This letter describes the use of a plasmonic optical head to achieve high-speed nanopatterning. A plasmonic optical head employs both a sharp-ridged nanoaperture and a nanogap control to maintain the nanogap required for near-field nanolithography. The nanogap control uses a gap error signal produced by evanescent coupling through the air-gap. We demonstrate that a plasmonic optical head achieves a patterning resolution of 70 nm and a patterning speed of 100 mm/s. The proposed combination of a surface plasmon nanoaperture and a nanogap servo system is one of the strategies used to achieve high-speed, high-resolution nanolithography.

In this paper, we report the enhancement of resolution of continuous wave (CW) stimulated emission depletion (STED) microscopy by a novel method of structured illumination of an excitation beam. Illumination by multiple excitation beams through the specific pupil apertures with high in-plane wave vectors leads to interference of diffracted light flux near the focal plane, resulting in the contraction of the point spread function (PSF) of the excitation. Light spot reduction by the suggested standing wave (SW) illumination method contributes to make up much lower depletion efficiency of the CW STED microscopy than that of the pulsed STED method. First, theoretical analysis showed that the full width at half maximum (FWHM) of the effective PSF on the detection plane is expected to be smaller than 25% of that of conventional CW STED. Second, through the simulation, it was elucidated that both the donut-shaped PSF of the depletion beam and the confocal optics suppress undesired contribution of sidelobes of the PSF by the SW illumination to the effective PSF of the STED system. Finally, through the imaging experiment on 40-nm fluorescent beads with the developed SW-CW STED microscopy system, we obtained the result which follows the overall tendency from the simulation in the aspects of resolution improvement and reduction of sidelobes. Based on the obtained result, we expect that the proposed method can become one of the strategies to enhance the resolution of the CW STED microscopy.

We propose dual-wavelength Fourier ptychography for topographic measurement. To extend the axial measurement range, a single light-emitting diode (LED) and two appropriate bandpass filters are employed. This provides a speckle-free phase image, and reduces the possibility of a systematic error, which yields a high-quality topographic image. The proposed system can measure the surface topography in the range of nano- to micro-structures. The performance of the system is experimentally verified.

Plasmonic lithography has been used in nanofabrication because of its utility beyond the diffraction limit. The resolution of plasmonic lithography depends on the nano-gap between the nanoaperture and the photoresist surface—changing the gap distance can modulate the line-width of the pattern. In this letter, we demonstrate solid-immersion lens based active non-contact plasmonic lithography, applying a range of gap conditions to modulate the line-width of the pattern. Using a solid-immersion lens-based near-field control system, the nano-gap between the exit surface of the nanoaperture and the media can be actively modulated and maintained to within a few nanometers. The line-widths of the recorded patterns using 15- and 5-nm gaps were 47 and 19.5 nm, respectively, which matched closely the calculated full-width at half-maximum. From these results, we conclude that changing the nano-gap within a solid-immersion lens-based plasmonic head results in varying line-width patterns.

The feasibility of stimulated emission depletion (STED) microscopy using a solid immersion lens was investigated. First, the theoretical feasibility of the considered system is discussed based on a vectorial field algorithm that uses a stratified medium composed of a SIL air-gap and test sample. Using the simulation, we verified that evanescent waves with much higher spatial frequencies corresponding to the high numerical aperture in the air-gap can be utilized to achieve a higher resolution than a confocal fluorescent image without a depletion beam. The simulated expectation was supported by actual imaging on two types of samples: fluorescent beads with a 20 nm diameter and an actin sample with a filamentous structure. The lateral resolution of the system was determined to be 34 nm via the imaging results on the nano-beads. The system was quite promising for achieving nano-scale surface imaging of biological samples; an even higher resolution was achieved by adjusting the wavelength and the intensity of the depletion beam.