Electric heating – Metal heating – By arc
Reexamination Certificate
2000-06-02
2002-08-13
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
By arc
C219S121680, C219S121650
Reexamination Certificate
active
06433306
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to pulsed laser, high power optical amplifier system and more particularly to pulsed semiconductor laser high power fiber amplifier systems for material processing such as in the case of thermally treating polymeric, ceramic and metal surfaces, including but not limited to, surface texturing, heat treatment, surface engraving, surface ablation, cutting, grooving, bump forming, coating, sealing, soldering, surface diffusion and surface conversion to a compound. A particular example is shown for surface texturing of disk surfaces, such as for texturing of magnetic disk substrate surfaces upon which is formed a thin magnetic film comprising a magnetic hard disk employed in digital magnetic recording systems.
BACKGROUND OF THE INVENTION
Material processing has been used with Nd:YAG lasers and gas lasers, e.g. CO
2
lasers, to process treat polymeric, ceramic and metal surfaces, including but not limited to surface texturing, heat treatment, surface engraving, micro-machining, surface ablation, cutting, grooving, bump forming, coating, sealing, surface diffusion and surface conversion to a compound. One such process example is surface texturing for magnetic disk media used in magnetic disk systems. In present day magnetic disk systems, particularly magnetic rigid disks used for recording data, the surfaces of the disks are textured, i.e., provided with a plurality of microscopic grooves or bumps across or in portions of the disk surfaces to improve the properties of the disk both mechanically and magnetically. Surface texturing mechanically removes the Johansson block effect which is the tendency for flying magnetic, air bearing slider in a magnetic head, employed in magnetic disk drives, to adhere to the flat substrate magnetic surface of a magnetic medium. This is referred to as stiction wherein the air bearing slider has been stationary on the magnetic recording surface for a period of time, the slider resists any transitional movement and is prone to adhere to the magnetic surface. Texturing removes, if not eliminates, such slider adhesion. Also, mechanically, the grooves provide a place or reservoir for loose microscopic materials developed over time to lodge out of the way of the flying head. Magnetically, surface texturing enhances the magnetic surface properties by reducing the magnetic radial component while intensifying the circumferential magnetic component. After surface texturing, a thin magnetic film is formed on the textured disk surfaces. Intermediate layers may be utilized prior to magnetic film formation to improve the adherence and magnetic properties of the film.
In the past, the texturing processing has been carried out using a fixed or free abrasive medium, such as a tape, applied to the surface of the disk substrate. See, for example, U.S. Pat. No. 4,964,242; 5,088,240; and 5,099,615 assigned to Exclusive Design Company, Inc. of San Mateo, Calif.
Texturing also has been accomplished employing a texturing pad in combination with a particle slurry as taught in U.S. Pat. No. 5,167,096. Also, chemical etching has been employed for texturing as disclosed in U.S. Pat. No. 5,576,918. Recently, the use of lasers have been applied for texturing substrate surfaces for magnetic disks. Examples of such laser texturing systems are disclosed in U.S. Pat. Nos. 5,062,021; 5,567,484; 5,550,696; and 5,528,922 for overcoming stiction between the magnetic disk medium and the magnetic head slider when the slider starts and stops relative to the magnetic disk surface or in texturing an outer annular surface of the disk for use in Contact Start/Stop (CSS) cycling of the magnetic head. In most of these cases, a CO
2
gas laser or Q-switched Nd:YAG (Nd:YLF or Nd:YVO
4
) laser having, for example, a wavelength around 1060 n m with a repetitive pulse rate of 70 kHz to 100 kHz and pulse with of about 60 or 70 &mgr;sec have been employed. In Q-switched Nd:YAG laser systems, the noise specification is around 2% rms. These laser systems are integrated into a laser texturing head where the output beam is split using waveplates or cubic beam splitters so that the split beam is routed to opposite surfaces of the disk to textured.
However, these systems have no ability for directly providing pulse stability, pulse-to-pulse repeatability as well as selected pulse width and shape configuration. As an example, the pulse width and shape in Q-switched Nd:YAG laser systems cannot be changed on-the-fly in pulse width and pulse shape with time such as double stepped amplitudes or ramp-up and ramp-down variations.
It is a primary object of this invention to provide a pulsed semiconductor laser high power fiber amplifier system for material processing.
It is another object of this invention to provide a modulated diode laser and fiber amplifier system capable of providing 10 mW of pulse input power and produce output powers in hundreds of watts to several kilowatts for material processing applications with very low pulse to pulse energy fluctuations.
Also in laser texturing as a exemplary example of material processing, what is desired is a laser texturing head that is lighter in weight and smaller in size that is not so bulky, compared to the task at hand, and are capable of the same and even higher power delivery for texturing with pulse stability and pulse-to-pulse repeatability, which is another object of this invention.
It is a another object of this invention is to provide a high power laser optical amplifier system of comparatively small compact size for texturing the surfaces of disk substrates employed in magnetic recording systems.
It is further object of this invention to provide a high power laser optical amplifier system that has sufficiently high power to process treat polymeric, ceramic and metal surfaces, including but not limited to, surface texturing, heat treatment, surface engraving, micro-machining, surface ablation, cutting, grooving, bump forming, coating, sealing, soldering, surface diffusion and surface conversion to a compound.
SUMMARY OF THE INVENTION
According to this invention, a pulsed semiconductor laser high power fiber amplifier system for material processing comprises at least one fiber amplifier capable of rejection of propagating ASE buildup in and between the amplifier stages as well as elimination of SBS noise providing output powers in the range of about 10 &mgr;J to about 100 &mgr;J or more resulting in low pulse to pulse energy fluctuations. The system is driven with a time varying drive signal from a modulated semiconductor laser signal source to produce an optical output allowing modification of the material while controlling its thermal sensitivity by varying pulse shapes or pulse widths supplied at a desire repetition rate via modulation of a semiconductor laser signal source to the system to precisely control the applied power application of the beam relative to the thermal sensitivity of the material to be processed.
A pulsed semiconductor laser fiber high power amplifier system of this invention further comprises a semiconductor laser pumped, multi-stage fiber amplifier with means for rejecting amplified stimulated emission (ASE) buildup in and between the amplifier stages which is a problem in achieving higher power outputs in fiber amplifier systems. ASE rejection means utilized in this invention comprises the employment of one or more of an optical circulator, a narrow band WDM, or a dB coupler with peak injection signal gratings at coupler terminal ports. The system may be operated cw or pulsed. The ASE inhibited fiber amplifying system provides a laser source and fiber amplifier system that is capable of providing an amplified modulated pulse output having high long term pulse stability, e.g., below 1% rms, with ability to provide pulse width and pulse contour selectability, not readily capable with YAG systems, and providing a pulse output up to 100 &mgr;J for delivery to an applied application such as in the exemplary application herein of disk texturing. The system with ASE rejection also has
Grubb Stephen G.
Welch David F.
Zanoni Raymond
Elve M. Alexandra
JDS Uniphase Corp.
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