The research focuses on metal hydride-coated Tilted Fiber Bragg Grating (TFBG) sensors for hydrogen detection. To overcome hysteresis issues linked to traditional sensing materials like palladium, tantalum (Ta) is introduced as an innovative alternative. The study details the establishment of optical constants for these novel materials via ellipsometry, involving the deposition of a nanometer-scale metal stack on a glass substrate. This thin film stack serves as the adhesion, sensing, and capping layer, enabling the selective absorption and desorption of hydrogen molecules, resulting in discernible changes in optical properties. The research includes comprehensive optical constant data, such as the complex refractive index, derived from ellipsometry measurements. Furthermore, the study incorporates these optical constants into a numerical model, examining mode propagation in TFBG sensors coated with Ta-based hydrogen-sensing materials. It explores mode coupling phenomena, characterizes transverse modes, and delves into key parameters, including electric field profiles, mode field diameters, and grating parameters essential for optimizing sensor performance.
Palladium thin films have been studied as hydrogen sensing materials and applied to variety of optical hydrogen sensors. Recently, tantalum has emerged as an attractive option for hydrogen sensing materials due to its broad sensing range and flexibility in tuning the sensing range by modifying the alloying composition or elements. Following the demand for optical hydrogen sensors for aerospace applications, testing the performance of hydrogen sensing materials is of interest. This work examines the optical response in respect to changing hydrogen concentrations and thermal expansion of palladium-gold (Pd0.65Au0.35) and tantalum-ruthenium (Ta0.97Ru0.03 and Ta0.91Ru0.09) thin films at temperatures similar to a hydrogen combustion engine. Our results suggest that tantalum-ruthenium alloys are suitable for sensing hydrogen from ambient temperatures up to 270°C because its low detection limit (0.01% of hydrogen in the atmosphere) is well below the explosive limit of hydrogen (4% of hydrogen in the atmosphere).
In this paper, the response of a graphene oxide (GO) coated long period grating (LPG) to the change in temperature and in humidity is reported. To create the probe, an improved Hummer’s method was used to synthesis the GO solution used as its basis, allowing coating of functionalized LPG by using a multi-layer dip coating technique. A consistent and stable response of the resonance peak intensity of the GO coated LPG was observed to the change in humidity, achieving a sensitivity of 0.15 dB / %RH with a linear correlation coefficient of 0.9804 over the relative humidity range from 60%RH to 95%RH at room temperature (25 °C). A blue shift of the resonance peak wavelength was recorded when the proposed sensor was exposed to varying temperature conditions from 25 °C to 70 °C and the response was found to be linear with a correlation coefficient of 0.9973. The GO coated LPG humidity sensor probe performed with a good stability and repeatability over a number of test cycles in this initial performance evaluation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.