Optical Devices

Abstract

To propose a reflection prevention or mirror type optical device improved in performance.SOLUTION: Regarding an optical device (1) suitable for transmitting and reflecting electromagnetic radiation within a wavelength range of an electromagnetic spectrum, the device (1) includes at least a first coating layer (10) made of a first material, a board (50) made of a material different from the first material, and surface texture treatment (60) for forming a cavity (61) in the device (1), a lower layer (50) arranged directly below the first coating layer (10) is either a second coating layer (20) made of a material different from the first material, or the board (50), the lower layer (50) has a prescribed thickness (E50), and the cavity (61) extends through the coating layer (20), and sinks in the lower layer (50) through at least one portion of the thickness (E50).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The invention relates to an optical device suitable for transmitting or reflecting radiation in a predefined wavelength range, for example of the ultraviolet, visible, infrared or microwave type.

[0002] The field of the invention is that of optical devices designed for example to equip imaging systems. In practice, the application depends on the wavelength range. [Background technology]

[0003] In a known manner, anti-reflection or mirror effects can be obtained by multilayer construction and / or by constructing optical devices.

[0004] The following documents describe different examples of optical devices: Patent document 1 describes a broadband diffractive device comprising a plurality of elementary zones and microstructures arranged to form an artificial material with an effective refractive index variation on the surface of the device. - Non-Patent Document 1 describes a multilayer construction combined with stochastic structures made by dry etching. Non-patent document 2 describes a theoretical study of the combination of multilayer structures with moth-eye type sequences. Non-Patent Document 3 describes the composition of several layers, focusing on improving certain surface behaviors. Non-patent document 4 describes the formation of diamond deposited by CVD to achieve an anti-reflection effect. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent Application Publication No. 3206059 [Non-patent literature]

[0006] [Non-Patent Document 1] BRUYNOOGHE (2016), "Broadband and wide-angle hybrid antireflection coatings prepared by combining interference multilayers with subwavelength structures", Journal of Nanophotonics, SPIE, International Society for Optics and Photonics. [Non-patent document 2] KUBOTA (2014), “Optimization of hybrid antireflection structure integrating surface texturing and multi-layer interference coating”, Thin Films for Solar and Energy Technology VI, Graduate School of Science and Engineering, Yamagata University, Japan. [Non-patent document 3] CAMARGO (2012), "Multi-scale structured, superhydrophobic and wide-angle, antireflective coating in the near-infrared region", Chem. Commun., 2012, 48, 4992~4994, Royal Society of Chemistry, UK. [Non-patent document 4] RALCHENKO (1999), "Fabrication of CVD Diamond Optics with Antireflective Surface Structures", phys. stat. sol., General Physics Institute, Moscow, Russia. [Non-Patent Document 5] YU (2013), “Femtosecond laser nanomachining initiated by ultraviolet multiphoton ionization”, Optics Express [Non-patent document 6] SEDAO (2012), “Large area laser surface micro / nanopatterning by contact microsphere lens arrays”, Applied Physics A Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the invention is to propose an optical device of anti-reflection or mirror type with improved performance. [Means for solving the problem]

[0008] To that end, the present invention is directed to an optical device suitable for transmitting / reflecting electromagnetic radiation in a wavelength range of the electromagnetic spectrum, said device comprising at least: - a first coating layer made of a first material; a substrate made of a material different from the first material; - Surface texturing to create cavities in the device Equipped with a lower layer disposed immediately below the first coating layer is either a second coating layer or a substrate made of a material different from the first material; the lower layer having a predetermined thickness; A cavity extends through the first coating layer and is characterized by a cavity that extends through at least a portion of its thickness and into the underlying layer.

[0009] Thus, the present invention allows the wavefront of an electromagnetic wave to be modified in a controlled manner.

[0010] Texturing allows the effective refractive index to vary across the surface of the textured device. In particular, texturing allows for a lower effective refractive index to be obtained in a controlled manner in the textured coating layer and in the textured region of the substrate. Texturing allows for an effective refractive index that is not directly achievable by using multiple layers. The refractive index is a variable that depends on the wavelength of the radiation.

[0011] The present invention also allows for an increased range of angles of incidence over which the effectiveness of the optical function is intriguing.

[0012] The structure of the device forms at least one two-layer system comprising a textured coating layer and a textured layer of the substrate, which are placed on top of a non-textured portion of the substrate.

[0013] According to a first application, an optical device has an anti-reflection function. The device is suitable for transmitting electromagnetic radiation in a wavelength range of the electromagnetic spectrum. The device comprises at least one substrate made of a first material that is transparent in said wavelength range, a coating layer made of a second material different from the first material that is also transparent in said wavelength range, and a surface texturing that forms a cavity in the device. The device is characterized in that the cavity extends through the coating layer and partially recesses into the substrate.

[0014] Advantageously, the present invention makes it possible to improve the transmittance of devices at the level of spectral width and maximum transmittance (and therefore minimum absorption) for untextured and uncoated substrates, textured and uncoated substrates, substrates coated with a textured coating layer that is not textured, and even substrates coated with a textured coating layer where the texture does not penetrate the substrate. This improvement depends on the device configuration, particularly the characteristics of the substrate / coating bond and the texturing.

[0015] Compared to textured and uncoated substrates, textured coating layers can improve transmittance by forming shallower cavities, and thus texturing is easier and faster to perform.

[0016] The surface behavior of the device is altered when compared to a substrate coated with an untextured coating layer.

[0017] In practice, the device does not allow for improved transmission across the entire electromagnetic spectrum, but can be configured for transmission across a range of wavelengths, depending on the properties of the substrate / coating combination and the properties of the texturing.

