Optical apparatus

Abstract

The invention relates to an optical device (1) adapted to transmit / reflect electromagnetic radiation in the wavelength range of the electromagnetic spectrum, said device (1) comprising at least: a first coating (10) made of a first material; a substrate (50) made of a material different from the first material; and a surface texturing (60) which forms a cavity (61) in the apparatus (1); wherein the lower layer (50) arranged directly below the first coating layer (10) is a second coating layer (20) or substrate (50) made of a material different from the first material; wherein the lower layer (50) has a predetermined thickness (E50); characterized in that the cavity (61) extends through the coating (20) and sinks into the underlying layer (50) through at least a portion of the thickness (E50).

Description

[0001] This application is a divisional application of a Chinese patent application with application number 2020800744316, filing date October 26, 2020, and invention title "Optical Device". Technical Field

[0002] The present invention relates to an optical device adapted to transmit or reflect radiation within a predetermined wavelength range (such as ultraviolet, visible, infrared or microwave type).

[0003] The field of the present invention is that of optical devices designed, for example, to equip imaging systems. In fact, the applications depend on the wavelength range. Background Art

[0004] In a known manner, an antireflection or mirror effect can be obtained by means of a multilayer structure and / or by means of a structured optical device.

[0005] The following documents describe different examples of optical devices.

[0006] - EP3206059A1 describes a broadband diffractive device comprising a plurality of elementary regions and microstructures arranged to form an artificial material with an effective refractive index variation on the surface of the device.

[0007] - 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. This document describes a multilayer structure combined with random structures made by dry etching.

[0008] - 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. This document describes the theoretical study of the combination of multi-layer structure and moth-eye type array.

[0009] - 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, United Kingdom. This document describes the structuring of several layers, with emphasis on improving certain surface behaviors.

[0010] - RALCHENKO (1999), "Fabrication of CVD Diamond Optics with Antireflective Surface Structures", phys. stat. sol., General Physics Institute, Moscow, Russia. This document describes the structuring of CVD-deposited diamond to achieve antireflection effect. Summary of the Invention

[0011] The object of the present invention is to provide an antireflection or mirror-type optical device with improved characteristics.

[0012] To this end, the object of the present invention is an optical device adapted to transmit / reflect electromagnetic radiation within the wavelength range of the electromagnetic spectrum, said device comprising at least: - A first coating made of a first material; - A substrate made of a material different from the first material; and - Surface texturing that forms cavities in the device; Wherein, the lower layer disposed directly below the first coating is a second coating or a substrate made of a material different from the first material; Wherein, the lower layer has a predetermined thickness; Characterized in that the cavity extends through the first coating and sinks into the lower layer through at least a part of the thickness.

[0013] Therefore, the present invention enables the wavefront of electromagnetic waves to be modified in a controlled manner.

[0014] Texturing enables the effective refractive index to vary on the surface of the texturing device. In particular, texturing enables a lower effective refractive index to be obtained in a controlled manner in the textured coating and the textured area of the substrate. Texturing enables a difficult-to-achieve effective refractive index to be directly obtained by using multiple layers. The refractive index is variable according to the wavelength of the radiation.

[0015] Moreover, the present invention enables the range of incident angles of interest for increasing the effectiveness of the optical function to be increased.

[0016] The structure of the device forms at least one two-layer system, which includes a textured coating and a textured layer of the substrate, covering the untextured part of the substrate.

[0017] According to a first application, the optical device has an anti-reflection function. The device is adapted to transmit electromagnetic radiation in the wavelength range of the electromagnetic spectrum. The device includes: at least one substrate made of a first material that is penetrable in the said wavelength range; a coating made of a second material different from the first material and also penetrable in the said wavelength range; and surface texturing that forms cavities in the device. The device is characterized in that the cavities extend through the coating and partially sink into the substrate.

[0018] Advantageously, the present invention enables the transmittance of the device to be improved at the levels of spectral width and maximum transmittance (thus minimum absorption rate) relative to an untextured and uncoated substrate, a textured but uncoated substrate, a coated substrate with an untextured coating, or even a coated substrate with a textured coating but whose texturing does not penetrate the substrate. This improvement depends on the construction of the device, especially the substrate / coating pair and the characteristics of the texturing.

[0019] Compared with a textured but uncoated substrate, the textured coating enables the transmittance to be improved by forming shallower cavities. Therefore, texturing is easier and faster to complete.

[0020] Compared with a coated substrate with an untextured coating, the surface behavior of the device is changed.

[0021] In fact, the device cannot improve the transmittance across the entire electromagnetic spectrum, but is configured for transmittance in a wavelength range, which depends on the substrate / coating pair and the characteristics of the texturing.

[0022] The wavelength ranges are defined according to the subdivisions recommended by the International Commission on Illumination (CIE): - Gamma rays: less than 10 pm - X-rays: 10 pm to 10 nm - Ultraviolet light: 10 nm to 380 nm - Visible light: 380 nm to 780 nm - IR-A (near IR): 0.78 μm to 1.4 μm - IR-B (mid IR): 1.4 μm to 3 μm - IR-C (far IR): 3 μm to 1 mm - Radio waves: greater than 1 mm For the IR range, the following subdivisions can also be used: - NIR (near IR): 0.75 μm to 1.4 μm - SWIR: 1.4 μm to 3 μm - MWIR: 3 μm to 8 μm - LWIR: 8 μm to 15 μm - FIR (far IR): 15 µm to 1 mm Regarding the transmittance, the different variants of the device are not necessarily more efficient than the devices of the prior art. However, the device according to the invention has other advantages: ease of manufacture, surface voltage, etc.

