Surface plasmon sensor with enhanced sensitivity using top nano dielectric layer

Abstract

Increasing the sensitivity of surface plasmon resonance (SPR) sensors is important to enable controlling small concentrations of materials in liquid solutions or for gas sensing. Upon using a 10-15 nm top layer of dielectric film with a high value of the real part ′ ε of the dielectric function, on top of an SPR sensor in the Kretschmann configuration, the sensitivity is improved by few times. The imaginary part ′′ ε of the top nano layer permittivity needs to be small enough in order to reduce the losses and get sharper dips. The stability of the sensor is also improved because the nano layer is protecting the silver from interacting with the environment. In the near infrared range, the sensitivity is enhanced contrary to the standard SPR mode without top nanolayer. The calculated evanescent field is enhanced near the top layer -analyte interface, thus the enhancement is partially due to this fact and partially due to an increase of the interaction length as a waveguiding effect.

Surface electromagnetic waves: A review

“…This technique can reduce the number of steps and time needed to perform the assays. Other researchers have concentrated on different refinements of detection such as spatially resolved measurements [116], miniaturization [117,118], increased sensitivity [118,119], and microarrays to perform high-throughput multiple assays [120].…”

“…The addition of a dielectric layer [64,119] between the metal and the analyte to be sensed has several benefits: the metal layer is protected, the field intensity is increased at the interface, and, as a result, sensitivity is increased. A thick layer [64] of an additional dielectric layer also allows for excitation with both s-and p-polarized light.…”

Optimized Dielectric Film for Maximum Sensitivity of Nearly Guided‐Wave Surface Plasmon Resonance Sensor

“…Refractive index (n) Extinction coefficient (k) References SF-11L glass 1.73205 0 [14] Ag 0.13 3.99 [14] Si 3.92 0.01 [14] AlAs 3.112 0 [15] TiO 2 2.2789 0 [18] Si 3 N 4 2.019 0 [15] Water 1.33 0 [14] Figure 3. Sensitivity as a function of dielectric film thickness for the NGWSPR sensor with Si, AlAs, TiO 2 , or Si 3 N 4 film.…”

“…Although it has been demonstrated that under the condition of the same thickness of the dielectric film a NGWSPR sensor with a higher refractive index dielectric film can achieve higher sensitivity, [15,19] it is still doubtful whether the dielectric film with higher refractive index is more beneficial for the sensitivity improvement, because the sensitivity of a NGWSPR sensor can be further improved by optimizing the thickness of the dielectric film. [20] So, to achieve the maximum sensitivity for a NGWSPR sensor, the material (or refractive index) and the thickness of the top dielectric film need to be optimized simultaneously, which has not been studied until now.…”

“…In last 2 decades, a few methods were proposed to improve the sensitivity of SPR sensor, for example, using long-range surface plasmons, [7,8] employing graphenebased multilayer structure, [9][10][11][12] and adding grating on top of the metal layer, [13] In 2008 and 2009, great progress was made for sensitivity enhancement by Lahav et al [14,15] They proposed a novel way for sensitivity improvement by using a nearly guided-wave SPR (NGWSPR) sensor, which is similar to the Kretschmann configuration with an addition of a thin dielectric film between the metal layer and the sample (as shown in Figure 1). Nearly four times angular sensitivity has been achieved by adding a 10 nm Si film on top of a conventional SPR sensor.…”