Dispersive elements are in general the key components of spectrometers and define mainly their performance. Prisms and filters are typically used for lower resolution applications, e.g. color measurement for industrial applications. Many high performance spectrometer applications are using gratings as dispersive elements instead. Different spectrometer layouts require various grating approaches in order to maintain the optical imaging performance. A frequent aim is a progressively optimization of the optical performance in balance to the mechanical parameters like weight, volume or robustness against variations of environmental conditions of a spectrometer module as well. Thus, the optical designer has to draw on additional design degrees of freedom. This in turn results often in more and more complex grating types featuring curved substrates and/or variable and bended grating lines. Especially the trend toward hyperspectral imaging applications demands appropriate options for enhanced field correction. The main ZEISS technology chain for grating manufacturing includes holography and reactive ion etching is a flexible base for these special types of gratings. A close entanglement between holography and accurate test procedures for the optical functionality of the holographic grating is a pre-condition for the ability to meet the often challenging specifications. Therefore, beside the brief description of the manufacturing technology in this text we show a set of newly developed measuring procedures supporting the holographic surface patterning approach.

The sensing performance of spectroscopic systems can be enhanced by improving their optical core-element: the optical grating. in particular for imaging spectrometers - especially Hyper-Spectral Imagers - beside the polarization sensitivity and efficiency the imaging quality of the diffraction grating is an important parameter. Optical elements within the spectrometer are manufactured while aiming on lowest wave front aberrations. Thus, least imaging aberration quality of the grating is required not to limit the overall imaging quality of the instrument. Different types of spectrometers (Offner, Czerny Turner) lead to different requirements for the grating surface figure. Beside wavefront aberrations the straylight of gratings will impact the optical performance of spectrometers too. Both parameters are crucially influenced by the manufacturing processes. During the manufacturing process of the grating substrate, a sequence of polishing steps can be applied in order to minimize the wavefront aberrations and roughness. Chemical assisted polishing in combination with classical techniques lead to least surface roughness. A good practice for the manufacturing of aspheres and freeform substrates is the generation of an initial figure close to the final shape only by a classical process, followed by a careful applied aspherization. The imaging performance (wavefront and straylight) of the grating is also optimized due to the recording setup of the holography - including all employed optics for the wave forming. Holographically manufactured gratings with adapted wave forming functions are used for transmission or reflection gratings on different types of substrates like prisms, convex and concave spherical and aspherical surface shapes, up to free-form elements. Numerous spectrometer setups (e.g. Offner, Rowland circle, Czerny-Turner system layout) work on the optical design principles of reflection gratings. All those manufactured gratings can be coated with adapted coatings to support their reflection or transmission operation. The present approach can be applied to manufacture high quality reflection gratings for the EUV to the IR. In this paper we report our results on designing and manufacturing high quality gratings based on holographic processes in order to enable diffraction limited complex spectrometric setups over certain wavelength ranges. Most beneficial is an optimization of the grating during spectrometer design phase while regarding the manufacturing as well. However, the initial optical design approach will show that gratings can be tailored to the specific requirements of the spectrometer (in order to enhance the imaging quality). The enhancement of the optical performance may lead to a specific wavefront shape after the grating element. this special capability for aberration reduction can be defined to the grating during the holographic process. In general, holography enables to manufacture gratings with a specific and adapted wavefront error compensation functions. Beside the results of low aberration gratings the results on straylight measurements will be presented. Recent results and optimization will be shown.

