| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 738890 | Sensors and Actuators A: Physical | 2015 | 6 Pages |
•We have improved optical sensitivity of FBG-based UV sensor with downsizing the diameter.•We have also enhance the sensitivity of the FBG configuration in combination of a UV transmitting cylindrical lens.•UV light induces a strain change of the functional polymer as fiber coating material and it makes the FBG stretched.•We use Azobenzene containing polymer as a mechanically stretchable material by UV light.•We measured the spectral response of the azobenzene coating material related to the absorption spectrum of the material.
We previously reported an ultraviolet (UV) optical sensor based on a fiber Bragg grating (FBG) coated with an azobenzene polymer [18] (Kim et al., 2010). UV light strains the coating material, leading to a change in the grating period and a resulting shift in the central wavelength. However, the induced strain was very small, resulting in a small wavelength shift. Here, we improved the sensitivity of this UV sensor by reducing the grating diameter and adding a UV-transparent cylindrical focal lens. The UV-induced strain greatly increased with smaller diameters. UV sensitivity was inversely proportional to the grating diameter squared. The UV-induced wavelength shift variation for the sensor was also modified by etching the grating. The UV lens focused the rays onto the polymer-coated area to maximize UV absorption. In addition, the proposed sensor has a wide measurable wavelength range from 230 to 450 nm, depending on the UV absorption performance of the azobenzene polymer.
