Compact write and read head for data recording on ceramic materials

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to a method for recording data in a layer of ceramic material, and a device for recording data in a layer of ceramic material. [Background technology]

[0002] The applicant of the present invention has developed a method for long-term storage of information and a storage medium therefor (see International Publication Nos. 2021 / 028035 and International Publication Nos. 2022 / 002418). According to one aspect of the 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 local areas of the writable plate. This method can, in principle, be performed using a laser beam with a fixed focus by mounting the writable plate to an XY positioning system and moving these local areas of the writable plate to the laser focus where encoding is to be performed, but this method is cumbersome and time-consuming.

[0003] Furthermore, U.S. Patent No. 4,069,487 and U.S. Patent No. 4,556,893 disclose laser-recordable recording media utilizing recording layer materials such as metal oxides and metal carbides. However, both recording methods are based on rotating disk technology, which is disadvantageous due to the slow recording process caused by the need to form pits sequentially along the recording spiral. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2021 / 028035 [Patent Document 2] International Publication No. 2022 / 002418 [Patent Document 3] U.S. Patent No. 4,069,487 [Patent Document 4] U.S. Patent No. 4,556,893 [Overview of the project]

[0005] Therefore, an object of the present invention is to provide an improved method for recording data on a layer of ceramic material, which is suitable for recording large amounts of data in a relatively short amount of time. A further object of the present invention is to provide an improved device for recording data on a layer of ceramic material, having a compact write head.

[0006] This objective is achieved by the method described in claim 1 and the device described in claim 23. Preferred embodiments of the present invention are described in the dependent claims.

[0007] Accordingly, the present invention relates to a method for recording data in a layer of ceramic material. According to the method, a layer of ceramic material is provided, and multiple regions of the layer of ceramic material are selectively irradiated with a laser beam using a digital micromirror device (DMD). The laser beam and irradiation time parameters for each of the selected regions are configured to ablate each of the selected regions in order to record data in the layer of ceramic material by forming recesses within the layer of ceramic material.

[0008] The laser beam is preferably generated from a picosecond or femtosecond laser. Utilizing a picosecond or femtosecond laser is highly advantageous for generating clearly defined depressions. The ablation technique disclosed in U.S. Patent No. 4,556,893 utilizes a focused, modulated laser diode beam that forms pits or bubbles depending on the laser power. Because the recording layer material is light-absorbing, the layer is locally heated and therefore melts and / or vaporizes. However, these processes are rather uncontrolled and typically result in unfavorable hole shapes. For example, as also shown in Figure 4 of U.S. Patent No. 4,556,893, rings of molten and then solidified material may form around the edge of the hole. This is unacceptable when forming extremely small depressions to increase data density, as it is necessary to form these depressions reproducibly and enable reproducible readout techniques.

[0009] The inventors of this invention conducted several experiments using different ablation techniques for ceramic materials. They found that utilizing picosecond or femtosecond lasers made it possible to generate extremely clearly defined holes with circular cross-sections and very sharp edges. This is thought to be due to the ablation process initiated by the picosecond or femtosecond laser. The picosecond or femtosecond laser pulse does not heat the ceramic material, but rather interacts with the electrons of the material. It is assumed that the picosecond or femtosecond laser pulse interacts with the outer valence electrons that carry the chemical bonds, and thus these valence electrons are separated from the atoms, leaving the atoms positively charged. Given the mutually repulsive state between the atoms whose chemical bonds have been broken, the material "explodes" into a plasma cloud of low-energy ions at a speed faster than that seen in thermal emission. This phenomenon is known as a Coulomb explosion and is distinctly different from conventional laser ablation, such as with nanosecond lasers, which heats the material on the surface, melting and evaporating it, leaving the molten material at the edges of the impact area. Coulomb explosion is a physical process, which is obviously limited to the region of laser shock, whereas thermal ablation suffers from an unclear heat flow within the material. Therefore, the Coulomb explosion is ideal in that it generates a vast number of small depressions, enabling a dramatic increase in data density compared to known techniques. While good results can be achieved using picosecond lasers, the use of femtosecond lasers is advantageous in this respect. Thus, the laser preferably has a pulse duration of less than 10 ps, ​​more preferably less than 1 ps.

[0010] The fluence of each of the multiple laser beams emitted by the DMD is 100 mJ / cm². 2 Greater than that, preferably 400 mJ / cm² 2 Greater than that, and more preferably 800 mJ / cm² 2 Larger than 1 J / cm², most preferably 1 J / cm² 2 It is preferable that it be larger than this.

[0011] Preferably, the laser beam passes through a prism or translucent mirror in sequence, strikes the digital micromirror device, and passes through the prism or translucent mirror again before selectively illuminating multiple areas of the ceramic material layer. Utilizing such a prism or translucent mirror is particularly advantageous in that it allows for a compact arrangement of the various components of the device used for recording. Preferably, the laser beam passes through a λ / 4 plate placed between the prism or translucent mirror and the digital micromirror device two more times. Changing the polarization of the laser beam with such a λ / 4 plate allows the laser beam from the laser to be guided through the prism or translucent mirror to the digital micromirror device, and then through the prism or translucent mirror again to selectively illuminate multiple areas of the ceramic material layer.

[0012] In the context of this invention, the term “recess” refers to a hole, groove, or indentation in a ceramic material. In other words, a recess forms a volume without any ceramic material present. The volume is in fluid communication with the atmosphere. In other words, each recess is open to the atmosphere and is not covered or closed.

