Hyun-Ki Kim

Signal Characteristics of Super-Resolution Near-Field Structure Disks with 100 GB Capacity

We report the basic characteristics of super resolution near-field structure (Super-RENS) media at a blue laser optical system (laser wavelength 405 nm, numerical aperture 0.85). Using a novel write once read many (WORM) structure for a blue laser system, we obtained a carrier-to-noise ratio (CNR) above 33 dB from the signal of the 37.5 nm mark length, which is equivalent to a 100 GB capacity with a 0.32 micrometer track pitch, and an eye pattern for 50 GB (2T: 75 nm) capacity using a patterned signal. Using a novel super-resolution material (tellurium, Te) with low super-resolution readout power, we also improved the read stability.

Random pattern signal characteristics of super-RENS disk in blue laser system

We report the random pattern signal characteristics of the super resolution near field structure (Super-RENS) disk in a blue laser optical system. (Laser wavelength 405 nm, numerical aperture 0.85) We introduced new structure for blue laser system, which results in 43 dB carrier to noise ratio (CNR) at the 75 nm mark length signal (which is equivalent to 50 GB capacity with 0.32 micrometer track pitch) and much better readout stability were obtained. The relatively clear eye pattern, phase locked loop (PLL) state and data to clock jitter of around 20% for a 50 GB (2T:75 nm) random pattern signal were realized.

Signal Characteristics of Super-Resolution Near-Field Structure Disk in Blue Laser System

We report the signal characteristics of a super-resolution near-field structure (super-RENS) disk in a blue laser system (laser wavelength, 405 nm; numerical aperture (NA), 0.85). By introducing a new structure for the blue laser system, a 42.5 dB carrier to noise ratio (CNR) at a 50-nm-mark-length-signal (which is equivalent to a 75 GB capacity with a 0.32 micrometer track pitch and a 1–7 modulation code (Blu-ray disc (BD) format)) and a much higher readout-stability were obtained. Transmission electron inicroscope (TEM) image analysis revealed that the new blue structure has clear diffusion protection barriers produced by continuous Pt particles, which is related to higher CNR and readout stability characteristics.

Error Rate Reduction of Super-Resolution Near-Field Structure Disc

We report the error rate improvement of super-resolution near-field structure (super-RENS) write-once read-many (WORM) and read-only-memory (ROM) discs in a blue laser optical system [laser wavelength (λ), 405 nm; numerical aperture (NA), 0.85]. We prepared samples of higher carrier level WORM discs and wider pit width ROM discs. Using controlled equalization (EQ) characteristics and an adaptive write strategy and an advanced adaptive partial response maximum likelihood (PRML) technique, we obtained a bit error rate (bER) of 10-4 level. This result shows the high feasibility of super-RENS technology for practical use.

Random Signal Characteristics of Super Resolution Near Field Structure Read-Only Memory Disc

We report the random pattern signal characteristics of the super resolution near field structure (Super-RENS) disk in a red laser optical system. (Laser wavelength 659 nm, numerical aperture 0.6) We improved the carrier to noise ratio (CNR) characteristics and the low frequency noise by optimizing the layer design and the pit structure, which results in 53 dB CNR at 173 nm pit length. It is equivalent to 50 GB capacity if it is converted by Blu-ray Disc (BD) specification according to the ratio of beam size. We also improved the readout power margin and the stability greatly by introducing the thermal control layer. The eye pattern under phase locked loop (PLL) state could be obtained through equalization adjustment (EQ). Through above improvements, we obtain the bER of 4.6×10-4 at 50 GB level by using partial response maximum likelihood (PRML) method.

Phase change materials in Super-RENS disk

Super-REsolution Near-field Structure (Super-RENS) is one of the most promising technologies for a subterabyte optical storage. In this paper, we will report effects of phase change material on the recording and readout characteristics of a Super-RENS disk.

Super Resolution Read Only Memory Disc Using Super-Resolution Near-Field Structure Technology

Super resolution near-field structure (super-RENS) technology is one of the promising technologies for a sub-terabyte optical storage of around 200 GB capacity. We confirmed the possibility of super-RENS read only memory (ROM) media with multilayer structure using the combination of the PtOx, AgInSbTe, ZnS-SiO2 films. The carrier to noise ratio (CNR) and readout cyclability was measured for the super-RENS ROM disc in both the red laser and the blue laser systems.

Phase Change Super Resolution near Field Structure ROM

We confirmed a super resolution phenomenon and a typical super resolution near field structure threshold phenomenon in a read only memory (ROM)-type sample disk. We found that this super resolution phenomenon originates from a phase-change layer and is closely related to the thermal properties of the super resolution layer. We also improved the readout stability using a co-sputtered layer with phase change (GST) and dielectric materials (ZnS-SiO2).

Improvement of Noise Characteristics in Super-Resolution Near-Field Structure Disc

The research interest in super-resolution near-field structure (Super-RENS) technology is shifting from the signal intensity (carrier-to-noise ratio, CNR) to the signal uniformity (jitter or bER). To achieve uniform signal characteristics, it is important to reduce signal fluctuation in the super-RENS disc. In this study, we investigated the relationship between signal fluctuation and low-frequency noise (LFN), and analyzed the LFN increase in recording and readout processes. It was found that signal fluctuation had a close relationship with LFN. It was also found that certain recorded mark shapes, such a bubble shape, and high readout power increased the LFN during recording and readout processes of a super-RENS disc. Therefore, using non bubble-type recording material and low super-resolution readout material, we markedly improved the LFN of a super-RENS disc.

Optimal Design of Slider Air-Bearing for Discrete Track Recording Technology

This paper suggests a design methodology for slider air bearings over a discrete track recording (DTR) disk using a simplified static analysis including the flying-height (FH) loss equation instead of a computationally expensive, time consuming transient dynamic analysis. Because a slider over a DTR disk has different flying characteristics than a slider over a continuous track recording (CTR) disk, the design of the slider requires modification. However, it is challenging to dynamically simulate slider air bearings over a DTR disk. Furthermore, it is nearly impossible to design the slider using an expensive dynamic analysis as a solver. Therefore, we define the flying characteristics of the DTR slider as a function of that of the CTR slider by using the FH loss equation based on averaged flow effect. A design optimization problem is formulated to meet the design requirements of the DTR slider, which include target FH, FH flatness, altitude FH drop, pitch and roll angle ranges, and altitude pitch drop. The design problem is changed to an inverse problem using a conventional static analysis for a CTR disk instead of an expensive dynamic analysis for a DTR disk. Simulation results showed that the optimally designed DTR slider can meet the target FH while satisfying all design requirements over the entire recording band.