Launch vehicles and other satellite users need launch services that are highly reliable, less complex, easier
to test, and cost effective. Being a very small molecule, hydrogen is prone to leakage through seals and
micro-cracks. Hydrogen detection in space application is very challenging; public acceptance of
hydrogen fuel would require the integration of a reliable hydrogen safety sensor. For detecting leakage of
cryogenic fluids in spaceport facilities, launch vehicle industry and aerospace agencies are currently
relying heavily on the bulky mass spectrometers, which fill one or more equipment racks, and weigh
several hundred kilograms. Therefore, there is a critical need for miniaturized sensors and instruments
suitable for use in space applications.
This paper describes a novel multi-channel integrated nano-engineered optical sensor to detect hydrogen
and monitor the temperature. The integrated optic sensor is made of multi-channel waveguide elements
that measure hydrogen concentration in real Time. Our sensor is based on the use of a high index
waveguide with a Ni/Pd overlay to detect hydrogen. When hydrogen is absorbed into the Ni/Pd alloy
there is a change in the absorption of the material and the optical signal in the waveguide is increased.
Our design uses a thin alloy (few nanometers thick) overlay which facilitates the absorption of the
hydrogen and will result in a response time of approximately few seconds.
Like other Pd/Pd-Ni based sensors the device response varies with temperature and hence the effects of
temperature variations must be taken into account. One solution to this problem is simultaneous
measurement of temperature in addition to hydrogen concentration at the same vicinity. Our approach
here is to propose a temperature sensor that can easily be integrated on the same platform as the hydrogen
sensor reported earlier by our group. One suitable choice of material system is silicon on insulator (SOI).
Here, we propose a micro ring resonators (MRR) based temperature sensor designed on SOI that
measures temperature by monitoring the output optical power.
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