Microstructured and Photonic Bandgap Fibers for Applications in the Resonant Bio- and Chemical Sensors
Figure 7
Planar photonic bandgap waveguide-based SPR sensor. (a) Schematic of a sensor. Low refractive index core is surrounded by the periodic photonic crystal reflector. Top side of the reflector is goldplated for plasmon excitation. Gold layer is bordered by aqueous analyte. field distribution in the fundamental core mode is shown on the right, while field distribution in a plasmonic mode is show on the left of a sensor schematic. (b) Band diagram of sensor modes. Dispersion relation and field distribution of the fundamental core mode (thick solid curve), and plasmonic mode (dashed curve). TM bandgap of a periodic reflector is shown as a clear region, while gray regions correspond to the continuum of the bulk reflector states. By design, the effective refractive index of a core-guided-mode can be made significantly smaller than that of the waveguide core material. (c) Upper part: solid curve shows loss of a waveguide core mode near the phase matching point with a plasmon at which modal loss peaks. Dashed line shows shift of the modal loss curve when refractive index of the analyte is varied. Lower part: dependence of the sensor amplitude sensitivity on wavelength.
