Abstract
A new type of cascaded taper integrated ultra-long-period fiber grating (ULPFG) based immunobiologic sensor has been developed that benefits from the self-assembled monolayer of class I hydrophobin HGFI. Due to the cascaded arc, discharge tapers constitute an ultra-long-period and circular symmetrical refractive index modulation along fiber axial direction, and by local integration in one period, the mode coupling would generate to the higher harmonic of LP(02), LP(03) and LP(04) modes in the wavelength range from 1300 nm to 1620 nm. The hydrophobic characteristic of the ULPFG surface is modified employing the HGFI, and the antibody molecule probes could be absorbed strongly on the HGFI nano-film, furthermore, the performances of immunobiologic sensing are investigated employing multiple control groups of matched and mismatched antigen molecule targets. The results show that it possesses higher sensing sensitivity of 4.5 nm/(µg/ml), faster response time about of 35 min, lower stability error of 8.8%, and excellent immuno-specificity. Moreover, this proposed ULPFG sensor has the advantages of low cost, simple fabrication and label-free, which is a powerful tool in the trace biomedical detection field.