Semiconductor lasers as integrated optical biosensors: sensitivity optimisation

Semiconductor lasers contain both a light source and waveguide, rendering them suitable for adaptation to evanescent field biosensing. One-dimensional simulations using the beam propagation method have been carried out for planar semiconductor waveguide structures, with a view to maximising sensitivity of the effective index to changes in the refractive index and thickness of a film on the waveguide surface. Various structural parameters are investigated and it is found that thinning the upper cladding layer maximises the sensitivity. Implications for laser operation are considered, and an optimised structure is proposed. Surface layer index and thickness resolutions of 0.2 and 2nm are predicted