For imaging spectrometers beside the polarization sensitivity and efficiency the imaging quality of the diffraction grating is essential. Low aberration imaging quality of the grating is required not to limit the overall imaging quality of the instrument. The wavefront aberration of an optical grating is a combination of the substrate wavefront and the grating wavefront. During the manufacturing process of the grating substrate different processes can be applied in order to minimize the wavefront aberrations. The imaging performance of the grating is also optimized due to the recording setup of the holography and a special technique to apply blazed profiles also in photoresist of curved substrates. This technology of holographically manufactured gratings is used for transmission and reflection gratings on different types of substrates like prisms, convex and concave spherical and aspherical surface shapes, free-form elements. All the manufactured gratings are monolithic and can be coated with high reflection and anti-reflection coatings. Prism substrates were used to manufacture monolithic GRISM elements for the UV to IR spectral range preferably working in transmission. Besides of transmission gratings, numerous spectrometer setups (e.g. Offner, Rowland circle, Czerny-Turner system layout) working on the optical design principles of reflection gratings. The present approach can be applied to manufacture high quality reflection gratings for the EUV to the IR. In this paper we report our latest results on manufacturing lowest wavefront aberration gratings based on holographic processes in order to enable at least diffraction limited complex spectrometric setups over certain wavelength ranges. Beside the results of low aberration gratings the latest achievements on improving efficiency together with less polarization sensitivity and multi-band performance of diffractive gratings will be shown.

Gratings are the core element of the spectrometer. For imaging spectrometers beside the polarization sensitivity and efficiency the imaging quality of the diffraction grating is essential. Lenses and mirrors can be produced with lowest wavefront aberrations. Low aberration imaging quality of the grating is required not to limit the overall imaging quality of the instrument. Different types of spectrometers will lead to different requirements on the wavefront aberrations for their specific diffraction gratings. The wavefront aberration of an optical grating is a combination of the substrate wavefront and the grating wavefront. During the manufacturing process of the grating substrate different processes can be applied in order to minimize the wavefront aberrations. The imaging performance of the grating is also optimized due to the recording setup of the holography. This technology of holographically manufactured gratings is used for transmission and reflection gratings on different types of substrates like prisms, convex and concave spherical and aspherical surface shapes, free-form elements. All the manufactured gratings are monolithic and can be coated with high reflection and anti-reflection coatings. Prism substrates were used to manufacture monolithic GRISM elements for the UV to IR spectral range preferably working in transmission. Besides of transmission gratings, numerous spectrometer setups (e.g. Offner, Rowland circle, Czerny-Turner system layout) working on the optical design principles of reflection gratings. The present approach can be applied to manufacture high quality reflection gratings for the EUV to the IR. In this paper we report our latest results on manufacturing lowest wavefront aberration gratings based on holographic processes in order to enable at least diffraction limited complex spectrometric setups over certain wavelength ranges. Beside the results of low aberration gratings the latest achievements on improving efficiency together with less polarization sensitivity of diffractive gratings will be shown for different grating profiles.

Spectral imaging systems lead to enhanced sensing properties when the sensing system provides sufficient spectral resolution to identify materials from its spectral reflectance signature. The performance of diffraction gratings provides an initial way to improve instrumental resolution. Thus, subsequent manufacturing techniques of high quality gratings are essential to significantly improve the spectral performance. The ZEISS unique technology of manufacturing real-blazed profiles and as well as lamellar profiles comprising transparent substrates is well suited for the production of transmission gratings. In order to reduce high order aberrations, aspherical and free-form surfaces can be alternatively processed to allow more degrees of freedom in the optical design of spectroscopic instruments with less optical elements and therefore size and weight advantages. Prism substrates were used to manufacture monolithic GRISM elements for UV to IR spectral range. Many years of expertise in the research and development of optical coatings enable high transmission anti-reflection coatings from the DUV to the NIR. ZEISS has developed specially adapted coating processes (Ion beam sputtering, ion-assisted deposition and so on) for maintaining the micro-structure of blazed gratings in particular. Besides of transmission gratings, numerous spectrometer setups (e.g. Offner, Rowland circle, Czerny-Turner system layout) working on the optical design principles of reflection gratings. This technology steps can be applied to manufacture high quality reflection gratings from the EUV to the IR applications with an outstanding level of low stray light and ghost diffraction order by employing a combination of holography and reactive ion beam etching together with the in-house coating capabilities. We report on results of transmission gratings on plane and curved substrates and GRISM elements with enhanced efficiency of the grating itself combined with low scattered light in the angular distribution. Beside of the results of straylight measurement the actual results on improving efficiency and lowering the polarization sensitivity for transmission gratings will be discussed on theoretical simulations compared to measured data over the entire wavelength range.

