Optical element having two operating states, optical device having an optical element, and use of an optical element

Abstract

The invention relates to an optical element (100), an optical device (200), and a use of an optical element (100) which has at least two operating states, the optical element comprising at least one element body (10) having an entry surface (22), a first and a second exit surface (24, 26) for electromagnetic radiation (56), and at least one boundary surface (18) between the entry surface (22) and the first exit surface (24). A material layer (20) on the boundary surface (18) automatically changes its optical effect for the radiation (52) depending on an intensity of the radiation (52) incident on the material layer (20), wherein in the first operating state, radiation (52) entering the entry surface (22) passes through the material layer (20) and exits from the first exit surface (24), and in the second operating state, radiation (52) entering the entry surface (22) is totally reflected off the material layer (20) and exits from the second exit surface (26).

Description

[0001] Description

[0002] Optical element with two operating states, optical device with one optical element and use of an optical element

[0003] State of the art

[0004] The invention relates to an optical element with at least two operating states, an optical device with at least one optical element, and a use of an optical element.

[0005] Optical limiting is the phenomenon that the optical transmission of a material decreases with increasing laser fluence. This property is important for protecting human eyes and sensors from intense laser radiation.

[0006] Conventional concepts for the optical limitation of high-intensity light sources are mostly based on either linear effects for passive beam attenuation or the nonlinear absorption and refraction of electromagnetic radiation. Tunable filters (e.g., nonlinear Bragg filters, acousto-optic modulators) represent active methods for beam attenuation. Sacrificial filters (e.g., metal oxides) and dispersive filters are another passive protection option.

[0007] A problem with applying linear effects for passive beam attenuation is that their blocking effect does not differentiate between high-intensity light and the light of a scene being recorded. With so-called in-band blocking, the transmission is automatically reduced in the spectral viewing range of the optics.

[0008] DLR-4333WO

[0009] Tunable filters (2025-09-19) exhibit switching times and / or delays in the microsecond range. Sacrificial filters are irreversible in their effect; that is, the sacrificial filter remains opaque and must be replaced once activated. Dispersive filters utilize the gradual change in the refractive index with temperature. This usually refers to thermal lenses, but also to the onset of total internal reflection.

[0010] DE 197 02 681 C2 describes a non-planar ring laser with a quality-control circuit operating in single-frequency mode. The ring laser comprises a diode laser as a pump light source, the pump light of which is coupled into a ring laser crystal. This crystal has at least three total internal reflection surfaces and a dielectrically coated crystal surface designed as an input and output coupling mirror. Due to a non-planar beam path, the polarization direction of the laser light is induced in a reciprocal rotation. Furthermore, via the Faraday effect in a permanent magnetic field, the polarization direction of the laser light is induced in a non-reciprocal rotation. The ring laser crystal consists of a laser material that exhibits saturable losses at the laser transition, i.e., at the wavelength of the laser emission.

[0011] WO 2019 / 025357 A1 discloses an optical system and its use for protecting an imaging sensor or the human eye from glare and / or damage caused by electromagnetic radiation. The optical system is designed to split incident electromagnetic radiation of a certain wavelength range into several spectrally separate wavelength bands.

[0012] DLR-4333WO

[0013] 2025-09-19 In several spatially separated output beam paths of the optical system, one or more of the wavelength bands can be generated by means of one or more optical multiband elements of the optical system in such a way that no wavelength band of one of the output beam paths spectrally overlaps with a wavelength band of another of the output beam paths.

[0014] WO 89 / 09945 A1 discloses an optical power limiter and circuit breaker that is transparent at low light intensity and opaque at high intensity. The power limiter and circuit breaker consists of a pair of right-angled triangular prisms separated by a liquid film whose refractive index changes in response to optical energy. An input lens focuses the optical radiation onto the liquid film at an angle smaller than the critical angle of total internal reflection at the prism-liquid interface. An output lens refocuses the optical radiation through an aperture to a detector. When the intensity of the optical radiation reaches a first predetermined level, the optical radiation is defocused and directed away from the detector.When the intensity of the optical radiation reaches a second, predetermined higher level, the critical angle is reached, whereupon the optical radiation is reflected away from the prism-liquid interface instead of passing through it. The liquid material of the film also contains an optically absorbing dye to attenuate optical radiation of predetermined wavelengths transmitted through the film before defocusing and total internal reflection. In this arrangement, an aperture is required to suppress the defocused radiation. Furthermore, total internal reflection upon evaporation of the liquid describes only the ultimate shielding state.

[0015] DLR-4333WO

[0016] 2025-09-19 This combination means the system is not optimized to utilize the phase transition as effectively as possible. The liquid film must be thick enough to enable the thermal lensing effect.

[0017] Disclosure of the invention

[0018] The object of the invention is to create an effective optical element with at least two operating states.

[0019] Another task is to create an optical device with at least one such optical element.

[0020] Another task is to specify a use for such an optical element.

[0021] The problems are solved by the features of the independent claims. Favorable embodiments and advantages of the invention become apparent from the further claims, the description, and the drawings.

