ELECTROMAGNETIC WAVEGUIDE

Description

Domaine technique

[0001] The present invention relates to the field of guiding electromagnetic waves, in particular by the Inhibited Coupling mechanism, and in particular waves in the fields of optics, Tera Hertz and Microwaves.

[0002] The invention provides a waveguide allowing single-mode guidance and, in certain cases, preservation of the polarization of the electromagnetic wave in the waveguide. État de la technique

[0003] Several types of hollow optical fibers are currently in use or under study.

[0004] Among these types of optical fibers are hollow fibers with photonic crystals or micro-structured hollow fibers, by guidance known as Photonic Band Gap, also called BIP. Such fibers are of interest in the fields of nonlinear optics, optical frequency conversion, and spectroscopy. However, this type of fiber shows limitations, particularly in terms of: a. linear losses: they amount to about 1dB / km for a wavelength of the order of 1.5 µm, this value increases rapidly for shorter wavelengths such as those in the visible range for which it is possible to achieve linear losses of the order of 1000dBIkm; b. offset for power lasers: due to a strong overlap of the guided mode in the fiber core with its silica contour, the damage threshold is barely higher than for solid core fibers of the same diameter; c. bandwidth: BIP hollow fibers have a narrow transmission band, of the order of 70THz. These transmission bands are too narrow for applications such as nonlinear optics, frequency conversion, very short laser pulses; d.Dispersion: Despite guidance in air, the dispersion in BIP hollow fibers is too high and structured, which poses a problem for applications such as high-resolution spectroscopy or for short laser pulses, but also limits single-mode guidance in this type of fiber.

[0005] Current hollow optical fibers guided by an inhibited coupling mechanism allow light to be guided over wide transmission bands with relatively low dispersion but with relatively high losses. Losses for this type of fiber are attenuated by using a hypocycloidal contour core.

[0006] Current research aims to further reduce losses for this type of optical fiber.

[0007] Furthermore, current optical fibers being intrinsically multimode, this limits their application in certain areas such as telecommunications for example.

[0008] Patent document WO2019 / 071921A1 discloses a hollow core anti-resonant optical fiber having multiple anti-resonant layers. Résumé de l'invention

[0009] The present invention relates to an electromagnetic waveguide, based on the inhibited coupling mechanism, comprising a hollow central part whose contour is at least partly defined by a first set of at least seven primary hollow tubes, distributed in an annular manner around the central hollow part, said primary hollow tubes being substantially of the same size, distant from each other. According to the invention, said waveguide further comprises a second set of tubes comprising at least one hollow secondary tube, when there are several of them, these secondary tubes are positioned in an annular manner around the primary tubes, the area of ​​the at least one hollow secondary tube being between 0.35 and 0.50 times the area of ​​the central hollow part.

[0010] The primary tubes can be attached to the secondary tubes or to a wall of a duct carrying the secondary tubes.

[0011] The area of ​​the central hollow part is understood to be the area of ​​the inscribed circle, internal to the annular arrangement of the first set of hollow tubes.

[0012] Advantageously, the ratio, or scaling law, between the area of ​​the central hollow part and the area of ​​the at least one hollow secondary tube makes it possible to limit the losses of the waveguide according to the invention.

[0013] Advantageously, the waveguide according to the invention in particular achieves monomodal guidance of the waves, for example by filtering the first four higher order modes of the core in order to retain only the fundamental mode of the core.

[0014] In a particularly advantageous embodiment, the at least one hollow secondary tube is positioned opposite a first hollow tube.

[0015] In another particularly advantageous embodiment, the at least one hollow secondary tube is positioned opposite a gap between two primary hollow tubes.

[0016] Advantageously, the primary tubes may have a section of one of the following shapes: a. a circle; b. an ellipse; c. a barred ellipse; d. at least two circles, including a first circle and at least one second circle inscribed in the first circle.

[0017] Advantageously, the primary hollow tubes may have a section composed of a first circle comprising at least one inscribed circle, in the case of several inscribed circles, these inscribed circles are distributed over the internal circumference of the first circle, said inscribed circles being distant from each other.

[0018] Advantageously, if the primary tubes have an elliptical section, the major axis of said ellipse is positioned radially relative to the center of the hollow central part, also called the hollow core.

[0019] Advantageously, if the primary tubes have a section in the shape of a barred ellipse, said ellipse is divided in two by a segment.

[0020] If the primary tubes have a barred ellipse-shaped section, the segment dividing the ellipse section in two is located on the minor axis of said ellipse.