Spectral imaging systems lead to enhanced sensing properties when the sensing system provides sufficient spectral resolution to identify materials from its spectral reflectance signature. The performance of diffraction gratings provides an initial way to improve instrumental resolution. Thus, subsequent manufacturing techniques of high quality gratings are essential to significantly improve the spectral performance. The ZEISS unique technology of manufacturing real-blazed profiles comprising transparent substrates is well suited for the production of transmission gratings. In order to reduce high order aberrations, aspherical and free-form surfaces can be alternatively processed to allow more degrees of freedom in the optical design of spectroscopic instruments with less optical elements and therefore size and weight advantages. Prism substrates were used to manufacture monolithic GRISM elements for UV to IR spectral range. Many years of expertise in the research and development of optical coatings enable high transmission anti-reflection coatings from the DUV to the NIR. ZEISS has developed specially adapted coating processes (Ion beam sputtering, ion-assisted deposition and so on) for maintaining the micro-structure of blazed gratings in particular. Besides of transmission gratings, numerous spectrometer setups (e.g. Offner, Rowland circle, Czerny-Turner system layout) working on the optical design principles of reflection gratings. This technology steps can be applied to manufacture high quality reflection gratings from the EUV to the IR applications with an outstanding level of low stray light and ghost diffraction order by employing a combination of holography and reactive ion beam etching together with the in-house coating capabilities. We report on results of transmission, reflection gratings on plane and curved substrates and GRISM elements with enhanced efficiency of the grating itself combined with low scattered light in the angular distribution. Focusing on the straylight characteristic a measurement of the actual straylight level, preferably with extremely high precision, was performed and will be discussed in this paper. Beside of the results of straylight measurement the actual results on improving efficiency for transmission and reflection gratings will be discussed on theoretical simulations compared to measured data over the entire wavelength range.

Die physikalisch-optischen Randbedingungen beim Einsatz von Beugungsgittern im Wellenlangen-Bereich um 13,5nm bedingen einen grosen Einfallswinkel. Die gebeugte Strahlung hinter einem solchen Grazing-Incidence-Gitter wird dabei an einer wesentlich groseren Flache umgelenkt, als dies bei ublichen Anwendungen in einem Wellenlangenbereich der Fall ware, in dem sich Schichtmaterialien mit hohem Reflexionsgrad verwenden liesen. Deshalb wirken sich Abweichungen von der Ebenheit bzw. Sollform des Gittersubstrats wesentlich starker aus. Durch das sehr grose Verhaltnis von Gitterperiode zu Wellenlange ist die Form der Blaze-Facetten der dominierend effizienzbestimmende Faktor. Sehr ungunstig sind in diesem Zusammenhang schlecht definierte Blaze-Facetten sowie auch Oberflachendefekte und Rauigkeit. Wir zeigen, dass die Herstellung dieser anspruchsvollen Gitter basierend auf einem holografischen Mastering in Photoresist in Kombination mit einem RIBE-Transfer-Prozess zu geeigneten Blaze-Strukturen fuhrt. Projekt-Partner: Zeiss: Holografie; IOM: Reaktives Ionenstrahlatzen; PTB: Messungen bei Arbeitswellenlange unter Nutzung von Synchrotron-Strahlung am Speicherring BESSY; TUI: wissenschaftliche Grundlagen zur Holografie

Monolithic diffraction gratings are one of the key components of high sensitive spectral imaging systems including spectrometer used in space instruments. These gratings are optimized for high efficiency, lowest line spacing errors and low scattering values to improve the performance of a spectral imaging system. Spectral imaging systems lead to enhanced remote sensing properties when the sensing system provides sufficient spectral resolution to identify materials from its spectral reflectance signature comprising low signal-to-noise ratios.

