Fig. 1. Principle of ISP-assisted thermal probe nanolithography. The inset on the upper left indicates the cross-sectional electric field illuminating a radially polarized beam.

Fig. 2. Super-focused mode of the plasmonic probe for both light and thermal fields. (a) One-dimensional light intensity distributions along the radial direction at the plane 10 nm distance away from the tip. The light is focused into the deep sub-wavelength region with an FWHM of 62 nm. The insets show the section intensity distributions across the symmetry axis. (b) Temperature profiles under the irradiation of a continuous-wave laser. The plasmonic probes with (left) and without (right) annular slits are simulated and compared. The super-focused mode reduces both the heating feature size and the required laser power. The insets show the section temperature field distributions.

Fig. 3. Thermal probe nanolithography system and the plasmonic probe sample. (a) Schematic of the nanolithography system consisting of a continuous-wave laser, an AFM, and several optical components. LP, linear polarizer; RPC, radial polarization converter. SEM image of the proposed plasmonic tip: (b) side view, (c) tip side view, and (d) backside view.

Fig. 4. AFM images of plasmonic nanolithography results on the thermal resist. (a) 13 nm line under the laser power of 50 mW. (b) 29 nm line under the laser power of 75 mW. (c) The pattern of logo “BJAST CTIC” under the laser power of 75 mW.

Fig. 5. The simulated super-focused mode of the plasmonic probe with different tip apex radii. The one-dimensional (a) light intensity and (b) temperature profiles prove the focus size for both light and thermal field decrease with the tip apex radius.

Fig. 6. Comparison of one-dimensional light intensity profiles for side and top incidences. The inset indicates the side incidence scheme.

Fig. 7. Polarization detection of the RP beam. The image of measured far-field intensity distributions of an RP beam (a) in the original state and filtered by a linear polarizer in the (b) horizontal direction and (c) vertical direction.

Fig. 8. Experimental setup of the thermal probe nanolithography system. (a) The nanolithography system consisting of a continuous-wave laser, a linear polarizer, a radial polarization converter, several mirrors, and an AFM. (b) The camera image of the RP illumination in alignment with the tip and the AFM feedback laser.

Fig. 9. Temperature profiles of the plasmonic probes with annular slits under the irradiation of the pulsed laser. Two different time durations of a laser pulse of 10 ps (red) and 10 ns (blue) are investigated in the numerical study. The heating feature size can be further improved down to 18 nm by properly reducing the pulse duration.

Fig. 10. Super-focused mode of the optimized plasmonic probes operating at 808 nm and 1550 nm wavelengths. (a) One-dimensional light intensity distributions along the radial direction at the plane 10 nm distance away from the tip. The insets show the section intensity distributions across the symmetry axis. (b) Temperature profiles of the plasmonic probes operating at 808 nm (left) and 1550 nm (right) wavelengths. The probes are heated to the threshold temperature by the continuous-wave laser with different irradiation powers of 10 mW and 46 mW, respectively. The insets show the section temperature field distributions.