TP-NSOM Resolution

The resolution of the TP-NSOM was determined by line scans through the fluorescence peaks in Figure 8.  As Figure 9 demonstrates, these line scans show a full-width at half-maximum of order 175 nm (< wavelength/4 ), thus demonstrating sub-diffraction limited resolution.

fig 9: TP-NSOM Resolution
 

Figure 9. Line scan through the fluorescence image of a single molecule.  The raw data is well fit by a Gaussian function with a FWHM of 160 nm.

This observed resolution of TP-NSOM surpasses the expected resolution limit of 1/2 the wavelength for uncoated tips operating with linear contrast mechanisms.4,5,6  The quadratic dependence of two-photon induced fluorescence on excitation intensity permits TP-NSOM to surpass this resolution limit and achieve resolution better than 1/2 the wavelength.

Photobleaching