On-chip microparticle detection and sizing using a dual-wavelength waveguide laser

An integrated intra-laser-cavity microparticle sensor based on a dual-phase-shift, dual-wavelength distributed-feedback channel waveguide laser in Al₂O₃:Yb³⁺ is presented. Real-time detection and accurate size measurement of single microparticles with diameters ranging between 1 μm and 20 μm are achieved, which represent the typical sizes of many fungal and bacterial pathogens as well as a large variety of human cells. The sensing principle relies on measuring changes in the frequency difference between the two longitudinal laser modes, as the evanescent field of the dual-wavelength laser interacts with micro-sized particles on the surface of the waveguide.