[0022] According to one aspect of the invention, an optical element with at least two operating states is proposed, comprising at least one element body with an entrance surface for electromagnetic radiation and a first exit surface for electromagnetic radiation, a second exit surface for electromagnetic radiation, and at least one interface between the entrance surface and the first exit surface, and at least one material layer arranged at the interface which automatically changes its optical effect for the electromagnetic radiation depending on the intensity of the electromagnetic radiation incident on the material layer.

[0023] DLR-4333WO

[0024] 2025-09-19 The material layer is designed such that, in the first operating state, electromagnetic radiation entering the inlet surface passes through the material layer and exits from the first exit surface, and in the second operating state, electromagnetic radiation entering the inlet surface is totally reflected at the material layer and exits from the second exit surface.

[0025] The material layer of the proposed optical element automatically switches its optical effect between a first operating state and a second operating state, depending on the intensity of the electromagnetic radiation incident on the material layer. In the second operating state, the incident electromagnetic radiation is deflected by total internal reflection. In the first operating state, electromagnetic radiation is transmitted through the optical element almost unchanged.

[0026] The inherent process is advantageously reversible. The material composition and the particles, molecules, and / or atoms optionally dissolved within it can be adapted relatively easily to a wide variety of requirements.

[0027] The passive principle works for both continuous and pulsed radiation. Due to the strongly nonlinear relationship of the effect with temperature, the angular range in which the boundary layer reflects can be significantly larger than with a (nearly) linearly correlated change in refractive index with temperature. This also has a positive effect on the threshold energy (phase transition), as it can be reduced by focusing.

[0028] DLR-4333WO

[0029] 2025-09-19 Another advantage is the great variability in size and shape, since in principle the functional material layer can be embedded in various geometries.

[0030] Another advantage is its use / functionality across a very large wavelength range, for example in sunlight.

[0031] With a favorable design of the optical element, the material layer can change its optical effect from transmission to total reflection or from total reflection to transmission, depending on the intensity of the incident electromagnetic radiation. At high intensities of incident electromagnetic radiation, the radiation can be deflected by total reflection. Electromagnetic radiation below the intensity threshold can be transmitted through the optical element almost unchanged.

[0032] With a favorable design of the optical element, the material layer can switch between transmission and total internal reflection within a time interval of less than one nanosecond at a given intensity threshold of the incident electromagnetic radiation. In particular, after the change in the optical effect of the material layer, the altered optical effect of the material layer can be maintained even with continued exposure to the electromagnetic radiation. Due to the high switching speed of the material layer, the optical element can be advantageously used as an optical limiter.

[0033] DLR-4333WO

[0034] 2025-09-19 According to a favorable design of the optical element, the refractive index of the material layer can change by at least 0.1 between the two operating states, depending on the intensity of the electromagnetic radiation incident on the material layer. This can advantageously result in a change in the optical effect of the material layer from transmission to total resection or from total reflection to transmission.

[0035] With a favorable design of the optical element, the material layer can exhibit a phase transition at a certain intensity threshold. The material layer of the proposed optical element can, for example, be optionally equipped with absorptive particles / molecules / atoms that cause a local phase change of the state of matter. For instance, the material layer could be a liquid with an added dye. The absorption bands can cover a wide wavelength range from visible light to the near-infrared region. If water is used as the liquid, gas bubbles can form through absorption of the electromagnetic radiation; these bubbles regenerate when the intensity of the incident electromagnetic radiation decreases. Advantageously, non-gassing liquids or liquids with high solubility for the corresponding gases can be used.

[0036] Advantageously, the phase transition can enable a simple and flexible protection structure for an optical detector.

[0037] Response times to changes in the intensity of the incident electromagnetic radiation can advantageously be in the nanosecond range.

[0038] DLR-4333WO

[0039] 2025-09-19 At high intensities of incident electromagnetic radiation, the incident electromagnetic radiation can be deflected by total internal reflection at the point of phase change. Electromagnetic radiation below the intensity threshold can be transmitted through the optical element at the phase boundary almost unchanged.

[0040] One type of reversible phase transition can advantageously be one of the following: solid to liquid, liquid to gaseous, solid to solid (for example, by recrystallization), liquid to liquid (where a large temperature range can be covered), liquid to solid to vacuum (where cavitation phenomena can play a role). A liquid to liquid phase transition is used, for example, in WO 89 / 09945 A1.

[0041] The type of interface of the material layer can be formed in different ways.

[0042] For an arrangement of the material layer between two interfaces, whereby liquids may be enclosed within transparent windows, the type of interfaces can be, for example, solid-liquid-solid, solid-liquid-liquid, solid-solid-solid, liquid-solid-liquid, liquid-liquid-liquid.

[0043] For an arrangement of the material layer at an interface, the type of interface can be, for example, solid-liquid, solid-solid, or liquid-liquid. A solid-liquid interface can significantly increase the regenerability of the optical element. Gas bubbles, for instance, can be more easily removed from the field of view. Advantageously, an absorber can be applied to the interface layer for this purpose.

[0044] DLR-4333WO

[0045] 2025-09-19 According to a favorable embodiment of the optical element, the element body can comprise at least one prism. In particular, the element body can comprise at least one prism with a triangular cross-section. A cross-section is understood to be a surface perpendicular to the incident electromagnetic radiation.

