Sub-mm disk waviness characteristics and slider flying dynamics under thermal FH control

The flying dynamics and flying stability of a slider are the key issues at sub-5 nm flying height (FH) under thermal FH control. The resonant frequencies of current sliders are at 100 kHz level. At present linear disk velocities, the disk waviness at sub-mm level and 10 micron level can excite the resonant modes of the slider and induce FH modulation. This work uses the triple-harmonic method to monitor the dynamic FH signal during the process of thermal FH control. As the FH reduces, the same disk waviness characteristics excite larger dynamic FH modulation.     

Effect of pattern shape on etching wall profile in slider fabrication

The effect of pattern shape on etching wall profile in slider fabrication is studied. The testing results show: (1) the wall profile of round pattern is steeper than that of long rectangular; (2) for round patterns, the smaller the radius is, the steeper the wall profile is; (3) the profile of outer angle is steeper than that of inner angle. The flying height offset caused by wall profile with different shapes can be 8% of total flying height, so it is necessary to consider the effect of pattern shape on etching wall profile in ABS design, especially for ultra low flying height slider.     

Towards fly- and lubricant-contact recording

Reducing the spacing between the magnetic head and the magnetic media is of crucial importance in enabling future high-density magnetic data storage. The magnetic spacing has been reduced to a level that we have to explore new schemes for the further reduction of the spacing. This paper reports authors’ efforts towards fly- and lubricant-contact recording scheme. The targeted objective is to minimize the mean-plane spacing between the slider and disk surfaces and to allow the further reduction of the overcoat thickness. The slider will still fly over the disk surface. The read/write head part of the slider will be protruded to contact lubricant—to minimize the mean-plane mechanical spacing. The key factors for achieving such a mechanism include super-smooth slider and disk surfaces, advanced slider air-bearing design to significantly reduce flying height modulation caused by disk waviness and flatness, nano-actuator design, position feedback control scheme to control the contact depth, and so on. The preliminary experimental data confirm the feasibility of such a lubricant-contact scheme. The slider air-bearing design presented in this work also indicates the feasibility of high-performance slider design, which can well follow the disk waviness. A parameter, anti-modulation factor, is introduced for the evaluation of slider's performance in reducing flying height modulation caused by disk waviness.     

基于多物理场的TFC磁头热传导机理及其影响因素仿真研究

为了利用微尺度热效应的热致飞高控制(TFC)磁头技术实现磁头飞行高度的精确控制,分析了工作状态下TFC滑块在多物理场综合作用下所呈现出来的传热特性及其主要影响因素,考虑了磁头磁盘间超薄气膜的稀薄效应,建立滑块导热、空气轴承表面传热、气膜流动等模型,利用有限元法,对磁头热变形作用机理及热传导特性对滑块动力学特性影响进行了仿真研究,结果表明,建立的传热模型及对雷诺方程的修正适用于求解磁头磁盘界面气膜传热问题和磁头滑块的动力学问题;影响滑块热力学性能的因素主要可以归结为加热器高度、热生成率以及材料的传热系数;空气轴承力及工作表面热变形的双重作用决定了滑块飞行高度的改变.仿真结果为磁头滑块加热器的设计及空气轴承动力学特性分析提供了依据.     

Ru/WCoCN as a seedless Cu barrier system for advanced Cu metallization

The properties of Ru(5 nm)/WCoCN(5 nm) stacked layers as a seedless Cu barrier system has been investigated. Its barrier properties compared to single 10 nm Ru film were investigated by sheet resistances, X-ray diffraction patterns, transmission electron microscopy, energy dispersive spectrometry spot analysis, line scans, and leakage currents. Thermal stability of the Ru(5 nm)/WCoCN(5 nm) improved by over 100 °C than that of Ru(10 nm) barrier. The results show that Ru(5 nm)/WCoCN(5 nm) can effectively block Cu diffusion up to 600 °C for 30 min. The Ru(5 nm)/WCoCN(5 nm) bilayer is a great Cu barrier candidate for seedless Cu interconnects.     

Observation of large magnetic resistance in weak magnetic fields using CuPt/SiO2/Si/SiO2/CuPt structure

The magnetoresistive effect of CuPt(8 nm)/SiO₂(5 nm)/Si(50,000 nm)/SiO₂(5 nm)/CuPt(8 nm) structure made by e-beam evaporation technique is studied in this work. Variation in magnetoresistance obtained by I-V measurements at 77 K and in the presence of less than 5 mT magnetic field applied in parallel to the surface is investigated. We have found that this structure exhibit large magnetoresistance in low magnetic fields (i.e. <5 mT). Our results also indicate that the variation in magnetoresistance in the presence of external magnetic field has oscillatory behavior and has the maximum value of 3295%. This structure due to its high sensitivity to low magnetic fields can also be used as an active element in magnetic field sensor devices.     

