Development of polymer optical waveguide-type alcohol sensor

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 n2 of cladding layer was set at slightly larger value than that of core (n1). 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 n1 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.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.