Surface Plasmon Resonance sensor showing enhanced sensitivity for CO_2 detection in the mid-infrared range

Abstract

Abstract:We present the first optical sensor based on Surface Plasmon Resonance (SPR) operating in the mid-infrared range. The experimental setup is based on a Kretschmann geometry with Ti/Au layers deposited on a CaF 2 prism where light excitation is provided by a Quantum Cascade Laser (QCL) source. Evidence of SPR is presented and the sensing capability of the system is demonstrated by using CO 2 and N 2 mixtures as test samples. Due to the absorption of CO 2 at this wavelength, it is shown that the sensitivity of this configuration is five times higher than a similar SPR sensor operating in the visible range of the spectrum.

Large dynamic range SPR measurements using a ZnSe prism

“…The higher index greatly reduces the dispersion in θ SPR between air and water (10° with ZnSe; 28° with borosilicate) which potentially generates other benefits. Higher index SF7 prisms (n ~ 1.7 [18]) have previously been used to reduce the SPR angle for water to  SPR ~ 57° [19]. Other higher index materials have also been used particularly for near and mid-infrared SPR work given many, such as CaF 2 (only slightly higher at n = 1.4339), ZnS, and ZnSe, transmit in this region and SPR resonances are much narrower.…”

“…Other higher index materials have also been used particularly for near and mid-infrared SPR work given many, such as CaF 2 (only slightly higher at n = 1.4339), ZnS, and ZnSe, transmit in this region and SPR resonances are much narrower. For example, CO 2 detection using a mid-infrared SPR sensor and a CaF 2 prism has been demonstrated [19] and long range SPR assisted Goos-Hänchen and Imbert-Fedorov shifts in a ZnSe prism at 1550 nm have been reported [20]. A ZnSe prism was also used in the infrared to monitor phospholipid membrane growth at 632.8 nm, near infrared 1.4-1.5 m and at 10.6 m [21].…”

Exposed core microstructured optical fiber surface plasmon resonance biosensor

“…Other metals, alloys and multilayer systems have also been used to increase sensitivity of SPR sensors. [12][13][14] Other factors, such as thickness of the metallic layer and type of excitation used, may influence sensitivity but to a smaller extent. 11 Increasing sensitivity through lowering the refractive index of a waveguide is a straight forward approach but it results in increase of the line width of SPR curves that in turn increases the resolution and detection limit of the SPR system.…”

Theoretical and experimental study of a 30 nm metallic slot array

“…The two most commonly used techniques are optical fiber based sensors [2][3][4], which can achieve a resolution down to 10 −5 refractive index unit (RIU), and surface plasmon resonance technique based sensors [5][6][7][8], with an obtained resolution as high as 10 −8 RIU [9]. Attempts for miniaturizing these sensors have been done using photonic crystal cavities [10], but decreasing the size of the sensor means decreasing its sensitivity proportionally to the interaction strength between light and analyte.…”