Scanning near-field optical microscopy (SNOM) is a crucial candidate to reach the submicron resolution, due to its capability of breaking through the diffraction limit. For SNOM, the optical fiber nano-probe is a key component, whose properties mainly depend on the probe shapeparameters, such as the cone angle and tip diameter. In order to characterize the probe properties, sophisticated and costly instruments are often demanded for experimental investigations.On the other hand, the numerical analysis on the probe performance is an alternative approachdue to the low cost and accessibility.In the reported literatures, enormous theoretical works have been fulfilled, while these efforts weremainly concentrated on the probes with linear shapesand systematic simulationsconsidering various probe shapes havenot been implemented yet.
Thus, under the guide of Pro. Tielin Shi and Zirong Tang, Dr. Wei Zhu in WNLO performe theoretical calculations forthe transmission efficienciesof parabolic nano-probes with different shapes.It shows that the transmittance will fluctuate dramatically with the variation of eitherwavelengthor probe shape, and the efficiency could be rather high even at long wavelengths. Subsequently, theythoroughly investigate this phenomenon and find that these fluctuations are due to the joint effect oflight propagating modesandsurface plasmon polaritonsmodes. It indicates that high transmittance can be achieved with the selection of appropriate wavelength and probe structure, providing remarkable improvement of transmittance for SNOM.
This work has been published on the journal Optics Express of OSA (Vol. 21, Issue 23, 28103-28110, 2013) andis financially supported by National Science Foundation of China (No. 51275195)and the National Instrument Development Specific Project of China (No. 2011YQ160002).