The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Julien Lumeau - One of the best experts on this subject based on the ideXlab platform.
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Versatile digital micromirror device-based method for the recording of multilevel Optical diffractive elements in photosensitive chalcogenide layers (AMTIR-1)
Optics Letters, 2016Co-Authors: Alexandre Joerg, Mael Vigneaux, Julien LumeauAbstract:A new alternative and versatile method for the production of Diffractive Optical Elements (DOEs) with up to 4 phase levels in AMTIR-1 (Ge33As12Se55) layers is demonstrated. The developed method proposes the use of the photosensitive properties of the layers and a specific in-situ Optical monitoring coupled with a reverse engineering algorithm to control the trigger points of the writing of the different diffractive patterns. Examples of various volume DOEs are presented. Chalcogenide glasses (ChG) are composed from a chalcogen element such as Sulphur, Selenium, and Tellurium. To create a glass network, some other atoms are added such as As, Ge, Sb, Ga, Si or P. ChG are particularly interesting due to their specific Optical properties. In fact they are transparent into the mid-infrared up to 20 µm depending on their chemical composition [1]. The refractive index is high n~2-3 and ChG possess also a high nonlinear refractive index n2 [2]. But one of the most striking property is their photosensitivity. Using light exposure with a wavelength below the Optical bandgap, the chemical bonds can be rearranged. This effect directly modifies the Optical properties of the ChG. This very specific property has led to different kinds of applications such as phase change memory [3]… As thin films, ChG were thoroughly studied and the impact of inserting a photosensitive layer into an Optical filter to modify its spectral response was demonstrated [4]. As an example, it was shown, a few years ago, that it is possible to use the photo-bleaching or photo-darkening [5] effects to adjust the central wavelength of a Fabry-Perot filter and therefore generate ultra-uniform bandpass filters [6]. The ChG studied in this paper is AMTIR-1. It is composed in molar percent with 33% of germanium, 12% of arsenic and 55% of selenium and was provided by Amorphous Material Company. AMTIR-1 was already deposited as thin films by pulsed laser deposition [7], thermal or e-beam evaporation, and showed excellent Optical properties [8]. Layers from AMTIR-1 were shown to be excellent candidates for the production of various Optical elements such as ring resonators [9]… We recently showed that these layers are also a good candidate for the production of a new kind of Optical elements [10]. Actually with the theoretical and experimental developments of diffractive Optical elements, metamaterials or metasurfaces, there is a higher and higher demand for 3D micro-and nanostructuring of multilayer stacks. 1D-structures are easily obtained by the Optical Coating technology, while 3D-structures require micro-or nano-engineering the local thickness of the deposited structures using lithographic processes combined with etching techniques. We showed that for coarse structures, i.e. for structures having a pitch with size much larger than the wavelength (i.e. with size larger than 10 µm), it is possible to create volume phase structures by locally controlling the local refractive index of a photosensitive layer. Such an approach was applied to the fabrication of binary DOEs. However, it is well known that for many applications and in order to achieve higher diffraction efficiency, especially for the production of asymmetrical beams, the use of multi-level DOEs is mandatory. In this paper we demonstrate the possibility to photo-structure a photosensitive chalcogenide layer with 4 levels in order to produce a Volume Diffractive Optical Element (VDOE). Methods of production and monitoring are detailed. The chalcogenide layers and thin film stacks were produced using electron beam physical vapor deposition in a Balzers BAK600 chamber. The residual pressure inside the vacuum chamber was around ~10-6 mbar and the deposition rate was 10 ± 1 A/s. In a previous works [8] using those parameters, we first demonstrated that AMTIR-1 materials provide broad transparency range above 850 nm, high refractive index (n = 2.74 @ 1 µm) and photosensitive properties such as photo-bleaching effect. This effect occurs into the AMTIR-1 layers when exposed to a light with a wavelength whose energy is below the bandgap. This effect allows generating refractive index decrement down to-0.04 at 1 µm that was then applied to binary DOEs. Moreover, it was shown that this refractive index change is