[0021] Advantageously, the at least one secondary tube may have a section of one of the following shapes: a. a circle; b. a hexagon; c. a square; d. a triangle; e. a shape whose outline is composed of an arc of a circle and three sides of a polygon, also called a petal shape.

[0022] The secondary tubes secondary tubes can be distant from each other.

[0023] Alternatively, the secondary tubes may touch each other

[0024] The sections of the secondary tubes can form a grid comprising at least one unit element.

[0025] The grid may consist of several unit elements of different shapes.

[0026] A unit element can be polyhedral in shape.

[0027] The sections of the secondary tubes can, for example, form a grid of hexagonal unit elements.

[0028] The sections of the secondary tubes can, for example, form a grid of triangular unit elements.

[0029] Alternatively, the sections of the secondary tubes may, for example, form a grid of substantially square unit elements.

[0030] Alternatively, the sections of the secondary tubes can, for example, form a grid of rectangular unit elements.

[0031] The secondary tubes may form a grid having more than one type of unit element and arranged to form a mesh, triangular, hexagonal, square or a combination of these arrangements.

[0032] The secondary tubes, whose outline is composed of an arc of a circle and three sides of a polygon, can be distributed so as to form at least one corolla surrounding the primary tubes. Each of the shapes composing the corolla can be contiguous with its neighbor.

[0033] In a particular embodiment of the invention, the waveguide may be an optical fiber.

[0034] The optical fiber can be a micro-structured optical fiber.

[0035] Both primary and secondary tubes can be made of dielectric material.

[0036] The first and secondary tubes can have walls of the same thickness, for example between 100nm and 2000nm.

[0037] The hollow central part, the first and secondary tubes can be filled with a gas such as air.

[0038] The waveguide according to the invention guides waves in particular by inhibited coupling.

[0039] The waveguide can guide waves among: has. waves from extreme ultraviolet to infrared; b. Tera-hertz waves; c. microwaves.

[0040] The material of the secondary tubes can be a low absorption coefficient material such as Teflon, having a refractive index greater than 1.2 times that of air.

[0041] Alternatively, the secondary tube material can be a highly reflective material such as a metal like copper.

[0042] Alternatively, the secondary tube material may be a low absorption coefficient material such as silica.

[0043] The material of the secondary tubes may be a transparent silica-type material having a refractive index jump greater than 1.2 times the refractive index of vacuum.

[0044] The waveguide according to the invention may, in a particularly advantageous embodiment, further comprise a set of rods, at least one rod being positioned between two primary tubes, at a distance from secondary tubes.

[0045] In such an embodiment, the waveguide maintains the polarization of the guided waves.

[0046] The at least one third tube may be of one of the following shapes: a. a solid cylindrical tube; b. a solid elliptical tube; c. a hollow cylindrical tube; d. a barred hollow cylindrical tube whose halves are separated along the entire length of the tube; e. a barred hollow elliptical tube whose halves are separated along the entire length of the tube.

[0047] According to the invention, the secondary tubes can be made in a sheath of the waveguide and the primary tubes can be fixed to the internal wall of said sheath.

[0048] In such a case, for example, the distance δ rr between the at least one secondary tube and the internal wall of the sheath is preferably less than 0.2*r tin for the case of a circular primary tube or less than 0.2*√(Area in / π) for a primary tube having an area equal to Area in .

[0049] According to the invention, each primary tube can be fixed to the wall of a secondary tube.

[0050] The invention thus provides for the case where the primary tubes are made in a vacuum but fixed to secondary tubes which can be made partially or totally in the sheath or made in a vacuum but fixed to a wall of a jacket for example. Description des figures

