Organic Contaminants Sensor Based on Microfiber Grating

Recently, the monitoring and cleaning of contaminants deposited on the surfaces of advanced optical components has attracted increasing attention. We proposed a scheme for monitoring organic contaminants using microfiber Bragg grating (MFBG). Since MFBG is covered by an organic contaminant film, the central reflection wavelength will be red-shifted. Theoretically, we numerically simulated the relationship between the offset of MFBG central reflection wavelength and the thickness of the organic contaminants, which indicates pronounced linearity. Moreover, the sensitivity can be further improved as the cladding diameter of MFBG decreases. Technically, MFBGs with diameters of
$8.02~\mu $
m,
$9.80~\mu $
m and
$10.01~\mu $
m, were fabricated by etching fiber Bragg gratings (FBGs) with 10% mass concentration HF solution. Additionally, we experimentally demonstrated the effectiveness and immediacy of our scheme. When the diameter of MFBG is about
$8~\mu $
m, the sensitivity is 3.5 pm/nm, which is consistent with the theoretical simulation results. According to the resolution of the grating demodulator, the minimum measurable surface mass density is 24.92 ng/mm
²
. As for the fiber with a diameter of
$9.90~\mu $
m, the sensitivity is 0.5 pm/nm and the minimum measurable surface mass density is 174.44 ng/mm
²
. The results suggested a feasible route to realizing the effective monitoring of organic contaminants.