[0018] The wavelength ranges are defined according to the subdivisions recommended by the International Commission on Illumination (CIE). - Gamma rays: less than 10 pm - X-ray: 10pm~10nm - Ultraviolet light: 10nm~380nm - Visible light: 380nm~780nm - IR-A (near IR): 0.78μm~1.4μm - IR-B (mid-IR): 1.4μm~3μm - IR-C (far IR): 3μm~1mm - Radio waves: greater than 1mm

[0019] The following subdivisions of the IR range may also be used: - NIR (near IR): 0.75μm~1.4μm - SWIR: 1.4μm~3μm - MWIR: 3μm~8μm - LWIR: 8μm~15μm - FIR (far IR): 15μm~1mm

[0020] In terms of transmittance, the different variants of the device are not necessarily more efficient than state of the art devices, but the devices according to the invention have other advantages, namely simple manufacturing, surface voltage, etc.

[0021] According to a second application, an optical device has a mirror function. The device is suitable for reflecting electromagnetic radiation in a wavelength range of the electromagnetic spectrum. The device comprises at least one substrate made of a first material that reflects in said wavelength range, a coating layer made of a second material different from the first material that also reflects in said wavelength range, and a surface texturing that forms a cavity in the device. The device is characterized in that the cavity extends through the coating layer and partially recesses into the substrate.

[0022] Thus, the present invention allows for improved device reflection relative to untextured and uncoated substrates, textured and uncoated substrates, or substrates coated with an untextured coating layer.

[0023] According to a variant, the optical device comprises at least one substrate having a mirror function and made of a first material that is transparent in said wavelength range, a coating layer made of a second material different from the first material that is also transparent in said wavelength range, and a surface texturing that forms a cavity in the device, the device being characterized in that the cavity extends through the coating layer and partially recesses into the substrate.

[0024] Alternatively (or in combination with reflectivity and transmittance functions), the optical device may have a function that alters the wavefront of the optical surface, different from the anti-reflection and mirror functions.

[0025] According to other advantageous characteristics of the invention, the following are carried out individually or in combination: The substrate is the lower layer, in which a cavity extends through the first coating layer and down through a portion of the thickness into the substrate. - the device comprises two coating layers, namely a first coating layer and a second coating layer, disposed on a substrate, in which a cavity extends through the first coating layer and drops through a portion of its thickness into the second coating layer without penetrating into the substrate. the device comprises several stacked coating layers, including a first coating layer and at least one second coating layer. A cavity extends through the first coating layer and down through the thickness into the second coating layer. - A cavity extends through all the stacked coating layers and down through the thickness into the substrate. The cavity has a cross-sectional area that decreases precisely in the direction of the substrate. The substrate preferably has a thickness of between 0.1 mm and 30 mm, for example between about 1 mm and 2 mm. The coating layer preferably has a thickness of 0.01 μm to 50 μm, for example about 0.5 μm or 2 μm for the IR range. - Cavities are formed in the substrate over a depth preferably between 0.5 μm and 10 μm, for example about 1 μm for the far IR range above 3 μm. - Cavities are formed in the substrate over a depth of preferably 0.08 μm to 3 μm, for example about 200 nm for the near IR or mid IR range of 780 nm to 3 μm. Cavities are formed in the substrate over a depth preferably between 1 nm and 600 nm, for example about 80 nm for the visible range. - Preferably, for IR applications, the substrate and coating layers are transmissive / reflective for all wavelengths from 1 μm to 50 μm. - Preferably, in the far IR range of 8 μm to 12 μm, the device allows for at least 90% transmission / reflection of incident infrared radiation for the diopter in question. The characteristics of the cavities (shape, size, distribution, etc.) depend on the texturing technique and the parameters used. Preferably, the cavities have a larger width or diameter of between 0.02 μm and 3 μm, in particular between 1 μm and 2 μm. For -IR applications, the substrate material is, for example, silicon Si, germanium Ge, zinc sulfide ZnS, zinc selenide ZnSe, etc. The substrate generally has a crystalline structure. - The coating layer material is, for example, amorphous carbon DLC ("diamond-like carbon"), silicon Si, germanium Ge, zinc sulfide ZnS, zinc selenide ZnSe, tantalum pentoxide Ta2O5, hafnium dioxide HfO2, alumina Al2O3, etc. - The coating can have an amorphous or crystalline structure. The coating layer can be made by thin layer deposition techniques such as PVD or CVD. The texturing can be done by any type of technique suitable for extending through the coating layer and partially recessing into the substrate, such as, for example, laser cutting, photolithography, nanoprinting, etc. Laser texturing is relatively economical and well controlled. - Texturing can be performed with ultrashort lasers with pulse durations in the femtosecond or picosecond range. The wavelength of the laser typically varies from 200 nm to 16,000 nm and should be selected according to the desired texturing characteristics (cavity shape and dimensions, pattern, etc.). The laser's opto-mechanical environment includes a motorized stage, a microscope lens (and / or a galvanometer scanner and / or a microsphere monolayer), an online viewing unit, etc. Preferably, the cavity has a continuous profile during the transition between the coating layer and the substrate. This continuous profile can be obtained by forming the cavity in the coating layer and the substrate during one and the same texturing operation, for example laser texturing. The continuous profile improves the control of the shape search of the wavefront. In practice, discontinuities can lead to diffraction or other unwanted effects. The cavity has a continuous contour in the direction of the substrate. The cavity may have a circular cross section. The cavity has a cross-sectional area that decreases precisely in the direction of the substrate. The cavity may have a concave shape in the axial plane with a cross-sectional area that decreases with depth. The cavity may have a symmetrical concave shape in the axial plane. The cavity may have an asymmetric concave shape in the axial plane. The cavities may have different dimensions, in particular different diameters, widths and / or depths. The dimensions of the cavity can vary periodically. The dimensions of the cavities can have a variable periodicity, evolving non-randomly according to a defined rule. The cavities may be randomly distributed over the surface of the device. The cavities may be distributed according to a regular array over the surface of the device. The cavities may be distributed according to an arrangement with a triangular, square, hexagonal, etc. mesh. The cavities may be distributed with variable periodicity over the surface of the device. - Variable periodicity evolves non-randomly according to prescribed rules. - Variable periodicity unfolds regularly. The cavities can have different periodicities between the center and the edge of the device. - The cavity may be closer to the center of the device. In the coating layer, the cavities have a density of 20% to 91%, i.e., a space-filling ratio of 20% to 91%, the 91% ratio corresponding to cavities arranged in a hexagonal pattern and touching each other. The device may comprise a single substrate and a single coating layer, in which case the substrate preferably has a refractive index greater than the refractive index of the coating before texturing. The device may comprise a substrate and several textured coating layers, where the substrate preferably has a refractive index greater than the refractive index of the coating before texturing, or alternatively, the substrate may have a refractive index less than that of at least one of the coating layers. - the device comprises at least one backside layer made of a material different from the substrate and the coating, a first coating layer being formed on a first side of the substrate and a backside layer being formed on a second side of the substrate opposite the first side. The back layer is made of, for example, zinc sulfide ZnS or any of the other materials mentioned above for the substrate or coating layer. The device may have two faces, each having a coating layer and a surface texturing that forms cavities that extend through the coating layer and partially penetrate the substrate. The device may comprise a first side having a first coating layer and a surface texturing that extends through the coating layer and forms a cavity partially penetrating the substrate, and a second side having another coating layer that does not have the texturing according to the invention or that may be subjected to a different texturing than the texturing of the first side, or may be untextured. The coating layers on the two sides may be different (material, thickness, etc.). The faces of the device may or may not be parallel. For example, the faces may be arranged in an inclined plane. According to another example, the faces may be concave or convex.

