Refractive index sensitivity

Fig. 3.8 Effective refractive index sensitivity to overlay RI changes vs. overlay thickness for different cladding modes...

As a preliminary test, the experimental setup just described was used to characterize the bare LPG. In Fig. 3.15 it is reported that the central wavelength and the transmission loss peak of the attenuation band centred around 1,300 nm (related to the cladding mode LP06) as a function of the SRI. The refractive index sensitivity of the bare LPG was found to be 5.06 nm/RIU (refractive index units) and 3.59 dB/ RIU, around the water refractive index, in terms of wavelength shift and amplitude... 

Fig. 21 Comparison of refractive index sensitivity for Ag nanoparticles with different geometries. The spherical nanoparticle ( ) has a sensitivity of 161 nm per RIU, the triangular nanoparticle (A) has a sensitivity of 197 nm per RIU, and the rodlike nanoparticle ( ) has a sensitivity of 235 nm per RIU. Reproduced with permission from [41]. Copyright 2003 American Chemical Society...

The detector. The parameters that have to be checked are wavelength accuracy detection, refractive index sensitivity, linearity, spectral quality (PDAD) short-term or long-term noise, drift, and flow sensitivity. 

The refractive index sensitivity affects gradient analysis and should be checked by measuring the absorbance when the cell is filled with methanol (n = 1.329) and cyclohexane (n = 1.427) at 270 nm. 

Here, m is the refractive-index sensitivity of the sensor Uadsorbate and Ubiank are the refractive indices of the adsorbate (i.e., analyte) and the bulk environment prior to the sensing event, respectively (iadsorbate is the effective thickness of the adsorbate layer and k is the characteristic electromagnetic field decay length associated with the sensor. 

Flat-surface SPR sensors have a large refi-active-index sensitivity ( 2 x 10 nm/RIU), which is the chief component of their overall sensitivity [54]. LSPR nanosensors have modest refractive-index sensitivity ( 2 x 10 nm/RIU) [55], in contrast. Nevertheless, both types of sensors have approximately equivalent sensitivity for a given adsorbate. In addition to the difference in refractive-index sensitivity, the electromagnetic field decay length Zdis also different for SPR and LSPR sensors. SPR sensors have a decay length on the order of 200 nm. For LSPR... 

Chong J, Shum P, Haryono H, Yohana A, Rao M, Lu C, Zhu Y (2004) Measurements of refractive index sensitivity using long-period grating refractometer. Opt Commun 229 65-69... 

BRIS Bulk refractive index sensitivity BSA Bovine semm albumin... 

By employing the approximate expressions for the bulk refractive index sensitivity of the effective index Eq. 58 and low-loss metal approximation of Ipd (Eq. 48), Eq. 63 can be reduced to ... 

In the following section, sensitivity of the sensor output to effective index of a surface plasmon is analyzed for selected sensor configurations, and the merit of different SPR sensor configurations in terms of bulk refractive index sensitivity is evaluated. 

Fig. 11 Bulk refractive index sensitivity as a function of wavelength for SPR sensors with wavelength modulation and prism coupler or grating coupler and three different grating periods. Prism-based sensor configimation BK7 glass prism, gold film, and a non-dispersive dielectric (refractive index 1.32). Grating-based sensor configuration a non-dispersive dielectric (refractive index 1.32) and gold grating...

The bulk refractive index sensitivity can be calculated from the instrumental sensitivity in a similar fashion as in previous sections for the angular and wavelength modulation. The sensitivity to bulk refractive index can be expressed as ... 

H. Chen et ah, Shape- and size-dependent refractive index sensitivity of gold nanoparticles, Langmuir, 24(10), 5233-5237 (2008). 

The molecular weights were determined on a Waters ISO GPC using a set of Waters Ultrahydrogel 120,250,1000, and 2000 columns (7.8 x 300 nun). Mobile Phase was 80 20 watenacetonitrile with 0.10 M sodium nitrate. Flow Rate 0.8 ml/min. (nominal). Column Temperature 35 C, Sample concentration 1.6 - 2.0 mg/ml. Injection Volume 200 pi. Detection Differential Refractive Index, Sensitivity -128, Calibration narrow PEO and PEG standards, MW = 963,000 to 620 (Polymer Laboratories, Amherst, MA). 

A systematic comparison of the methods should include the simulation of the several (the more—the better) test problems by these methods running on the same hardware. Such comparisons were performed for dielectric particles, see, e.g. Refs. [20-22], but they are not relevant for the plasmonics. On contrary, in plasmonics such comparisons are very rare. We can cite three examples, which both considered a single specific scattering problem, making it hard to generalize the conclusions. In particular, the FDTD and the FEM were compared for computation of near-field around 50-nm silver cube interacting with 600-nm plane-wave [12]. Accuracy of the FEM was worse than that of the FDTD but still satisfactory. The FEM simulation required 4 hours on a single 3.4 GHz processor, while FDTD—8 hours on 256 double-core 2.6 GHz processors. Another comparison [14] addressed the DDA and the FIT (the latter implemented in the commercial software) for simulation of refractive index sensitivity of rhombic hybrid Au-Ag nanostructure array. Both methods obtained the same value of sensitivity, but the DDA was faster (not specified how much). 

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