[0013] Open recesses are advantageous over techniques described in U.S. Patent No. 4,069,487, as they allow for clean and complete ablation of the material present within the recess before ablation. This is particularly important when forming extremely small recesses to increase data density, as it is necessary to form these recesses reproducibly and enable reproducible readout techniques.

[0014] A DMD comprises an array or matrix of micromirrors, which allows for the selective illumination of a given pixel on a ceramic material by adjusting each micromirror in the array or matrix. Thus, a vast number of pixels on the ceramic material can be illuminated simultaneously and in a well-controlled manner, and this can be easily automated. Depending on the number of micromirrors present in the DMD, millions of selected areas (i.e., pixels) in a layer of ceramic material can be operated simultaneously within a sufficient time to ablate one selected area for data recording. Such digital micromirror devices are readily available and can be easily implemented in recording devices.

[0015] Preferably, pixels on the ceramic material, i.e., predetermined locations in the portions where recesses can be formed, are arranged in a regular matrix or array, i.e., in a repeating two-dimensional pattern having a grid structure or lattice-like structure. Particularly preferred matrices or arrays include, for example, square patterns or hexagonal patterns. Such matrices or arrays enable an optimized data density that is substantially greater than the data density of, for example, CDs, DVDs, or Blu-ray discs, because individual pixels or bits are not separated by a track pitch (e.g., 320 nm for Blu-ray discs) that exceeds twice the size of the individual pixels in the bit dimension (e.g., 150 nm for Blu-ray discs). Conventional disc-type recording media are also limited with respect to the maximum rotational speed that can be safely achieved during recording or reading. Therefore, the write / read speeds achievable by such matrices or arrays are much greater than the write / read speeds achievable by spirally arranged pits.

[0016] Preferably, the recess has a circular cross-section. The recess may extend only partially into the ceramic layer or may form a through-hole within the ceramic layer. In the former case, recesses or holes of different depths may be formed, each depth corresponding to a predetermined bit of information as described in International Publication No. 2022 / 002418. For this purpose, a layer of ceramic material may be irradiated with two or more laser pulses, and the micromirrors of the DMD are adjusted between subsequent pulses to achieve multiple regions of the layer of ceramic material, such as (i) not irradiated at all, (ii) irradiated once with a single laser pulse, or (iii) irradiated twice with two laser pulses.

[0017] Previous experiments by the applicant have shown that a CrN layer with a thickness of 5 μm can be visually and reliably manipulated by a single femtosecond laser pulse (see International Publication No. 2022 / 002418). Therefore, the method of the present invention makes it possible to encode at least several thousand to several million pixels within several hundred femtoseconds. Thus, the recording speed of the method of the present invention is limited only by the number of micromirrors in the DMD and the time required to adjust the micromirrors.

[0018] Preferably, the layer of ceramic material is moved laterally or translated during recording by an XY positioning system (with the z-axis perpendicular to the surface of the layer), such as a scanning stage. Thus, once an array or matrix of pixels is recorded, an adjacent array or matrix of pixels can be recorded by simply moving the layer of ceramic material to an adjacent area.

[0019] Therefore, the method of the present invention preferably includes a step of selectively irradiating a plurality of regions within a first area of a layer of ceramic material, which can be coated by DMD, with a laser beam using DMD; a step of translating the layer of ceramic material so that a second area different from the first area can be coated by DMD; and a step of selectively irradiating a plurality of regions within the second area of the layer of ceramic material with a laser beam using DMD.

[0020] When both the DMD and the XY positioning system are properly controlled, a data recording speed of at least 10 MB / s, preferably at least 100 MB / s, preferably at least 1 GB / s, and more preferably at least 10 GB / s can be achieved.

[0021] Preferably, the laser beam (i.e., a plurality of laser beams emitted from the DMD) is focused onto the layer of ceramic material by a lens (or a more complex optical system) having a high numerical aperture, preferably at least 0.5, more preferably at least 0.8. Preferably, an immersion optical system is used to further increase the numerical aperture. When an immersion optical system is used, the numerical aperture can be at least 1.0, preferably at least 1.2.

[0022] It is more preferable to utilize a beam shaping device to form a specific beam shape advantageous for data recording. For example, a matrix of laser zone plates may be transmitted by a plurality of laser beams generated from the DMD. These laser zone plates can be adapted, for example, to form needle-shaped Bessel beams for each of the plurality of laser beams.

[0023] The Bessel beam has the advantage that the depth of focus is substantially increased. The focal length of a regular Gaussian beam is on the order of the wavelength of the focused light, while the focal length achievable with a Bessel beam is at least four times the wavelength of the focused light. At the same time, the width of the focus is about 1 / 2 of the focal width achievable with a Gaussian beam.

[0024] Generally, the size of the features (e.g., the diameter of the recess in the ceramic material) achievable by the method of the present invention varies between 2 / 3λ (air) and 1 / 2λ (immersion) for a Gaussian beam and between 1 / 3λ (air) and 1 / 4λ (immersion) for a Bessel beam (λ is the wavelength of the laser light). Thus, the Bessel beam shape is advantageous in that it can achieve smaller process features and thus a higher recording data density. Moreover, the increase in the focal length of the Bessel beam is advantageous in that, for example, deeper recesses can be generated. This is relevant particularly when features of different depths should be generated, for example, to encode information by the depth of the recess. Since the focus of a Gaussian beam is conical, increasing the depth of the recess means increasing the diameter of the recess at the surface. In contrast, the more cylindrical focus of the Bessel beam allows for the formation of much deeper recesses with a substantially constant diameter.