[0046] Such a prism can advantageously have an interface on which the material layer can be arranged and can switch between transmission and total reflection at the intensity threshold of the incident electromagnetic radiation.

[0047] With a favorable design of the optical element, the element body can incorporate a prism, and the material layer can form the first exit surface. This allows for advantageous switching between transmission through the first exit surface and reflection through the second exit surface, depending on the intensity of the incident electromagnetic radiation.

[0048] In a favorable embodiment of the optical element, the element body can comprise two prisms placed opposite each other, enclosing the material layer between them. Such an arrangement can advantageously include an interface between the prisms, which are adjacent to each other with their hypotenuses. The material layer can be located on this interface and can switch between transmission and total internal reflection at the intensity threshold of the incident electromagnetic radiation.

[0049] DLR-4333WO

[0050] 2025-09-19 According to a favorable design of the optical element, the material layer can be enclosed in a space between the prisms. Advantageously, for example, a liquid with optionally absorptive particles / molecules / atoms can be arranged in this space, which can switch between transmission and total internal reflection at the intensity threshold of the incident electromagnetic radiation and the onset of a phase transition.

[0051] With a favorable design of the optical element, the element body can comprise two prisms positioned opposite each other, with the material layer being formed within the second prism. In particular, the two prisms can be configured as a single cuvette, with one diagonal half of the cuvette forming one prism and the other diagonal half forming the material layer. This allows for a simple and compact arrangement of the element body.

[0052] With a favorable design of the optical element, the entrance surface can be located in one prism, and during transmission through the material layer, one exit surface can be located in the other prism, while during reflection at the material layer, the other exit surface can be located in the prism containing the entrance surface. In this way, the transmitted and reflected radiation can be further processed by different optical components.

[0053] With a favorable design of the optical element, the element body can exhibit a periodic structure as an interface. In particular, the periodic structure can have a triangular function with an angle of 45° to the direction of incidence of the electromagnetic radiation. If the refractive indices are sufficiently large, other similar angles can also be used.

[0054] DLR-4333WO

[0055] 2025-09-19 In particular, the element body can be designed as a Fresnel prism or retroreflector. Such an arrangement allows for a very compact design that can be implemented cost-effectively. Furthermore, back-reflection towards the original direction of incidence is advantageously possible.

[0056] For example, in periodic structures, back reflection can occur if the interface of the element body describes a triangular function with an angle of 45°. In this case, the 45° angle lies in a plane of the incident radiation relative to the direction of the incident radiation.

[0057] This can also favor particularly pure liquid-solid interfaces between the element body and the material layer, since the periodic structure is only determined by the solid side.

[0058] By switching to total internal reflection, the radiation can be reflected back in its original direction within a plane. Another variation of this can be a retroreflector structure as a periodic interface structure.

[0059] With a favorable design of the optical element, the entrance surface and the second exit surface can be identical. In this way, the incident electromagnetic radiation, for example in the case of a retroreflector as an element body with a material layer, can be reflected back towards the original direction of incidence.

[0060] DLR-4333WO

[0061] 2025-09-19 According to a favorable embodiment of the optical element, the material layer can comprise at least one of the following: inorganic solid, organic solid, inorganic liquid, organic liquid, oily liquid, silicone-containing liquid, or one or more mixtures thereof. In particular, dyes and / or salts can be dissolved in the liquids. Such passive as well as active, absorbing materials can advantageously exhibit suitable phase transitions for switching between the two operating states.

[0062] According to a favorable embodiment of the optical element, the material layer can have one or more coatings or be designed as one or more coatings. In particular, the coating can be at least one of the following: an absorbing coating, a polarizing coating, or an expanding coating.

[0063] An absorbing coating can be optically activated, for example, by heating. A polarizing coating can, for example, act as a polarization filter.

[0064] In a favorable embodiment of the optical element, the material layer at the interface can have a thickness of at least the wavelength of the incident radiation. In particular, the material layer can have a thickness of up to 100 pm, preferably up to 50 pm. This facilitates the switching process between the two operating states. If the material layer is arranged, for example, between two prisms of the optical element, a minimum thickness of at least 1 pm is advantageous. A small volume of the material layer is beneficial for achieving a short response time when switching the optical effect.

[0065] DLR-4333WO

[0066] 2025-09-19 To create a thermal lensing effect, the material layer must have a greater thickness. With a thicker layer, the capillary action is then, unfortunately, present throughout the entire area of ​​the layer.

[0067] According to a further aspect of the invention, an optical device is proposed comprising at least one optical element as described above, a receiver for electromagnetic radiation entering an entrance surface of the at least one optical element, passing through an interface and exiting through a first exit surface of the at least one optical element, and a beam trap for electromagnetic radiation entering the entrance surface of the at least one optical element and exiting through a second exit surface of the at least one optical element.

[0068] The material layer of the optical element automatically switches its optical effect between a first operating state and a second operating state, depending on the intensity of the electromagnetic radiation incident on the material layer. In the second operating state, the incident electromagnetic radiation is deflected by total internal reflection. In the first operating state, electromagnetic radiation is transmitted through the optical element almost unchanged.

