Christophe Mihalcea

Heat-Assisted Magnetic Recording

Due to the limits of conventional perpendicular magnetic recording, it appears that alternative technologies are needed at areal densities >500 Gb/in2. Heat-assisted magnetic recording (HAMR) is a promising approach to extend areal densities to 1 Tb/in2 and beyond. All of the unique components necessary for a working HAMR system have been demonstrated. Although HAMR permits writing on high Hc media with lower magnetic fields and can produce higher write gradients than conventional magnetic recording, head/media spacing and the development of high Hc media with small grains remains challenging

Light Delivery Techniques for Heat-Assisted Magnetic Recording.

Heat-assisted magnetic recording (HAMR), also known as hybrid recording, has been proposed to enable storage densities greater than 1 Tb/in2 in hard disc drives while circumventing the superparamagnetic limit. Light is delivered in the near field to the recording medium to heat just the spot which is to be recorded. Techniques based on apertures, antennas, waveguides, and solid immersion lenses have been suggested for delivering substantial amounts of optical power into subwavelength spots in the near field. A practical transducer for HAMR may require a combination of techniques.

Miniature planar solid immersion mirror with focused spot less than a quarter wavelength.

We describe a microoptical planar waveguide solid immersion mirror with high optical throughput, and show that it can focus light to spot sizes of ~90 nm at a wavelength of 413 nm. Scanning near field optical microscope images of the light within the device are in good agreement with a simple theoretical model. This device is accurately mass-produced with lithographic and thin film deposition techniques known from modern integrated circuit processing.

Near Field Heat Assisted Magnetic Recording with a Planar Solid Immersion Lens

In this paper we present experimental heat assisted magnetic recording results using a planar solid immersion mirror (PSIM) fabricated on an Al2O3–TiC slider. The heads were flown at a velocity of 14 m/s, 20–25 nm above a Co/Pt multilayer medium which was deposited on a 60 mm glass disk. It was found that the track width and carrier-to-noise-ratio (CNR) increased with the applied magnetic field. Recording experiments were also performed with PSIMs terminated with 125 µm apertures. This led to narrower tracks and smaller CNR values for the same applied fields compared to recording with a PSIM only.

Near-field optical recording using a planar solid immersion mirror

A near-field planar solid immersion mirror (PSIM) has been developed and applied to the writing and reading of marks in a phase-change material. Light focusing of a PSIM is realized by a two-dimensional parabolic reflective surface integrated in a planar waveguide. Using a PSIM fabricated out of a waveguide consisting of a 100nm Ta2O5 core layer and a SiO2 cladding layer on an Al2O3–TiC substrate, we have recorded marks with dimensions of λ∕4.A near-field planar solid immersion mirror (PSIM) has been developed and applied to the writing and reading of marks in a phase-change material. Light focusing of a PSIM is realized by a two-dimensional parabolic reflective surface integrated in a planar waveguide. Using a PSIM fabricated out of a waveguide consisting of a 100nm Ta2O5 core layer and a SiO2 cladding layer on an Al2O3–TiC substrate, we have recorded marks with dimensions of λ∕4.

Focusing characteristics of a planar solid-immersion mirror

The focusing characteristics of a planar waveguide solid-immersion mirror with parabolic design have been investigated. The solid-immersion mirror is integrated into an optical waveguide, and light focusing is achieved with a parabolic mirror parallel to the waveguide plane and waveguide mode confinement normal to the waveguide plane. Optical-quality tantala silica planar waveguides can be obtained by evaporation. The parabolic sidewall reflects over 50% of the incident waveguide mode and generates a diffraction-limited focus. The measured spot size for the solid-immersion mirror described here is less than one third of the wavelength. Polarization analysis shows that the electric field near the focal region has components parallel and normal to the polarization state of the incident beam. The planar solid-immersion mirror is essentially free of chromatic aberration, and the alignment of the illumination beam is within a fraction of degrees.

Spin stand characterization of dielectric optical waveguides fabricated on AlTiC sliders for heat-assisted magnetic recording

Heat-assisted magnetic recording (HAMR), also known as hybrid recording, is one of the technologies proposed for extending hard disk drive areal densities beyond a Tb/in2. Due to their planar nature and compatibility with existing hard disk drive head fabrication techniques, dielectric optical waveguides have been suggested as a means for delivering light directly to the recording medium or near field optical transducer. In this paper we present spin stand experimental results from a dielectric optical slab waveguide fabricated on an AlTiC slider.

Fabrication of dielectric optical waveguides on AlTiC sliders for heat-assisted magnetic recording

In this paper we show the feasibility to integrate waveguide optics into magnetic recording sliders using current recording head manufacturing techniques. Thin film planar waveguides were deposited on ceramic substrates and structured to yield rectangular waveguides positioned on the front face of recording sliders that fly at 20 nm spacing over a glass disk. The thin film waveguide is equipped with a diffraction grating that allows light to be coupled into the waveguide and directed towards the air bearing surface. Optical properties of selected waveguide stacks are presented together with photographs of etched waveguide structures on AlTiC sliders.

Investigations of Sputtered Silver Oxide Deposits for the SUPER–RENS High Density Optical Data Storage Application

Abstract : Thin silver oxide films used as mask layers in super-Resolution Nearfield Structure (super-RENS) disks for high density optical data storage were reactively sputter-deposited and their composition was determined by spectroscopic means. We found that the stoichiometry of the films changed with the oxygen content in the sputtering gas atmosphere. With a stepwise increase in the percentage of O2 from 0 - 100%, the corresponding layers consist of Ag, mixtures of Ag and Ag2O, Ag2O, mixtures of Ag2O and AgO and AgO. Laser activation of such oxidic phase containing deposits results in the decomposition of the material and excitation of strong local plasmons in the remaining silver clusters. This was confirmed by acquiring surface enhanced Raman spectra (SERS) of benzoic acid (BA), copper phthalocyanine (CP) and internal carbon impurities on silver oxide substrates. From this data, we conclude that the sub-wavelength resolution obtained in super-RENS disks is mediated by local surface plasmons on small silver particles forming in the mask layer.

Fabrication of Silver Nano-Noodles

We report that silver nanowires can easily be fabricated from organic solution including silver ions by focusing a laser beam on a light absorbing material surface. Focusing a laser beam on a Si film (100-nm thickness on a glass substrate) in silver oxide (AgOx) saturated benzoic acid (BA) (10-3 M)-2-propanol (IPA) solution produced noodle-like silver nanowires with diameters of less than 50 nm. It was suggested that the Ag nanowires were formed by super-cooling effect at local heating and solubility around the laser spot region, and transported to the laser spot area by thermal convection.