[0023] According to a second application, the optical device has a mirror function. The device is adapted to reflect 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 made of a second material different from the first material and that also reflects in said wavelength range; and a surface texturing that forms cavities in the device. The device is characterized in that the cavities extend through the coating and partially sink into the substrate.

[0024] Thus, the present invention makes it possible to improve the reflection of the device relative to an untextured and uncoated substrate, a textured but uncoated substrate, or a substrate coated with an untextured coating.

[0025] According to a variant, the optical device has a mirror function and comprises: at least one substrate made of a first material that is penetrable in said wavelength range; a coating made of a second material different from the first material and that is also penetrable in said wavelength range; and a surface texturing that forms cavities in the device. The device is characterized in that the cavities extend through the coating and partially sink into the substrate.

[0026] Alternatively (or in combination with the reflection and transmission functions), the optical device may have a function of modifying the wavefront of the optical surface that is different from the anti-reflection and mirror functions.

[0027] According to other advantageous features of the invention taken alone or in combination: - The substrate is the lower layer, and the cavity extends through the first coating and sinks into the substrate through a part of the thickness.

[0028] - The device includes two coatings (i.e., the first coating and the second coating) arranged on the substrate, and the cavity extends through the first coating and sinks into the second coating through a part of the thickness without penetrating into the substrate.

[0029] - The device includes a plurality of stacked coatings, which include the first coating and at least one second coating.

[0030] - The cavity extends through the first coating and sinks into the second coating through a part of the thickness.

[0031] - The cavity extends through all the stacked coatings and sinks into the substrate through a part of the thickness.

[0032] - The cavity has a cross-sectional area that strictly decreases in the direction of the substrate.

[0033] - The substrate preferably has a thickness between 0.1 and 30 mm (e.g., about 1 or 2 mm).

[0034] - The coatings preferably have a thickness between 0.01 and 50 μm (e.g., about 0.5 μm or 2 μm for the IR range).

[0035] - For the far IR range above 3 μm, the depth of the cavity formed in the substrate is preferably between 0.5 and 10 μm, e.g., about 1 μm.

[0036] - For the near IR or mid IR range between 780 nm and 3 μm, the depth of the cavity formed in the substrate is preferably between 0.08 μm and 3 μm, e.g., about 200 nm.

[0037] - For the visible light range, the depth of the cavity formed in the substrate is preferably between 1 nm and 600 μm, e.g., about 80 nm.

[0038] - Preferably, for IR applications, the substrate and the coatings are penetrable / reflectable for the entire wavelength range between 1 μm and 50 μm.

[0039] - Preferably, for the far IR range between 8 μm and 12 μm, the device achieves a transmittance / reflection rate of at least 90% of the incident infrared radiation for the diopter in question.

[0040] - The characteristics of the cavities (shape, size, distribution, etc.) depend on the texturing technique and parameters used.

[0041] - Preferably, the cavities have a greater width or diameter between 0.02 and 3 μm, especially between 1 and 2 μm.

[0042] - For IR applications, the material of the substrate is, for example, silicon Si, germanium Ge, zinc sulfide ZnS, zinc selenide ZnSe, etc.

[0043] - The substrate usually has a crystalline structure.

[0044] - The material of the coating 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, aluminum oxide Al2O3, etc.

[0045] - The coating can have an amorphous or crystalline structure.

[0046] - The coating can be made by thin film deposition techniques (such as PVD or CVD).

[0047] - Texturing can be done by any suitable technique for extending through the coating and partially sinking into the substrate, such as laser ablation, lithography, nanoimprinting, etc. Laser texturing is relatively economical and well-controlled.

[0048] - Texturing can be done by an ultrashort laser, the pulse duration of which is in the femtosecond or picosecond range. The laser wavelength, which usually varies between 200 and 16000 nm, is selected according to the desired texturing characteristics (shape and size of the cavities, pattern, etc.).

[0049] - The optical-mechanical environment of the laser includes a motorized stage, microscope lenses (and / or an electrical scanner and / or a monolayer of microspheres), an in-line observation unit, etc.

[0050] - Preferably, the cavities have a continuous profile during the transition between the coating and the substrate. Such a continuous profile can be obtained by forming cavities in the coating and the substrate during the same texturing operation (such as laser texturing). The continuous profile improves the control of the sought wavefront shape. In fact, discontinuities may generate diffraction or other undesirable effects.

[0051] - The cavities have a continuous profile in the direction of the substrate.

[0052] - The cavities can have a circular cross-section.

[0053] - The cavities have a cross-sectional area that strictly decreases in the direction of the substrate.

[0054] - The cavity can have a concave profile in the axial plane, with an area cross-section that decreases according to depth.

[0055] - The cavity can have a symmetric concave profile in the axial plane.

[0056] - The cavity can have an asymmetric concave profile in the axial plane.

[0057] - The cavity can have different dimensions, particularly different diameters, widths, and / or depths.

[0058] - The dimensions of the cavity can vary periodically.

[0059] - The dimensions of the cavity can have a variable periodicity that evolves according to defined rules rather than randomly.

[0060] - The cavities can be randomly distributed on the surface of the device.

[0061] - The cavities can be distributed on the surface of the device according to a regular array.

[0062] - The cavities can be distributed according to an array with a triangular, square, hexagonal grid, etc.

[0063] - The cavities can be distributed on the surface of the device with a variable periodicity.

[0064] - The variable periodicity evolves according to defined rules rather than randomly.

[0065] - The variable periodicity evolves regularly.