[0069] Frustrated total internal reflection of the electromagnetic radiation incident on the material layer can also be used to reduce the radiation arriving at the receiver by orders of magnitude, instead of deflecting the radiation completely in the second operating state. For an optical element consisting of two prisms, this can be achieved, for example, by varying the distance between the prisms, perhaps even dynamically using piezoelectric actuators.

[0070] DLR-4333WO

[0071] 2025-09-19 The beam trap can absorb electromagnetic radiation which, in the second operating state, exits through the second exit surface of the at least one optical element.

[0072] In this way, for example, a receiver that measures the transmitted radiation can be protected from damage caused by excessively high intensity of the incident electromagnetic radiation. Alternatively, the radiation trap can also be used to detect and, for example, analyze the reflected radiation.

[0073] According to a favorable embodiment of the device, the beam trap can have sensors for localizing and / or evaluating the electromagnetic radiation with regard to at least one of wavelength, power, polarization, repetition rate.

[0074] This allows typical laser properties or essential parameters of the incident electromagnetic radiation to be measured and advantageously modified and / or adjusted as desired.

[0075] With a favorable design, the beam trap can make electromagnetic radiation available to a user. The material layer of the optical element can also be used as a switching element to initiate a specific application. A high-intensity beam pulse can thus be filtered out from the incident electromagnetic radiation and directed to a particular application. The dead time of the switching process allows other radiation, such as an optical data signal, to be directed to a suitable detector.

[0076] DLR-4333WO

[0077] 2025-09-19 The optical element can be used as a switch for the targeted, externally controlled switching of an optical (data) receiver.

[0078] The task of a directional data receiver is to focus a transmitted beam in a controlled manner onto a receiver, in particular a photodiode, and to suppress unwanted signals as well as ambient radiation or background radiation as much as possible.

[0079] In this way, a good signal-to-noise ratio can be achieved during reception. This can be advantageously accomplished through a mechanism for aligning the receiver and the use of the smallest possible photodiode. A compact photodiode also allows for low electrical capacitance, which in turn results in a high bandwidth. Nevertheless, a very high bandwidth can still be achieved with one or a few moderately sized photodiodes. It is advisable to ensure that ambient or background radiation does not contribute to signal noise.

[0080] Since the optical circuit breaker only switches from transmission to reflection at points where a certain threshold power is exceeded, an external, intense laser pulse can be used in close proximity to an optical communication transmitter, particularly a laser-optical communication transmitter, to activate it. In this way, only light relevant for communication is reflected and received by the receiver. Depending on the dead time of the optical circuit breaker, it is necessary to repeat this "switching pulse" to maintain the connection and, if necessary, to compensate for relative movements between transmitter and receiver, especially a change in the resulting viewing / receiving direction of the receiver.

[0081] DLR-4333WO

[0082] 2025-09-19 According to a favorable embodiment of the device, at least one optical element can be associated with a device for influencing the beam diameter of the electromagnetic radiation at the interface. Thus, the beam diameter at the interface can be influenced by optical components such as a lens.

[0083] The use of an aperture or diaphragm to influence the beam diameter can also be incorporated. In this way, when a camera acts as a receiver, the plane of the camera's sensor can be imaged onto the optical element. Alternatively, the optical element can be positioned close to the sensor.

[0084] In a favorable embodiment of the device, at least one optical element can be assigned at least one notch filter, in particular a tunable one, and / or at least one rotatable polarizing filter. Based on the analyzed electromagnetic radiation, tunable notch filters or rotatable polarizing filters can also be placed upstream of the optical element.

[0085] Notch filters of varying optical density can be used to block specific incident laser wavelengths. The detector then no longer detects the wavelength blocked by the notch filter, and the scene or captured image can continue to be displayed up to the filtered wavelength. The same principle applies to polarizing filters used with polarized radiation. After analyzing the deflected beam with a polarimeter, the upstream polarizing filter can be rotated so that the incident polarized radiation is filtered out and no longer reaches the detector.

[0086] DLR-4333WO

[0087] 2025-09-19 According to a further aspect of the invention, the use of an optical element as a radiation limiter or as a dynamic aperture is proposed, in particular as an optical limiter for at least one of laser protection, optical measuring device, receiver, camera, sunshade, satellite communication, satellite sensor technology, in particular for optical communication and / or for laser measurement technology.

[0088] An optical limiter can be advantageously used, for example, as laser protection in laser safety glasses, in detectors such as photomultipliers, avalanche photodiodes, and photodiodes, in cameras, for example with CCD or CMOS sensors, and / or as sun protection, for example in binoculars. A dynamic aperture can be used to suppress background photons, for example in optical communication or in laser measurement technology, such as in laser spectroscopy.