[0026] The present invention is also directed to a method for manufacturing an optical device suitable for transmitting / reflecting electromagnetic radiation in a wavelength range of the electromagnetic spectrum, said method comprising at least the following steps: - forming at least one combination of a first coating layer made of a first material and a substrate made of a material different from the first material, and then - performing a surface texturing process to form cavities in the device Including, a lower layer disposed immediately below the first coating layer is either a second coating layer or a substrate made of a material different from the first material; the lower layer having a predetermined thickness; A cavity extends through the first coating layer and is characterized by a cavity that extends through at least a portion of its thickness and into the underlying layer.

[0027] The present invention may have many applications in the field of optical devices. - IR applications: cameras, lenses, optical windows, camouflaged surfaces, lures, etc. - Visible and near IR applications: optical windows for imaging device cameras, lenses, mirrors, laser lines, laser shaping, etc. - Radio wave applications: radar, etc.

[0028] The invention will be better understood from the following description, given by way of non-limiting example only, and made with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic cross-sectional view of a device according to the invention comprising a silicon Si substrate, an amorphous carbon DLC coating layer, and texturing to form cavities in the device, the cavities extending through the coating layer and partially recessed into the substrate. [Figure 2] FIG. 2 is a cross-sectional view similar to FIG. 1 showing a device constructed with an untextured SI substrate and an untextured DLC coating. [Figure 3] FIG. 2 is a cross-sectional view similar to FIG. 1, showing a device constructed with a textured, uncoated Si substrate. [Figure 4] FIG. 2 is a cross-sectional view similar to FIG. 1 showing a device constructed with an untextured Si substrate and a textured DLC coating. [Figure 5]FIG. 2 is a cross-sectional view similar to FIG. 1, showing a device constructed with an untextured and uncoated Si substrate. [Figure 6] FIG. 2 is a schematic top view of the device of FIG. 1. [Figure 7] 6 is a graph showing the evolution of the transmittance (T from 0 to 1) according to wavelength (WL from 3 to 15 μm) for each of the devices of FIGS. 1 to 5. [Figure 8] 3 is a graph showing the evolution of the transmittance (T as %) for the device of FIGS. 1 and 2 according to the angle of incidence of the radiation on the surface of the device (angles between 0 and 80°); [Figure 9] 9 is a graph similar to FIG. 8 showing the evolution of the transmittance (T as %) according to the angle of incidence (angles from 0 to 60°) for the devices of FIGS. 1 and 2. [Figure 10] FIG. 2 shows the evolution of the transmittance (T as %) according to the wavelength (WL between 3 and 15 μm) and the angle of incidence (angles between 0 and 80°) for the device of FIG. 1 according to the invention. [Figure 11] 11 is a view similar to FIG. 10 for the device of FIG. 2. [Figure 12] 8 is a graph similar to FIG. 7 showing the evolution of the transmittance (T from 0.7 to 1) according to the wavelength (WL from 0.8 to 3 μm) for five different devices constructed as in FIGS. 1 to 5, with a zinc selenide ZnSe substrate and in some cases a silicon dioxide SiO coating layer. [Figure 13] 13 is a graph similar to FIG. 9 for the two devices whose transmittance is represented in FIG. 12, namely, a device according to the invention with a textured substrate and a textured coating, and a device with a non-textured substrate and a non-textured coating. [Figure 14] 8 is a graph similar to FIG. 7 showing the evolution of the transmittance (T from 0.96 to 1) according to the wavelength (WL from 0.3 to 1 μm) for five different devices constructed as in FIGS. 1 to 5, with a silicon dioxide SiO2 substrate and in some cases a magnesium fluoride MgF2 coating layer. [Figure 15] 15 is a graph similar to FIG. 9 showing the transmittance of the two devices shown in FIG. 14, namely, a device according to the present invention with a textured substrate and a textured coating, and a device not according to the present invention with a non-textured substrate and a non-textured coating. [Figure 16] 8 is a graph similar to FIG. 7 showing the evolution of the transmittance (T from 0.966 to 1) according to the wavelength (WL from 0.3 to 1 μm) for five different devices constructed as in FIGS. 1 to 5, with an alumina Al2O3 substrate and in some cases a silicon dioxide SiO2 coating layer. [Figure 17] 10 is a schematic top view of a variant of a device according to the invention, the cavities of which are closer at the centre than at the edge of the device, and thus have a variable periodicity across the surface of the device. FIG. [Figure 18] 3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention in which the cavity has a symmetrical concave shape that decreases with depth and has a non-cylindrical cross-section. [Figure 19] 3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention in which the cavity has an asymmetric concave shape. [Figure 20] 3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention in which the cavity has a variable depth. [Figure 21] 3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention in which the cavity has a variable diameter. [Figure 22] 3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention, comprising a stack of four coating layers, the cavity being formed only in the first two coating layers. [Figure 23]3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention, comprising a stack