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Versatile digital micromirror device-based method for the recording of multilevel Optical diffractive elements in photosensitive chalcogenide layers (AMTIR-1)
Optics Letters, 2016Co-Authors: Alexandre Joerg, Mael Vigneaux, Julien LumeauAbstract:A new alternative and versatile method for the production of Diffractive Optical Elements (DOEs) with up to 4 phase levels in AMTIR-1 (Ge33As12Se55) layers is demonstrated. The developed method proposes the use of the photosensitive properties of the layers and a specific in-situ Optical monitoring coupled with a reverse engineering algorithm to control the trigger points of the writing of the different diffractive patterns. Examples of various volume DOEs are presented. Chalcogenide glasses (ChG) are composed from a chalcogen element such as Sulphur, Selenium, and Tellurium. To create a glass network, some other atoms are added such as As, Ge, Sb, Ga, Si or P. ChG are particularly interesting due to their specific Optical properties. In fact they are transparent into the mid-infrared up to 20 µm depending on their chemical composition [1]. The refractive index is high n~2-3 and ChG possess also a high nonlinear refractive index n2 [2]. But one of the most striking property is their photosensitivity. Using light exposure with a wavelength below the Optical bandgap, the chemical bonds can be rearranged. This effect directly modifies the Optical properties of the ChG. This very specific property has led to different kinds of applications such as phase change memory [3]… As thin films, ChG were thoroughly studied and the impact of inserting a photosensitive layer into an Optical filter to modify its spectral response was demonstrated [4]. As an example, it was shown, a few years ago, that it is possible to use the photo-bleaching or photo-darkening [5] effects to adjust the central wavelength of a Fabry-Perot filter and therefore generate ultra-uniform bandpass filters [6]. The ChG studied in this paper is AMTIR-1. It is composed in molar percent with 33% of germanium, 12% of arsenic and 55% of selenium and was provided by Amorphous Material Company. AMTIR-1 was already deposited as thin films by pulsed laser deposition [7], thermal or e-beam evaporation, and showed excellent Optical properties [8]. Layers from AMTIR-1 were shown to be excellent candidates for the production of various Optical elements such as ring resonators [9]… We recently showed that these layers are also a good candidate for the production of a new kind of Optical elements [10]. Actually with the theoretical and experimental developments of diffractive Optical elements, metamaterials or metasurfaces, there is a higher and higher demand for 3D micro-and nanostructuring of multilayer stacks. 1D-structures are easily obtained by the Optical Coating technology, while 3D-structures require micro-or nano-engineering the local thickness of the deposited structures using lithographic processes combined with etching techniques. We showed that for coarse structures, i.e. for structures having a pitch with size much larger than the wavelength (i.e. with size larger than 10 µm), it is possible to create volume phase structures by locally controlling the local refractive index of a photosensitive layer. Such an approach was applied to the fabrication of binary DOEs. However, it is well known that for many applications and in order to achieve higher diffraction efficiency, especially for the production of asymmetrical beams, the use of multi-level DOEs is mandatory. In this paper we demonstrate the possibility to photo-structure a photosensitive chalcogenide layer with 4 levels in order to produce a Volume Diffractive Optical Element (VDOE). Methods of production and monitoring are detailed. The chalcogenide layers and thin film stacks were produced using electron beam physical vapor deposition in a Balzers BAK600 chamber. The residual pressure inside the vacuum chamber was around ~10-6 mbar and the deposition rate was 10 ± 1 A/s. In a previous works [8] using those parameters, we first demonstrated that AMTIR-1 materials provide broad transparency range above 850 nm, high refractive index (n = 2.74 @ 1 µm) and photosensitive properties such as photo-bleaching effect. This effect occurs into the AMTIR-1 layers when exposed to a light with a wavelength whose energy is below the bandgap. This effect allows generating refractive index decrement down to-0.04 at 1 µm that was then applied to binary DOEs. Moreover, it was shown that this refractive index change is
Alexandre Joerg - One of the best experts on this subject based on the ideXlab platform.
