007
N2 - This paper investigates the feasibility of a micro-optical sensor for species concentration. A theoretical analysis was carried out to model the sensor performance followed by a series of experiments. The measurement concept is based on optical mode shifts of dielectric spheres with diameters of the order of 100 μm. The optical modes, which are also called the "whispering gallery modes" (WGM), are excited by coupling light into the sphere using an optical fiber. A change in the index of refraction of the medium surrounding the sphere induces a shift in the optical modes of the sphere. Therefore, by monitoring the WGM shifts, one can determine the concentration of a given species in the medium surrounding the sphere. In the theoretical analysis, we used a simple, heuristic approach to model the WGMs in the sphere that is based on geometric optics and the basic electromagnetic equations of wave reflection. The resulting equations describe the dependence of WGMs on the refraction index of the surrounding medium. These equations indicate that the WGMs are not sensitive enough to index of refraction changes in the case of gas media. However, they can be sufficiently sensitive for the development of micro-sensors in liquid media. Experiments were carried out to validate the theoretical analysis and to provide a first order assessment of this sensor concept. The concentration of two types of salts, potassium carbonate and sodium bicarbonate were measured in water.
AB - This paper investigates the feasibility of a micro-optical sensor for species concentration. A theoretical analysis was carried out to model the sensor performance followed by a series of experiments. The measurement concept is based on optical mode shifts of dielectric spheres with diameters of the order of 100 μm. The optical modes, which are also called the "whispering gallery modes" (WGM), are excited by coupling light into the sphere using an optical fiber. A change in the index of refraction of the medium surrounding the sphere induces a shift in the optical modes of the sphere. Therefore, by monitoring the WGM shifts, one can determine the concentration of a given species in the medium surrounding the sphere. In the theoretical analysis, we used a simple, heuristic approach to model the WGMs in the sphere that is based on geometric optics and the basic electromagnetic equations of wave reflection. The resulting equations describe the dependence of WGMs on the refraction index of the surrounding medium. These equations indicate that the WGMs are not sensitive enough to index of refraction changes in the case of gas media. However, they can be sufficiently sensitive for the development of micro-sensors in liquid media. Experiments were carried out to validate the theoretical analysis and to provide a first order assessment of this sensor concept. The concentration of two types of salts, potassium carbonate and sodium bicarbonate were measured in water.
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M3 - Conference contribution
AN - SCOPUS:34250845059
SN - 1563478900
SN - 9781563478901
T3 - Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting
SP - 14276
EP - 14286
BT - Collection of Technical Papers - 45th AIAA Aerospace Sciences Meeting
T2 - 45th AIAA Aerospace Sciences Meeting 2007
Y2 - 8 January 2007 through 11 January 2007
ER -