of four coating layers, in which the cavity extends completely through the stack except for the last layer and partially recesses into the last layer. [Figure 24] 3 is a cross-sectional view similar to FIG. 2, showing a variant of the device according to the invention, with a back layer made of a different material than the substrate and coating; [Figure 25] 3 is a cross-sectional view similar to FIG. 2 showing a variant of a device according to the invention having two faces, each comprising a substrate, a coating layer, and a surface texturing that forms a cavity that extends through the coating layer and partially penetrates into the substrate. [Figure 26] 3 is a cross-sectional view similar to FIG. 2 showing a variant of a device according to the invention, in which a first side comprises a coating layer and a surface texturing that forms cavities that extend through the coating layer and partially penetrate into the substrate, and a second side comprises a coating layer that has no texturing or that has a texturing different from that of the first side. [Figure 27] 3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention, which has a central substrate and two faces, each with two coating layers and a texturing treatment. [Figure 28] FIG. 1 illustrates the reversibility of the device. [Figure 29] FIG. 1 illustrates the optical equivalence of a compound device and two simple devices. [Figure 30] 3 is a cross-sectional view similar to FIG. 2 showing a variant of the device according to the invention, comprising a stack of four alternating coating layers and a substrate layer, in which a cavity extends through the first coating layer and partially sinks into the second coating layer according to its depth. [Figure 31]8 is a graph similar to FIG. 7 showing the evolution of the transmittance (T) according to wavelength (WL from 340 to 840 nm) for three different devices, including one textured and one non-textured device: a device consisting of a single ZnSe layer, and two devices with an alternating stack of two SiO and two HfO coating layers deposited on a ZnSe substrate. [Figure 32] 8 is a graph similar to FIG. 7 showing the evolution of the transmittance (T) according to the wavelength (WL from 1 to 2.4 μm) for three different devices, including one textured and one non-textured device, namely, a device consisting of a single ZnSe layer and two devices with an alternating stack of two Si3N4 and two SiO2 coating layers deposited on a ZnSe substrate. [Figure 33] 32 is a graph similar to FIG. 9 for the multilayer device whose transmittance is shown in FIG. [Figure 34] 8 is a graph similar to FIG. 7 showing the evolution of the transmittance (T) according to the wavelength (WL between 7 and 15 μm) for three different devices, including one textured and one non-textured device: a device consisting of a single Si layer and two devices with an alternating stack of two TiO2 and two DLC coating layers deposited on a Si substrate. [Figure 35] 34 is a graph similar to FIG. 9 for the two multilayer devices whose transmittance is shown in FIG. [Figure 36] 8 is a graph similar to FIG. 7 showing the evolution of the transmittance (T) according to the wavelength (WL between 7 and 15 μm) for three different devices, including one textured and one non-textured device: a device consisting of a single Si layer and two devices with an alternating stack of two TiO2 and two DLC coating layers deposited on a Si substrate. [Figure 37]36 is a graph similar to FIG. 9 for the two multilayer devices whose transmittance is shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0030] In Figures 1 and 6 an anti-reflective optical device (1) according to the invention is represented.

[0031] The device (1) is suitable for transmitting electromagnetic radiation in the far IR wavelength range (LWIR) from 7 μm to 15 μm.

[0032] The device (1) is provided with an amorphous carbon coating layer (10), also called DLC, with a thickness (E20) of 1425 nm, which has a refractive index n=1.8 and is transparent in the wavelength range mentioned above.

[0033] The device (1) comprises a silicon (Si) substrate (50) having a thickness (E10) of, for example, 1 mm or 2 mm. The substrate (50) has a refractive index n=3.43 and is transparent in the wavelength range mentioned above. The coating layer (10) is deposited on the substrate (50).

[0034] The device (1) includes a surface texturing (60) that forms individual cavities (61) that extend through the coating layer (10) and partially recess into the substrate (50). The cavities (61) are distributed along a regular array across the surface of the device (1). The cavities (61) have a periodicity (L61) of 2 μm, a diameter (D61) of 1.6 μm, and a depth (P61) of approximately 2.34 μm. The cavities (61) penetrate into the substrate (50) in the textured layer (51) with a depth (P51) of 915 nm, a thickness (E50) that is significantly less than the thickness (E50) of the substrate (50). The texturing (60) allows for the effective refractive index in the textured layer (51) of the substrate (50) to be lowered in a controlled manner.

[0035] The texturing (60) can be performed by any type of technique suitable for extending through the coating layer (10) and partially recessing into the substrate (10), such as laser ablation, photolithography, nanoprinting, etc. Laser texturing is relatively inexpensive and well-controlled. In particular, the texturing (60) can be performed with ultrashort lasers having pulse durations in the femtosecond or picosecond range. The wavelength of the laser typically varies from 200 nm to 16,000 nm and should be selected according to the desired characteristics of the texturing (60), i.e., the shape and dimensions of the cavities (61), the pattern, the periodicity, etc.

