Design and simulation of label-free biosensor based on the dynamic distributed feedback laser emission

Label-free biosensor based on the dynamic distributed feedback (DFB) laser emission is proposed. The sensitivity of the sensor is substantially realized by the refractive index of the cladding layer that influences the effective refractive index (n_eff) of the whole waveguide structure. The designed multilayer structure consists of the substrate (n=1.51), the low refractive index mesoporous silica film (n=1.1~1.3), the dye-doped gain layer (n=1.58) and the high refractive index TiO₂ (n=2.1) thin film. We used the finite difference time domain (FDTD) algorithm to simulate the influence of the mesoporous silica film and the TiO₂ layer to the n_eff of the fundamental transverse electric (TE₀) mode and the sensitivity in the DFB structure. It was found that the increase of refractive index of the mesoporous silica and the thickness of TiO₂ layer can slightly increase the n_eff of the structure. And the sensitivity of the sensor can be enhanced not only by the introduction of mesoporous silica, but also by a thicker TiO₂ layer.