Development of Polymer Optical Waveguide-Type Alcohol Sensor

摘要

Recently, alcohols such as methanol and ethanol have a wide attention as important fuel in next generation. However, As is known, many alcohols have a toxic and explosive nature. To prevent accidents caused by alcohol, development of a safety and highly sensitive sensor is required strongly. In addition, it is desired to be simple and low-cost. So, in this paper, polymer waveguide-type optical alcohol sensors such as fiber-type and channel waveguide-type have been studied. In these sensor head, refractive index n_2 of cladding layer was set at slightly larger value than that of core (n_1). Therefore, in the state without alcohol, the sensor head operate as a leaky waveguide. On the other hand in the state with alcohol, cladding polymer causes swelling and its refractive index becomes lower than n_1 in core. Based on this principle, large change in output light intensity occurs and detection of alcohol concentration becomes possible even for vapor phase alcohol. In the experiment using a fiber-type sensor with a core size of 0.25 mm, detection of 1% methanol vapor could easily be obtained. Furthermore, using a channel waveguide-type sensor head with a core size of about 50μm × 40μm, large increase in sensitivity was observed.