Lasers based on semiconductor whispering gallery mode (WGM) resonators represent a perfect platform for active small footprint high-sensitive devices for biodetection. Biochemical samples typically require aqueous solution, and the resonator should be placed into a cuvette with water or in a microfluidic chip. The characteristics of modern semiconductor WGM lasers with an active region based on InAs/InGaAs quantum dots (QDs) make them promising for creating compact highly sensitive devices for biodetection. Deep localization of carriers in InAs/InGaAs QDs and suppressed lateral migration helps us to obtain room-temperature lasing in microdisk lasers immersed in an aqueous medium. In this work, we studied the sensitivity of the microdisk laser resonance spectral position to the refractive index of the surrounding material by changing the salinity of the water solution. We also successfully detected model proteins (secondary antibodies attached to the microdisk surface) via measurement of the lasing threshold power. The proteinprotein interaction on the microdisk surface manifests itself by an increase in the laser threshold power. Thus, in this work we demonstrated, for the first time, the possibility of using QD semiconductor microdisk lasers for detection of proteins in a microfluidic device.
We present a study of resonant optical properties of paired silver hemispheroids grown on a glass substrate using out-diffusion technique combined with thermal poling of the glass. Atomic force microscopy was used to characterize the morphology of the grown nanostructures. Dark-field spectroscopy and numerical simulation were applied to study the optical properties of the coupled nanoparticles (NPs) depending on the interparticle gap and size difference of the hemispheroids in a pair. Raman spectroscopy testing of the coupled hemispherical NPs showed that they can provide signal enhancement factor exceeding one of a single hemispherical NP.