[0066] - The cavities can have different periodicities between the center and the edge of the device.

[0067] - The cavities can be denser at the center of the device.

[0068] - In the coating, the cavities have a density between 20% and 91%, i.e., the ratio of filled space is between 20% and 91%. A ratio of 91% corresponds to hexagonally arranged cavities that are in contact with each other.

[0069] - The device can include a single substrate and a single coating. In this case, preferably, the refractive index of the substrate is greater than the refractive index of the coating before texturing.

[0070] - The device can include a substrate and several textured coatings. In this case, preferably, the refractive index of the substrate is greater than the refractive index of the coating before texturing. Alternatively, the refractive index of the substrate can be less than the refractive index of at least one coating.

[0071] - The device includes at least one back layer made of a material different from the substrate and the coating. A first coating is formed on a first side of the substrate, and the back layer is formed on a second side of the substrate opposite to the first side.

[0072] - The back layer is made of, for example, zinc sulfide ZnS or other materials used for the substrate or coating as described above.

[0073] - The device may include two faces, each having a coating and a surface texturing that forms cavities extending through the coating and partially penetrating the substrate.

[0074] - The device may include: a first face having a first coating and a surface texturing that forms cavities extending through the coating and partially penetrating the substrate; and a second face having another coating, which may not have the texturing according to the present invention, or may receive a treatment different from the texturing of the first face, or may not receive a treatment.

[0075] - The coatings of the two faces may be different (materials, thickness, etc.).

[0076] - The faces of the device may be parallel or non - parallel. For example, the faces may be arranged in an inclined plane. According to another example, the faces may be concave or convex.

[0077] An object of the present invention also lies in 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 made of a first material and a substrate made of a material different from the first material; and then - Performing a surface texturing for forming cavities in the device, wherein the lower layer disposed directly below the first coating is a second coating or a substrate made of a material different from the first material; wherein the lower layer has a predetermined thickness; characterized in that the cavities extend through the first coating and sink into the lower layer through at least a part of the thickness.

[0078] The present invention may have many applications in the field of optical devices: - IR applications: cameras, lenses, optical windows, camouflage surfaces, decoys, etc.

[0079] - Visible light and near - IR applications: optical windows, lenses, mirrors for imaging device cameras, laser lines, laser shaping, etc.

[0080] - Radio wave applications: radars, etc. Description of the Drawings

[0081] The present invention will be better understood from the following description, which is given by way of non-limiting example only and with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-sectional view of a device according to the present invention, the device comprising a silicon Si substrate, an amorphous carbon DLC coating, and a texturing that forms a cavity in the device, the cavity extending through the coating and partially sinking into the substrate.

[0082] Figure 2 is similar to Figure 1 and shows a cross-section of a device consisting of an untextured Si substrate and an untextured DLC coating.

[0083] Figure 3 is similar to Figure 1 and shows a cross-section of a device consisting of a textured but uncoated Si substrate.

[0084] Figure 4 is similar to Figure 1 and shows a cross-section of a device consisting of an untextured Si substrate and a textured DLC coating.

[0085] Figure 5 is similar to Figure 1 and shows a cross-section of a device consisting of an untextured and uncoated Si substrate.

[0086] Figure 6 is Figure 1 a schematic top view of the device.

[0087] Figure 7 shows Figures 1 to 5 the evolution of the transmittance (T from 0 to 1) of the respective devices according to the wavelength (WL from 3 to 15 μm).

[0088] Figure 8 shows Figure 1 and Figure 2 the evolution of the transmittance (T as %) of the devices according to the angle of incidence of the radiation (Angle from 0° to 80°) on the surface of the device.

[0089] Figure 9 is similar to Figure 8 and shows Figure 1 and Figure 2 the evolution of the transmittance (T as %) of the devices according to the angle of incidence (Angle from 0° to 60°).

[0090] Figure 10 shows Figure 1 the evolution of the transmittance (T as %) of the devices according to the present invention according to the wavelength (WL from 3 to 15 μm) and the angle of incidence (Angle from 0° to 80°).

[0091] Figure 11 is Figure 2 similar to that of the device Figure 10 of the figure.

[0092] Figure 12 is similar to Figure 7 the curve graph that shows, as Figures 1 to 5 constructed in [reference], the evolution of the transmittance (T ranging from 0.7 to 1) according to the wavelength (WL ranging from 0.8 to 3 μm) of five different devices (having a zinc selenide ZnSe substrate and for some having a silicon dioxide SiO2 coating).

[0093] Figure 13 is similar to Figure 12 the curve graph of two devices whose transmittance is shown in Figure 9 [reference], namely the device according to the present invention including a textured substrate and a textured coating and the device including an untextured substrate and an untextured coating.

[0094] Figure 14 is similar to Figure 7 the curve graph that shows, as Figures 1 to 5 constructed in [reference], the evolution of the transmittance (T ranging from 0.96 to 1) according to the wavelength (WL ranging from 0.3 to 1 μm) of five different devices (having a silicon dioxide SiO2 substrate and for some having a magnesium fluoride MgF2 coating).

[0095] Figure 15 is similar to Figure 14 the curve graph of two devices whose transmittance is shown in Figure 9 [reference], namely the device according to the present invention including a textured substrate and a textured coating and the device including an untextured substrate and an untextured coating that is not according to the present invention.

[0096] Figure 16 is similar to Figure 7 the curve graph that shows, as Figures 1 to 5 constructed in [reference], the evolution of the transmittance (T ranging from 0.966 to 1) according to the wavelength (WL ranging from 0.3 to 1 μm) of five different devices (having an aluminum oxide Al2O3 substrate and for some having a silicon dioxide SiO2 coating).

