The subject matter of this invention is a spacial diffraction grid applied on the surface of crystal-structure stone, through which electromagnetic wave can flow, in particular visible light. The invention is applied in engineering processes using precision systems and machining methods for small surfaces on which such a grid is applied, preferably in jewellery. Thereby, the invention is of significance particularly for precious stones. Commonly known is acquiring complicated surfaces of ornamental stones, in particular precious ones, by grinding, polishing and engraving them. Especially difficult is acquiring a number of flat surfaces with ever smaller areas so that various angles of light incident on the machined stone could give an impression of luminescence either by reflection or refraction of light. In refraction, the light which gets inside can be better released and permeate back into the environment thanks to multiplied structure of surface walls. Luminescent effects are enriched by various technical manipulations used independently on pre-prepared flat multiplied stone surfaces. Some actions are intended to acquire a unique character of luminescent impressions, some are aimed at product identification, and through identification, also protection as a result of hallmarking.

Hence, European patent no. EP2566653 makes known using a marker for diamond identification not visible to the naked eye, and a method of determining stone genuineness due to verification of this marking by means of exposure. In this solution, at least two interference pictures are recorded as an identification mark including information on location in a specific area and angle of incidence of sampling irradiation. However, the energy of engraving laser must be adjusted so that marking forming could not influence diamond purity or its considerable darkening. This is an adverse effect of interfering with the surface structure of ornamental stones, at least partly transparent, in particular precious ones.

European patent no. EP0648445 makes known applying diffraction grid as ornament onto a decoration composed of a light-transmitting material containing a number of cutout walls, where fine grooves constituting the specious grid are formed in at least one or more than one decoration wall. Preferably, groove gaps are almost equal, and are 0.1 μηι up to 1000 μηι, where e.g. diamond, glass, plastics or zirconium form the transmitting material. Both the grooves and the gaps enable diffraction of incident white light ray within the ornament area, where diffraction leads to illuminating with rainbow colours the area with the diffraction grid applied. The diffraction grid can be composed of sub-areas in which parallel grooves are located, and the grooves of adjacent areas are set against one another at an angle within the range of 0-180 degrees. However, the grooves can assume a shape of centric circles or waves, thus creating a pattern. This solution intends to bring into relief the diffraction grid applied from the area not covered by it.

European patent no. EP0839098 makes known a method of generating an information mark invisible to unaided eye on the polished diamond wall using mask and radiation in the presence of reagent which reacts in the irradiated part of crystal wall surface with that crystal, and causes creation of the mark constituting the spacial diffraction grid preferably not greater than 100 nm and not lesser than 1 nm.

Application for invention no. US2006144821 makes known engraving of unique pattern on diamond surface, which subsequently constitutes the spacial diffraction grid, where the entire diamond surface can be covered by unique pattern. Pattern can be at least one pattern selected from a group composed of a photo, print, drawing or signature.

Another European pattern no. EP1042132 makes known a method of generating diffraction grid in the form of marking on the diamond or stone surface, which is composed of one or more alphanumeric characters or similar ones made of grooves, comprising a stage of groove forming on this diamond or stone surface, and the mark is such that it cannot be read out with the naked eye, and the grooves cause a visible diffraction effect in certain lighting conditions, such that the mark can be read out in certain magnification conditions. Irrespective of using the methods mentioned previously, cutting the surface or etching it is, as stated above, by all means unfavourable due to substantial likelihood of darkening of the surface of the stone on which diffraction grid is being applied, and thereby losing the ability to emit light from it.

Hence, British patent no. GB748142 makes known another shape of diffraction grid applied on a transparent jewel to generate colourful effects similar to prismatic dispersion effects related to reflected or refracted light on the diffraction grid. In this case, diffraction grid grooves have a cross-section shape of saw teeth, and a maximum width of a single tooth is λ/2η, where n is the centre refractive index, and λ is the mean length of incident light wave, which gets broken down into constituent colours on the grid.