Design and fabrication of ultra-high precision thin-film polarizing beam splitter

An ultra-high precision thin-film polarizing beam splitter (PBS) has been designed and fabricated. Using Needle optimization technology, we design the thin-film polarizing beam splitter that is transparent for P polarization and reflective for S polarization with ultra-high precision at 64.8° angle of incidence and 632.8 ± 10 nm wavelength band. The experiments with the fabricated thin-film PBS demonstrate that both the reflectance of P polarization and transmittance of S polarization at 64.8° angle of incidence and 632.8 nm wavelength point are less than 0.02%, which is ultra-high for reported PBSs.     

Design and fabrication of a 900-1700 nm hyper-spectral imaging spectrometer

This paper presents a 900-1700 nm hyper-spectral imaging spectrometer which offers low distortions, a low F-number, a compact size, an easily-fabricated design and a low cost (is presented in this paper). The starting point for its optical design is discussed according to the geometrical aberration theory and Rowland circle condition. It is shown that these methods are useful in designing a push-broom hyper-spectral imaging spectrometer that has an aperture of f/2.4, modulation transfer functions of less than 0.8 at 25 cycles/mm, and spot sizes less than 10 μm. A prototype of the optimized hyper-spectral imaging spectrometer has been fabricated using a high precision machine and the experimental demonstration with the fabricated hyper-spectral imaging spectrometer is presented.     

Fabrication of highly ordered CuInSe2 films with hollow nanocones for anti-reflection

Highly ordered CuInSe₂ films with hollow nanocones were fabricated by electron beam evaporation and nanospheres lithograph. From the AFM analyses, polystyrene nanospheres with diameter of 220 nm are assembled regularly on glass substrates. After reaction ion etching under different powers and residues removal, different and new surface morphologies of substrates have been obtained, such as smooth nanocones and hollow nanocones. The diffuse reflection spectra demonstrate that films on the substrates with periodic nanopatterned structure have less reflection over wavelengths ranged from 200 nm to 2500 nm due to light trapping. Especially, reflection for hollow nanocone arrays has the larger suppression value than nanocone-patterned films, which proves that surface pattern of hollow nanocones has better anti-reflection effect. Furthermore, while hollow depth increases from 6 nm to 9 nm, its optical antireflective effect becomes remarkable. These results could yield new options for solar-cell design with higher energy conversion efficiency.     

Preparation and characterization of C54 TiSi2 nanoislands on Si (1 1 1) by laser deposition of TiO2

We present the preparation of C54 TiSi₂ nanoislands on Si (1 1 1) with a method of the pulsed laser deposition of titanium oxide thin films. The TiO₂ thin films with nominal thicknesses of 1 nm on Si (1 1 1) were annealed at 850 °C for about 4 h in situ. The X-ray diffraction patterns and the X-ray photoelectron spectra indicate that the nanoislands are in C54 TiSi₂ phase. The characterization using a scanning tunneling microscope shows that the nanoislands with triangular, polygonal and rod-like shapes on Si (1 1 1) exhibit the Volmer-Weber growth mode. The sizes of the polygonal islands distribute in two separated ranges. For the small islands, they have a narrow lateral size distribution centered at 4 nm and a height range in 0.6-3.6 nm, while for the large islands, their lateral sizes are in the range of 12-40 nm and the heights in the range of 4-9 nm. The sizes of the well-shaped triangular islands are intermediate with the lateral sizes in range of 5-20 nm and the heights of 2-3.5 nm. The rod-like islands are about 50-200 nm in length, 5 nm in height and about 15-20 nm in width. The origination of the various shapes of the nanoislands is attributed to the symmetry of Si (1 1 1) substrate and the lattice mismatch between the C54 TiSi₂ and the Si (1 1 1) surface.     

Consideration and compensation of calibration falloff for optical flying height measurement

In sub-10 nm low flying height (FH) region, system calibration is a significant challenge to achieve precise FH measurement. Unloading calibration mechanism is utilized for every FH measurement using three-wavelength interferometry. Our experiment has shown that the cutoff frequency of photodetectors and the bandwidth of optical filters induce calibration falloff during the calibration process. As a result, the FH measured is underestimated, i.e., the FH measured is lower than its true value. In this paper, mathematical models are proposed to eliminate the side effects due to the bandwidth of optical filters and the cutoff frequency of photodetectors. Results indicate that the proposed compensation schemes are effective in terms of improving the calibration accuracy.     

Tunable double-clad ytterbium-doped fiber laser based on a double-pass Mach-Zehnder interferometer

We have demonstrated an adjustable double-clad Yb³⁺-doped fiber laser using a double-pass Mach-Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach-Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output.     

Field emission properties of nano-structured phosphorus-doped diamond

Nano-structured phosphorus-doped diamonds were fabricated for field emitters and their field emission properties were characterized. Two kinds of nano-structures were prepared; tip array structures and whiskers on tip structures. The tips, which have 100 nm radius and 10 μm height, are used in tip array structures; whiskers have tip radii of 5 nm and height of 500 nm. Following nano-structure formation, a reduction of threshold fields is observed compared to non-patterned flat surfaces. This is ascribed to field concentration at the tips. However, at higher electric fields, a saturation of the emission current is observed due to non-negligible bulk resistances in tips and whiskers.     