[0097] Figure 17 is a schematic top view of a variant of the device according to the present invention, the cavity of which has a variable periodicity on the surface of the device by being denser at the center of the device than at the edges.

[0098] Figure 18 is similar to Figure 2The cross-section shows a variant of the device according to the invention, where the cavity has a symmetric concave profile with a cross-section decreasing according to the depth, instead of a cylindrical profile.

[0099] Figure 19 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, where the cavity has an asymmetric concave profile.

[0100] Figure 20 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, where the cavity has a variable depth.

[0101] Figure 21 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, where the cavity has a variable diameter.

[0102] Figure 22 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, which includes a stack of four coatings, and the cavity is formed only in the first two coatings.

[0103] Figure 23 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, which includes a stack of four coatings, and the cavity extends completely through the stack except for the last layer into which the cavity partially sinks.

[0104] Figure 24 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, which includes a back layer made of a material different from the substrate and the coatings.

[0105] Figure 25 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, which has two faces, each face including a substrate, a coating, and a surface texturing that forms a cavity extending through the coating and partially penetrating the substrate.

[0106] Figure 26 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, which has: a first face including a coating and a surface texturing that forms a cavity extending through the coating and partially penetrating the substrate; and a second face including a coating without texturing or receiving a treatment different from the texturing of the first face.

[0107] Figure 27 is similar to Figure 2The cross-section shows a variant of the device according to the invention, which has a central substrate and two faces, each face including two coatings and texturing.

[0108] Figure 28 is a scheme illustrating the reversibility of the device.

[0109] Figure 29 is a scheme illustrating the optical equivalence of a complex device and two simple devices.

[0110] Figure 30 is similar to Figure 2 The cross-section shows a variant of the device according to the invention, which includes a stack of four alternating coatings and a substrate layer, with a cavity extending through the first coating and partially sinking into the second coating according to its depth.

[0111] Figure 31 is similar to Figure 7 The graph shows the evolution of the transmittance (T) of three different devices according to the wavelength (WL from 340 to 840 nm), namely a device consisting of a single ZnSe layer and two devices with two SiO2 coatings and two HfO2 coatings deposited alternately on a ZnSe substrate (including a textured device and an untextured device).

[0112] Figure 32 is similar to Figure 7 and shows the evolution of the transmittance (T) of three different devices according to the wavelength (WL from 1 to 2.4 µm), namely a device consisting of a single ZnSe layer and two devices with two Si3N4 coatings and two SiO2 coatings deposited alternately on a ZnSe substrate (including a textured device and an untextured device).

[0113] Figure 33 is a graph similar to Figure 32 of a multi-layer device whose transmittance is shown in Figure 9

[0114] Figure 34 is similar to Figure 7 and shows the evolution of the transmittance (T) of three different devices according to the wavelength (WL from 7 to 15 µm), namely a device consisting of a single Si layer and two devices with two TiO₂ coatings and two DLC coatings deposited alternately on a Si substrate (including a textured device and an untextured device).

[0115] Figure 35 is a graph similar to Figure 34 of two multi-layer devices whose transmittance is shown in Figure 9 ​The curve graph of

[0116] Figure 36 is similar to Figure 7 The curve graph, which shows the evolution of the transmittance (T) according to the wavelength (WL from 7 to 15 µm) of three different devices, namely a device composed of a single Si layer and two devices (including a textured device and an untextured device) with two TiO2 coatings and two DLC coatings deposited alternately stacked on a Si substrate.

[0117] Figure 37 is the transmittance in Figure 36 of two multi-layer devices similar to Figure 9 The curve graph of Detailed implementation mode

[0118] In Figure 1 and Figure 6 an antireflection optical device (1) according to the present invention is shown.

[0119] The device (1) is very suitable for emitting electromagnetic radiation in the far IR wavelength range (LWIR) of 7 to 15 μm.

[0120] The device (1) includes an amorphous carbon coating (10) with a thickness (E20) of 1425 nm, also known as DLC. DLC has a refractive index n = 1.8 and is penetrable in the above wavelength range.

[0121] The device (1) includes a silicon Si substrate (50) with a thickness (E10) of, for example, 1 or 2 mm. The substrate (50) has a refractive index n = 3.43 and is penetrable in the above wavelength range. The coating (10) is deposited on the substrate (50).

[0122] The device (1) includes a surface texturing (60) that forms separate cavities (61). The cavities extend through the coating (10) and partially sink into the substrate (50). The cavities (61) are distributed in a regular array on 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 a textured layer (51) with a depth (P51) of 915 nm, which is much smaller than the thickness (E50) of the substrate (50). The texturing (60) enables the effective refractive index in the textured layer (51) of the substrate (50) to be reduced in a controlled manner.

[0123] Texturing (60) can be accomplished by any type of technique suitable for extending through the coating (10) and partially sinking into the substrate (10), such as laser ablation, lithography, nanoimprinting, etc. Laser texturing is relatively inexpensive and well-controlled. In particular, texturing (60) can be accomplished by an ultrashort laser with a pulse duration in the femtosecond or picosecond range. The laser wavelength, which typically varies between 200 and 16,000 nm, is selected according to the characteristics of the desired texturing (60), such as the shape and size of the cavities (61), the pattern, the periodicity, etc.

[0124] The laser system can be configured with reference to the following references: -YU (2013), "Femtosecond laser nanomachining initiated by ultraviolet multiphoton ionization", Optics Express.