The solutions presented have certain common features with the solutions encountered in photonic crystal structures used as amplifiers or electromagnetic wave filters, most often in electronics. Such structures are created using dielectric materials by layered application of structures properly calculated for a given wave length.

The indicated filtration applications have been revealed in the Korean patent no. KRl 01455063. The essence of this solution is a multi-layered structure in which at least one layer is etched using photosensitive matrix created by laser beams. The etched layer has holes located structurally, thus creating a diffraction nano-grid. Application for invention JP2013061645 makes known a photonic crystal structure containing a layer composed of many nano-particles of various dimensions at certain distances from one another, where the photonic crystal layer is located on the nano- structure layer and configured so that is reflects light of a certain wave length λ. A configuration is possible that can have several specific wave lengths reflected. Application no. KR20130025721 of SAMSUNG ELECTRONICS makes known a layered-structure photonic crystal, and one with no. KR20100040649 as a filtration system.

Another invention of the same company for which patent has already been granted is the solution indicated under no. JP5580001B2. Photonic crystal is created on the base with diffraction grid structure in two dimensions by placing unit blocks in nano size with determined spacing. The shape of the wave of light reflected selectively by a filter for a certain colour results from both the base material and unit block size. Unit blocks are created in hexagonal or square structure, and the photonic crystal is formed as a single layer or many layers, where blocks are spaced from 100 nm up to 500 nm of one another. The objective of the solution according to the invention is to acquire intensification of luminosity emanating from the crystal-structure stone with modified surface structure of spacial diffraction grid type. To date, this assertion has seemed to be contradictory and unfeasible, as any contravention and interference in the surface structure of this type of stones is associated with surface layer darkening, and thereby retaining the light inside the crystal, which light is hampered in getting out of it. Another objective is a possibility of influencing the light colour, as electromagnetic wave, coming out or reflected off the crystal-structure stone more than the other colours, over the distance of infrared and ultraviolet waves respectively. This objective can be attained by using a structure similar to that of the photonic crystals, to date only used in electronics, and not encountered in the jewellery industry.

According to the invention, the spacial diffraction grid is applied on the crystal-structure stone as a modified surface structure of that stone. The modified surface structure, in particular that of a transparent stone with regular and homogeneous inner material is a structure at least over the area of one ground outer wall of nano-grid type for reflecting, and simultaneously or alternately, refracting electromagnetic wave in the inner material as the centre of propagation of that electromagnetic wave. The modified surface structure causes the cross-section to assume the shape of a broken line with periodically repeating shape, and the modified surface structure in the form of nano-grid constitutes numerous recesses in the inner material, with spacing between the recesses. The invention is characterised by that the maximum width of single recess equals 150% of the length of the electromagnetic wave λ, for which the reflective index of propagation centre n is the lowest, and the recess takes the form of a spatial solid. The adjacent recesses are arranged so that each recess has at least three further recesses in its immediate vicinity, preferably four, or preferably six further recesses, where the electromagnetic wave is a type of visible light wave or ultraviolet wave, or infrared wave. The spatial solid recess can preferably be a solid of revolution, ideally a type of cylinder, cone or hemisphere, or possibly a truncated cone or partial hemisphere with flat vertex. The spatial solid recess can preferably be a regular solid, ideally cube or regular tetrahedron or rectangular prism or pyramid, or possibly truncated pyramid. The broken line with periodically repeating shape preferably has an outline of rectangular wave or trapezoid wave, or possibly one of curved sides. The period preferably equals up to 150% of the maximum width of single recess. Single recess depth preferably equals as much as the maximum width of that recess, ideally 75% of that value. The nano-grid structure can be applied over the area of all the ground outer walls. At least on one ground outer wall a nano-grid structure can be applied with parameters other than those in the nano-grid applied on the other ground outer walls. The recesses located on the same ground outer wall can be of the same type. The recesses located on different ground outer walls can be of different types. The recesses located on different ground outer walls can have a different number of adjacent recesses, and it's preferable that they have the same number of adjacent recesses for a specifically selected ground outer wall. The nano-grid on the ground outer walls, while it constitutes a photonic structure, it's also preferably an identification marker.