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Versatile digital micromirror device-based method for the recording of multilevel Optical diffractive elements in photosensitive chalcogenide layers (AMTIR-1)
Optics Letters, 2016Co-Authors: Alexandre Joerg, Mael Vigneaux, Julien LumeauAbstract:A new alternative and versatile method for the production of Diffractive Optical Elements (DOEs) with up to 4 phase levels in AMTIR-1 (Ge33As12Se55) layers is demonstrated. The developed method proposes the use of the photosensitive properties of the layers and a specific in-situ Optical monitoring coupled with a reverse engineering algorithm to control the trigger points of the writing of the different diffractive patterns. Examples of various volume DOEs are presented. Chalcogenide glasses (ChG) are composed from a chalcogen element such as Sulphur, Selenium, and Tellurium. To create a glass network, some other atoms are added such as As, Ge, Sb, Ga, Si or P. ChG are particularly interesting due to their specific Optical properties. In fact they are transparent into the mid-infrared up to 20 µm depending on their chemical composition [1]. The refractive index is high n~2-3 and ChG possess also a high nonlinear refractive index n2 [2]. But one of the most striking property is their photosensitivity. Using light exposure with a wavelength below the Optical bandgap, the chemical bonds can be rearranged. This effect directly modifies the Optical properties of the ChG. This very specific property has led to different kinds of applications such as phase change memory [3]… As thin films, ChG were thoroughly studied and the impact of inserting a photosensitive layer into an Optical filter to modify its spectral response was demonstrated [4]. As an example, it was shown, a few years ago, that it is possible to use the photo-bleaching or photo-darkening [5] effects to adjust the central wavelength of a Fabry-Perot filter and therefore generate ultra-uniform bandpass filters [6]. The ChG studied in this paper is AMTIR-1. It is composed in molar percent with 33% of germanium, 12% of arsenic and 55% of selenium and was provided by Amorphous Material Company. AMTIR-1 was already deposited as thin films by pulsed laser deposition [7], thermal or e-beam evaporation, and showed excellent Optical properties [8]. Layers from AMTIR-1 were shown to be excellent candidates for the production of various Optical elements such as ring resonators [9]… We recently showed that these layers are also a good candidate for the production of a new kind of Optical elements [10]. Actually with the theoretical and experimental developments of diffractive Optical elements, metamaterials or metasurfaces, there is a higher and higher demand for 3D micro-and nanostructuring of multilayer stacks. 1D-structures are easily obtained by the Optical Coating technology, while 3D-structures require micro-or nano-engineering the local thickness of the deposited structures using lithographic processes combined with etching techniques. We showed that for coarse structures, i.e. for structures having a pitch with size much larger than the wavelength (i.e. with size larger than 10 µm), it is possible to create volume phase structures by locally controlling the local refractive index of a photosensitive layer. Such an approach was applied to the fabrication of binary DOEs. However, it is well known that for many applications and in order to achieve higher diffraction efficiency, especially for the production of asymmetrical beams, the use of multi-level DOEs is mandatory. In this paper we demonstrate the possibility to photo-structure a photosensitive chalcogenide layer with 4 levels in order to produce a Volume Diffractive Optical Element (VDOE). Methods of production and monitoring are detailed. The chalcogenide layers and thin film stacks were produced using electron beam physical vapor deposition in a Balzers BAK600 chamber. The residual pressure inside the vacuum chamber was around ~10-6 mbar and the deposition rate was 10 ± 1 A/s. In a previous works [8] using those parameters, we first demonstrated that AMTIR-1 materials provide broad transparency range above 850 nm, high refractive index (n = 2.74 @ 1 µm) and photosensitive properties such as photo-bleaching effect. This effect occurs into the AMTIR-1 layers when exposed to a light with a wavelength whose energy is below the bandgap. This effect allows generating refractive index decrement down to-0.04 at 1 µm that was then applied to binary DOEs. Moreover, it was shown that this refractive index change is
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Versatile digital micromirror device-based method for the recording of multilevel Optical diffractive elements in photosensitive chalcogenide layers (AMTIR-1)