[0051] Other advantages and particularities of the invention will appear on reading the detailed description of implementations and embodiments which are in no way limiting, and the following appended drawings: [ fig.1a ] There figure 1a represents a first example of a waveguide according to the invention comprising a hollow core and two concentric annular structures, of which the first annular structure comprises seven tubes and the second annular structure comprises one tube; [ fig.1b ] There figure 1b represents different possible shapes for tubes making up a first annular structure of the waveguide according to the invention; [ fig.1c ] There figure 1c represents different possible shapes for tubes making up a second annular structure of the waveguide according to the invention; [ fig.2 ] There figure 2 represents a second example of a waveguide according to the invention comprising two tubes in the second annular structure, positioned facing a gap between two tubes of the first annular structure comprising eight tubes; [ fig.3 ] There figure 3 represents a third example of a waveguide according to the invention comprising four tubes in the second annular structure positioned facing a gap between two tubes of the first annular structure comprising eight tubes; [ fig.4 ] There figure 4 represents a fourth example of a waveguide according to the invention comprising two tubes in the second annular structure positioned facing a tube of the first annular structure comprising eight tubes; [ fig.5 ] There figure 5 represents a fifth example of a waveguide according to the invention comprising four tubes in the second annular structure positioned facing a tube of the first annular structure comprising eight tubes; [ fig.6 ] There figure 6 represents a sixth example of a waveguide according to the invention comprising eight tubes in the first annular structure and comprising eight tubes in the second annular structure, according to the invention; [ fig.7 ] There figure 7 represents a seventh example of a polarization-maintaining waveguide according to the invention; [ fig.8 ] There figure 8 represents an eighth example of a single-mode, polarization-maintaining waveguide according to the invention; [ fig.9 ] There figure 9 represents several possible shapes for stems present in the first annular structure; [ fig.10 ] There figure 10 represents a ninth example of a waveguide according to the invention comprising nine tubes in the first annular structure and a second annular structure comprising petal-shaped tubes; [ fig.11 ] There figure 11 represents a tenth example of a waveguide according to the invention comprising nine tubes in the first annular structure and comprising a second annular structure notably composed of a grid of square unitary pattern; [ fig.12 ] There figure 12 represents an eleventh example of a waveguide according to the invention comprising seven tubes in the first annular structure and comprising a second annular structure notably composed of a grid of hexagonal unitary pattern; [ fig.13a ] There figure 13a represents a first alternative to the first ring of a waveguide according to the invention comprising nine tubes with circular section each comprising another tube with circular section; [ fig.13b ] There figure 13b represents a second alternative to the first ring of a waveguide according to the invention comprising nine tubes with circular section each comprising three other tubes with circular section; [ fig.13c ] There figure 13c represents a third alternative to the first ring of a waveguide according to the invention comprising ten tubes of elliptical section; [ fig.13d ] There figure 13d represents a fourth alternative of a structure of the first ring of a waveguide according to the invention comprising ten tubes of barred elliptical section.

[0052] An objective of the present invention is in particular to reduce the losses for a given order propagation mode and to increase the losses for higher order propagation modes. Description détaillée de l'invention

[0053] The object of the present invention is in particular to propose an electromagnetic waveguide having a hollow central part delimited by a first set of tubes insulated from each other, carried by a first tubular structure, and arranged so as to form a ring, called for example an internal ring or first ring, and a second annular structure or external ring. The second annular structure may advantageously comprise a second set of tubes positioned around the ring formed by the tubes of the internal ring.

[0054] The present invention can be applied in different fields and in particular for guiding waves in the field of optics, Tera Hertz, microwaves.

[0055] There figure 1a represents a first example of an electromagnetic waveguide 1 according to the invention. The first electromagnetic waveguide 1 may be a hollow optical fiber with inhibited coupling guidance.

[0056] The waveguide 1 comprises a hollow central part or hollow core 2 which can be filled with either air, a neutral gas or a vacuum. The hollow core 2 can have a minimum diameter 2 R c , R c corresponding to a radius of the hollow core 2. Around the hollow core 2 is a first ring 4 or cylindrical internal ring 4 or first annular structure 4, contained in the void like the hollow core 2, extending over the entire length of the waveguide. The internal ring 4 has an internal radius R c and for external radius R st .

[0057] The inner ring 4 comprises several primary hollow tubes 8, 9, 10, 11, 12, 13, 14 spaced apart from each other. For example, as shown in the figure 1a , the first waveguide 1 may comprise seven primary tubes of circular section. A distance between two primary tubes may be δ tt . The distance δ tt is preferably greater than zero. The distance δ tt is preferably, but not limited to, equal to or less than 0.1 r tin for tubes of the first ring of circular shape of radius r tin , Or 0.1 Aire in / π for a non-circular tube having an area of Aire in . The distance δ tt can be between 800nm ​​and 2µm.

[0058] R c ,r tin and δ tt can be linked by the following relationship: r tin = R c sin π N − δ tt 2 1 − sin π N with N, the number of primary tubes of the inner ring 4.

[0059] For non-circular tubes, the relationship remains valid by replacing Rc, r tin by 0.1 Aire C / π And 0.1 Aire in / π respectively

[0060] A waveguide according to the invention advantageously comprises at least seven primary tubes. The waveguide may however comprise more than seven primary tubes.

[0061] For example, a waveguide comprising six primary tubes has a smaller core size than a waveguide comprising seven primary tubes. Using at least seven primary tubes minimizes losses, particularly because the core is larger than with seven primary tubes.

