Detection of coating fluorophores' densities in improved Q-factor cavities

摘要

This work investigates the relationship between the Q factor of a silica-microsphere coated with nonlinear optical molecules and the surface density of the molecules. Two types of nonlinear molecules are studied: poly {1-[p-(3'-carboxy-4'-hydroxyphenylazo) benzenesulfonamido]-1, 2-ethandiyl} (PCBS), and Procion Brown MX-GRN (PB). In our experiments, we coat silica microspheres with ionic self-assembled multilayer (ISAM) films with different thickness values as well as different PCBS/PB chromophore densities. The Q factors of the coated microspheres are limited to the range of 10~6-10~7, which can be attributed to the optical absorption of the coated chromophores. This work can be used to experimentally determine the effective density of chromophores assembled on the silica microsphere. It may also find applications in chemical / biological sensing.