Optics Letters, 2016Co-Authors: Alexandre Joerg, Mael Vigneaux, Julien LumeauAbstract:A new alternative and versatile method for the production of Diffractive Optical Elements (DOEs) with up to 4 phase levels in AMTIR-1 (Ge33As12Se55) layers is demonstrated. The developed method proposes the use of the photosensitive properties of the layers and a specific in-situ Optical monitoring coupled with a reverse engineering algorithm to control the trigger points of the writing of the different diffractive patterns. Examples of various volume DOEs are presented. Chalcogenide glasses (ChG) are composed from a chalcogen element such as Sulphur, Selenium, and Tellurium. To create a glass network, some other atoms are added such as As, Ge, Sb, Ga, Si or P. ChG are particularly interesting due to their specific Optical properties. In fact they are transparent into the mid-infrared up to 20 µm depending on their chemical composition [1]. The refractive index is high n~2-3 and ChG possess also a high nonlinear refractive index n2 [2]. But one of the most striking property is their photosensitivity. Using light exposure with a wavelength below the Optical bandgap, the chemical bonds can be rearranged. This effect directly modifies the Optical properties of the ChG. This very specific property has led to different kinds of applications such as phase change memory [3]… As thin films, ChG were thoroughly studied and the impact of inserting a photosensitive layer into an Optical filter to modify its spectral response was demonstrated [4]. As an example, it was shown, a few years ago, that it is possible to use the photo-bleaching or photo-darkening [5] effects to adjust the central wavelength of a Fabry-Perot filter and therefore generate ultra-uniform bandpass filters [6]. The ChG studied in this paper is AMTIR-1. It is composed in molar percent with 33% of germanium, 12% of arsenic and 55% of selenium and was provided by Amorphous Material Company. AMTIR-1 was already deposited as thin films by pulsed laser deposition [7], thermal or e-beam evaporation, and showed excellent Optical properties [8]. Layers from AMTIR-1 were shown to be excellent candidates for the production of various Optical elements such as ring resonators [9]… We recently showed that these layers are also a good candidate for the production of a new kind of Optical elements [10]. Actually with the theoretical and experimental developments of diffractive Optical elements, metamaterials or metasurfaces, there is a higher and higher demand for 3D micro-and nanostructuring of multilayer stacks. 1D-structures are easily obtained by the Optical Coating technology, while 3D-structures require micro-or nano-engineering the local thickness of the deposited structures using lithographic processes combined with etching techniques. We showed that for coarse structures, i.e. for structures having a pitch with size much larger than the wavelength (i.e. with size larger than 10 µm), it is possible to create volume phase structures by locally controlling the local refractive index of a photosensitive layer. Such an approach was applied to the fabrication of binary DOEs. However, it is well known that for many applications and in order to achieve higher diffraction efficiency, especially for the production of asymmetrical beams, the use of multi-level DOEs is mandatory. In this paper we demonstrate the possibility to photo-structure a photosensitive chalcogenide layer with 4 levels in order to produce a Volume Diffractive Optical Element (VDOE). Methods of production and monitoring are detailed. The chalcogenide layers and thin film stacks were produced using electron beam physical vapor deposition in a Balzers BAK600 chamber. The residual pressure inside the vacuum chamber was around ~10-6 mbar and the deposition rate was 10 ± 1 A/s. In a previous works [8] using those parameters, we first demonstrated that AMTIR-1 materials provide broad transparency range above 850 nm, high refractive index (n = 2.74 @ 1 µm) and photosensitive properties such as photo-bleaching effect. This effect occurs into the AMTIR-1 layers when exposed to a light with a wavelength whose energy is below the bandgap. This effect allows generating refractive index decrement down to-0.04 at 1 µm that was then applied to binary DOEs. Moreover, it was shown that this refractive index change is
Alexander V. Tikhonravov - One of the best experts on this subject based on the ideXlab platform.
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Mathematical investigation of the error self-compensation mechanism in Optical Coating technology
Inverse Problems in Science and Engineering, 2017Co-Authors: Alexander V. Tikhonravov, Igor V. Kochikov, Anatoly G. YagolaAbstract:AbstractThe inverse problem of Optical Coatings control during their deposition is an important practical and industrial problem. The paper presents the mathematical investigation of the layer thickness errors self-compensation effect that is quite important for the quality production of modern types of thin film Optical Coatings. It studies the mechanism of thickness errors correlation in the case of direct monitoring of Optical Coating production by broadband online spectral photometric devices. The mathematical description of this mechanism is provided. The obtained results make it possible to predict the existence of a strong error self-compensation effect when theoretical Optical Coating design and parameters of the monitoring procedure are known. Mathematical results of the conducted research are confirmed by computational experiments with the data obtained for the Optical Coating design problem where a very strong error self-compensation effect has been practically observed.