[0025] Such Bessel beams can also be generated by other beam shaping devices. A particularly preferred example of a beam shaping device is a spatial light modulator, which is particularly versatile since it can be used to form a Bessel beam, enable optical proximity control, and provide a phase shift mask.

[0026] Preferably, the ceramic material layer includes metal nitrides such as CrN, CrAlN, TiN, TiCN, TiAlN, ZrN, AlN, VN, Si3N4, ThN, HfN, BN, and / or metal carbides such as TiC, CrC, Al4C3, VC, ZrC, HfC, ThC, B4C, SiC, and / or metal oxides such as Al2O3, TiO2, SiO2, ZrO2, ThO2, MgO, Cr2O3, Zr2O3, V2O3, and / or metal borides such as TiB2, ZrB2, CrB2, VB2, SiB6, ThB2, HfB2, WB2, WB4, and / or metal silicides such as TiSi2, ZrSi2, MoSi2, WSi2, PtSi, Mg2Si. Particularly preferred materials are B4C, HfC, Cr2O3, ZrB2, CrB2, SiB6, Si3N4, ThN, CrN, and CrAlN. These materials provide sufficient hardness and resistance to environmental degradation for the long-term storage of recorded data.

[0027] Preferably, the step of providing a layer of ceramic material includes the steps of providing a substrate and coating the substrate with a layer of ceramic material different from the material of the ceramic substrate. Thus, structural integrity is achieved using a robust and potentially less expensive substrate, while potentially requiring only small amounts of more expensive coating material. The layer of ceramic material preferably has a thickness of 10 μm or less, more preferably 5 μm or less, more preferably 2 μm or less, more preferably 1 μm or less, even more preferably 100 nm or less, and most preferably 10 nm or less.

[0028] Preferably, the substrate has a thickness of less than 1 mm, preferably less than 250 μm, more preferably less than 200 μm, and most preferably less than 150 μm.

[0029] Furthermore, the use of a substrate can enable the creation of an optical contrast between the substrate (where holes are created within the coating) and the surrounding coating material. Therefore, the step of selectively irradiating multiple regions of a layer of ceramic material with a laser beam using a digital micromirror device preferably includes a step of ablating sufficient material in each region so that the depressions extend toward the substrate. Preferably, the manipulation of the selected areas makes these areas distinguishable from the surrounding material. In some applications, this may involve achieving optical distinguishability. However, in other examples (especially when the encoded structures are too small), these areas may only be distinguishable from the surrounding material by means of, for example, a scanning electron microscope, or by measuring changes in other physical parameters such as magnetic, dielectric, or conductive properties.

[0030] Preferably, the ceramic substrate contains an oxide ceramic, and more preferably, the ceramic substrate contains at least 90% by weight, most preferably at least 95% by weight, of one or a combination of Al2O3, TiO2, SiO2, ZrO2, ThO2, MgO, Cr2O3, Zr2O3, and V2O3. These materials are known to be particularly durable under various conditions and / or resistant to environmental degradation. Therefore, these materials are particularly suitable for long-term storage under different conditions. The ceramic substrate is particularly preferably to contain one or a combination of sapphire (Al2O3), silica (SiO2), zirconium silicate (Zr(SiO4)), zirconium oxide (ZrO2), boron monoxide (B2O), boron trioxide (B2O3), sodium oxide (Na2O), potassium oxide (K2O), lithium oxide (Li2O), zinc oxide (ZnO), and magnesium oxide (MgO).

[0031] Preferably, the ceramic substrate comprises a non-oxide ceramic, and more preferably, the ceramic substrate comprises at least 90% by weight, most preferably at least 95% by weight, of one or a combination of metal nitrides such as CrN, CrAlN, TiN, TiCN, TiAlN, ZrN, AlN, VN, Si3N4, ThN, HfN, BN, metal carbides such as TiC, CrC, Al4C3, VC, ZrC, HfC, ThC, B4C, SiC, metal borides such as TiB2, ZrB2, CrB2, VB2, SiB6, ThB2, HfB2, WB2, WB4, and metal silicides such as TiSi2, ZrSi2, MoSi2, WSi2, PtSi, Mg2Si. These materials are known to be particularly durable under various conditions and / or resistant to environmental degradation. Therefore, these materials are particularly suitable for long-term storage under different conditions. The ceramic substrate is particularly preferably made of one or a combination of BN, CrSi2, SiC, and SiB6.

[0032] Preferably, the ceramic substrate comprises one or a combination of Ni, Cr, Co, Fe, W, Mo, or other metals having a melting point above 1,400°C. Preferably, the ceramic material and the metal form a metal matrix composite material in which the ceramic material is dispersed in the metal or metal alloy. Preferably, the metal constitutes 5 to 30% by weight, preferably 10 to 20% by weight, of the ceramic substrate, i.e., the metal matrix composite material. Particularly preferred metal matrix composite materials are WC / Co-Ni-Mo, BN / Co-Ni-Mo, TiN / Co-Ni-Mo, and / or SiC / Co-Ni-Mo.