A diffraction grating is one of the key-components of spectral imaging spectrometers. Spectral imaging systems lead to enhanced remote sensing properties when the sensing system provides sufficient spectral resolution to identify materials from its spectral reflectance signature. The performance of diffraction gratings provide an initial way to improve instrumental resolution. Thus, subsequent manufacturing techniques of high quality gratings are essential to significantly boost spectral performance. ZEISS has developed advanced fabrication techniques to manufacture monolithic, high groove density gratings with low stray light, high diffraction efficiency and low polarization sensitivity characteristic. Gratings at ZEISS can be generated holographically in combination with ion beam plasma etching to enhance the grating profile or made by using gray-scale laser lithography technology. Holographic recording in combination with plasma etching enable the fabrication of various grating profiles to optimize efficiency including polarization behavior. Typical profile shapes are blazed type gratings, sinusoidal profiles and binary profiles allowing to optimize efficiency and polarization requirements exactly towards the required spectral range. Holographic gratings can be fabricated on plane and curved (convex, concave or free-form shape) substrates. As grating manufacturing techniques continue to cope with the challenges of enhanced remote sensing capabilities, ZEISS also can pattern large-area diffraction gratings with high resolution in the visible and shortwave infrared by using gray-scale lithography.

A flexible illumination system for Talbot lithography is presented, in which the Talbot mask is illuminated by discrete but variable incidence angles. Changing the illumination angle stepwise in combination with different exposure doses for different angles offers the possibility to generate periodic continuous surface relief structures. To demonstrate the capability of this approach, two exemplary micro-optical structures were manufactured. The first example is a blazed grating with a stepsize of 1.5 μm. The second element is a specific beam splitter with parabolic-shaped grating grooves. The quality of the manufacturing process is evaluated on the basis of the optical performance of the resulting micro-optical elements.

The main challenges of fabricating diffraction gratings for use in earth monitoring spectrometers are given by the requirements for low stray light, high diffraction efficiency and a low polarization sensitivity. Furthermore the use in space also requires a high environmental stability of these gratings.We found that holography in combination with ion beam plasma etching provides a way to obtain monolithic, robust fused silica gratings which are able to meet the above mentioned requirements for space applications. Holography accompanied by plasma etching allows the fabrication of a wide range of different grating profiles to optimize the efficiency including the polarization behavior according to a wealth of applications. Typical profile shapes feasible are blazed gratings, sinusoidal profiles and binary profiles and this allows to tailor the efficiency and polarization requirements exactly to the spectral range of the special application. Holographic gratings can be fabricated on plane and also on curved substrates as core components of imaging spectrometers.In this paper we present our grating fabrication flow for the example of plane blazed gratings and we relate the efficiency and stray light measurement results to certain steps of the process. The holographic setup was optimized to minimize stray light and ghosting recorded by the photoresist during the exposure. Low wave front deviations require the use of highly accurate grating substrates and high precision optics in the holographic exposure.

Microstructured Optics enable a new class of optics - new in terms of enabling functionality that has not been achieved so far, as well as in terms of reducing size while increasing performance of existing solutions significantly. In modern optics several demands exist for implementing microstructured optical components. For example, diffractive optical elements (DOEs) are of considerable advantage in combination with refractive lenses to form so-called hybrid optical systems. The inverse chromatic dispersion of diffraction in contrast to refraction opens new possibilities for the compensation of chromatic aberrations. Furthermore, the realization of a diffraction grating on a concave optical surface allows the functional integration of imaging and dispersing in one single optical component, which is a key enabler for miniaturization of spectroscopic systems. In the sophisticated illumination systems microstructured beam shaping elements play an essential role. Micro- and nanostructures in the subwavelength range open alternative solutions for antireflective properties and polarization management.

Diffractive optical elements (DOEs) are of enormous importance for applications in spectroscopic and imaging systems. We demonstrate that modified Talbot-Lithography is a fast and flexible technology for the mastering of micro-optical components, especially to manufacture high efficient spectroscopic diffractive gratings with an extended profile depth. The characteristics of DOEs also open up new opportunities for their integration in variable elastomeric optical components. We present theoretical investigations of the mechanical deformation of an initial Blazed-like diffractive grating and its impact on the optical diffraction efficiency.