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advantages and challenges of Optical Coating production with indirect monochromatic monitoring
Applied Optics, 2015Co-Authors: Jinlong Zhang, Alexander V. Tikhonravov, Michael K. Trubetskov, Chong Cao, Artur Gorokh, Xinbin Cheng, Zhanshan WangAbstract:In this paper, we present our recent studies on raising the quality of Optical Coating production with an indirect monochromatic monitoring system. Preproduction error analysis and computational manufacturing are used to estimate potential advantages of application of indirect Optical monitoring. It is then demonstrated that a key issue for realization of this advantage is accurate specification of tooling factors for layer thicknesses on test glasses. The tooling factors are precalibrated using single layer depositions and then are corrected using results of reverse engineering for the first production run. It is found that a gradual variation of tooling factors of low index layers is the main error factor in the first deposition run. Finally, we redeposit our Coating with a modified monitoring strategy, taking into account this factor. The new experimental results show excellent correspondence with the theoretical spectral performance.
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modern design tools and a new paradigm in Optical Coating design
Applied Optics, 2012Co-Authors: Alexander V. Tikhonravov, Michael K. TrubetskovAbstract:Several modern Optical Coating designs tools are discussed in the frame of a new design paradigm proposing the search not for a formally optimal solution with the lowest possible merit function value but for the most practical solution that takes into account additional feasibility demands. Considered design tools include a stochastic optimization procedure that takes into account upper and lower constraints for layer Optical thicknesses. This procedure allows one to obtain multiple solutions to a design problem, which presents additional opportunities for choosing a practically optimal design. Two special design techniques involving integer optimization also take into account additional demands. The first one is aimed at designing multicavity narrow bandpass filters with quarter wave or multiple quarter wave layer Optical thicknesses. It enables obtaining bandpass filters with extremely steep transmittance slopes, bandwidths of several tens of nanometers, and very small ripples in transmission zones. The second technique is aimed at covering design problems that have been traditionally solved using the theory of equivalent layers. One more technique considered in this paper is aimed at reducing the influence of noncorrelated thickness errors on design spectral characteristics.
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Optical parameters of oxide films typically used in Optical Coating production
Applied Optics, 2011Co-Authors: Alexander V. Tikhonravov, Tatiana V. Amotchkina, Michael K. Trubetskov, Gary W Debell, Vladimir Pervak, Anna Sytchkova, Maria Luisa Grilli, Detlev RistauAbstract:Wavelength dependencies of refractive indices of thin film materials differ for various deposition conditions, and it is practically impossible to attribute a single refractive index wavelength dependence to any typical thin film material. Besides objective reasons, differences in the Optical parameters of thin films may also be connected with nonadequate choices of models and algorithms used for the processing of measurement data. The main goal of this paper is to present reliable wavelength dependencies of refractive indices of the most widely used slightly absorbing oxide thin film materials. These dependencies can be used by other researchers for comparison and verification of their own characterization results.
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Design and monitoring approaches for the production of high quality Optical Coatings
Seventh International Conference on Thin Film Physics and Applications, 2010Co-Authors: Alexander V. Tikhonravov, Michael K. TrubetskovAbstract:ABSTRACT Modern design and monitoring approaches are discussed from the point of view of their ability to provide a production of high quality Optical Coatings at the lowest possible cost and in the most reasonable time frame. Keywords: Interference Coatings, design, monitoring, computational manufacturing 1. INTRODUCTION The invention of the needle optimization technique 1 and further modifications of this technique 2, 3 provided Optical Coating engineers with the most effective tools for designing of Optical Coatings of any type. An outstanding computational efficiency of modern design techniques has resulted in a new paradigm of designing of Optical Coatings. 4 This new paradigm proposes to look for a practically optimal design instead of a formally optimal design characterized by the lowest possible merit function value. The concept of a practically optimal design is tightly connected with a monitoring approach used for Optical Coating production. At the modern state of art in production of innovative Optical Coatings, especially in production of high quality Optical coa tings for challenging applications, it is necessary to perform a combined choice of design and monitoring approach that should be applied for Optical Coating manufacturing. Modern design techniques can provide a great number of excellent theoretical designs and it is too expensive and time consuming to perform test manufacturing runs in order to choose the most practical design with the best expectation for a high manufacturing yield. An excellent alternative to real test manu facturing runs is provided by a series of experiments with computational manufacturing of Optical Coatings.
Mael Vigneaux - One of the best experts on this subject based on the ideXlab platform.
