3. Interrogation of plasmonic TFBG immunosensors
Transmitted amplitude spectra of gold-coated TFBGs were recorded
by means of an optical vector analyzer from Luna Technologies,
which was chosen for both its high measurement resolution
(1.25 pm) and fast scanning rate (1 s to cover the full TFBG spectrum).
This analyzer gathers a narrowband tunable laser source and a
detector. It can work either in transmission or in reflection. A linear
polarizer was placed behind the optical source to control and orient
the state of polarization (SOP) of the light launched into the TFBG. It
is worth mentioning that care was taken to avoid polarization instabilities
(use of short fiber lengths, strong curvatures avoided and
ambient temperature kept constant to within 1 °C).
Fig. 3 depicts the orthogonally-polarized transmitted amplitude
spectra of a gold-coated TFBG immersed in salted water