[0125] -SEDAO (2012), "Large area laser surface micro / nanopatterning by contact microsphere lens arrays", Applied Physics A.

[0126] In Figures 2 to 5 different devices (2, 3, 4, 5) not according to the present invention are shown. Except for the differences described in detail below, the coating (10), the substrate (50), and the texturing (60) have the same characteristics as the device (1) described above.

[0127] In Figure 2 device (2) consists of a silicon Si substrate (50) and a DLC coating (10), both of which are not textured.

[0128] In Figure 3 device (3) consists of a textured but uncoated silicon Si substrate (50). The substrate (50) of device (3) has the same thickness as that of device (1). The cavities (61) have the same depth (P61) for both devices (1, 3).

[0129] In Figure 4 device (4) consists of an untextured silicon Si substrate (50) and a textured DLC coating (10). The cavities (61) extend through the coating (10) but do not penetrate into the substrate (50).

[0130] In Figure 5In [reference], the device (5) consists of an untextured and uncoated Si substrate (50). The substrate (50) of the device (3) has the same thickness as the substrate (50) of the device (1).

[0131] In Figure 7 the graph includes five curves that show the evolution of the transmittance (T1, T2, T3, T4, T5) of the devices (1, 2, 3, 4, 5) according to the wavelength (WL). 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.

[0132] - The transmittance curve (T1) corresponds to the Figure 1 and Figure 6 device (1) according to the invention as shown.

[0133] - The transmittance curve (T2) corresponds to the Figure 2 device (2) as shown.

[0134] - The transmittance curve (T3) corresponds to the Figure 3 device (3) as shown.

[0135] - The transmittance curve (T4) corresponds to the Figure 4 device (4) as shown.

[0136] - The transmittance curve (T5) corresponds to the Figure 5 device (5) as shown.

[0137] As shown in the graph in Figure 7 at the spectral width and maximum transmittance (and thus minimum absorbance), the transmittance (T1) of the device (1) is improved with respect to each of the devices (2, 3, 4, 5).

[0138] The transmittance (T1, T3) has an interruption of approximately 3 to 5 μm, which may be related to the depth of the cavity (61) penetrating into the substrate (50).

[0139] In Figure 8 and Figure 9 the graph includes two curves that show the evolution of the transmittance (T , T2) of the devices (1, 2) according to the angle of incidence (Angle). Note that the angular transmittance width of the device (1) is greater than the angular transmittance width of the device (2).

[0140] In Figure 10 and Figure 11In these, the diagrams show the evolution of the transmittances (T1, T2) according to the wavelength (WL) and the angle of incidence (Angle). The evolution of the transmittances (T1, T2) is presented chromatically as 2D. Note that, except for wavelengths (WL) of approximately 3 to 5 μm, the transmission range of device (1) is greater than that of device (2).

[0141] The structure of device (1) forms a two - layer system that includes a textured coating (10) and a textured layer (51) of a substrate (50), which covers the non - textured part of the substrate (50).

[0142] Due to the texturing (60), the structure of device (1) enables improved antireflection performance to be obtained with respect to devices (2, 3, 4, 5).

[0143] The antireflection performance of device (1) is comparable to that of a multi - layer system including several stacked coatings. Performing the texturing (60) is particularly advantageous when applying a multi - layer coating is impossible, impractical, or undesirable.

[0144] In Figure 12 a graph similar to Figure 7 is shown, which depicts the evolution of the transmittances (T1, T2, T3, T4, T5) of five devices (1, 2, 3, 4, 5) constructed as in Figures 1 to 5 with a silicon dioxide SiO2 coating (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 - IR and mid - IR ranges. On the y - axis, the transmittance (T) varies from 0.7 to 1.

[0145] For devices (1, 2, 3, 4, 5), the zinc selenide ZnSe substrate (50) has a refractive index n = 2.46.

[0146] For devices (1, 2, 4), the silicon dioxide SiO2 coating (10) has a thickness (E10) of 230 nm and a refractive index n = 1.44.

[0147] For devices (1, 3, 4), the cavity (61) has a periodicity (L61) of 320 nm and a diameter (D61) of 265 nm.

[0148] For devices (1, 4), the cavity (61) has a depth (P61) of approximately 400 nm.

[0149] Device (1) is very suitable for transmitting electromagnetic radiation in the near - and mid - IR wavelength range between 0.8 and 3 μm.

[0150] As in FigureAs shown by the curves in, at the spectral width and maximum transmittance (and thus minimum absorbance), the transmittance (T1) of device (1) is improved relative to each of devices (2, 3, 4, 5).

[0151] In ​ it, the curve includes two curves that show the evolution of the transmittances (T1, T2) of the devices (1, 2) described above according to the ​ angle of incidence (Angle). Note that the angular transmittance width of device (1) is greater than that of device (2).

[0152] In ​ it, a curve similar to ​ is shown that shows the evolution of the transmittances (T1, T2, T3, T4, T5) of five devices (1, 2, 3, 4, 5) constructed as in ​ where a magnesium fluoride MgF2 coating (10) is deposited on a silica SiO2 substrate (50). On the x-axis, the wavelength (WL) varies from 0.3 to 1 μm in the visible, near-IR, and mid-IR ranges. On the y-axis, the transmittance (T) varies from 0.96 to 1.

[0153] For devices (1, 2, 3, 4, 5), the silica SiO2 substrate (50) has a refractive index n = 1.44.

[0154] For devices (1, 2, 4), the magnesium fluoride MgF2 coating (10) has a thickness (E20) of 57 nm and a refractive index n = 1.38.

