Gas environment independent temperature sensor via double-metal surface plasmon resonance

As the sensitivity of the optical temperature sensor increases, one of the most important noise sources may be from the fluctuation of the surrounding gas environment (refractive index change). In this work, we have designed and fabricated an optical temperature sensor with a device size of 15 μm². The sensor is constructed by a titanium dioxide grating on top of a double-metal surface plasmon resonance (SPR) structure. Our design can provide minimal gas environment dependence without compromising the performance in terms of temperature sensitivity. In addition, the design also facilitates a generous dimensional tolerance in the device fabrication. Based on the design, a proof-of-concept device has been fabricated and characterized. The obtained sensitivity of the fabricated sensor reaches 135 pm/℃. Meanwhile, the measured resonance wavelength shift is ∼0.004 pm in different gases (air, CH₄, and CO₂). The presented temperature sensor should be convenient and valuable for high-accuracy temperature measurements and integrated opto-electronic sensing chips.