[0033] The ceramic material layer is preferably coated directly onto the ceramic substrate, i.e., without any intermediate layer, to achieve a strong bond between the ceramic substrate and the ceramic material layer. The coated ceramic substrate is preferably tempered before and / or after recording to achieve such a strong bond. Tempering can create a sintered interface between the ceramic substrate and the ceramic material layer. The sintered interface may contain at least one element from both the substrate material and the ceramic material, as one or more elements from one of the two adjacent layers can diffuse into the other layer of the two adjacent layers. The presence of a sintered interface can further strengthen the bond between the ceramic substrate and the ceramic material layer.

[0034] Preferably, tempering a coated ceramic substrate involves heating the coated ceramic substrate to a temperature in the range of 200°C to 4,000°C, more preferably in the range of 1,000°C to 2,000°C. The tempering process may include a heating step with a temperature increase of at least 10 K / hour, a plateau step at a peak temperature for at least 1 minute, and finally, a cooling step with a temperature decrease of at least 10 K / hour. The tempering process may help to harden the ceramic substrate and / or permanently bond the ceramic material to the ceramic substrate.

[0035] Laser ablation of a selected area of ​​the ceramic material layer exposes the underlying ceramic substrate, which can result in an (optically) distinguishable contrast of the working area to the rest of the ceramic material layer.

[0036] According to a particularly preferred embodiment of the present invention, the substrate is transparent to the wavelength of the laser beam. Preferably, the substrate has a transmittance of at least 95%, more preferably at least 97%, and most preferably at least 99% to light having the wavelength of the laser beam. The substrate may include, for example, glassy transparent ceramic materials or crystalline ceramic materials such as sapphire (Al2O3), silica (SiO2), zirconium silicate (Zr(SiO4)), zirconium oxide (ZrO2), boron monoxide (B2O), boron trioxide (B2O3), sodium oxide (Na2O), potassium oxide (K2O), lithium oxide (Li2O), zinc oxide (ZnO), and magnesium oxide (MgO).

[0037] Particularly suitable crystalline ceramic materials include sapphire (Al2O3), silica (SiO2), zirconium silicate (Zr(SiO4)), zirconium oxide (ZrO2), and magnesium oxide (MgO).

[0038] Such transparent materials are particularly advantageous because they allow for selective illumination of multiple regions of the ceramic material layer (coated on the substrate) through a transparent substrate. Therefore, debris generated during recording occurs on the surface of the coated substrate opposite to the recording optical system. Thus, the surface can be easily cleaned and / or cooled without affecting the recording optical system.

[0039] Due to the high transmittance of the transparent substrate material, the laser light does not interact with the substrate and simply passes through it, for example, to ablate only the coating. In particular, the substrate material is not substantially heated by the laser beam.

[0040] Preferably, the laser beam (i.e., each of the multiple laser beams emitted from the DMD) has a minimum focal diameter of 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, and most preferably 100 nm or less.

[0041] Preferably, the wavelength of the laser beam is less than 700 nm, preferably less than 650 nm, more preferably less than 600 nm, even more preferably less than 500 nm, and most preferably less than 400 nm. Smaller wavelengths allow for the formation of smaller structures, and therefore, greater data density. Moreover, the energy per photon (action quantum) increases as the wavelength decreases.

[0042] The present invention further relates to a device for recording data on a layer of ceramic material. The device comprises a laser source, a digital micromirror device (DMD) adapted to emit multiple laser beams, a prism or translucent mirror positioned between the laser source and the DMD, a substrate holder for mounting a substrate, and a focusing optical system adapted to focus each of the multiple laser beams emitted by the DMD onto a substrate mounted on the substrate holder.

[0043] The device preferably further comprises a collimating optical system for collimating laser light emitted onto the DMD by a laser source.

[0044] Preferably, the device further comprises a λ / 4 plate positioned between the prism or translucent mirror and the DMD.

[0045] The prism or translucent mirror is preferably positioned between the laser source and the DMD such that the light emitted from the laser source passes, in sequence, through the prism or translucent mirror, optionally a λ / 4 plate, and then through the prism or translucent mirror again before striking the DMD and selectively illuminating multiple areas of the substrate.

[0046] The fluence of each of the multiple laser beams emitted by the DMD is preferably 100 mJ / cm². 2 Greater than that, preferably 400 mJ / cm² 2 Greater than that, and more preferably 800 mJ / cm² 2Larger than 1 J / cm², most preferably 1 J / cm² 2 It is larger than that.

[0047] The laser source preferably includes a picosecond laser or a femtosecond laser. The laser source preferably has a pulse duration of less than 10 ps, ​​more preferably less than 1 ps.

[0048] All of the desirable features described above in the context of the method of the present invention can also be used in the device of the present invention, and vice versa.

[0049] The fluence of the laser beam is preferably adapted to sufficiently manipulate the layer of ceramic material in order to record data on or within the layer of the ceramic material. Preferably, the fluence of the laser beam allows for ablation of the aforementioned ceramic material.

[0050] The focusing optical system preferably includes a lens (or a more complex optical system) having a high numerical aperture, preferably at least 0.5, more preferably at least 0.8. If an immersion optical system is used, the numerical aperture may be at least 1.0, more preferably at least 1.2.