[0155] For devices (1, 3, 4), the cavity (61) has a periodicity (L61) of 202 nm and a diameter (D61) of 160 nm.

[0156] For devices (1, 4), the cavity (61) has a depth (P61) of approximately 94 nm.

[0157] Device (1) is well-suited for transmitting electromagnetic radiation in the visible light wavelength range between 0.38 and 0.78 μm.

[0158] As ​ shown by the curves in, at the spectral width and maximum transmittance (and thus minimum absorbance), the transmittance (T1) of device (1) is improved relative to the transmittances (T2, T5) of devices (2, 5). However, the transmittance (T1) of device (1) is relatively close to the transmittances (T3, T4) of devices (3, 4).

[0159] In ​ it, the curve includes two curves that show the evolution of the transmittances (T1, T2) of the devices (1, 2) described above according to the ​Evolution of the transmittance (T1, T2) of the described devices (1, 2) as a function of the angle of incidence (Angle). Note that the angular transmittance width of device (1) is greater than that of device (2).

[0160] In ​ is shown a graph similar to ​ which shows the evolution of the transmittance (T1, T2, T3, T4, T5) of five devices (1, 2, 3, 4, 5) constructed as in ​ on an alumina Al2O3 substrate (50) on which a silica SiO2 coating (10) is deposited. On the x-axis, the wavelength (WL) varies from 0.3 to 1 μm in the visible, near-IR and mid-IR ranges. On the y-axis, the transmittance (T) varies from 0.96 to 1.

[0161] For devices (1, 2, 3, 4, 5), the alumina Al2O3 substrate (50) has a refractive index n = 1.69.

[0162] For devices (1, 2, 4), the silica SiO2 coating (10) has a thickness (E20) of 83 nm and a refractive index n = 1.44.

[0163] For devices (1, 3, 4), the cavity (61) has a periodicity (L61) of 176 nm and a diameter (D61) of 159 nm.

[0164] For devices (1, 4), the cavity (61) has a depth (P61) of approximately 156 nm.

[0165] Device (1) is very suitable for transmitting electromagnetic radiation in the visible, near and mid-IR wavelength ranges between 0.3 and 1 μm.

[0166] As ​ shown in the graph, at the spectral width and maximum transmittance (and thus minimum absorption), especially for the near and mid-IR wavelength ranges, the transmittance (T1) of device (1) is improved with respect to each of devices (2, 3, 4, 5).

[0167] ​ Other variants of device (1) according to the invention are shown in

[0168] In ​In it, the cavities (61) are distributed on the surface of the device (1) in a variable periodic manner. This variable periodicity evolves according to a defined rule rather than randomly. The cavities (61) are separate and not connected to each other. The variations are controlled and they are not due to the irregular surface state of the device (1) and / or the imprecision of the texturing method. The periodicity is different between the center and the edge of the device (1). The cavities (61) are denser at the center than at the edge.

[0169] In ​ it, the cavity (61) has a symmetric concave profile in the axial plane, which has a diameter (D61) and an area cross-section that decrease with the depth (P61).

[0170] In ​ it, the cavity (61) has an asymmetric concave profile in the axial plane, which has a larger dimension (D61) and an area cross-section that decrease with the 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 fact, the texturing (30) produces different optical effects depending on the orientation of the incident radiation. This phenomenon is enhanced by the asymmetry of the cavities (61).

[0171] In ​ it, the cavities (61) have different depths (P61a, P61b).

[0172] In ​ it, the cavities (61) have different diameters (D61a, D61b).

[0173] In ​ it, the device (1) includes a stack of four coatings (10, 20, 30, 40). Preferably, the layers (10, 30) are made of a first material, while the layers (20, 40) are alternately made of a second material different from the first material. For simplicity, the layers (10 - 40) can be deposited on a substrate not shown. The cavities (61) are formed only in the coatings (10, 20) that receive the incident radiation and are oriented on the upper side. In the case of the multi-layer anti-reflection broadband device (1), this solution makes it possible to improve the correction of the wavefront compared to an untextured multi-layer device. Moreover, this solution shows a time saving compared to the multi-layer device, as described below, all the layers (10, 40) of the multi-layer device are extended through by the cavities (61).

[0174] In ​ it, the device (1) also includes a stack of four coatings (10, 20, 30, 40). For simplicity, the layers (10 - 40) can be deposited on a substrate not shown. The cavities (61) extend completely through the stack except for the last layer (40) into which the cavities (61) partially sink.

[0175] In ​ , the device (1) includes a back layer (70) made of a material different from the substrate (50) and the coating (10). The coating (10) is formed on the first side of the substrate (50), while the back layer (70) is formed on the second side of the substrate (50) opposite to the first side. The back layer (70) has a function different from that of the coating (10). For example, in the case of the antireflection device (1), the back layer (70) can ensure antireflection and mechanical functions on the back surface, while the coating (10) has a broadband antireflection function. According to another example, in the case of the mirror device (1), the back layer (70) can be designed to reflect some radiation.

[0176] In ​ , the device (1) includes two faces constructed according to the present invention, which have a central substrate (50). Each face includes a coating (10) and a texturing (60), and the texturing (60) forms cavities (61) that extend through the coating (10) and partially penetrate the substrate (50). The two coatings (10) can be the same or different (material, thickness, etc.).

[0177] As ​ illustrated, in the absence of diffraction orders, the surface behavior of the device (1) does not depend on the direction of the optical path. That is, the direction of light passing from air to the device (1) or from the device (1) to air does not change the reflectance and transmittance of the device (1). ​ It is schematically shown that, therefore, under these conditions, for incident light radiation (I), the reflected light radiation (R) and the transmitted light radiation (T) are the same regardless of the direction of the device (1).

