• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.8-9
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• 2001

• Optical Science and Technology
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• v.6 no.1
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• pp.13-18
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• 2002

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.168-169
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• 2000

We have tried to enhance the density of the near-field optical memory and to improve the recording/readout speed. The current optical memory has the limitation in both density and speed. This barrier due to the far-field nature can be overcome by the use of the near-field$^{(1)}$ . The optical data storage density can be increased by reducing the size of the nanometric aperture where the near-field is obtained. To fabricate the aperture in precise dimension, we applied the orientation-dependent / anisotropic etching property of crystal Si often employed in the field of MEMS$^{(2)}$ . And so we fabricated the 10$\times$10 aperture array. This array will be also the indispensable part for speeding up. One will see the possibility of the multi-tracking pickup in the phase changing type memory through this array$^{(3)}$ . This aperture array will be expected to write the bit-mark whose size is about 100nm. We will show the recent result obtained. (omitted)

• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.241-246
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• 2010

In this paper, we propose an electric field enhanced postexposure baking (EFE-PEB) method to obtain deep and high aspect ratio pattern profile in near-field recording. To describe the photoacid distribution under an external electric field during the PEB, we derived the governing equations based on Fick's second law of diffusion. From the results of the numerical calculations, it is found that the vertical movement of photoacid increases while the lateral movement is stationary as electric field varies from 0 to $8.0{\times}10^6\;V/m$. Also, it is proven that the profile of near-field recording is improved by using the EFE-PEB method with increased depth, higher aspect ratio and larger sidewall angle.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.162-163
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• 2000

근접장 주사 광학 현미경(Near-field scanning optical microscope)에서 가장 중요한 부분은 바로 근접장 탐침(Near-field optical probe)이다. 가간 널리 사용되는 근접장 탐침은 끝 부분에 매우 작은 구멍만 남기고 나머지 부분은 금속으로 코팅한 뾰족한 광섬유(Metal-clad tapered optical fiber)이다. 탐침의 끝에 형성된 작은 구멍은 진행하지 못하는 근접장(Near-field)을 진행하는 먼장(Far-field)으로 바꾸어줌으로서 회절한계를 뛰어넘는 분해능을 가능하게 한다. 그러나, 이러한 작은 구멍은 매우 작은 투과 효율(Transmission efficiency)을 가지기 때문에 고밀도 광기록(High-density optical recording)등에 이용하는데 큰 어려움이 있었다.$^{(1).(3)}$ 따라서 금속이 코팅된 뾰족한 광섬유 내에서 빛이 어떻게 진행되는지에 대한 연구를 통해 보다 높은 효율을 가지는 근접장 탐침을 개발하는 것이 중요한 과제가 되고 있다. 본 연구에서는 금속이 코팅된 뾰족한 광섬유 도파로 내에서 구멍의 크기와 빛의 투과 효율의 관계를 보고한다. (중략)

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.4-11
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• 2005

In this paper, we propose novel optics design for media inside near-field recording (NFR) using hemispherical solid immersion lens (HMS). To obtain strong advantage of data protection and high data capacity simultaneously, HMS based near field optics using aplanatic position of super hemisphere is designed. In this design, to improve small optical tolerance of this aplanatic position, additional aspheric lens surface is added on top of the HMS and it is combined with zoom optics which composed of two single lenses having low numerical aperture (NA). Also, to compensate chromatic aberration which happens seriously in optics using blue laser diode, diffractive optical element is used. Using zoom optics, additional aspheric lens surface, and diffractive optical element together, wavefront aberration and chromatic aberration are effectively reduced in broad range of cover layer thickness and wavelength variation. In addition, In this paper, effect of gap induced aberration is investigated by analyzing different behavior of each TM and TE wave for designed media inside dual-layer NFR optics.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.13-20
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• 2006

In this paper, we propose novel optics design for media inside near-field recording(NFR) using hemispherical solid immersion lens(HMS). To obtain strong advantage of data protection and high data capacity simultaneously, HMS based near field optics using aplanatic position of super hemisphere is designed. In this design, to improve small optical tolerance of this aplanatic position, additional aspheric lens surface is added on top of the HMS and it is combined with zoom optics which composed of two single lenses having low numerical aperture(NA). Also, to compensate chromatic aberration which happens seriously in optics using blue laser diode, diffractive optical element is used. Using zoom optics, additional aspheric lens surface, and diffractive optical element together, wavefront aberration and chromatic aberration are effectively reduced in broad range of cover layer thickness and wavelength variation. In addition, in this paper, effect of gap induced aberration is investigated by analyzing different behavior of each TM and TE wave for designed media inside dual-layer NFR optics.

• Transactions of the Society of Information Storage Systems
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• v.3 no.3
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• pp.123-125
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• 2007

We report the readout stability improvement results of super-resolution near field structure (Super-RENS) writeonce read-many (WORM) disk at a blue laser optical system. (Laser wavelength 405nm, numerical aperture 0.85) By using diffusion barrier structure (GeSbTe sandwiched by GeN) and high transition temperature recording material ($BaTiO_3$), material diffusion of phase change layer and recording mark degradation were greatly improved during high power (Pr=2.0mW) readout process up to $1{\times}10^5$ times.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.3
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• pp.164-171
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• 2003

Dynamic analysis using impulse responses is formulated to estimate effect of slider rail shape on dynamic responses in near-field optical recording drive. Impulse responses are obtained on numerical nonlinear model including rigid motion of a slider and fluid motion of an air bearing under the slider. Dynamic characteristics of slider motion are evaluated by utilizing the decay ratio of impulse responses and modal frequencies from frequency response functions. The dynamic characteristics of the designed NFR slider are checked by comparing those of a HDD slider(Nutcracker). Also, sensitivities of slider Position conditions and rotation speed on the dynamic characteristics are investigated.

• Transactions of the Society of Information Storage Systems
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• v.5 no.1
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• pp.41-46
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• 2009

In SIL-based NFR servo systems, the residual error and the overshoot that are occurred in the process of the modes-witching servo which consists of approach, gap-control modes, and safety mode are reduced by using PID controller. However, the design method of conventional PID controller is not sufficient for the stable air gap control system. Therefore, the optimal PID controller using LQR manner is more useful to find the designed parameters of PID controller. In this paper, we show that the performance of the optimal PID controller is better than that of the lead-lag controller.