[0051] The device further comprises a beam shaping device, preferably a matrix of laser zone plates or a spatial light modulator, for example, to form the multiple Bessel beams described above. Such a beam shaping device is preferably positioned in front of the focusing optical system. In this case, preferably multiple lenses, preferably Fresnel lenses, are positioned directly behind the beam shaping device to focus the Bessel beams, for example. The device preferably further comprises a flat-top beam shaping device located in the optical path, preferably in front of a prism or a translucent mirror.

[0052] In the substrate, each of the multiple laser beams is preferably a Bessel beam. In the substrate, each of the multiple laser beams has a minimum focal diameter of preferably 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less, and most preferably 100 nm or less.

[0053] The substrate holder is preferably mounted on an XY positioning system such as a scanning stage. The device preferably includes a processor configured to control the DMD and the XY positioning system to sequentially illuminate adjacent areas or pixel arrays of the substrate mounted on the substrate holder.

[0054] The processor (or additional processing unit) is preferably adapted and configured to receive a set of data to be recorded (i.e., analog or digital data such as text, digits, arrays of pixels, or QR codes) and to control the components of the device (in particular, the DMD and XY positioning system, and optionally the beam shaping device) to perform the method of the present invention to record the received set of data on or within a layer of ceramic material.

[0055] Preferably, the wavelength of the laser source is less than 700 nm, preferably less than 650 nm, more preferably less than 600 nm, even more preferably less than 500 nm, and most preferably less than 400 nm.

[0056] The device preferably further comprises a reading device configured to image the recorded data. Thus, a single write and read head can be used for both encoding (writing) data in a layer of ceramic material and decoding (reading) the data encoded in such a data carrier. The use of the prism or translucent mirror described above makes it possible to design such a combined write and read head in a particularly compact form.

[0057] The device preferably further comprises a beam splitter between the prism or translucent mirror and the focusing optical system to allow light emitted from the substrate to pass through the reading device. The device preferably further comprises a further light source (e.g., an LED) adapted to illuminate the substrate through the prism or translucent mirror and DMD during reading / decoding. Preferably, the light source emits linearly polarized light.

[0058] The reading device may include a digital camera or other optical detector. Preferably, the reading device includes a single optical sensor in which each “pixel” on the data carrier is addressed by a DMD that allows each “pixel” to be illuminated at once. In alternative reading modes utilizing SIM or SSIM, a specific illumination pattern (“structured illumination”) may be generated by the DMD. In this case, the reading device should include a digital camera or other multi-pixel detector. In further reading modes, planar illumination can be achieved by simply setting all the micromirrors of the DMD to “on”. In this case as well, the reading device should include a digital camera or other multi-pixel detector.

[0059] The device preferably further comprises a processor configured to decode captured and recorded data. The processor may be adapted, for example, to perform SIM and / or SSIM analysis and control the DMD accordingly.

[0060] Preferred embodiments of the present invention will be further described with reference to the following drawings. [Brief explanation of the drawing]

[0061] [Figure 1] This is a schematic diagram of a device for recording data according to a preferred embodiment. [Figure 2a] This is a schematic diagram illustrating the first alternative recording method. [Figure 2b]This is a schematic diagram illustrating a second alternative recording method. [Figure 3] This figure schematically illustrates a device for recording data according to another preferred embodiment. [Figure 4] This is a schematic diagram of the combination of polarizer, zone plate, and lens, as well as a graph of the resulting beam shape and focal length along the axis of the laser beam. [Figure 5] This figure schematically illustrates a device for recording data according to another preferred embodiment. [Figure 6] This figure schematically illustrates a device for recording data according to another preferred embodiment. [Figure 7] This figure schematically illustrates a device for recording data according to another preferred embodiment. [Modes for carrying out the invention]

[0062] Figure 1 shows a schematic diagram of a device for recording data on a layer of ceramic material according to a preferred embodiment of the present invention. The device comprises a laser source 2 that emits laser light onto a DMD 3 having a plurality of micromirrors 3a arranged in an array. The DMD 3 is adapted to emit a plurality of laser beams 4 for each micromirror in the "off" state along either a first direction (i.e., for recording) or a second direction (indicated by reference numeral 9), and to deflect those laser beams 9 into a beam dump (not shown). Typically, the device further comprises a collimating optical system (not shown in Figure 1) for collimating the laser light emitted onto the DMD 3 by the laser source 2. The device further comprises a substrate holder 6 for mounting a substrate 7 and a focusing optical system 8 adapted to focus each of the plurality of laser beams 4 emitted by the DMD onto the substrate 7 mounted on the substrate holder. The focusing optical system 8 may include, for example, a standard microoptical system with a high numerical aperture. The substrate holder 6 is adapted to support, preferably mount, the substrate 7, and may be mounted on or part of an XY stage.

[0063] In the example shown in Figure 1, the substrate 7 comprises a ceramic coating or layer 1 of a ceramic material that is locally ablated by a focused laser beam 4. In Figure 1, the ceramic coating 1 is provided on the substrate 7 (see also Figure 2a). Alternatively, the ceramic coating may be provided on the bottom or back surface of the substrate 7, as shown in Figure 2b. In this case, the laser beam 4 must pass through the substrate 7, so the material of the substrate 7 must be transparent to the wavelength of the laser light in this case. Furthermore, in this case, it is preferable that the substrate holder 6 comprises a frame 6a that supports only the outer edge of the substrate 7 (the substrate may be fully supported in the case of upper ablation, as shown in Figure 2a). Therefore, the portion of the ceramic coating 1 exposed to ablation is not supported by the free space 6b beneath that portion (see Figure 2b).