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Versatile digital micromirror device-based method for the recording of multilevel Optical diffractive elements in photosensitive chalcogenide layers (AMTIR-1)
Optics Letters, 2016Co-Authors: Alexandre Joerg, Mael Vigneaux, Julien LumeauAbstract:A new alternative and versatile method for the production of Diffractive Optical Elements (DOEs) with up to 4 phase levels in AMTIR-1 (Ge33As12Se55) layers is demonstrated. The developed method proposes the use of the photosensitive properties of the layers and a specific in-situ Optical monitoring coupled with a reverse engineering algorithm to control the trigger points of the writing of the different diffractive patterns. Examples of various volume DOEs are presented. Chalcogenide glasses (ChG) are composed from a chalcogen element such as Sulphur, Selenium, and Tellurium. To create a glass network, some other atoms are added such as As, Ge, Sb, Ga, Si or P. ChG are particularly interesting due to their specific Optical properties. In fact they are transparent into the mid-infrared up to 20 µm depending on their chemical composition [1]. The refractive index is high n~2-3 and ChG possess also a high nonlinear refractive index n2 [2]. But one of the most striking property is their photosensitivity. Using light exposure with a wavelength below the Optical bandgap, the chemical bonds can be rearranged. This effect directly modifies the Optical properties of the ChG. This very specific property has led to different kinds of applications such as phase change memory [3]… As thin films, ChG were thoroughly studied and the impact of inserting a photosensitive layer into an Optical filter to modify its spectral response was demonstrated [4]. As an example, it was shown, a few years ago, that it is possible to use the photo-bleaching or photo-darkening [5] effects to adjust the central wavelength of a Fabry-Perot filter and therefore generate ultra-uniform bandpass filters [6]. The ChG studied in this paper is AMTIR-1. It is composed in molar percent with 33% of germanium, 12% of arsenic and 55% of selenium and was provided by Amorphous Material Company. AMTIR-1 was already deposited as thin films by pulsed laser deposition [7], thermal or e-beam evaporation, and showed excellent Optical properties [8]. Layers from AMTIR-1 were shown to be excellent candidates for the production of various Optical elements such as ring resonators [9]… We recently showed that these layers are also a good candidate for the production of a new kind of Optical elements [10]. Actually with the theoretical and experimental developments of diffractive Optical elements, metamaterials or metasurfaces, there is a higher and higher demand for 3D micro-and nanostructuring of multilayer stacks. 1D-structures are easily obtained by the Optical Coating technology, while 3D-structures require micro-or nano-engineering the local thickness of the deposited structures using lithographic processes combined with etching techniques. We showed that for coarse structures, i.e. for structures having a pitch with size much larger than the wavelength (i.e. with size larger than 10 µm), it is possible to create volume phase structures by locally controlling the local refractive index of a photosensitive layer. Such an approach was applied to the fabrication of binary DOEs. However, it is well known that for many applications and in order to achieve higher diffraction efficiency, especially for the production of asymmetrical beams, the use of multi-level DOEs is mandatory. In this paper we demonstrate the possibility to photo-structure a photosensitive chalcogenide layer with 4 levels in order to produce a Volume Diffractive Optical Element (VDOE). Methods of production and monitoring are detailed. The chalcogenide layers and thin film stacks were produced using electron beam physical vapor deposition in a Balzers BAK600 chamber. The residual pressure inside the vacuum chamber was around ~10-6 mbar and the deposition rate was 10 ± 1 A/s. In a previous works [8] using those parameters, we first demonstrated that AMTIR-1 materials provide broad transparency range above 850 nm, high refractive index (n = 2.74 @ 1 µm) and photosensitive properties such as photo-bleaching effect. This effect occurs into the AMTIR-1 layers when exposed to a light with a wavelength whose energy is below the bandgap. This effect allows generating refractive index decrement down to-0.04 at 1 µm that was then applied to binary DOEs. Moreover, it was shown that this refractive index change is
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Versatile digital micromirror device-based method for the recording of multilevel Optical diffractive elements in photosensitive chalcogenide layers (AMTIR-1)