[0062] The primary tubes may be carried by an internal wall 5 of a sheath 3.

[0063] On the figure 1a , the primary tubes 8, 9, 10, 11, 12, 13, 14 are represented according to a first circular section shape 16 as represented in the figure 1b .

[0064] On the figure 1b other possible shapes are found for the primary tubes 16, 17, 19, 103, 104. A second shape may be of circular section 17 and comprise at least one other tube of circular section 18, 100, 101, 102. For example and as shown in the figure 1b , the second form may comprise a tube of circular section 18. A third form may alternatively comprise two or three tubes 100, 101, 102 contained in a first tube 19, of circular shape.

[0065] For example, the tubes 100, 101, 102 included in the primary tubes 19 may be distant from each other, and in contact with the internal surface of the primary tubes 19.

[0066] A fourth cross-sectional shape for the primary tubes may be an ellipsoidal shape 103, 104 as shown in FIG. figure 1b The major axis of the ellipse may be oriented radially, i.e. in the direction of the center of the first waveguide 1. In a particular embodiment, the ellipse 104 may be a barred ellipse, for example according to its small diameter. The bar 105 may extend over the entire length of the first elliptical section tube 104.

[0067] It is also possible that the primary tubes have a different cross-sectional shape from each other.

[0068] As shown on the figure 1a , the first waveguide 1 according to the invention further comprises the sheath 3 which constitutes a second ring also called external ring 3 comprising at least one hollow cylindrical secondary tube 6 of diameter 2 R tout . The ray R tout can be included in the interval [ 0,6 × R c ; 0,7 × R c ] . Preferably R tout =0,66 × R c .

[0069] The interior of the outer ring 3 is formed from a solid material into which the at least one hollow secondary tube 6 is inserted.

[0070] The distance between the at least one secondary tube 6 and the external surface of the internal ring 4 is δ rr .δ rr can be negative. Preferably δ rr < 0.2 r tin for the case of a circular tube or δ rr < 0.2 Aire in / π for a tube having an area equal to A ire in .

[0071] On the figure 1a , the secondary tube 6 is positioned opposite a gap between two consecutive primary tubes 8 and 14, for example. The secondary tube 6 can alternatively be positioned opposite a first tube 8, 9, 10, 11, 12, 13, 14.

[0072] There figure 1c represents several examples of possible shapes for the section of the at least one secondary tube. A first shape may be a circular section 106, a second shape may be a polygonal section shape, for example square 107, or triangular, a third shape may be a hexagonal section 108. A fourth shape 109 may be a section composed of a portion of a circle closed by a portion of a hexagon or polygon, for example with three branches. The fourth shape 109 may be called a petal shape.

[0073] Advantageously, it is possible to have at least one secondary tube of a shape such as shown in the figure 1c and other secondary tubes of different shapes, for example the other shapes shown in the figure 1c , the shapes represented on the figure 1b .

[0074] The secondary tubes of circular section can be spaced apart from each other.

[0075] The sections of the secondary tubes may form a grid comprising at least one unit element of one of the section shapes shown in the figure 1c . For example, the sections of the secondary tubes may form a grid of hexagonal unit elements. Alternatively, the sections of the secondary tubes may form a grid of triangular unit elements. In another possible embodiment, the sections of the secondary tubes may form a grid of substantially square unit elements.

[0076] Generally, the sections of the secondary tubes may form a grid comprising more than one unit element, said unit elements being arranged to form a triangular, hexagonal, square mesh or a combination of these arrangements.

[0077] On the figure 1a , a second tubular structure 7 can form a jacket of the waveguide according to the invention. The secondary tube 6 can be carried by the second tubular structure 7.

[0078] Advantageously, such a waveguide makes it possible to maintain fairly low energy losses for the mode to be propagated and to increase the losses for the higher order modes. Indeed, the higher order modes can leak through the gaps between two consecutive primary tubes when they are not placed opposite the secondary tubes. Alternatively, the higher order modes can leak through the secondary tubes when these are in contact with the primary tubes.

[0079] There figure 2 represents a second example of a waveguide 20 according to the invention.

[0080] The second waveguide 20, like the first waveguide 1, comprises a core 29 surrounded by a first ring 24 consisting of eight primary tubes 200, 201, 202, 203, 204, 205, 206, 207. The eight primary tubes 200, 201, 202, 203, 204, 205, 206, 207 are supported by the inner wall 27 of a sheath 25 forming an outer ring.

[0081] The second waveguide 20 also comprises two secondary tubes 21, 22 forming part of an external ring 25. The two secondary tubes 21, 22 are positioned opposite the core 2 and two intervals between two consecutive primary tubes 200, 201 and 204, 205.