[0064] This is a particularly preferred embodiment because the debris generated during ablation is separated from the focusing optical system 8 by the substrate 7. Rather, the material being ablated from the ceramic layer 1 is released into the free space 6b of the sample holder 6, from which it can be extracted or aspirationed. Therefore, the focusing optical system 8 is not adversely affected by the debris, and it is much easier to clean the surface of the ceramic coating 1 immediately after or during recording.

[0065] Preferably, the substrate thickness is adapted to the focusing optical system of the device being used. For example, the substrate thickness should be less than the focal length of the focusing optical system in order to reach the ceramic coating.

[0066] Furthermore, the arrangement shown in Figure 2b also allows for cooling of the ceramic coating 1 during ablation, for example, by flowing a cooling fluid along the ceramic coating 1. This improves the accuracy of the ablation process because heat transfer from the laser focus to the surrounding area can be eliminated. For example, for this purpose, a cross-jet of air (e.g., an air blade) or a liquid such as water or another immersion fluid can be performed. In addition, the cross-jet can expel debris generated during ablation.

[0067] Such cross-jet formation can also be performed in the arrangement shown in Figure 2a. However, the cross-jet in this embodiment must be designed so as not to interfere with the optical system. For example, when an immersion optical system is used, the immersion fluid may be supplied in a cross-flow, preferably laminar flow, to avoid optical effects due to turbulence within the immersion fluid.

[0068] Such cross-jets of air or liquid can generate vibrations that could jeopardize recording accuracy, and using cross-jets for the embodiment shown in Figure 2a is complex; therefore, it is preferable to provide a negatively charged mesh or sheet 15 as shown in Figures 2a and 2b. As described above, the use of a picosecond or femtosecond laser forms a plasma within the ceramic material to be ablated. Briefly, portions of the atomic shell of the ceramic material are removed by interaction with the laser pulse. The remaining positively charged atomic cores are then ejected in a so-called Coulomb explosion. These positively charged atomic cores can then be attracted by the negatively charged mesh or sheet 15. This is particularly advantageous in the embodiment shown in Figure 2a, where the laser beam 4 can pass through openings in the mesh or plate. All debris is then collected by the charged mesh or plate, and therefore the debris does not adversely affect, for example, the focusing optical system 8.

[0069] Further details of another preferred embodiment of the device of the present invention are shown in Figure 3. For example, Figure 3 shows a collimating optical system 5 for collimating the laser light emitted onto the DMD 3 by the laser source 2, as well as further optical components such as spatial filters 10, 11. The substrate holder 6 is an XY positioning system for translating the substrate 7 along the xy plane (z is perpendicular to the surface of the substrate 7) in the case of Figure 3. Both the DMD 3 and the XY positioning system 6 are controlled by a computer 13 configured to control the DMD 3 and the XY positioning system 6 to perform the following steps: 1) irradiating a laser beam selectively onto multiple areas within a first area of ​​a layer 1 of ceramic material using the DMD 3, such that the first area can be covered by the DMD 3; 2) translating the layer 1 of ceramic material (i.e., the entire substrate 7 in this example) so that a second area different from the first area can be covered by the DMD 3; and 3) irradiating a laser beam selectively onto multiple areas within a second area of ​​the layer 1 of ceramic material using the DMD 3.

[0070] As mentioned above, the device preferably includes a beam shaping device for achieving, for example, a Bessel beam. For example, a matrix of laser zone plates 12 may be provided between the DMD 3 and the focusing optical system 8 to shape each of the laser beams 4 (see Figure 1) into a Bessel beam shape. Each Bessel beam is then focused onto the substrate 7 by an accompanying lens (e.g., a Fresnel lens) 8. Additional collimating optical systems 14a and 14b may be provided to properly illuminate the matrix of the laser zone plates 12. This principle is further illustrated in Figure 4, which shows how a Bessel beam is generated (for a single beamlet) by a combination of an optical element 12a that forms circular polarization and a binary phase element 12b for forming a Bessel beam, and the Bessel beam is then focused onto the substrate 7 by an accompanying high NA lens 8 (or Fresnel lens 8). As also shown in Figure 4, by using such a Bessel beam, a focal length of at least four times the wavelength of the laser light can be achieved. Moreover, the focal point has a more cylindrical shape than a Gaussian beam.

[0071] Further details of another preferred embodiment of the device of the present invention are shown in Figure 5. For example, Figure 5 further shows an optional flat-top beam shaper 21 positioned between the collimating optical system 5 and the DMD 3. More importantly, the preferred embodiment shown in Figure 5 includes a prism 16. The prism 16 (which may be replaced by a translucent mirror) is positioned between the laser source 2 and the DMD 3 such that light emitted from the laser source 2 passes, in order, through the prism 16, the λ / 4 plate 17a, and strikes the DMD 3, passing through the λ / 4 plate 17a and the prism 16 again before selectively illuminating multiple areas of the substrate 7.

[0072] Linearly polarized light from the upper optical path that collides with prism 16 is reflected to the right, i.e., towards DMD3. By passing through the λ / 4 plate 17a twice, the polarization axis of the laser light rotates by a total of 90°. Therefore, linearly polarized light that collides with prism 16 from the right optical path passes through prism 16.