[0089] drawing

[0090] Further advantages will become apparent from the following description of the drawings. The figures illustrate exemplary embodiments of the invention. The figures, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0091] They show, for example:

[0092] Fig. 1 shows an optical device with an optical element according to an embodiment of the invention in a first operating state;

[0093] DLR-4333WO

[0094] 2025-09-19 Fig. 2 the optical device according to Figure 1 in a second operating state;

[0095] Fig. 3 shows an optical device with an optical element according to a further embodiment of the invention in a first operating state;

[0096] Fig. 4 shows the optical device according to Figure 3 in a second operating state;

[0097] Fig. 5 shows an optical device with an optical element according to a further embodiment of the invention in a first operating state;

[0098] Fig. 6 shows the optical device according to Figure 5 in a second operating state;

[0099] Fig. 7 shows an optical device with an optical element according to a further embodiment of the invention in a first operating state;

[0100] Fig. 8 shows the optical device according to Figure 7 in a second operating state; and

[0101] Fig. 9 shows a representation of a total internal reflection area of ​​the at least one optical element and of a pulse energy of transmitted and reflected electromagnetic radiation when switching from a first operating state of transmission to a second operating state of reflection.

[0102] Embodiments of the invention

[0103] In the figures, similar or equivalent components are numbered with the same reference symbols. The figures merely show examples and are not to be understood as limiting.

[0104] DLR-4333WO

[0105] 2025-09-19 The directional terminology used below, including terms such as "left," "right," "above," "below," "in front," "behind," "after," and the like, serves only to improve the understanding of the figures and is in no way intended to limit their generality. The components and elements depicted, their interpretation, and their use may vary according to the considerations of a person skilled in the art and be adapted to the respective applications.

[0106] Figure 1 shows an optical device 200 with an optical element 100 according to an embodiment of the invention in a first operating state. Figure 2 shows the optical device 200 in a second operating state.

[0107] In this embodiment, the optical element 100 consists of a prism 12. A layer of material 20, for example containing a liquid in which particles are suspended, is located on the hypotenuse of the prism 12, which forms the interface 18. Depending on the intensity h of the incident electromagnetic radiation 52, the material layer 20 switches its optical action between a first operating state with transmission of the electromagnetic radiation 54 and a second operating state with total resection of the electromagnetic radiation 56. The material layer 20 can exhibit a phase transition depending on the intensity h.

[0108] Advantageously, the refractive index of the material layer 20 can change by at least 0.1 between the two operating states, depending on the intensity h of the electromagnetic radiation 52 incident on the material layer 20. This can favorably result in a change in the optical effect of the material layer 20 from transmission to total resection or from total resection to transmission.

[0109] DLR-4333WO

[0110] 2025-09-19 In the non-limiting case, here the first operating state, electromagnetic radiation 52 can be transmitted through the structure almost unimpeded. Above a certain intensity threshold Io, shown in Figure 2, incident radiation 52 is deflected by total internal reflection at a specific angle, here 90°, relative to the transmission path. In this process, a large portion of the radiation intensity is reflected, for example, into a radiation trap 70.

[0111] The materials of material layer 20 can be adapted to the application in various configurations. Furthermore, the geometry of the optical element 100 can be customized, for example as a sawtooth or triangular shape.

[0112] The receiver 60 can be used depending on the application. Suitable receiver 60 devices include eyes, CCD / CMOS cameras, photomultiplier tubes, photodiodes, or similar systems.

[0113] In addition, instead of the beam trap 70, the reflected electromagnetic radiation 56 can also be used for other purposes, for example for localization / evaluation of the electromagnetic radiation 56 with regard to wavelength and / or power and / or polarization and / or pulse duration, but also for physical processes that require high power densities.

[0114] The optical device 200 shown in Figure 1 comprises, in addition to the optical element 100, the receiver 60 for electromagnetic radiation 52, 54, which enters an entrance surface 22 of the optical element 100, passes the interface 18 and exits through a first exit surface 24 of the optical element 100.

[0115] DLR-4333WO

[0116] 2025-09-19 Furthermore, the optical device 200 comprises the beam trap 70 for electromagnetic radiation 56, which enters the entrance surface 22 of the optical element 100 and exits through a second exit surface 26 of the optical element 100, as shown in Figure 2 in a second operating state.

[0117] The electromagnetic radiation 52, which enters the optical element 100, is generated in a radiation source 50, for example a laser radiation source.

[0118] The optical element 100 comprises an element body 10 with the entrance surface 22 for electromagnetic radiation 52 and the first exit surface 24 for electromagnetic radiation 54, the second exit surface 26 for electromagnetic radiation 56 and at least one interface 18 between the entrance surface 22 and the first exit surface 24.

[0119] In this embodiment, the element body 10 of the optical element 100 comprises two opposing prisms 12 and 14 in the form of triangular prisms, each with its hypotenuse in contact with the other. Between them is a layer of material 20, for example containing a fluid in which particles are suspended. The material layer 20 is thus advantageously enclosed in a space between the prisms 12 and 14.

[0120] In this case, the entrance surface 22 is located in one prism 12, and upon transmission through the material layer 20, one exit surface 24 is located in the other prism 14. Upon reflection at the material layer 20, the other exit surface 26 is located at the prism 12 with the entrance surface 22.

[0121] DLR-4333WO

[0122] 2025-09-19 Alternatively, prisms 12, 14 can also be designed as Fresnel prisms.

[0123] The prisms 12, 14 can deviate from the equilateral right-angled triangular shape as long as the conditions for total reflection are met.

[0124] At least one material layer 20 is arranged at the interface 18, which automatically changes its optical effect for the electromagnetic radiation 52 depending on the intensity h of the electromagnetic radiation 52 incident on the material layer 20.

