Taeseob Kim

High-speed plasmonic nanolithography with a solid immersion lens-based plasmonic optical head

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.

Application of Solid Immersion Lens-Based Near-Field Recording Technology to High-Speed Plasmonic Nanolithography

In this paper, we proposed a high-speed and high-throughput plasmonic nanolithography technique that uses a fabricated sharp-ridged nanoaperture on a solid immersion lens (SIL) and a precise active nanogap control algorithm. This plasmonic lithography with high throughput can make an optical spot with a diameter of the order of 10 nm and can perform nanopatterning at sub-m/s speed. An optical high-throughput head was designed on a metallic aluminum aperture by optimizing the geometric parameters of a sharp-ridged antenna on the basis of the optical intensity and spot size. Using the evanescent field generated from the SIL, the plasmonic SIL could be maintained below 20 nm above a photoresist-coated Si-wafer and could move at a speed of greater than 200 mm/s without friction; the patterning of lines could be performed under this condition. We achieved patterning with a line width (full-width at half-magnitude, FWHM) of 130 nm.

Multiple excitation of localized surface plasmon to create a 10 nm × 10 nm strong optical spot using an Au nanoparticle array-based ridge waveguide

We present a description of a multiple excitation of localized surface plasmons (LSPs) from an Au nanoparticle (NP) array-based ridge waveguide to create a small optical spot size with an extremely strong intensity. Using a numerical finite-difference time-domain method, we find that the optical intensity of the ridge waveguide with an Au NP array is about 700% higher than that of a simple ridge waveguide. Moreover, the spacing between the NPs plays an important role in the multiple excitation of LSPs. The spot size, calculated at FWHM, is 10 nm x 10 nm at a distance of 5 nm from the exit plane.

Experimental demonstration of line-width modulation in plasmonic lithography using a solid immersion lens-based active nano-gap control

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.

Effects of dielectric substrate properties for optical phenomena in a nanoscale ridge aperture

In this paper, we show that the increase in power throughput is dependent on the thickness and the relative permittivity of the dielectric substrate in the aperture-on-dielectric-substrate configuration. We also show that, similar to a metal nanoparticle, an increase in the medium dielectric constant results in a red-shift in the plasmon resonance of a nanoscale ridge aperture. These results, which are verified by a numerical analysis, provide a new understanding of the phenomenon of surface-plasmon-enhanced transmission. We demonstrate that the red-shifted wavelength and dielectric properties can compensate for the optical loss due to plasmon red-shift. In addition, the dielectric substrate layer behaves like a Fabry?P?rot optical resonator, resulting in coherent constructive interference. The simulation results show that the |E|2 intensity of the triangular aperture is ?200% greater when this dielectric effect and red-shift resonance are considered.

Improved Nanogap Servo System Using an Error-Based Disturbance Observer for High-Speed in Solid Immersion Lens-Based Plasmonic Lithography

We proposed an advanced nanogap servo system using the error-based disturbance observer (EDOB) system. To achieve the feedback control over the nanogap based on the gap error signal (GES) in the near-field region, a precise gap-curve was obtained experimentally between a solid immersion lens and a photoresist-coated wafer using a piezo nanoposition actuator. With an accurate nanogap servo system, the EDOB was designed with a low-pass filter of 2.0 kHz bandwidth. Due to the powerful properties of the EDOB, which include stable robustness and disturbance rejection, a high-speed nanogap servo was achieved with up to 400 and 300 mm/s at the desired gaps of 20 and 15 nm, respectively. The disturbance rejection performance was evaluated from the GES, and the maximum deviation value was reduced by approximately 40% over that of the servo system without the EDOB.

Optical Performance Evaluation and Aligning Method for Solid Immersion Lens Assembly with Wedge Plate Lateral Shearing Interferometer

We present a simple and stable optical performance evaluation and aligning method for a solid immersion lens (SIL) assembly with a wedge plate lateral shearing interferometer (LSI). There are many advantages in the use of the wedge plate LSI compared with a current SIL measurement method using a Twyman–Green interferometer. We designed the thicknesses, wedge angles, materials, and reflectances of the first and second surfaces of the wedge plate to be 1 mm, 0.02°, fused silica and 21, and 30%, respectively. Simulation and experimental results are well matched in quantitative analyses at shear ratios of 10, 40, and 70%. On the basis of simulation results for an aberrated SIL assembly with many misaligned cases, we suggested the use of the aligning process with the wedge plate LSI.

Protected nanoaperture based on multi-excitation of the localized surface plasmon between a ridge nanoaperture and metal nanoparticle

To protect a ridge nanoaperture from environmental rigors and to minimize losses created by a dielectric protection layer, we developed a multi-excited nanoaperture by combining a ridge nanoaperture with an aluminum nanoparticle. We observed that the aluminum nanoparticle propagated the optical field from the nanoaperture to the exit plane via plasmon coupling, which facilitated confinement of the optical field. Additionally, even when the exit plane of the multi-excited nanoaperture was covered with a dielectric protection layer, the aluminum nanoparticle still confined the optical field in a small, localized region. The resulting spot size from a pure ridge nanoaperture, covered with a protection layer, was 166 × 86 nm2 (full-width at half maximum) at a distance of 10 nm from the protection layer. For the protected multi-excited nanoaperture configuration, the spot size at the full-width at half maximum was 32 × 30 nm2 at a distance of 10 nm from the protection layer.

Improved Air Gap Error Using Frequency Estimation and Peak Filter in Solid Immersion Lens-Based Plasmonic Lithography System

The performance of plasmonic lithography depends on how small the air gap is. In this paper, we focus on rejecting the dominant frequency of disturbance. In order to do this, frequency estimation and peak filter are used in this paper. We achieve about 12% and 10% reduction in the standard deviation and maximum peak to peak of Gap Error Signal (GES) respectively. This work will improve the quality of plasmonic lithography in the size and stability of patterns.Copyright

Focusing Error Detection Method in Microholographic Data Storage System Using Polarization Characteristics

We present a disk-focusing error detection method for microholographic data storage systems using polarization characteristics. In high-speed optical storage systems, disturbances exist along the vertical direction of a disk. The diffraction efficiency of a readout signal depends on the distance between the focusing point of the reference beam and the vertical center of the microholographic grating. The proposed disk focusing error detection method uses only one laser source, unlike most existing systems, which use two laser sources. By using polarization characteristics, disk-focusing and reading beams are inserted in the media without interference, and the proposed system achieves the simultaneous reading of microholograms and disk-focusing control. By evaluating the focus error signal, we verified the reliability of the optical path and tolerable S-curve (FES) balance (1.8%) for the proposed system. It is possible to achieve a diffraction efficiency of over 90% at the best focus position using the proposed disk-focusing method.