[0073] To convert linearly polarized light to circularly polarized light, an additional λ / 4 plate 17b may be provided, which is particularly advantageous for forming a Bessel beam in the laser zone plate 12. As described above, the Bessel beam allows for the formation of a clearly defined cylindrical recess.

[0074] A preferred embodiment shown in Figure 5 further comprises a reading device 18 configured to image the recorded data. Thus, a single write and read head can be used for both encoding (writing) data in a layer of ceramic material and decoding (reading) the encoded data in such data carriers. A beam splitter 19 between the prism 16 and the focusing optical system 8 allows light emitted from the substrate to pass through the reading device 18. A further light source 20 (e.g., an LED) is adapted to illuminate the substrate through the prism 16 and DMD 3 during reading / decoding. For this purpose, a further beam splitter 23 is provided. By passing through the λ / 4 plate 17b twice, the polarization axis of the laser light generated from the light source 20 rotates again by 90°. Thus, the linearly polarized light that collides with the beam splitter 19 passes through the beam splitter 19.

[0075] Of course, other arrangements of the optical components of the device shown in Figure 5 are also possible. For example, the reading device 18 may also be positioned on the fourth surface of the prism 16, as shown in Figure 6, rather than on the optical axis of the focusing optical system 8, as shown in Figure 5. In this case, the beam splitter 19 is no longer required. The λ / 4 plate 17b again ensures that the laser light generated from the light source 20 rotates a total of 90°. Thus, the linearly polarized light that collides with the prism 16 is reflected towards the reading device 18.

[0076] In read mode, the DMD3 can be used in different ways to illuminate the data carriers with light emitted by an additional light source 20. As described above, the data carriers can be illuminated pixel by pixel using the DMD3. In this case, only a single detector is required in the read device, and the scanning of the image is performed by the DMD3.

[0077] In alternative reading modes utilizing SIM or SSIM, a specific illumination pattern ("structured illumination") is generated by the DMD3. In this case, the reading device 18 should be equipped with a digital camera or other multi-pixel detector.

[0078] In a further reading mode, planar illumination can be achieved by simply setting all the micromirrors of the DMD3 to "on". In this case as well, the reading device 18 should be equipped with a digital camera or other multi-pixel detector.

[0079] Of course, if the DMD3's functionality is not used (planar illumination), the reading optical path does not need to incorporate the DMD3. Rather, the data carrier can be illuminated by an additional light source arranged, for example, as shown in Figure 7. Here, linearly polarized light emitted by the light source 20 is reflected toward the data carrier 7 by the beam splitter 24. The light is circularly polarized after passing through the λ / 4 plate 17b, so the light passes through the beam splitter 19 and collides with the data carrier 7. The light reflected or otherwise emitted from the data carrier 7 passes through the beam splitter 19 and λ / 4 plate 17b again. The light is then linearly polarized again (rotated 90°) and thus passes through the beam splitter 24 to reach the reading device 18. This specification discloses the following embodiments. (Embodiment 1) A method for recording data on a layer of ceramic material, The steps include providing a layer of ceramic material, The steps include selectively irradiating multiple regions of the layer of the ceramic material with a laser beam using a digital micromirror device, Includes, The laser beam and irradiation time parameters for each of the selected regions are configured to ablate each of the selected regions in order to record data in the layer of the ceramic material by forming recesses within the layer of the ceramic material. The laser beam is generated from a picosecond laser or a femtosecond laser and, in sequence, passes through a collimating optical system (5), a prism or translucent mirror, and a λ / 4 plate (17a), strikes the digital micromirror device, passes again through the λ / 4 plate (17a) and the prism or translucent mirror, passes through a focusing optical system (8), and selectively irradiates multiple regions of the layer of the ceramic material. method. (Embodiment 2) A device for recording data on a layer of ceramic material (1), A laser source (2) including a picosecond laser or a femtosecond laser, A digital micromirror device (3) adapted to emit multiple laser beams (4), A prism (16) or a translucent mirror is placed between the laser source (2) and the digital micromirror device (3), A circuit board holder (6) for mounting the circuit board (7), A focusing optical system (8) is provided, which is adapted to focus each of the plurality of laser beams (4) emitted by the digital micromirror device (3) onto a substrate (7) attached to the substrate holder (6), A λ / 4 plate (17a) is placed between the prism (16) or the translucent mirror and the digital micromirror device (3), A collimating optical system (5) for collimating the laser light emitted by the laser source (2) onto the digital micromirror device (3), Equipped with, device. (Embodiment 3) The focusing optical system (8) includes a lens having an numerical aperture of at least 0.5. The device described in Embodiment 2. (Embodiment 4) The device further comprises a beam shaping device, a flat-top beam shaping device (21), a matrix of laser zone plates (12), or a spatial light modulator. The device described in Embodiment 2. (Embodiment 5) The system further comprises a processor configured to control the digital micromirror device and an XY positioning system to which the substrate holder is attached. The device described in Embodiment 2. (Embodiment 6) The fluence of each of the plurality of laser beams (4) emitted by the digital micromirror device (3) is 100 mJ / cm². 2 Larger than The device described in Embodiment 2. (Embodiment 7) The prism (16) or the translucent mirror is positioned between the laser source (2) and the digital micromirror device (3) such that the light emitted from the laser source (2) passes through the prism (16) or the translucent mirror in sequence, strikes the digital micromirror device (3), and passes through the prism (16) or the translucent mirror again before selectively illuminating multiple areas of the substrate. The device described in Embodiment 2. (Embodiment 8) The system further comprises a reading device (18) configured to capture the recorded data, The device described in Embodiment 2. (Embodiment 9) The beam splitter (19) is further provided between the prism (16) or the translucent mirror and the focusing optical system (8) to allow light emitted from the substrate to pass through the reading device (18). The device described in Embodiment 8. (Embodiment 10) The further comprising a further light source (20) adapted to irradiate the substrate via the prism (16) or the translucent mirror and the digital micromirror device (3) and / or via the beam splitter (19), The device described in Embodiment 9. (Embodiment 11) The reading device (18) comprises a single optical sensor. The device described in Embodiment 10. (Embodiment 12) The further light source (20) is arranged to irradiate the substrate via a further λ / 4 plate (17b) and via the beam splitter (19), The device described in Embodiment 10. (Embodiment 13) The further λ / 4 plate (17b) and the beam splitter (19) are arranged between the reading device (18) and the focusing optical system (8). The device described in Embodiment 12. (Embodiment 14) The system further comprises a processor configured to decode the captured and recorded data. The device described in Embodiment 8. (Embodiment 15) The processor is adapted to perform SIM and / or SSIM analysis. The device described in Embodiment 14. (Embodiment 16) Using the device described in any one of Embodiments 2 to 15, The method according to Embodiment 1. (Embodiment 17) A method for decoding data encoded in a layer of ceramic material by recesses in the layer of the ceramic material, The steps include providing a layer of ceramic material having a recess, The steps include selectively irradiating multiple regions of the layer of the ceramic material with a laser beam using a digital micromirror device, The steps include detecting light reflected from each of the aforementioned multiple regions, Includes, The layer of the ceramic material is encoded according to Embodiment 1. method. (Embodiment 18) Using the device described in Embodiment 8, The method described in Embodiment 17.