[0036] The following references can be consulted to configure the laser system: - Non-patent document 5 - Non-patent document 6

[0037] In Figures 2 to 5, different devices (2, 3, 4, 5) not according to the present invention are shown, in which the coating layer (10), substrate (50) and texturing (60) have the same properties as device (1) described above, except for the differences detailed below.

[0038] In Figure 2, the device (2) consists of a silicon Si substrate (50) and a DLC coating (10), both of which are untextured.

[0039] In Figure 3, device 3 is constructed with a textured but uncoated silicon (Si) substrate 50. The substrate 50 of device 3 has the same thickness as device 1. The cavity 61 has the same depth (P61) in both devices 1 and 3.

[0040] In Figure 4, the device (4) consists of an untextured silicon Si substrate (50) and a textured DLC coating (10). A cavity (61) extends through the coating (10) but does not penetrate into the substrate (50).

[0041] In Figure 5, device (5) is composed of an untextured and uncoated Si substrate (50). The substrate (50) of device (3) has the same thickness as the substrate (50) of device (1).

[0042] In Figure 7, the graph contains five curves showing the evolution of the transmittance (T1, T2, T3, T4, T5) according to the wavelength (WL) for devices (1, 2, 3, 4, 5). On the x-axis, the wavelength (WL) varies from 3 to 15 μm. On the y-axis, the transmittance (T) varies from 0 to 1. The transmittance curve (T1) corresponds to the device (1) according to the invention shown in FIGS. - The transmittance curve (T2) corresponds to the device (2) shown in FIG. - The transmittance curve (T3) corresponds to the device (3) shown in FIG. - The transmittance curve (T4) corresponds to the device (4) shown in FIG. - The transmittance curve (T5) corresponds to the device (5) shown in FIG.

[0043] As shown in the graph of FIG. 7, the transmittance (T1) of device (1) is improved relative to each of devices (2, 3, 4, 5) in spectral width and maximum transmittance (and therefore minimum absorptance).

[0044] The transmittances (T1, T3) have a discontinuity of about 3 to 5 μm, possibly linked to the depth of the cavities (61) penetrating into the substrate (50).

[0045] 8 and 9, the graphs include two curves showing the evolution of the transmittance (T1, T2) according to the angle of incidence (angle) for devices (1, 2). Note that the angular transmittance range is larger for device (1) than for device (2).

[0046] In Figures 10 and 11, the diagrams show the evolution of the transmittance (T1, T2) and the angle of incidence (angle) according to the wavelength (WL). The evolution of the transmittance (T1, T2) is represented as 2D by the color shading. It should be noted that the transmittance range is larger for device (1) than for device (2), except for wavelengths (WL) of about 3-5 μm.

[0047] The structure of the device (1) forms a two-layer system, comprising a textured coating layer (10) and a textured layer (51) of the substrate (50), which are placed on top of the non-textured part of the substrate (50).

[0048] Thanks to the texturing (60), the structure of device (1) allows for improved anti-reflection performance for devices (2, 3, 4, 5).

[0049] The anti-reflection performance of the device (1) is comparable to that of multi-layer systems comprising several superimposed coating layers. The implementation of texturing (60) is particularly advantageous when the application of multiple coating layers is not possible, practical, or desirable.

[0050] In Figure 12, a graph similar to Figure 7 is presented, showing the evolution of the transmittance (T1, T2, T3, T4, T5) for five devices (1, 2, 3, 4, 5) constructed as in Figures 1 to 5 and having a silicon dioxide SiO2 coating layer (10) deposited on a zinc selenide ZnSe substrate (50). On the x-axis, the wavelength (WL) varies from 0.8 to 3 µm, in the near and mid-IR range. On the y-axis, the transmittance (T) varies from 0.7 to 1.

[0051] For devices (1, 2, 3, 4, 5), the zinc selenide ZnSe substrate (50) has a refractive index n=2.46.

[0052] For devices (1, 2, 4), the silicon dioxide SiO2 coating layer (10) has a thickness (E10) of 230 nm and a refractive index n=1.44.

[0053] For devices (1, 3, 4), the cavity (61) has a periodicity (L61) of 320 nm and a diameter (D61) of 265 nm.

[0054] For devices (1, 4), the cavity (61) has a depth (P61) of about 400 nm.

[0055] The device (1) is suitable for the transmission of electromagnetic radiation in the near and mid-IR wavelength range of 0.8 μm to 3 μm.

[0056] As shown in the graph of FIG. 12, the transmittance (T1) of device (1) is improved relative to each of devices (2, 3, 4, 5) in spectral width and maximum transmittance (and therefore minimum absorptance).

[0057] In Figure 13, the graph includes two curves showing the evolution of the transmittance (T1, T2) according to the angle of incidence (angle) for devices (1, 2) described above along with Figure 12. Note that the angular transmittance range is larger for device (1) than for device (2).

[0058] In Figure 14, a graph similar to Figure 7 is presented, showing the evolution of the transmittance (T1, T2, T3, T4, T5) for five devices (1, 2, 3, 4, 5) constructed as in Figures 1 to 5 and having a magnesium fluoride MgF2 coating layer (10) deposited on a silicon dioxide SiO2 substrate (50). On the x-axis, the wavelength (WL) varies from 0.3 to 1 µm in the visible, near and mid-IR range. On the y-axis, the transmittance (T) varies from 0.96 to 1.

[0059] For devices (1, 2, 3, 4, 5), the silicon dioxide SiO2 substrate (50) has a refractive index n=1.44.

[0060] For devices (1, 2, 4), the magnesium fluoride MgF2 coating layer (10) has a thickness (E20) of 57 nm and a refractive index n=1.38.

[0061] For devices (1, 3, 4), the cavity (61) has a periodicity (L61) of 202 nm and a diameter (D61) of 160 nm.