[0082] The configuration of the secondary tubes opposite a gap between two primary tubes is particularly relevant when the distance between two consecutive primary tubes is relatively large.

[0083] A second tubular structure 26 can form a jacket of the waveguide according to the invention. The secondary tubes 21, 22 can be carried by the second tubular structure 26.

[0084] There figure 3 represents a third example of a waveguide 30 with monomodal wave propagation according to the invention.

[0085] The second waveguide 30, like the first waveguide 1, comprises a core 38 surrounded by a first ring 39 consisting of eight primary tubes 300, 301, 302, 303, 304, 305, 306, 307. The eight primary tubes 300, 301, 302, 303, 304, 305, 306, 307 are supported by the inner wall 37 of a sheath 35 forming an outer ring.

[0086] The second waveguide 30 also comprises four secondary tubes 31, 32, 33, 34 forming part of a second ring 35. The four secondary tubes 31, 32, 33, 34 are positioned opposite a gap between two of the primary tubes of the first ring 39. Respectively on the figure 3 , the four secondary tubes 31, 32, 33, 34 are positioned opposite the interstices between the primary tubes 304 and 305, 306 and 307, 300 and 301, 302 and 303.

[0087] A second tubular structure 36 can form a jacket of the waveguide according to the invention. The secondary tubes 31, 32, 33, 34 can be carried by the second tubular structure 36.

[0088] There figure 4 represents a fourth example of a waveguide 40 with monomodal wave propagation according to the invention.

[0089] The fourth waveguide 40, like the third waveguide 30, comprises a core 41 surrounded by a first ring 42 consisting of eight primary tubes 400, 401, 402, 403, 404, 405, 406, 407. The eight primary tubes 400, 401, 402, 403, 404, 405, 406, 407 are supported by the inner wall 44 of a sheath 43 forming an outer ring. The eight primary tubes 400, 401, 402, 403, 404, 405, 406, 407 are for example but not necessarily regularly distributed in the first ring 42. The fourth waveguide 40 also comprises two secondary tubes 47, 48 forming part of a second ring 43. The two secondary tubes 47, 48 are positioned opposite one of the primary tubes of the first ring 42.

[0090] A second tubular structure 45 may form a jacket of the waveguide according to the invention. The secondary tubes 47, 48 may be carried by the second tubular structure 45.

[0091] Advantageously, the alignment of primary tubes 47, 48 with secondary tubes 402, 406 allows unwanted propagation modes to be leaked. This type of waveguide architecture is particularly relevant when the spaces between the primary tubes are relatively small.

[0092] There figure 5 represents a fifth example of a single-mode wave propagation waveguide 50 according to the invention.

[0093] The fifth waveguide 50 comprises eight primary tubes 501, 502, 503, 504, 505, 506, 507, 508 distributed over a first ring 57 around the core 56. The primary tubes 501, 502, 503, 504, 505, 506, 507, 508 may be carried by the internal wall 59 of a sheath 55 forming an external ring.

[0094] The fifth waveguide 50 further comprises a second ring 55 comprising secondary tubes 51, 53, 52, 54. The secondary tubes are respectively located opposite the primary tubes 502, 504, 506, 508. The secondary tubes 502, 504, 506, 508 may be distant from each other.

[0095] A second tubular structure 58 can form a jacket of the waveguide according to the invention. The secondary tubes 51, 53, 52, 54 can be carried by the second tubular structure 58.

[0096] There figure 6 represents a sixth example of a single-mode propagation waveguide 80 according to the invention.

[0097] The sixth waveguide 80 comprises eight primary tubes 84, 85, 86, 87, 88, 89, 800, 801 distributed over a first ring 82 around the core 81. The sixth waveguide 80 further comprises a second ring 83 comprising eight secondary tubes 802, 803, 804, 805, 806, 807, 808, 809. The secondary tubes 802, 803, 804, 805, 806, 807, 808, 809 are respectively located opposite the primary tubes 84, 85, 86, 87, 88, 89, 800, 801. On the figure 6 and for example, each primary tube 84, 85, 86, 87, 88, 89, 800, 801 is in direct contact with the secondary tube 802, 803, 804, 805, 806, 807, 808, 809 respectively opposite. The primary and secondary tubes are thus fixed two by two and suspended in the void. Each secondary tube is fixed to a wall 810, which can be the internal wall of a sheath or other jacket for example.