Claims

1. A method for recording data on a layer of ceramic material, The steps include providing a layer of ceramic material, The steps include selectively irradiating multiple regions of the layer of the ceramic material with a laser beam using a digital micromirror device, Includes, The laser beam and irradiation time parameters for each of the selected regions are configured to ablate each of the selected regions in order to record data in the layer of the ceramic material by forming recesses within the layer of the ceramic material. The laser beam is generated from a picosecond laser or a femtosecond laser and, in sequence, passes through the collimating optical system (5), a prism or translucent mirror, and a λ / 4 plate (17a), strikes the digital micromirror device, passes again through the λ / 4 plate (17a) and the prism or translucent mirror, passes through the focusing optical system (8), and selectively irradiates multiple regions of the layer of the ceramic material. method.

2. A device for recording data on a layer of ceramic material (1), A laser source (2) including a picosecond laser or a femtosecond laser, A digital micromirror device (3) adapted to emit multiple laser beams (4), A prism (16) or a translucent mirror is placed between the laser source (2) and the digital micromirror device (3), A circuit board holder (6) for mounting the circuit board (7), A focusing optical system (8) is provided, which is adapted to focus each of the plurality of laser beams (4) emitted by the digital micromirror device (3) onto a substrate (7) attached to the substrate holder (6), A λ / 4 plate (17a) is disposed between the prism (16) or the translucent mirror and the digital micromirror device (3), A collimating optical system (5) for collimating the laser light emitted by the laser source (2) onto the digital micromirror device (3), Equipped with, device.

3. The focusing optical system (8) includes a lens having an numerical aperture of at least 0.

5. The device according to claim 2.

4. The device further comprises a beam shaping device, a flat-top beam shaper (21), a matrix of laser zone plates (12), or a spatial light modulator. The device according to claim 2.

5. The system further comprises a processor configured to control the digital micromirror device and an XY positioning system to which the substrate holder is attached. The device according to claim 2.

6. The fluence of each of the plurality of laser beams (4) emitted by the digital micromirror device (3) is 100 mJ / cm². ２ Larger than The device according to claim 2.

7. The prism (16) or the translucent mirror is positioned between the laser source (2) and the digital micromirror device (3) such that the light emitted from the laser source (2) passes through the prism (16) or the translucent mirror in sequence, strikes the digital micromirror device (3), and passes through the prism (16) or the translucent mirror again before selectively illuminating multiple areas of the substrate. The device according to claim 2.

8. The system further comprises a reading device (18) configured to capture the recorded data, The device according to claim 2.

9. The beam splitter (19) is further provided between the prism (16) or the translucent mirror and the focusing optical system (8) to allow light emitted from the substrate to pass through the reading device (18). The device according to claim 8.

10. The further comprising a further light source (20) adapted to irradiate the substrate via the prism (16) or the translucent mirror and the digital micromirror device (3) and / or via the beam splitter (19), The device according to claim 9.

11. The reading device (18) comprises a single optical sensor. The device according to claim 10.

12. The further light source (20) is arranged to irradiate the substrate via a further λ / 4 plate (17b) and via the beam splitter (19). The device according to claim 10.

13. The further λ / 4 plate (17b) and the beam splitter (19) are arranged between the reading device (18) and the focusing optical system (8). The device according to claim 12.

14. The system further comprises a processor configured to decode the captured and recorded data. The device according to claim 8.

15. The processor is adapted to perform SIM and / or SSIM analysis. The device according to claim 14.

16. Using the device described in any one of claims 2 to 15, The method according to claim 1.

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