摘要： Electrospun polymer submicroscale fibers normally have flexible cylindrical waveguide geometries and can be produced with ultra-long and functional materials. Hence, they are promising building blocks for small optical devices. However, the propagation loss in the fibers is still higher than that in submicroscale polymer fibers produced by melt and solution drawing. In this study, thermal drawing of electrospun fibers was found to reduce their propagation loss. Fivefold thermal drawing of as-electrospun polymer fibers significantly reduced their diameters (e.g., from 1.121 μm to 0.497 μm) and propagation loss (e.g., from 16 dB cm?1 to 6.6 dB cm?1 at 521-nm wavelength). Because fluctuations in the fiber diameter significantly reduced after thermal drawing, the propagation loss reduction could be attributed to the reduced fluctuations in addition to the reduced density inhomogeneity in the fibers. These findings pave the way for low-loss electrospun fiber waveguides and their application in small optical devices.