[0098] There figure 7 represents a seventh example of a waveguide 90. The seventh waveguide 90 is a polarization-maintaining waveguide. Polarization maintenance is ensured by the presence of rods, for example four rods, distributed in every other gap between primary tubes forming part of a first ring surrounding a hollow core 91. The rods may have a section whose area is <0.2xArea in (the area of ​​a tube of the first set).

[0099] The seventh waveguide 90 may comprise a first ring 92 comprising, for example, eight primary tubes 95, 96, 97, 98, 99, 900, 901, 902 surrounding the hollow core 91. Further, the seventh waveguide 90 may comprise four rods 904, 905, 906, 907 positioned in the first ring 92. For example, a first rod 904 may be inserted between a primary tube 95 and a subsequent primary tube 96 on the first ring 92 by rotating clockwise. A second rod 905 may be inserted between a primary tube 97 and a primary tube 98. A third rod 906 may be inserted between a primary tube 99 and a primary tube 900. The gap between primary tubes 902 and 95, 96 and 97, 98 and 99, 900 and 901 does not include a rod.

[0100] The rods 904, 905, 906, 907 like the first tubes 95, 96, 97, 98, 99, 900, 901, 902 are carried by an internal wall of a sheath 93 surrounding the first ring 92.

[0101] Advantageously, the positioning of the rods 904, 905, 906, 907 in every other gap separating the primary tubes makes it possible to maintain the polarization of the wave propagating in the seventh waveguide.

[0102] There figure 8 represents an example of an eighth single-mode, polarization-maintaining waveguide 110 according to the invention.

[0103] The eighth waveguide 110 as shown in the figure 10 combines the advantages and features of the seventh polarization-maintaining 90 waveguide and the third single-mode propagation 30 waveguide.

[0104] The eighth waveguide 110 comprises a hollow core 111 surrounded by a first ring 112. The first ring 112 comprises eight primary tubes 1120, 1121, 1122, 1123, 1124, 1125, 1126, 1127. In every other interval between two consecutive primary tubes is inserted a rod 1128, 1129, 1130, 1131. For example a first rod 1128 can be inserted between two primary tubes 1120, 1121, a second rod 1129 can be inserted between two primary tubes 1122 and 1123, a third rod 1130 can be inserted between two primary tubes 1124 and 1125, a fourth rod 1131 can be inserted between two primary tubes 1126 and 1127.

[0105] Furthermore, the eighth waveguide 110 comprises a second ring 113 comprising four secondary tubes 116, 117, 118, 119. The secondary tubes may for example be positioned opposite the intervals between the primary tubes 1121 and 1122, 1123 and 1123, 1125 and 1126, 1127 and 1120, between which no rod has been inserted.

[0106] Advantageously, the positioning of the rods 1128, 1129, 1130, 1131 in every other gap separating the primary tubes 1120, 1121, 1122, 1123, 1124, 1125, 1126, 1127 makes it possible to maintain the polarization of the wave propagating in the waveguide according to the invention. The positioning of the secondary tubes 116, 117, 118, 119 opposite every second gap separating the primary tubes, said second gaps not comprising rods, makes it possible to increase the losses for the modes of orders higher than the mode preferentially guided in the core of the waveguide according to the invention.

[0107] There figure 9 represents different sections of rods that can be used in the context of the invention. A first type of rods can be a solid cylindrical tube 150. A second type of rod can be a solid tube with an ellipsoidal section 151, also called an elliptical rod 151. A third type of rod can be a hollow cylinder 153. A fourth type of rod 154 can be a hollow cylindrical tube with a longitudinal separation, dividing said cylinder into two cylinder portions, the fourth type of rod can be called a barred tube 154. A fifth type of rod 152 can be a hollow tube with an elliptical section with a separation along the entire length of the rod 152 along the major axis of the elliptical section, the fifth type of guide can be called a barred elliptical tube 152.

[0108] There figure 10 represents a ninth example of a waveguide 120 according to the invention.

[0109] On the figure 10 , the ninth waveguide 120 comprises a hollow core 121 surrounded by a first ring 122.

[0110] The first ring 112 may comprise nine primary tubes 123. The primary tubes 123 may have one of the shapes shown in the figure 1b The primary tubes 123 may be carried by the first annular structure 124.

[0111] The first ring 122 is surrounded by a second ring 125. The second ring 125 may comprise secondary tubes 126 in the form of petals 109, as shown in the figure 1c .

[0112] On the figure 10 and by way of example the second ring 125 comprises eleven primary tubes 126 in the form of petals distributed homogeneously on this second ring 125. For example on the figure 10 , the petals are contiguous and form a first corolla. It is possible in an alternative embodiment to have at least a second corolla surrounding the first corolla.