Tunable, μs-pulsed ytterbium fiber laser system with a linewidth below 2.7 GHz

We report on a widely tunable, pulsed laser system with narrow spectral linewidth based on a continuous wave ytterbium fiber oscillator, a pulse shaper and a power amplifier stage. The system is tunable from 1055 nm to 1085 nm and provides a maximum pulse energy of 155 μJ with a pulse duration of 1-5 μs. The linewidth is less than 2.7 GHz over the whole tuning range.     

Bend-optimized optical fiber with S+C+L bands for FTTH applications

A multi-clad waveguide, which provide more bandwidth for WDM with S+C+L bands, is illustrated in this study. The bending loss is optimized for the FTTH applications. The fiber is manufactured by PCVD process; the test results are identical with the theoretic calculation. This fiber has nearly flat dispersion from 1460 nm to 1625 nm. The MFD at 1310 nm and 1550 nm are 8.2 and 9.4 μm, respectively. Bending loss is less than 0.1 dB/Turn at a bending radius of 7.5 mm. With low-water-peak manufacture technologies, the fiber is suitable for FTTH applications.     

Design of wide-spectrum polymer Mach-Zehnder interferometer electro-optic switches using two symmetric N-th order phase-generating couplers

To enlarge the output spectrum, a novel reasonable structure of one kind of Mach-Zehnder interferometer (MZI) electro-optic (EO) switches containing two symmetric N-th order phase generating couplers (PGCs) is presented, and thorough model, analysis and design technique are proposed. A non-linear least square method is investigated for optimizing the PGC structure to eliminate the phase difference error caused by the wavelength variation. Under the central wavelength of 1550 nm, optimization and simulation are performed on three MZI EO switches using two first, second and third order PGCs, respectively. The switches exhibit a low switching voltage of 1.156 V with an active region length of 4 mm. The output spectrums covering the whole S-C-L bands are as wide as 320, 390 and more than 435 nm, respectively, the insertion loss are less than 5.57, 5.98 and 7.90 dB, respectively, and the crosstalk is less than −30 dB over the wide wavelength ranges, for the three designed switches. The design technique is supported to be feasible by the comparison with beam propagation method (BPM).     

Diode-pumped 593.5 nm cw yellow laser by type-I CPM LBO intracavity sum-frequency-mixing

A design of LD-pumped Nd:YVO₄ laser that generates simultaneous laser action at wavelengths 1064 and 1342 nm by optimizing film design is presented. An optimized continuous-wave (cw) yellow laser at 593.5 nm in room temperature is obtained for the first time. Using type-I critical phase-matching (CPM)LBO crystal, a yellow laser at 593.5 nm is obtained by 1064 and 1342 nm intracavity sum-frequency mixing. The maximum laser output power of 85 mW is obtained when an incident pump laser of 1.8 W is used. The optical-to-optical conversion is up to 4.7%, and the power stability in 24 h is better than ±2.8%.     

Atomic force microscopic characterization of films grown by inverse pulsed laser deposition

Carbon nitride films have been deposited by KrF excimer laser ablation of a rotating graphite target in 5 Pa nitrogen ambient in an inverse pulsed laser deposition configuration, where the backward motion of the ablated species is utilised for film growth on substrates lying in the target plane. Topometric AFM scans of the films, exhibiting elliptical thickness distribution, have been recorded along the axes of symmetry of the deposition area. High resolution AFM scans revealed the existence of disk-like, or somewhat elongated rice-like features of 5-10 nm average thickness and ∼100 nm largest dimension, densely packed over the whole, approximately 14 × 10 cm² deposition area. The RMS roughness of the film decreased from 9 nm near to the laser spot down to 2 nm in the outer regions. Even the highest RMS value obtained for IPLD films was less than half of the typical, 25 nm roughness measured on simultaneously deposited PLD films.     

Improvement of optical sensing performances of a double-slot-waveguide-based ring resonator sensor on silicon-on-insulator platform

We demonstrate a label-free photonic biosensor with double slots based on micro-ring resonator. The footprint is less than 25 μm × 15 μm. Finite-difference time-domain (FDTD) method is used to analyze the influence of several key parameters on the performance of the double-slots micro-ring resonators. An asymmetric structure is considered for the ring waveguide in order to improve the sensor's bending efficiency. Our numerical analysis shows that the sensitivity of double-slot micro-ring resonator sensor with the radius of 5 μm reaches a value of 708 nm/RIU. The quality factor of 580 and the free spectral range (FSR) of 33 nm are achieved.     

Experimental and theoretical studies on a double-pass C-band bismuth-based erbium-doped fiber amplifier

Performance of a Bismuth-based Erbium-doped fiber amplifier is experimentally and theoretically investigated using 1480 nm pumping with double-pass scheme. In the theoretical analysis, the rate and power propagation equations are solved to examine the optimum length for the C-band operation as well as the gain and noise figure characteristics. The calculated small signal gain is 38 dB with gain variation of less than 3 dB. The measured gain is 4 dB lower due to spurious reflections which were ignored in the theoretical analysis. At input signal power of 0 dBm, a gain of 14.5 dB is obtained experimentally with gain variation of less than 1 dB within the wavelength region from 1530 to 1565 nm. The noise figure is less than 12 dB within this region.