[0062] For devices (1, 4), the cavity (61) has a depth (P61) of about 94 nm.

[0063] The device (1) is suitable for the transmission of electromagnetic radiation in the visible wavelength range of 0.38 μm to 0.78 μm.

[0064] As shown in the graph of Figure 14, the transmittance (T1) of device (1) is improved in spectral width and maximum transmittance (and therefore minimum absorption) relative to the transmittance (T2, T5) of devices (2, 5), but is relatively close to the transmittance (T3, T4) of devices (3, 4).

[0065] In Figure 15, the graph includes two curves showing the evolution of the transmittance (T1, T2) according to the angle of incidence (angle) for devices (1, 2) described above along with Figure 14. Note that the angular transmittance range is larger for device (1) than for device (2).

[0066] In Figure 16, a graph similar to Figure 7 is presented, showing the evolution of the transmittance (T1, T2, T3, T4, T5) for five devices (1, 2, 3, 4, 5) constructed as in Figures 1 to 5 and having a silicon dioxide SiO2 coating layer (10) deposited on an alumina Al2O3 substrate (50). On the x-axis, the wavelength (WL) varies from 0.3 to 1 µm in the visible, near and mid-IR range. On the y-axis, the transmittance (T) varies from 0.96 to 1.

[0067] For devices (1, 2, 3, 4, 5), the alumina Al2O3 substrate (50) has a refractive index n=1.69.

[0068] For devices (1, 2, 4), the silicon dioxide SiO2 coating layer (10) has a thickness (E20) of 83 nm and a refractive index n=1.44.

[0069] For devices (1, 3, 4), the cavity (61) has a periodicity (L61) of 176 nm and a diameter (D61) of 159 nm.

[0070] For devices (1, 4), the cavity (61) has a depth (P61) of about 156 nm.

[0071] The device (1) is suitable for the transmission of electromagnetic radiation in the visible, near and mid-IR wavelength ranges from 0.3 μm to 1 μm.

[0072] As shown in the graph of FIG. 16, the transmittance (T1) of device (1) is improved relative to each of devices (2, 3, 4, 5) in spectral width and maximum transmittance (and therefore minimum absorptance), particularly for the near and mid-IR wavelength ranges.

[0073] Other variants of the device (1) according to the invention are shown in Figures 17 to 37. For simplicity, components equivalent to those of the first embodiment described above have the same reference numbers.

[0074] In Figure 17, cavities (61) are distributed with a variable periodicity on the surface of device (1). This variable periodicity develops non-randomly according to a defined rule. The cavities (61) are separate and do not communicate with each other. The variation is controlled. The variation is not due to the irregular surface condition of device (1) and / or imprecision of the texturing method. The periodicity differs between the center and the edge of device (1). The cavities (61) are closer together at the center than at the edge.

[0075] In FIG. 18, the cavity (61) has a symmetrical concave shape in the axial plane, with a diameter (D61) and cross-sectional area that decrease with depth (P61).

[0076] In Figure 19, the cavity (61) has an asymmetric concave shape in the axial plane, with a larger dimension (D61) and cross-sectional area decreasing with depth (P61). If the cross-section is circular, the largest dimension (D61) is the diameter; otherwise, for a non-circular cross-section, the largest dimension (D61) is the length. In effect, the texturing (30) produces different optical effects depending on the direction of the incident radiation. This phenomenon is reinforced by the asymmetry of the cavity (61).

[0077] In FIG. 20, the cavity (61) has different depths (P61a, P61b).

[0078] In FIG. 21, the cavity (61) has different diameters (D61a, D61b).

[0079] In FIG. 22, the device (1) comprises a stack of four coating layers (10, 20, 30, 40). Preferably, layers (10, 30) are made of a first material, while layers (20, 40) are alternatively made of a second material different from the first material. Layers (10-40) can be deposited on a substrate, not shown for simplicity's sake. A cavity (61) is formed only in the coating layers (10, 20) that receive incident radiation oriented upward. For multilayer, anti-reflective broadband devices (1), this solution allows for improved wavefront correction compared to non-textured multilayer devices. This solution also represents a time saving over multilayer devices, in which all layers (10, 40) have a cavity (61) extending through them, as described below.

[0080] In Figure 23, the device (1) also comprises a stack of four coating layers (10, 20, 30, 40). The layers (10-40) may be deposited on a substrate, which is not shown for simplicity. A cavity (61) extends completely through the stack, except for the last layer (40), which is partially recessed.

[0081] In Figure 24, the device (1) comprises a back layer (70) made of a material different from the substrate (50) and the coating layer (10). The coating (10) is formed on a first side of the substrate (50), while the back layer (70) is formed on a second side of the substrate (50) opposite the first side. The back layer (70) has a different function from the coating layer (10). For example, in the case of an anti-reflection device (1), this back layer (70) makes it possible to ensure the anti-reflection function and mechanical function on the back surface, while the coating layer (10) has a broadband anti-reflection function. According to another example, in the case of a mirror device (1), this back layer (70) can be designed to reflect a portion of the radiation.

[0082] In Figure 25, device (1) comprises a central substrate (50) with two faces constructed in accordance with the present invention. Each face comprises a coating layer (10) and a texturing (60) forming a cavity (61) that extends through the coating layer (10) and partially penetrates the substrate (50). The two coating layers (10) may be the same (material, thickness, etc.) or different.

[0083] As illustrated in Figure 28, in the absence of diffraction orders, the behavior of the surface of device (1) is independent of the direction of the light path. That is, the reflection and transmission of device (1) do not change depending on the direction of light passage from the air to device (1) or from device (1) to the air. Figure 28 shows schematically that under these conditions, the reflected (R) and transmitted (T) optical radiation are the same whatever the orientation of device (1) and therefore the incident optical radiation (I).