[0113] The secondary tubes 126 are carried by a sheath or jacket 127 surrounding the second ring 125.

[0114] There figure 11 represents a tenth example of a waveguide 130 according to the invention.

[0115] On the figure 11 the tenth waveguide 130 comprises a hollow core 131 surrounded by a first ring 132.

[0116] The first ring 132 comprises, for example, nine primary tubes 133. The primary tubes 133 may have one of the shapes shown in the figure 1b .

[0117] The first tubes 133 can be supported by a grid 134.

[0118] The tenth waveguide 130 further comprises a second ring 135 comprising secondary tubes 136 forming a grid 134 of square unitary pattern. The grid is cut so as to form the second ring 135 around the first ring 132 and so as to have an external contour 137 of circular shape.

[0119] On the figure 11 a jacket 138 is shown, said jacket 138 surrounding the second ring 135.

[0120] There figure 12 represents an eleventh example of a waveguide 140 according to the invention.

[0121] On the figure 12 , the eleventh waveguide 140 comprises a hollow core 141.

[0122] The hollow core 141 is surrounded by a first ring 142 comprising primary hollow tubes 143. For example, on the figure 12 , seven primary hollow tubes 143 are shown.

[0123] The primary hollow tubes 143 may be of any of the shapes shown in the figure 1b .

[0124] The first hollow tubes 143 may be carried by a first tubular structure 145.

[0125] The eleventh waveguide 140 further comprises a second ring 146. The secondary tubes of the second ring 146 are arranged to form a hexagonal unitary pattern grid such as a Kagomé structure, for example. The hexagonal unitary pattern grid is cut to have a circular inner contour and an outer contour.

[0126] Generally, the secondary tubes forming the second ring may form a grid comprising at least one unit element. The unit element may have a section of one of the shapes shown in the figures 1b, 1c , or even a triangular shape.

[0127] Alternatively, the grid may be composed of several different unitary patterns among the shapes represented on the figures 1b, 1c , a triangular shape.

[0128] Thus, the secondary tubes can form a grid of triangular, or substantially square, or rectangular unit elements.

[0129] On the figure 12 a jacket 147 of the eleventh waveguide is also shown, surrounding the second ring 146.

[0130] There figure 13a represents an example of a first alternative structure of a first ring 150 of a waveguide according to the invention. On the figure 13a an example of an arrangement of primary tubes 151 according to the invention is shown. The primary tubes 151 shown in the figure 13a are of the second form of the primary tubes 16 shown on the figure 1b . Each first tube 151 therefore comprises another tube with circular section 152 as shown in the figure 1b .

[0131] On the figure 13a , nine primary tubes 151 are shown for the example. The other nine tubes are for example arranged around the perimeter of the internal diameter of the first ring 150, so as to maximize their distance from the center of the first ring 150.

[0132] There figure 13b represents an example of a second alternative of a structure of a first ring 160 of a waveguide comprising a hollow core 162, according to the invention. For the second alternative, the first ring comprises primary tubes 163 themselves comprising other tubes, for example three other tubes 161 such as the other tubes 100, 101, 102 shown in the figure 1b .

[0133] For example the figure 13b represents a first ring 160 comprising nine primary tubes 161. Each of the nine primary tubes 161 comprises three other tubes 163. The other tubes 163 are for example carried by the inner circumference of the primary tubes 161. Advantageously, the other tubes 163 are arranged so that an interval between two other tubes 163 is located opposite the center of the first ring 160.

[0134] There figure 13c represents a third alternative of a structure of a first ring 170 of a waveguide according to the invention. The first ring 170 surrounds a hollow core 171. The primary tubes 172 shown in Figure 15c have an ellipsoidal type section 103 as shown in the figure 1b .

[0135] On the figure 13c for the example, ten primary tubes 172 of ellipsoidal section are shown. For example, the primary tubes 172 of ellipsoidal section can be arranged so that the major axis of the ellipse forming the section of each first tube 172 is directed towards the center of the core 171.

[0136] There figure 13d represents a fourth alternative of a structure of a first ring 180 of a waveguide according to the invention. The first ring 180 surrounds a hollow core 181. The primary tubes 182 shown in the figure 13d have a barred ellipsoidal type section 104, 105 as shown in the figure 1b . On the figure 13d for the example, ten primary tubes 182 of ellipsoidal section are shown. For example, the primary tubes of ellipsoidal section can be arranged so that the major axis of the ellipse forming the section of each first tube 182 is directed towards the center of the core 181.