Optics Letters, 2016Co-Authors: Alexandre Joerg, Mael Vigneaux, Julien LumeauAbstract:A new alternative and versatile method for the production of Diffractive Optical Elements (DOEs) with up to 4 phase levels in AMTIR-1 (Ge33As12Se55) layers is demonstrated. The developed method proposes the use of the photosensitive properties of the layers and a specific in-situ Optical monitoring coupled with a reverse engineering algorithm to control the trigger points of the writing of the different diffractive patterns. Examples of various volume DOEs are presented. Chalcogenide glasses (ChG) are composed from a chalcogen element such as Sulphur, Selenium, and Tellurium. To create a glass network, some other atoms are added such as As, Ge, Sb, Ga, Si or P. ChG are particularly interesting due to their specific Optical properties. In fact they are transparent into the mid-infrared up to 20 µm depending on their chemical composition [1]. The refractive index is high n~2-3 and ChG possess also a high nonlinear refractive index n2 [2]. But one of the most striking property is their photosensitivity. Using light exposure with a wavelength below the Optical bandgap, the chemical bonds can be rearranged. This effect directly modifies the Optical properties of the ChG. This very specific property has led to different kinds of applications such as phase change memory [3]… As thin films, ChG were thoroughly studied and the impact of inserting a photosensitive layer into an Optical filter to modify its spectral response was demonstrated [4]. As an example, it was shown, a few years ago, that it is possible to use the photo-bleaching or photo-darkening [5] effects to adjust the central wavelength of a Fabry-Perot filter and therefore generate ultra-uniform bandpass filters [6]. The ChG studied in this paper is AMTIR-1. It is composed in molar percent with 33% of germanium, 12% of arsenic and 55% of selenium and was provided by Amorphous Material Company. AMTIR-1 was already deposited as thin films by pulsed laser deposition [7], thermal or e-beam evaporation, and showed excellent Optical properties [8]. Layers from AMTIR-1 were shown to be excellent candidates for the production of various Optical elements such as ring resonators [9]… We recently showed that these layers are also a good candidate for the production of a new kind of Optical elements [10]. Actually with the theoretical and experimental developments of diffractive Optical elements, metamaterials or metasurfaces, there is a higher and higher demand for 3D micro-and nanostructuring of multilayer stacks. 1D-structures are easily obtained by the Optical Coating technology, while 3D-structures require micro-or nano-engineering the local thickness of the deposited structures using lithographic processes combined with etching techniques. We showed that for coarse structures, i.e. for structures having a pitch with size much larger than the wavelength (i.e. with size larger than 10 µm), it is possible to create volume phase structures by locally controlling the local refractive index of a photosensitive layer. Such an approach was applied to the fabrication of binary DOEs. However, it is well known that for many applications and in order to achieve higher diffraction efficiency, especially for the production of asymmetrical beams, the use of multi-level DOEs is mandatory. In this paper we demonstrate the possibility to photo-structure a photosensitive chalcogenide layer with 4 levels in order to produce a Volume Diffractive Optical Element (VDOE). Methods of production and monitoring are detailed. The chalcogenide layers and thin film stacks were produced using electron beam physical vapor deposition in a Balzers BAK600 chamber. The residual pressure inside the vacuum chamber was around ~10-6 mbar and the deposition rate was 10 ± 1 A/s. In a previous works [8] using those parameters, we first demonstrated that AMTIR-1 materials provide broad transparency range above 850 nm, high refractive index (n = 2.74 @ 1 µm) and photosensitive properties such as photo-bleaching effect. This effect occurs into the AMTIR-1 layers when exposed to a light with a wavelength whose energy is below the bandgap. This effect allows generating refractive index decrement down to-0.04 at 1 µm that was then applied to binary DOEs. Moreover, it was shown that this refractive index change is
Michael K. Trubetskov - One of the best experts on this subject based on the ideXlab platform.
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advantages and challenges of Optical Coating production with indirect monochromatic monitoring
Applied Optics, 2015Co-Authors: Jinlong Zhang, Alexander V. Tikhonravov, Michael K. Trubetskov, Chong Cao, Artur Gorokh, Xinbin Cheng, Zhanshan WangAbstract:In this paper, we present our recent studies on raising the quality of Optical Coating production with an indirect monochromatic monitoring system. Preproduction error analysis and computational manufacturing are used to estimate potential advantages of application of indirect Optical monitoring. It is then demonstrated that a key issue for realization of this advantage is accurate specification of tooling factors for layer thicknesses on test glasses. The tooling factors are precalibrated using single layer depositions and then are corrected using results of reverse engineering for the first production run. It is found that a gradual variation of tooling factors of low index layers is the main error factor in the first deposition run. Finally, we redeposit our Coating with a modified monitoring strategy, taking into account this factor. The new experimental results show excellent correspondence with the theoretical spectral performance.