[0084] In addition, as shown in Figure 29, the device (1) shown in Figure 25 can be considered to be an assembly of two independent simple devices (1a, 1b) placed side by side, if the coherence length of the light does not exceed the thickness of the device (1). The transmittance of the illustrated device (1) is thus the multiplication of the transmittances of these two independent simple devices.

[0085] This configuration makes it possible to improve the performance of the device (1), since the optical system thus comprises a double wavefront correction device. This solution is advantageous for improving the correction of the wavefront, since it makes it possible to use two surfaces of one and the same device (1) to correctly correct the wavefront twice, instead of adding a second device in addition to the first. The overall bulk remains moderate.

[0086] In FIG. 26, a device (1) comprises a first surface configured in accordance with the present invention, having a texture (60) partially penetrating into a coating layer (10) and a substrate (50), and a second surface having a coating layer (10) that is either not textured, has no texture, or has a texture different from that of the first surface. Following the explanations given above, with reference to FIGS. 25, 28, and 29, this configuration makes it possible to have the equivalent of two additional devices (1). The second surface is suitable for the texture or treatment, and this solution makes it possible to select the desired effect for one or more wavelength ranges. In a first example, different treatments can be applied in one and the same wavelength range, for example, a V-shaped anti-reflection treatment and a broadband anti-reflection treatment. In a second example, different treatments can be applied in different wavelength ranges. In a third example, one and the same treatment can be applied in two separate, parallel, or overlapping wavelength ranges. If the two wavelength ranges processed by each of the faces are aligned or overlapping, the device (1) can be used to process a wider range than a single-face device. Alternatively, if the two wavelength ranges processed by each of the faces are distinct, the device (1) can ensure the role of a filter. Depending on the particular application, it is possible to have a first wavefront correction process for a first wavelength range associated with a first detector and a second wavefront correction process for a second wavelength range associated with a second detector.

[0087] In Figure 27, the device (1) comprises a central substrate layer (50) and two faces constructed in accordance with the present invention. Each face comprises two coating layers (10, 20) and a texturing treatment (60) forming a cavity (61) that extends through the first coating layer (10) and partially penetrates the second coating layer (20). The coating layers (10, 20) on the two faces may be the same (material, thickness, etc.) or different.

[0088] In Figure 30, the device (1) comprises four coating layers (10, 20, 30, 40) and a substrate (50). A cavity (61) is formed only in the layers (10+20) that receive the incident radiation directed at the top. Several tests were carried out with such a configuration.

[0089] The first test concerns wavelengths in the visible light region of 350 nm to 750 nm. The device (1) is configured as follows. - Layers (10, 30) are made of SiO2, layers (20, 40) are made of HfO2 and the substrate (50) is made of ZnSe. The first coating thickness (E10) has a value of 98 nm. The second coating thickness (E20) has a value of 409 nm. - The third coating thickness (E30) has a value of 174 nm. - The fourth coating thickness (E40) has a value of 73 nm. - The thickness of the substrate layer (50) is not given. The cavities (61) of the texture (60) have a depth of 377 nm and therefore extend through the first coating layer (10) and partially sink into the second substrate layer (20). The cavities (61) are circular with a diameter of 138 nm and are regularly distributed along a square array with steps of 174 nm.

[0090] Figure 31 shows - Transmittance curve (T2) of a device with the same stack (10-50) but without texturing (60), - Transmittance curve for a device with a single amorphous carbon substrate layer (T1) 1 shows the transmittance curve (T3) of this device (1) compared to

[0091] It can be clearly seen that a device (1) according to the above configuration makes it possible to obtain an improved transmission over a very wide wavelength range with respect to the two other configurations.

[0092] The second test concerns wavelengths in the near-infrared region of 1 μm to 2 μm. The device (1) is configured as follows. - Layers (10, 30) are made of Si3N4, layers (20, 40) are made of SiO2 and the substrate (50) is made of ZnSe. The first coating thickness (E10) has a value of 228 nm. - The second coating thickness (E20) has a value of 452 nm. - The third coating thickness (E30) has a value of 461 nm. - The fourth coating thickness (E40) has a value of 166 nm. - The thickness of the substrate layer (50) is not given. The cavities (61) of the texture (60) have a depth of 351 nm and therefore extend through the first coating layer (10) and partially sink into the second coating layer (20). The cavities (61) are circular with a diameter of 255 nm and are regularly distributed along a square array with steps of 320 nm.

[0093] Figures 32 and 33 are - Transmittance curve (T2) of a device with the same stack (10-50) but without texturing (60), - Transmittance curve (T1) of a device with a single ZnSe substrate layer (50) (only in Figure 32) 1 shows the transmittance curve (T3) of device (1) compared to that of device (2).

[0094] It can be clearly seen in FIG. 32 that the device (1) according to the above configuration makes it possible to obtain an improved transmission over a very wide wavelength range with respect to the two other configurations.

[0095] It can be seen in FIG. 33 that the transmittance (T3) of the device (1) improves relative to the transmittance (T2) according to the angle of incidence of the optical radiation on the device (1).

[0096] The third test concerns wavelengths in the mid-infrared region of 7 μm to 15 μm. The device (1) is configured as follows. - Layers (10, 30) are made of TiO2, layers (20, 40) are made of DLC and the substrate (50) is made of Si. The first coating thickness (E10) has a value of 1393 nm. The second coating thickness (E20) has a value of 541 nm. - The third coating thickness (E30) has a value of 2843 nm. - The fourth coating thickness (E40) has a value of 838 nm. - The thickness of the substrate layer (50) is not given. The cavities (61) of the texture (60) have a depth of 1934 nm and therefore extend through the first coating layer (10) and partially sink into the second coating layer (20). The cavities (61) are circular with a diameter of 1600 nm and are regularly distributed along a square array with steps of 2000 nm.

