Estimation of One Photon Average Electric Field Strength Confined in Silica Glass Microsphere

In this paper, we present measurement results for estimation of the average electric field strength of one photon confined in the single whispering-gallery-mode (WGM) within a micro-scale space in a silica glass microsphere. With the precise control of microsphere diameter, fiber taper size, and a distance between sphere surface and collecting fiber taper, we can obtain single 1550nm-WGM emissionfrom erbium doped microsphere silica glass pumped by 980nm laser beam. Using Poyntings vector theory, which describes the relation between the intensity over the electric field strength of an electromagnetic wave in a given area, we calculated the average electric field of one photon confined in WGM at silica microsphere surface. Our measured results well agree with the theoretical value within the measurement uncertainty. The average one photon electric field strength plays important role in applications such as optical trapping and tweezers, biological and chemical sensors.