[0125] The material layer 20 is designed such that in the first operating state, which is shown in Figure 1, electromagnetic radiation 52 entering the entrance surface 22 passes through the material layer 20 and exits from the first exit surface 24.

[0126] In the second operating state, shown in Figure 2, electromagnetic radiation 52 entering the inlet surface 22 is reflected, in particular totally reflected, at the material layer 20 and exits from the second outlet surface 26. The exiting electromagnetic radiation 56 can be collected in the beam trap 70.

[0127] Depending on the intensity h of the electromagnetic radiation 52 incident on the material layer 20, its optical effect can change from transmission to total reflection or from total reflection to transmission. The material layer 20 switches between transmission and total reflection within a time interval of less than one nanosecond at an intensity threshold Io of the incident electromagnetic radiation 52.

[0128] DLR-4333WO

[0129] 2025-09-19 For example, a water film forming material layer 20 can evaporate instantly upon reaching or exceeding the intensity limit Io. While the electromagnetic radiation 52 can previously pass through the material layer 20, which is formed as a water film, at a lower intensity h, the electromagnetic radiation 52 is totally reflected at the interface 18 as soon as the water has evaporated.

[0130] In particular, after the change in the optical effect of the material layer 20 under further influence of the electromagnetic radiation 52, the changed optical effect of the material layer 20 is present.

[0131] The material layer 20 can, for example, be an inorganic solid, an organic solid, an inorganic liquid, an organic liquid, an oily liquid, a silicone-containing liquid, or one or more mixtures thereof. In particular, dyes and / or salts can be dissolved in the liquids. The liquids can advantageously be arranged in a container with at least transparent passage windows.

[0132] For this purpose, the material layer 20 can advantageously exhibit a phase transition at an intensity limit Io. The material layer 20 can, for example, be optionally provided with absorptive particles / molecules / atoms that cause a local phase change of the state of matter. At high intensity h of the incident electromagnetic radiation 52, the incident electromagnetic radiation 52 can be deflected by total internal reflection at the point of the phase change. Electromagnetic radiation 52 with an intensity h below an intensity limit Io can be transmitted almost unchanged at the phase boundary through the optical element 100.

[0133] DLR-4333WO

[0134] 2025-09-19 Alternatively, the material layer 20 can have one or more coatings or be designed as one or more coatings. In particular, the coating can be an absorbing coating, a polarizing coating, or an expanding coating. Such a coating can be applied directly to the interface 18 of the prism 12 of the optical element 100.

[0135] In an expanding coating, the liquid undergoing the phase transition can be laterally displaced by the expansion, thereby favorably altering the geometry of the optical image. Advantageously, the expansion can occur so rapidly that it triggers cavitation in the liquid, causing the liquid film to rupture.

[0136] The material layer 20 can advantageously have a thickness of at least the wavelength of the incident radiation 52, in particular up to a maximum of 100 pm, preferably up to a maximum of 50 pm.

[0137] The radiation trap 70 can, for example, have sensors for localizing and / or evaluating the electromagnetic radiation 56 with regard to at least one of wavelength, power, polarization, pulse duration.

[0138] Alternatively, the electromagnetic radiation 56 can also be made available to a user through the radiation trap 70.

[0139] DLR-4333WO

[0140] 2025-09-19 The optical device 200 can include a device for influencing the beam diameter of the electromagnetic radiation 52 at the interface 18, for example a lens or an aperture or diaphragm. This allows the beam diameter of the incident electromagnetic radiation 52 to be limited in a suitable manner.

[0141] The optical element 100 arranged in the optical device 200 can advantageously be used as a radiation limiter or as a dynamic aperture. In particular, the optical element 100 can be used as an optical limiter for at least one of the following applications: laser protection, optical measuring device, receiver, camera, sunshade, satellite communication, satellite sensor technology, and / or also for optical communication and / or laser measurement technology.

[0142] Figure 3 shows an optical device 200 with an optical element 100 according to a further embodiment of the invention in a first operating state, while Figure 4 shows the optical device according to Figure 3 in a second operating state.

[0143] Element body 10 has a prism 12 in the form of a triangular prism. Alternatively, element body 10 can also be configured as a Fresnel prism.

[0144] The material layer 20 forms the first exit surface 24.

[0145] The arrangement shown in Figure 3 does not exhibit total internal reflection at the exit surface 24 if it is inclined accordingly towards the incident radiation 52. Optionally, the interface 18 can also be structured to locally change the inclination, for example with a grating.

[0146] DLR-4333WO

[0147] 2025-09-19 Alternatively, the receiver 60 can also be in direct contact with the exit surface 24 or via an optical transition material, so that there is no air between them. In this case, total internal reflection does not occur at the exit surface 24.

[0148] Figure 3 shows the first operating state, which is present when the intensity h of the incident electromagnetic radiation 52 is below the intensity limit Io and the electromagnetic radiation 54 is transmitted and falls on the receiver 60.

[0149] In contrast, Figure 4 shows the second operating state, when the intensity h of the incident electromagnetic radiation 52 is above the intensity limit Io and the electromagnetic radiation 56 is reflected at the interface 18, in particular totally reflected, and falls onto the beam trap 70.