In this contribution we simulate theoretically the resulting 3D Talbot-carpets of different initial close-packed 2D mask structures. Especially, we investigate the transition from regular periodic to quasi-periodic tessellations. For the pure periodic mask structure a hexagonally tessellation was selected. The calculated field distribution adjacent to the mask still shows a lateral six-fold symmetry but also a rather complex characteristics in the propagation direction. In particular, the appearance and the repetition of self-imaging planes deviate significantly from the classical Talbot-effect.For the quasi-periodic tessellation a Penrose tapestry based on rhombus pairs was chosen. A pronounced lateral five-fold symmetry becomes visible in the field distribution. In the propagation direction dominant planes with increased intensity are observed clearly, but, instead of a simple periodicity, a complex behavior becomes obvious. The numerical algorithm used in our simulations is based on a modified angular spectrum method, in which Bluestein's fast Fourier (FFT) algorithm is applied. This approach allows to decouple the sampling points in the real space and in the spatial frequency domain so that both parameter can be chosen independently. The introduced fast and flexible algorithm requires a minimized number of numerical steps and a minimal computation time, but still offers high accuracy.

The diffraction efficiencies of modified sinusoidal and blazed gratings are investigated in the high spatial frequency regime by rigorous numerical methods and are compared to experimentally manufactured gratings. The introduced modifications take actual technological induced variations of the profile geometries, such as specific corner rounding, into account. The high spatial frequency regime (resonance regime) is characterized by a local grating period, g, to wavelength, λ , ratio of 0.7 ≤ g/ λ ≤ 4 and shows an important relevance for applications in spectroscopy and diffractive imaging. The investigations are carried out for both reflection on metallic surfaces and transmission of dielectric structures over a broad range of grating periods and incidence angles. It was found that near the grating resonance, the more simply producible sine gratings can compete in diffraction efficiency with sawtooth structures. Additionally, for certain application conditions, holographically modified sine structures achieve higher efficiencies than the ideal sine profile. It is also shown that holographic sinusoidal-like profiles measured by AFM can be fitted to a super-Gaussian shape, which is then used to inversely reconstruct the structure profiles from efficiency data.

Interferenzlitographisch hergestellte holographisch-optische Bauelemente (HOEs) stellen eine leistungsfahige Alternative zu beugungsoptischen Bauelementen dar, die mit klassischen lithographischen Verfahren hergestellt werden. Eine generelle Problemstellung ist dabei die Anpassung der beugenden Strukturen an eine bestimmte Anwendungswellenlange. Oft besteht jedoch auch der Anspruch, derartige Elemente fur mehrere Wellenlangen oder, wie z.B. in der Spektralsensorik, fur grosere spektrale Bandbreiten auszulegen. Zur Beeinflussung bzw. Umverteilung der spektralen Effizienzcharakteristik ist die gezielte Modulation der Profilform (Hohenvariation, Blazewinkel) uber das gesamte Element anwendbar. Technologische Herausforderung ist dabei die Generierung einer modulierten Resistmaske bereits im holografischen Prozess. Wir diskutieren die Profilentstehung an Hand eigener Simulationsrechnungen zur Resiststrukturierung mit gegenlaufigen Wellen sowie experimentell gewonnener Daten. Das nutzbare Prozessfenster, innerhalb dessen sich effiziente Blazestrukturen mit lokal variierender Tiefe bei unverandertem Interferenzfeld generieren lassen, wird dabei abgeleitet.

Blazed gratings are in general the best choice for achieving the maximal diffraction efficiencies in a moderate wide wavelength band. However, a number of applications such as typical spectrometer systems need a broader spectral range. Here the drop of diffraction efficiency for the employed order towards the edges of the addressed spectrum limits the dynamics of the spectral sensor system. Thus we present a systematic approach based on a combination of interference lithography and ion beam etching. It provides a tuneable spectral response curve even for imaging gratings by mixing the characteristics of different blazed angles without influencing the systems spectral resolution.