The modified surface structure is performed using a laser or focused ion beam, where both the photonic structure arrangement and laser work are operated by means of a computer system. The invention has been presented in the performance example on a drawing on which Fig.1 presents the spacial diffraction grid applied on a crystal diamond stone in the form of ground walls and photonic structure. Fig.2 presents in the diagram the dependence of the refractive index 'n' on the length of the electromagnetic wave 'λ' of visible light. Fig.3 presents a periodically repeating pattern of the diffraction grid as photonic structure, in magnification, performed on all outer walls of the stone except one wall with a different pattern. Fig.4 presents a periodically repeating pattern of the diffraction grid as photonic structure, in magnification, performed on the outer side of the stone, containing an applied pattern with truncated cone recesses other than the pattern on the other walls. Fig. 5 presents a broken line constituting a diamond-air boundary of visible light wave propagation centres for the cylinder recess photonic structures used. Fig. 6 presents a broken line constituting a diamond-air boundary of visible light wave propagation centres for the truncated cone recess photonic structures used.

An example of the spacial diffraction grid applied on crystal-structure stone 1 is a modified surface structure 2 of that stone 1 which is a transparent diamond of regular and homogeneous inner material 3. Over the area of all ground outer walls 4 of stone 1, there is structure 5 applied of nano-grid type 5', 5" for both reflection and refraction of electromagnetic wave in inner material 3 as the propagation centre on that electromagnetic wave. Cross-section of modified surface structure 2 has the form of broken line 6 with periodically repeating shape of rectangular wave 6' for almost all outer walls 4, and modified surface structure 2 in the form of nano-grid 5', 5", constitutes numerous recesses 7 in inner material 3, with spacing 8 between recesses 7. Maximum width of single recess 7 equals the length of electromagnetic wave λ, for which the diamond reflective index n is the lowest for the case of visible light electromagnetic wave, and mean wave length was adopted, for which recess T width was allocated equalling 600 nm. Recess 7' is a spatial solid in shape, and adjacent recesses 7' are arranged so that every recess T has further recesses T in its immediate vicinity. Recess 7' in a form of spatial solid is a solid of revolution - cylinder. The period equals up to 150% of the maximum width of single recess T, and takes the value of 800 nm by keeping that rule for the performance example. Single recess depth 7', 7" equals as much as the maximum width of that recess 7', 7", ideally 75% of that value, which means conformity for the value of 400 nm by keeping that rule for the performance example. The structure of nano-grid 5' type is applied in this form over the area of all ground outer walls 4' except one 4", for which the structure of nano-grid 5" has parameters other than those in the nano-grid 5' applied on the other ground outer walls 4'. This one recessed outer wall 4" has recesses 7" in the form of truncated cone with its smaller base directed inward towards the diamond, and every recess 7" has only four direct adjacent further recesses 7", and - including farther vicinity - it has eight adjacent recesses 7", and broken line 6" takes the form of trapezoid wave. Recesses 7" are 500 nm deep, where the diameter of the large base is 600 nm, the diameter of the small base is 300 nm, and the period of repeatability of nano-grid 5 is 700 nm. Recesses 7 located on the same ground outer wall 4 are of the same type. Recesses T, 7" located on different respective ground outer walls 4', 4" are of different type - cylinder recesses T and truncated cone recesses 7" respectively. Recesses 7', 7" located on different respective ground outer walls 4', 4" have a different number of adjacent respective recesses 7', 7", and they have the same number of adjacent recesses 7 for specifically selected ground outer wall 4. Nano-grid 5 on ground outer walls 4, while it constitutes a photonic structure, it's also an identification marker, as the luminous effect of outer walls 4' with the structure applied, so-called brilliance, is improved by 30% as compared to brilliance of a diamond devoid of such structure. The amount of light of the stone's selected outer wall 4" with a different photonic structure is smaller than the rest of the example diamond, although it is still improved by 10% as compared to the non-photonic structure diamond, that is one without the spacial diffraction grid.