[0150] Figure 5 shows an optical device 200 with an optical element 100 according to a further embodiment of the invention in a first operating state, while Figure 6 shows the optical device according to Figure 5 in a second operating state.

[0151] In this embodiment, the element body 10 has two prisms 12 and 14 positioned opposite each other. The second prism 14 represents the material layer 20. In particular, it can be a cuvette 16, wherein one diagonal half of the cuvette 16 is formed from solid glass and represents one prism 12, and the other diagonal half of the cuvette 16 is, for example, filled with a liquid and represents the material layer 20.

[0152] DLR-4333WO

[0153] 2025-09-19 Figure 5 shows the first operating state, which is present when the intensity h of the incident electromagnetic radiation 52 is below the intensity limit Io and the electromagnetic radiation 54 is transmitted and falls on the receiver 60.

[0154] In contrast, Figure 6 shows the second operating state, when the intensity h of the incident electromagnetic radiation 52 is above the intensity limit Io and the electromagnetic radiation 56 is reflected at the interface 18, in particular totally reflected, and falls onto the beam trap 70.

[0155] Figure 7 shows an optical device 200 with an optical element 100 according to a further embodiment of the invention in a first operating state, while Figure 8 shows the optical device according to Figure 7 in a second operating state.

[0156] In this embodiment, the element body 10 has a periodic structure 28 as its interface 18, which describes a triangular function with an angle of 45°. The 45° angle lies in a plane of the incident radiation 52 relative to the direction of the incident radiation 52, as marked in Figure 7. If the refractive indices are sufficiently large, other similar angles can also be used. One part of the element body 10 between the inlet surface 22 and the interface 18 can be designed as a glass body, and the other part between the interface 18 and the first outlet surface 24 can be designed as a material layer 20. For example, the element body 10 can be designed as a cuvette 16, with the material layer 20 being represented by a liquid filled into the hollow part of the cuvette 16.

[0157] DLR-4333WO

[0158] 2025-09-19 In particular, the element body 10 can also be designed as a Fresnel prism or retroreflector in this way.

[0159] Figure 7 shows the first operating state, which is present when the intensity h of the incident electromagnetic radiation 52 is below the intensity limit Io and the electromagnetic radiation 54 is transmitted and falls on the receiver 60.

[0160] Figure 8, on the other hand, shows the second operating state, where the intensity h of the incident electromagnetic radiation 52 exceeds the intensity limit Io and the electromagnetic radiation 56 is reflected at the interface 18, in particular totally reflected, and reflected back in the direction of the incident radiation 52. The entrance surface 22 of the element body 10 simultaneously represents the second exit surface 26. The radiation source 50 can have a radiation trap 70 or be configured as a radiation trap 70.

[0161] Figure 9 shows a representation of the total internal reflectance area 500 in units of square pixels x gray value of the at least one optical element 100, as well as a pulse energy 520 in joules of transmitted electromagnetic radiation 550 and reflected electromagnetic radiation 540 during switching from a first operating state of transmission to a second operating state of reflection. The values ​​are plotted as a function of time 510 in milliseconds.

[0162] The switching process between the first and second operating states occurs at a time of approximately 15 ms. During this time, the characteristic curve 530 of the reflective surface 500 rises rapidly to a value of approximately 20 WE, drops briefly, and then rises continuously from a value of 15 to a saturation value of approximately 25.

[0163] DLR-4333WO

[0164] 2025-09-19 The pulse energy 520 of the transmitted electromagnetic radiation 550 is at 0 Joules from this time onwards, while the pulse energy 520 of the reflected electromagnetic radiation 540 increases monotonically.

[0165] DLR-4333WO 2025-09-19 Reference number

[0166] 10 element bodies

[0167] 12 prisms

[0168] 14 prisms

[0169] 16 cuvettes

[0170] 18 Interface

[0171] 20 Material layer

[0172] 22 Entrance area

[0173] 24 first exit surface

[0174] 26 second exit surface

[0175] 28 periodic structure

[0176] 50 radiation source

[0177] 52 incident ray

[0178] 54 transmitted beam

[0179] 56 Totally reflected beam

[0180] 60 recipients

[0181] 70 radiation sink

[0182] 100 optical elements

[0183] 200 optical devices

[0184] 500 total internal reflectance area

[0185] 510 Time

[0186] 520 pulse energy

[0187] 530 characteristic curve

[0188] 540 reflected electromagnetic radiation

[0189] 550 transmitted electromagnetic radiation

[0190] DLR-4333WO

[0191] 2025-09-19

Claims

Claims 1. Optical element (100) with at least two operating states, comprising at least one element body (10) with an entrance surface (22) for electromagnetic radiation (52) and a first exit surface (24) for electromagnetic radiation (54), a second exit surface (26) for electromagnetic radiation (56), and at least one interface (18) between the entrance surface (22) and the first exit surface (24), and at least one material layer (20) arranged at the interface (18) which automatically changes its optical effect for the electromagnetic radiation (52) depending on an intensity (h) of the electromagnetic radiation (52) incident on the material layer (20), wherein the material layer (20) is configured such thatthat in the first operating state, electromagnetic radiation (52) entering the inlet surface (22) passes through the material layer (20) and exits from the first outlet surface (24), and in the second operating state, electromagnetic radiation (52) entering the inlet surface (22) is totally reflected at the material layer (20) and exits from the second outlet surface (26).