[0178] In addition, as ​ illustrated, if the coherence length of light does not exceed the thickness of the device (1), then ​ the illustrated device (1) can be considered as a component of two independent simple devices (1a, 1b), and the two devices (1a, 1b) will be juxtaposed. Therefore, the transmittance of the illustrated device (1) is the product of the transmittances of the two independent simple devices.

[0179] Since the optical system is thus equipped with a dual-wavefront correction device, this configuration makes it possible to improve the performance of the device (1). This solution is beneficial for improving the correction of the wavefront because this solution makes it possible to use two faces of the same device (1) to correctly correct the wavefront twice instead of adding a second device in addition to the first device. The overall volume remains moderate.

[0180] In ​In [description], device (1) includes: a first face constructed according to the present invention, having a coating (10) and a texturing (60) that penetrates partially into a substrate (50); and a second face having a coating (10), which does not have a texturing, or does not have a treatment, or undergoes a treatment different from the texturing of the first face. According to the description given above, with reference to ​ , ​ and ​ , such a construction enables having equivalents of two additional devices (1). Since the second face is suitable in terms of treatment or texturing, this solution enables choosing one or more effects sought for one or more wavelength ranges. In a first example, different treatments can be applied within the same wavelength range, such as V-shaped antireflection treatment and broadband antireflection treatment. According to a second example, different treatments can be applied within different wavelength ranges. According to a third example, the same treatment can be applied within two separate, juxtaposed, or overlapping wavelength ranges. If the two wavelength ranges treated by the respective faces are juxtaposed or overlapping, device (1) can be used to treat a wider range than a single-face device. Alternatively, if the two wavelength ranges treated by the respective faces are separate, device (1) can ensure the function of a filter. Depending on the specific application, there can be a first wavefront correction treatment for a first wavelength range associated with a first detector and a second wavefront correction treatment for a second wavelength range associated with a second detector.

[0181] In ​ , device (1) includes two faces constructed according to the present invention, which have a central substrate layer (50). Each face includes two coatings (10, 20) and a texturing (60), which forms a cavity (61) that extends through the first coating (10) and penetrates partially into the second coating (20). The coatings (10, 20) of the two faces can be the same or different (material, thickness, etc.).

[0182] In ​ , device (1) includes four coatings (10, 20, 30, 40) and a substrate (50). The cavity (61) is formed only in the layer (10 + 20) that receives incident radiation and is oriented on the upper side. From this construction, several tests have been carried out.

[0183] The first test concerns wavelengths in the visible field between 350 nm and 750 nm. Device (1) is constructed as follows: - Layers (10, 30) are made of SiO2, layers (20, 40) are made of HfO2, and substrate (50) is made of ZnSe; - The first coating thickness (E10) is 98 nm; - The second coating thickness (E20) is 409 nm; - The thickness of the third coating (E30) is 174 nm; - The thickness of the fourth coating (E40) is 73 nm; - The thickness of the underlayer (50) is not imposed; - The textured (60) cavity (61) has a depth of 377 nm and thus extends through the first coating (10) and partially sinks into the second underlayer (20). The cavity (61) is circular with a diameter of 138 nm and is regularly distributed along a square matrix with a pitch of 174 nm.

[0184] ​ The transmittance curve (T3) of the device (1) is shown, comparing: - The transmittance curve (T2) of a device including the same stack (10 - 50) but without texturing (60); - The transmittance curve (T1) of a device including a single amorphous carbon underlayer.

[0185] It can be clearly seen that the device (1) constructed according to the above makes it possible to obtain improved transmittance relative to the other two configurations and over a much larger wavelength range.

[0186] The second test concerns wavelengths in the near - infrared field between 1 and 2 µm. The device (1) is constructed as follows: - The layers (10, 30) are made of Si3N4, the layers (20, 40) are made of SiO2, and the substrate (50) is made of ZnSe; - The thickness of the first coating (E10) is 228 nm; - The thickness of the second coating (E20) is 452 nm; - The thickness of the third coating (E30) is 461 nm; - The thickness of the fourth coating (E40) is 166 nm; - The thickness of the underlayer (50) is not imposed; - The textured (60) cavity (61) has a depth of 351 nm and thus extends through the first coating (10) and partially sinks into the second coating (20). The cavity (61) is circular with a diameter of 255 nm and is regularly distributed along a square matrix with a pitch of 320 nm.

[0187] ​ and ​ The transmittance curve (T3) of the device (1) is shown, comparing: - The transmittance curve (T2) of a device including the same stack (10 - 50) but without texturing (60); - The transmittance curve (T1) of a device including only a single ZnSe underlayer (50) only at​ in).

[0188] In ​ it can be clearly seen that the device (1) constructed as described above enables an improved transmittance to be obtained with respect to the other two configurations and over a much larger wavelength range.

[0189] In ​ it is seen that, depending on the angle of incidence of the light radiation on the device (1), the transmittance (T3) of the device (1) is improved with respect to the transmittance (T2).

[0190] The third test concerns wavelengths in the mid-infrared field between 7 and 15 µm. The device (1) is constructed as follows: - The layers (10, 30) are made of TiO2, the layers (20, 40) are made of DLC, and the substrate (50) is made of Si; - The first coating thickness (E10) is 1393 nm; - The second coating thickness (E20) is 541 nm; - The third coating thickness (E30) is 2843 nm; - The fourth coating thickness (E40) is 838 nm; - The thickness of the substrate layer (50) is not imposed; - The textured (60) cavity (61) has a depth of 1934 nm and thus extends through the first coating (10) and partially sinks into the second coating (20). The cavity (61) is circular with a diameter of 1600 nm and is regularly distributed along a square matrix with a step of 2000 nm.