[0137] The bar 183 of the ellipse 182 can be arranged in the ellipse 182 according to its small diameter for example.

[0138] Of course, the various features, forms, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. In particular, all the variants and embodiments described above may be combined with each other.

Claims

1. Electromagnetic waveguide (1), based on the inhibited-coupling mechanism, comprising a hollow central portion (2) the contour of which is at least partially defined by a first set of at least seven primary hollow tubes (8,9,10,11,12,13,14), distributed annularly around the central hollow portion, said primary hollow tubes being substantially of the same size, distant from one another, said waveguide being characterized in that it also comprises a second set of tubes comprising at least one hollow secondary tube (6), when there are several thereof, these secondary tubes are positioned annularly around the primary tubes, the area of the at least one hollow secondary tube being comprised between 0.35 and 0.50 times the area of the central hollow portion.

2. Waveguide according to claim 1, characterized in that it is configured to perform single-mode waveguiding.

3. Waveguide according to any one of claims 1 to 2, characterized in that the at least one hollow secondary tube is positioned opposite one of the primary hollow tube.

4. Waveguide according to any one of claims 1 to 2. characterized in that the at least one hollow secondary tube is positioned opposite a gap between two primary hollow tubes.

5. Waveguide according to any one of the preceding claims, characterized in that the primary hollow tubes exhibit a cross section having a shape from among the following shapes: a. a circle; b. an ellipse; c. a barred ellipse; d. at least two circles, including a first circle and at least one second circle inscribed within the first circle.

6. Waveguide according to any one of the preceding claims, characterized in that the at least one hollow secondary tube exhibits a cross section having a shape from among the following shapes: a. a circle; b. a hexagon; c. a square; d. a triangle; e. a shape the contour of which is composed of an arc of a circle and of three sides of a polygon.

7. Waveguide according to the preceding claim, characterized in that the cross sections of the hollow secondary tubes form a grid comprising at least one unitary element or several unitary elements having different shapes.

8. Waveguide according to any one of the preceding claims, characterized in that said waveguide is a microstructured optical fibre.

9. Waveguide according to any one of the preceding claims, characterized in that the primary hollow tubes and the hollow secondary tubes are made from a dielectric material.

10. Waveguide according to any one of the preceding claims, characterized in that the primary hollow tubes and the hollow secondary tubes have walls of the same thickness.

11. Waveguide according to any one of the preceding claims, characterized in that the hollow central portion, the primary hollow and hollow secondary tubes are filled with a gas or air.

12. Waveguide according to any one of the preceding claims, characterized in that it is configured to guide the waves by inhibited coupling.

13. Waveguide according to any one of the preceding claims, characterized in that it is configured to guide a wave from among: a. a wave from extreme ultraviolet to infrared; b. a terahertz wave; c. a microwave.

14. Waveguide according to any one of the preceding claims, characterized in that the material of the hollow secondary tubes is a material having a low absorption coefficient such as quartz, or silica having a refractive-index step greater than 1.2 times the refractive index of the void, or Teflon™ having a refractive index greater than 1.2 times that of air.

15. Waveguide according to any one of claims 1 to 13, characterized in that the material of the hollow secondary tubes is a highly reflective material such as a metal like copper.

16. Waveguide according to any one of the preceding claims, characterized in that it also comprises a set of rods, at least one rod being positioned between two primary hollow tubes, at a distance from hollow secondary tubes.

17. Waveguide according to claim 16, characterized in that the at least one rod exhibits one of the following forms: a. a cylindrical solid tube; b. an elliptical solid tube; c. a cylindrical hollow tube; d. a barred cylindrical hollow tube, the two halves of which are separated over the whole length of the tube; e. a barred elliptical hollow tube, the two halves of which are separated over the whole length of the tube.

18. Waveguide according to any one of the preceding claims, characterized in that the hollow secondary tubes are produced in a cladding (3) of the waveguide and in that the primary hollow tubes are fixed to the inner wall (5) of said cladding.

19. Waveguide according to any one of the preceding claims, characterized in that each primary hollow tube is fixed to the wall of a hollow secondary tube.

20. Waveguide according to any one of claims 1 to 18, characterized in that in that the hollow secondary tubes are made in a waveguide sheath (3) and in that the primary hollow tubes are fixed to the internal wall (5) of said sheath, and in that the distance δrr between the at least one hollow secondary tube and the inner wall (5) of the cladding (3) is less than 0.2*rtin for the case of a primary hollow tube that is circular or less than 0.2*√(Areain / π) for a primary hollow tube having an area equal to Areain.