2. Optical element according to claim 1, wherein the material layer (20) changes its optical effect from transmission to total resection or from total resection to transmission depending on the intensity (h) of the electromagnetic radiation (52) incident on the material layer (20). DLR-4333WO 2025-09-19 3. Optical element according to claim 1 or 2, wherein the material layer (20) switches between transmission and total reflection within a time interval of less than one nanosecond at an intensity limit (Io) of the incident electromagnetic radiation (52), in particular wherein, after the change in the optical effect of the material layer (20) upon further exposure to the electromagnetic radiation (52), the changed optical effect of the material layer (20) is present.

4. Optical element according to one of the preceding claims, wherein a refractive index of the material layer (20) changes by at least 0.1 between the two operating states, depending on an intensity (h) of the electromagnetic radiation (52) incident on the material layer (20).

5. Optical element according to one of the preceding claims, wherein the material layer (20) exhibits a phase transition at an intensity limit (Io).

6. Optical element according to one of the preceding claims, wherein the element body (10) has at least one prism (12, 14), in particular at least one prism (12, 14) with a triangular cross-section.

7. Optical element according to one of the preceding claims, wherein the element body (10) has a prism (12) and the material layer (20) forms the first exit surface (24).

8. Optical element according to one of the preceding claims, wherein the element body (10) has two prisms (12, 14) placed opposite each other, which enclose the material layer (20) between them. DLR-4333WO 2025-09-19 9. Optical element according to claim 8, wherein the material layer (20) is enclosed in a space between the prisms (12, 14).

10. Optical element according to one of the preceding claims, wherein the element body (10) has two prisms (12, 14) placed opposite each other, wherein the material layer (20) is formed in the second prism (14), in particular wherein the two prisms (12, 14) are formed as a cuvette (16), wherein one diagonal half of the cuvette (16) forms one prism (12) and the other diagonal half of the cuvette (16) forms the material layer (20).

11. Optical element according to one of claims 8 or 10, wherein the entrance surface (22) is located in one prism (12) and, in the case of transmission through the material layer (20), one exit surface (24) is located in the other prism (14) and, in the case of reflection at the material layer (20), the other exit surface (26) is located at the prism (12) with the entrance surface (22).

12. Optical element according to one of the preceding claims, wherein the element body (10) has a periodic structure (28) as an interface (18), in particular wherein the periodic structure (28) has a triangular function with an angle of 45° to the direction of incidence of the electromagnetic radiation (52), in particular wherein the element body (10) is designed as a Fresnel prism or retroreflector.

13. Optical element according to one of the preceding claims, wherein the entrance surface (22) and the second exit surface (26) are identical. DLR-4333WO 2025-09-19 14. Optical element according to one of the preceding claims, wherein the material layer (20) comprises at least one of the following: inorganic solid, organic solid, inorganic liquid, organic liquid, oily liquid, silicone-containing liquid, one or more mixtures thereof, in particular wherein dyes and / or salts are dissolved in the liquids.

15. Optical element according to one of the preceding claims, wherein the material layer (20) has one or more coatings or is designed as one or more coatings, in particular at least one of the following: absorbing coating, polarizing coating, expanding coating.

16. Optical element according to one of the preceding claims, wherein the material layer (20) at the interface (18) has a thickness of at least the wavelength of the incident radiation (52), in particular up to a maximum of 100 pm, preferably up to a maximum of 50 pm.

17. Optical device (200) with at least one optical element (100) according to one of the preceding claims, with a receiver (60) for electromagnetic radiation (52, 54, 56) entering an entrance surface (22) of the at least one optical element (100), passing through an interface (18) and exiting through a first exit surface (24) of the at least one optical element (100), and a beam trap (70) for electromagnetic radiation (54, 56) entering the entrance surface (22) of the at least one optical element (100) and exiting through a second exit surface (26) of the at least one optical element (100). DLR-4333WO 2025-09-19 18. Device according to claim 17, wherein the beam trap (70) has a sensor for localizing and / or evaluating the electromagnetic radiation (56) with respect to at least one of wavelength, power, polarization, repetition rate.

19. Device according to claim 17 or 18, wherein the beam trap (70) makes the electromagnetic radiation (56) available to a user.

20. Device according to one of claims 17 to 19, wherein the at least one optical element (100) is associated with a device for influencing a beam diameter of the electromagnetic radiation (52) at the interface (18).

21. Device according to one of claims 17 to 20, wherein at least one optical element (100) is associated with at least one, in particular tunable, notch filter and / or at least one rotatable polarizing filter.

22. Use of an optical element (100) according to one of claims 1 to 16 as a radiation limiter or as a dynamic aperture, in particular as an optical limiter for at least one of laser protection, optical measuring device, detector, camera, sunshade, satellite communication, satellite sensor technology, in particular for optical communication and / or for Laser measurement technology. DLR-4333WO 2025-09-19

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