[0191] ​ and ​ shows the transmittance curve (T3) of the device (1), comparing: - The transmittance curve (T2) of a device including the same stack (10 - 50) but without texturing (60); - The transmittance curve (T1) of a device including only a single Si substrate layer (50) only in ​ in).

[0192] In ​ it can be clearly seen that the device (1) constructed as described above enables an improved transmittance to be obtained with respect to the other two configurations and over a much larger wavelength range.

[0193] In ​ it is seen that, depending on the angle of incidence of the light radiation on the device (1), the transmittance (T3) of the device (1) is improved with respect to the transmittance (T2).

[0194] The fourth test also concerns the wavelength of the mid-infrared field between 7 and 15 µm. The device (1) is constructed as follows: - The layers (10, 30) are made of TiO2, the layers (20, 40) are made of DLC, and the substrate (50) is made of Si; - The first coating thickness (E10) is 1054 nm; - The second coating thickness (E20) is 2160 nm; - The third coating thickness (E30) is 142 nm; - The fourth coating thickness (E40) is 1293 nm; - The thickness of the substrate layer (50) is not imposed; - The textured (60) cavity (61) has a depth of 1968 nm, thus extending through the first coating (10) and partially sinking into the second coating (20). The cavity (61) is circular with a diameter of 1600 nm and is regularly distributed along a square matrix with a step of 2000 nm.

[0195] ​ and ​ The transmittance curve (T3) of the device (1) is shown, for comparison: - The transmittance curve (T2) of a device including the same stack (10 - 50) but without texturing (60); - The transmittance curve (T1) of a device including a single Si substrate layer (50) only in ​ ).

[0196] In ​ it can be clearly seen that the device (1) constructed according to the above enables an improved transmittance to be obtained with respect to the other two constructions and over a much wider wavelength range.

[0197] In ​ it is seen that, depending on the angle of incidence of the light radiation on the device (1), the transmittance (T3) of the device (1) is improved with respect to the transmittance (T2).

[0198] Moreover, without departing from the scope of the invention defined by the claims, the device (1) can be shaped differently. In addition, the technical features of the various above-described embodiments and variants can be combined either in whole or only in part. Thus, the device (1) can be adapted in terms of cost, function, and performance. ​ ​

Claims

1. An optical device (1) adapted to transmit / reflection electromagnetic radiation within a wavelength range of the electromagnetic spectrum, said device (1) comprising at least: - A first coating (10) made of a first material; - A substrate (50) made of a material different from said first material; and - A surface texturing (60) that forms cavities (61) in said device (1) such that the effective refractive index varies on the surface of said device; Wherein, said substrate (50) has a predetermined thickness (E50); Said cavities (61) extend through said first coating (10) and sink into said substrate (50) through at least a part of said thickness (E50), characterized in that said substrate (50) is located centrally, and each face of said substrate (50) includes a coating (20) and a cavity (61), said cavity (61) extends through said coating (20) and partially penetrates said substrate (50) in a direction towards said substrate (50) from each coating (20), so as to make a double-wavefront correction device; said two coatings are made of different materials such that the coating on the first face of said substrate is made of a material different from the coating on the second face of said substrate.

2. The device (1) according to claim 1, characterized in that, Said device (1) includes two coatings (10, 20) arranged on said substrate (50), namely said first coating (10) and said second coating (20), and said cavity (61) extends through said first coating (10) and sinks into said second coating (20) through a part of said thickness (E20) without penetrating into said substrate (50).

3. The device (1) according to claim 1, characterized in that, Said device (1) includes a number of stacked coatings (10 - 40) which include said first coating (10) and at least one second coating (20).

4. The device (1) according to claim 3, characterized in that, Said cavity (61) extends through said first and second coatings (10) and sinks into said second coating (20) through a part of said thickness (E20).

5. The device (1) according to claim 1, characterized in that, Said cavity (61) extends through all said stacked coatings (10 - 40) and sinks into said substrate (50) through a part of said thickness (E50).

6. The device (1) according to one of the preceding claims, characterized in that, Said cavity (61) has a cross-sectional area that strictly decreases in a direction towards said substrate (50).

7. The device (1) according to one of the preceding claims, characterized in that, Said cavity (61) has a continuous profile in a direction towards said substrate (50).

8. The device (1) according to one of the preceding claims, characterized in that, Said cavity (61) has a circular cross-section.

9. A method for manufacturing an optical device adapted to transmit / reflection electromagnetic radiation within a wavelength range of the electromagnetic spectrum, said method comprising at least the following steps: - Forming at least one combination of two coatings made of a first material and a substrate made of a material different from said first material such that each face of said substrate (50) includes a coating; Then - Performing a surface texturing (60) that forms cavities (61) in said device (1) such that the effective refractive index varies on the surface of said device, Wherein, said substrate (50) has a predetermined thickness (E50); The cavity (61) extends through the coating (10) and sinks into the substrate (50) through at least a part of the thickness (E50). It is characterized in that the substrate (50) is located in the center, and each surface of the substrate (50) includes a coating (20) and a cavity (61). The cavity (61) extends through the coating (20) and partially penetrates the substrate (50) in the direction from each coating (20) towards the substrate (50) so as to fabricate a double wavefront correction device; the two coatings are made of different materials such that the coating on the first surface of the substrate is made of a different material from the coating on the second surface of the substrate.

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