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US-12626722-B2 - Data recording on ceramic material

US12626722B2US 12626722 B2US12626722 B2US 12626722B2US-12626722-B2

Abstract

The present invention relates to a method for recording data in a layer of a ceramic material and to a device for recording data in a layer of a ceramic material.

Inventors

  • Christian Pflaum

Assignees

  • Ceramic Data Solutions GmbH

Dates

Publication Date
20260512
Application Date
20231019
Priority Date
20200811

Claims (11)

  1. 1 . A device for recording data in a layer of a ceramic material on a substrate, the device comprising: a laser source comprising a picosecond laser or a femtosecond laser; a digital micromirror device adapted to emit multiple laser beams; collimating optics adapted to collimate laser light emitted by the laser source onto the digital micromirror device; a substrate holder adapted to mount the substrate; focusing optics adapted to focus each of the multiple laser beams emitted by the digital micromirror device onto the substrate mounted on the substrate holder; and a negatively charged mesh or sheet adapted to collect positively charged debris ablated from the layer of ceramic material by the multiple laser beams; wherein a fluence of each of the multiple laser beams emitted by the digital micromirror device is greater than 100 mJ/cm 2 .
  2. 2 . The device of claim 1 , wherein the focusing optics comprise a lens having a numerical aperture of at least 0.8.
  3. 3 . The device of claim 1 , further comprising a beam shaping device.
  4. 4 . The device of claim 3 , wherein the beam shaping device comprises a matrix of laser zone plates or a spatial light modulator.
  5. 5 . The device of claim 1 , wherein each of the multiple laser beams at the substrate has a minimum focal diameter no greater than 1000 nm.
  6. 6 . The device of claim 1 , further comprising a processor adapted to control the digital micromirror device.
  7. 7 . The device of claim 6 , wherein the processor is further adapted to control an XY positioning system on which the substrate holder is mounted.
  8. 8 . The device of claim 1 , wherein a wavelength of the laser source is smaller than 700 nm.
  9. 9 . The device of claim 1 , wherein the substrate holder is positioned between the focusing optics and the negatively charged mesh or sheet.
  10. 10 . The device of claim 1 , wherein the negatively charged mesh or sheet is positioned between the focusing optics and the substrate holder.
  11. 11 . The device of claim 10 , wherein the negatively charged mesh or sheet comprises an opening which allows the multiple laser beams to pass therethrough.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation of U.S. patent application Ser. No. 17/936,628, filed Sep. 29, 2022 (allowed), which is a continuation of International (PCT) application Serial No. PCT/EP2021/069827, filed Jul. 15, 2021, which claims priority to European Patent Application Serial No. 20190446.3, filed Aug. 11, 2020. Priority is claimed to these applications, and they are incorporated herein by reference in their entireties. INTRODUCTION The present invention relates to a method for recording data in a layer of a ceramic material and to a device for recording data in a layer of a ceramic material. The applicant of the present invention has developed a method for long-term storage of information and a storage medium therefor (see Int'l (PCT) published patent applications WO 2021/028035 and WO 2022/002418). According to one aspect of said method for long-term storage of information, information is encoded on a writable plate comprising a ceramic material by using a laser beam to manipulate localized areas of the writable plate. While this method can, in principle, be performed with a laser beam having a fixed focal point by mounting the writable plate on an XY positioning system and moving those localized areas of the writable plate to the laser focus where encoding is to take place, said method is cumbersome and time-consuming. U.S. Pat. Nos. 4,069,487 and 4,556,893 also disclose laser-recordable recording media utilizing recording layer materials such as metal oxides and metal carbides. However, recording in both cases is based on a rotating disc technology which is disadvantageous due to the slow recording process caused by the fact that one pit after the other along the recording spiral has to be created. SUMMARY It is thus an object of the present invention to provide an improved method for recording data in a layer of a ceramic material, which is suitable for recording a large amount of data in a relatively small amount of time. Accordingly, the present invention relates to method, devices, and systems for recording data in a layer of a ceramic material. According to said method, a layer of a ceramic material is provided and a plurality of regions of the layer of the ceramic material are selectively illuminated with a laser beam using a digital micromirror device (DMD). The parameters of the laser beam and the time of illumination for each of the selected regions are configured so as to ablate each of the selected regions in order to record data in the layer of the ceramic material by creating recesses in the layer of the ceramic material. The laser beam preferably originates from a picosecond laser or from a femtosecond laser. Utilizing a picosecond laser or a femtosecond laser is highly advantageous for generating well-defined recesses. The ablation technique disclosed in U.S. Pat. No. 4,556,893 utilizes a focused, modulated laser-diode beam which, depending on the laser power, creates pits or bubbles. Since the recording layer material is light absorbing said layer is locally heated and thus melts and/or vaporizes. These processes are, however, rather uncontrolled and typically lead to disadvantageous hole shapes. For example, a ring of molten and subsequently solidified material may be formed around the edge of the hole as also indicated in FIG. 4 of U.S. Pat. No. 4,556,893. This is not acceptable when creating extremely small recesses in order to increase data density as it is required to reproducibly create these recesses and to allow for reproducible read-out technology. The inventor of the present invention has performed multiple experiments with different ablation techniques for ceramic materials. It has turned out that utilizing a picosecond laser or a femtosecond laser allows for generating extremely well-defined holes having a circular cross-section and a very sharp edge. It is believed that this is due to the ablation process initiated by a picosecond laser or a femtosecond laser. A picosecond or femtosecond laser pulse does not heat the ceramic material but rather interacts with the electrons of said material. It is assumed that a picosecond or femtosecond laser pulse interacts with outer valence electrons responsible for chemical bonding, which valence electrons are thus stripped from the atoms, leaving the latter positively charged. Given a mutually repulsive state between atoms whose chemical bonds are broken, the material “explodes” into a small plasma cloud of energetic ions with higher velocities than seen in thermal emission. This phenomenon is known as Coulomb explosion and clearly differs from regular laser ablation with e.g. nanosecond lasers, which heats the material on the surface to melt and evaporate leaving molten materials at the rim of the impact area. Coulomb explosion is a physical process, which is clearly restricted to the region of laser impact, whereas ablation caused by heat suffers from an ill-defined heat flow within the material. The