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modern design tools and a new paradigm in Optical Coating design
Applied Optics, 2012Co-Authors: Alexander V. Tikhonravov, Michael K. TrubetskovAbstract:Several modern Optical Coating designs tools are discussed in the frame of a new design paradigm proposing the search not for a formally optimal solution with the lowest possible merit function value but for the most practical solution that takes into account additional feasibility demands. Considered design tools include a stochastic optimization procedure that takes into account upper and lower constraints for layer Optical thicknesses. This procedure allows one to obtain multiple solutions to a design problem, which presents additional opportunities for choosing a practically optimal design. Two special design techniques involving integer optimization also take into account additional demands. The first one is aimed at designing multicavity narrow bandpass filters with quarter wave or multiple quarter wave layer Optical thicknesses. It enables obtaining bandpass filters with extremely steep transmittance slopes, bandwidths of several tens of nanometers, and very small ripples in transmission zones. The second technique is aimed at covering design problems that have been traditionally solved using the theory of equivalent layers. One more technique considered in this paper is aimed at reducing the influence of noncorrelated thickness errors on design spectral characteristics.
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Optical parameters of oxide films typically used in Optical Coating production
Applied Optics, 2011Co-Authors: Alexander V. Tikhonravov, Tatiana V. Amotchkina, Michael K. Trubetskov, Gary W Debell, Vladimir Pervak, Anna Sytchkova, Maria Luisa Grilli, Detlev RistauAbstract:Wavelength dependencies of refractive indices of thin film materials differ for various deposition conditions, and it is practically impossible to attribute a single refractive index wavelength dependence to any typical thin film material. Besides objective reasons, differences in the Optical parameters of thin films may also be connected with nonadequate choices of models and algorithms used for the processing of measurement data. The main goal of this paper is to present reliable wavelength dependencies of refractive indices of the most widely used slightly absorbing oxide thin film materials. These dependencies can be used by other researchers for comparison and verification of their own characterization results.
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Design and monitoring approaches for the production of high quality Optical Coatings
Seventh International Conference on Thin Film Physics and Applications, 2010Co-Authors: Alexander V. Tikhonravov, Michael K. TrubetskovAbstract:ABSTRACT Modern design and monitoring approaches are discussed from the point of view of their ability to provide a production of high quality Optical Coatings at the lowest possible cost and in the most reasonable time frame. Keywords: Interference Coatings, design, monitoring, computational manufacturing 1. INTRODUCTION The invention of the needle optimization technique 1 and further modifications of this technique 2, 3 provided Optical Coating engineers with the most effective tools for designing of Optical Coatings of any type. An outstanding computational efficiency of modern design techniques has resulted in a new paradigm of designing of Optical Coatings. 4 This new paradigm proposes to look for a practically optimal design instead of a formally optimal design characterized by the lowest possible merit function value. The concept of a practically optimal design is tightly connected with a monitoring approach used for Optical Coating production. At the modern state of art in production of innovative Optical Coatings, especially in production of high quality Optical coa tings for challenging applications, it is necessary to perform a combined choice of design and monitoring approach that should be applied for Optical Coating manufacturing. Modern design techniques can provide a great number of excellent theoretical designs and it is too expensive and time consuming to perform test manufacturing runs in order to choose the most practical design with the best expectation for a high manufacturing yield. An excellent alternative to real test manu facturing runs is provided by a series of experiments with computational manufacturing of Optical Coatings.
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Optical Coating design approaches based on the needle optimization technique
Applied Optics, 2007Co-Authors: Alexander V. Tikhonravov, Michael K. Trubetskov, Gary W DebellAbstract:Design approaches for Optical thin films that recognize the key role of a design's total Optical thickness are presented. These approaches are based primarily on the needle optimization technique but also utilize other optimization procedures. Using the described design approaches, an Optical Coating engineer can obtain a set of theoretical designs with different combinations of principal design metrics (merit function value, number of layers, and total design Optical thickness); this extends opportunities for choosing the most practical and manufacturable design. We also show that some design problems have multiple solutions with nearly the same combinations of principal design metrics.