[0097] Figures 34 and 35 show - Transmittance curve (T2) of a device with the same stack (10-50) but without texturing (60), - Transmittance curve (T1) of a device with a single Si substrate layer (50) (only in Figure 34) 1 shows the transmittance curve (T3) of device (1) compared to that of device (2).

[0098] It can be clearly seen in FIG. 34 that the device (1) according to the above configuration makes it possible to obtain an improved transmission over a very wide wavelength range with respect to the two other configurations.

[0099] It can be seen in FIG. 35 that the transmittance (T3) of the device (1) improves relative to the transmittance (T2) according to the angle of incidence of the optical radiation on the device (1).

[0100] The fourth test also concerns wavelengths in the mid-infrared region between 7 μm and 15 μm. The device (1) is constructed as follows. - Layers (10, 30) are made of TiO2, layers (20, 40) are made of DLC and the substrate (50) is made of Si. The first coating thickness (E10) has a value of 1054 nm. - The second coating thickness (E20) has a value of 2160 nm. - The third coating thickness (E30) has a value of 142 nm. - The fourth coating thickness (E40) has a value of 1293 nm. - The thickness of the substrate layer (50) is not given. The cavities (61) of the texture (60) have a depth of 1968 nm and therefore extend through the first coating layer (10) and partially sink into the second coating layer (20). The cavities (61) are circular with a diameter of 1600 nm and are regularly distributed along a square array with steps of 2000 nm.

[0101] Figures 36 and 37 show - Transmittance curve (T2) of a device with the same stack (10-50) but without texturing (60), - Transmittance curve (T1) for a device with a single Si substrate layer (50) (only in Figure 36) 1 shows the transmittance curve (T3) of device (1) compared to that of device (2).

[0102] It can be clearly seen in FIG. 36 that the device (1) according to the above configuration makes it possible to obtain an improved transmission over a very wide wavelength range with respect to the two other configurations.

[0103] It can be seen in FIG. 37 that the transmittance (T3) of the device (1) improves relative to the transmittance (T2) according to the angle of incidence of the optical radiation on the device (1).

[0104] Furthermore, device 1 can be shaped differently from Figures 1-37 without departing from the scope of the present invention, as defined by the claims. Furthermore, the technical characteristics of the various embodiments and variations mentioned above can be combined in whole or in part. Thus, device 1 can be adapted in terms of cost, functionality, and performance. [Explanation of symbols]

[0105] 1. Anti-reflection optical devices, mirror devices 2 Devices 3 Devices 4 Devices 5 Devices 10 Coating layer, coating 20 Coating layer, lower layer 30 coating layers 40 coating layers 50 Lower layer, substrate, center substrate, center substrate layer 51 Textured Layers 60 Surface Texture Processing 61 Cavity 70 Back layer 80 coating layers

Claims

1. An optical device (1) suitable for transmitting / reflecting electromagnetic radiation in a wavelength range of the electromagnetic spectrum, comprising at least: a first coating layer (10) made of a first material; a substrate (50) made of a material different from said first material; a cavity (61) in the optical device (1); Equipped with a lower layer (20; 50) disposed immediately below the first coating layer (10) is the substrate (50); the substrate (50) has a predefined thickness (E50), the cavity (61) extends through the first coating layer (10) and down into the substrate (50) through at least a portion of the thickness (E50); the substrate (50) is a central substrate, each side of the central substrate being provided with a coating layer and a cavity (61), the cavity (61) extending through the coating layer (10) and partially penetrating the substrate (50); the coating layer on one side of the substrate (50) and the coating layer on the other side of the substrate (50) have different thicknesses and are made of different materials; An optical device (1) characterized in that said cavity (61) has an asymmetric concave shape in the axial plane with a larger dimension (D61) and cross-sectional area that decreases with depth (P61).

2. 2. An optical device (1) according to claim 1, characterized in that it comprises several stacked coating layers (10-40) including the first coating layer (10) and at least one second coating layer (20).

3. 3. The optical device (1) according to claim 2, characterized in that the cavity (61) extends through all the stacked coating layers (10-40) and sinks into the substrate (50) through the thickness (E50).

4. Optical device (1) according to any one of the preceding claims, characterized in that the cavity (61) has a cross-sectional area that decreases in the direction of the substrate (50).

5. The optical device (1) according to any one of claims 1 to 4, characterized in that the cavities (61) are distributed on the surface of the optical device (1) with a variable periodicity that develops non-randomly according to a defined rule, for example with a periodicity that differs between the center and the edge of the optical device (1).

6. The optical device (1) according to any one of claims 1 to 5, characterized in that the cavity (61) has a continuous contour starting from the first coating layer (10) in the direction of the substrate (50).

7. Optical device (1) according to any one of the preceding claims, characterized in that the cavity (61) has a circular cross section.

8. A method for manufacturing an optical device (1) suitable for transmitting / reflecting electromagnetic radiation in a wavelength range of the electromagnetic spectrum, comprising at least the following steps: forming at least one combination of a first coating layer made of a first material and a substrate made of a material different from said first material; performing a surface texturing process (60) to form a cavity (61) in the optical device (1); Including, a lower layer (50) disposed immediately below the first coating layer (10) is the substrate (50); the substrate (50) has a predefined thickness (E50), the cavity (61) extends through the first coating layer (10) and down into the substrate (50) through at least a portion of the thickness (E50); the substrate (50) is a central substrate, each side of the central substrate being provided with a coating layer and a cavity (61), the cavity (61) extending through the coating layer (10) and partially penetrating the substrate (50); the coating layer on one side of the substrate (50) and the coating layer on the other side of the substrate (50) have different thicknesses and are made of different materials; The method is characterized in that the cavity (61) has an asymmetric concave shape in the axial plane with a larger dimension (D61) and cross-sectional area that decreases with depth (P61).

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