Amplitude and phase modulating using optical element and accumulating optical element

Abstract

Method of operating an optical element, comprising a cover on a support and a means, the means is arranged to move the cover between cover contour profiles, wherein the optical element further comprises a substrate on a side of the support opposite the cover, a cavity being defined between the cover and the substrate, movement of the cover resulting in changing light interaction between the light and the cover, the method comprising, based on a desired phase response for the optical element and a desired amplitude response, controlling the means to cause the optical element to exhibit a response corresponding to the desired phase response and the desired amplitude response.

Description

[0001] AMPLITUDE AND PHASE MODULATING USING OPTICAL ELEMENT AND

[0002] ACCUMULATING OPTICAL ELEMENT

[0003] The current application relates to an optical element comprising, a cover having a first surface and a second surface, a support, and a means. The cover is orientated with the first surface directed towards the support, a part of the first surface is attached to the support, a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile, and the means is arranged to move the cover from a first cover contour profile to a further cover contour profile which is different from the first cover contour profile.

[0004] An optical element is known from e.g. WO 2021 / 032752 Al and WO 2018 / 228671 Al . This document discloses optical devices of specific interest. The working principle is that when a cover is provided that has some desired optical behaviour, e.g. reflecting light, transmitting only some light, etc. the interaction of incident light can be changed by changing the cover contour profile. To facilitate the cover changing shape to facilitate changing the optical behaviour of the optical device, the cover is made relatively thin, in terms of WO 2021 / 032752 Al 2 -dimensional. As an example, a single graphene layer cover is presented, with a coating on top to obtain desirable optical behaviour. Since the optical device is very small, they can be used to act like a pixel in a larger collection of similar devices. Control of scattering, reflection and / or interference behaviour can be used to turn a pixel on or off and / or vary its colour. This way, images can be generated and / or manipulated.

[0005] Several principles of operation are available with such optical devices. A first operational principle is shown in figures 1A - 1C, which correspond to figures 9 - 11 of WO 2021 / 032752 Al. These figures show respectively an optical device with a flat cover, a convex cover, and a concave cover. Light incident on the flat cover (fig. 1A) is reflected as if hitting a smooth and straight surface, i.e. parallel incident rays remain parallel after reflection. As such, specular reflection takes place at the cover. In the convex and concave positions of the cover, parallel incident rays are no longer parallel after reflection, thus causing diffused reflection. By changing the shape of the cover, it is thus possible to alternate between specular and diffused reflection. To suit this first operational principle, the cover is sufficiently reflective towards the incident light. In this example, the light is incident on the second surface, which may also be called the outside of the optical device.

[0006] Figures 2A - 2C, which correspond to figures 12 - 14 of WO 2021 / 032752 Al, show a second operational principle. Reference is first made to the substrate which spans the support on an opposite side of the cover, in order to define a cavity between the cover and the substrate. The substrate is partly reflective and partly transmissive. The cover is relatively reflecting. Light incident on the substrate is thus partly transmitted and partly reflected. The transmitted light reflects on the first surface of the cover, i.e. coming from the inside, and is transmitted back through the substrate, where it interferes with the light reflected by the substrate. Depending on the wavelength of the light and the distance between the cover and the substrate, the interaction can be constructive or destructive. Since that distance changes when the cover changes shape, the interferometric characteristics of the optical device can be changed.

[0007] Figures 4 and 5 show even other ways of using the changing cover contour profile. In the case of figure 4, an optical element is shown with a substrate 106 that is relatively reflective. The cover 101 in this case is relatively absorbing. Nevertheless, of an incoming light beam 601, at least some light may be transmitted towards the substrate 106 as transmitted light beam 603. This reflects back via the substrate 106 as reflected light 604. Due to interference of the transmitted light beam 603 and the reflected light 604, a pattern of nodes and antinodes is present. The cover 101 can then be moved, e.g. by changing its cover contour profile or its position with respect to the support, to place the cover at an antinode for absorbing the light, or at a node for not or absorbing less the light. Accordingly, the exiting light 605 can be present in less or more intensity by controlling the cover. This principle is called interferometric absorption.

[0008] Figure 5 shows the principle of interferometric reflection, similar to fig. 2, but with light 601 incident the cover. In this case, light is partially transmitted through the cover 101, and reflected at the substrate 604, which for that purpose is reflective. The cover 101 reflects some light 605, but also transmits some light 603. After reflecting 604 from the substrate 106, light passing through the cover 101 again interferes with the reflected light 605. By controlling the position or cover contour profile of the cover 101, control is possible of wavelengths of light that do or do not interfere constructively.

[0009] In both cases, light transmitted through the cover may actually be refracted. However, since the figures show a specific example of light incident normal to the cover, the wording transmitting was used. The invention can however be applied, depending on the use-case, to nonnormal light also. These principles have been described only briefly herein, as the operational principles involved are in themselves known, and have been applied e.g. in WO 2018 / 228671 Al (see figures 1 and 2).

[0010] These principles thus show that by varying the reflectance and / or transmittance and / or absorbance of the cover and the substrate, and the direction at which light is incident (from outside or inside the optical device), it is possible to cause the cover to create a certain interaction with the light, optionally in cooperation with the substrate. The interaction changes when the cover shape changes, i.e. when the cover contour profile changes.

[0011] The optical device described above has been used successfully to modulate light, but there remains a need to further influence the range of possible modulations. The invention stems in part from the realization that such an optical element can be made more versatile depending on its use. In particular, the applicant has realized that it is possible to control not only the amplitude of light, but also its phase. In particular, it is possible to control the amplitude and phase independently. By providing both amplitude and phase modulation in dependence of a desired response, but optionally independent of each other, the optical element can be used in a variety of applications, amongst which holography. While light with any suitable characteristic may be used, it is envisioned to use monochromatic light as a source. One such example is coherent light such as light generated by a laser or a laser diode.

[0012] According to the invention therefore, the optical element described in claim 1 is controlled to exhibit the desired phase and amplitude modulation. WO 2021 / 032752 Al is silent with regards to controlling the amplitude / phase modulation in dependence of a desired phase response, and therefore lacks the versatility presented by the method of claim 1.

[0013] Of course any optical system has an amplitude and a phase response at any time. However, the invention differs from known systems in that both a desired amplitude response and a desired phase response are used as an input, instead of a desired response for only one of these two values, where the other would follow. The invention thus in part stems from the fact that given that versatility can be achieved by taken as an input a desired phase response separate from a desired amplitude response, and controlling accordingly.

[0014] According to the invention, it is thus possible for a particular amplitude response, to achieve different phase responses, and vice versa. The two desired responses may thus actively but separately be controlled for.

[0015] There may be multiple ways of controlling the amplitude and phase of modulated light. WO 2021 / 032752 Al already explains some methods of controlling the element, all of which could be used to create a desired response. However, said desired response does not account for phase change. Instead, any modulation in WO 2021 / 032752 Al inherently has a phase response, but this was not taken into account, nor achieved in dependence of a desired phase response.

[0016] In line with the invention, it is possible to control the cover such that a desired phase response is achieved. Then, it is possible to further control the element to also provide a desired amplitude response.

[0017] As an example, instead of remaining in a single position corresponding to the desired phase response, it is possible to move the cover back and forth between that position and another in which the optical element outputs little to no light. Depending on the residence time in these positions (i.e. cover contour profdes), the total perceived amplitude of light output can be changed. This switching between positions is referred to as temporal dithering.

[0018] As another example, the cover could have optical properties that can be changed. As an example, the cover may be configured to have a changeable absorbance. In such a case, the position of the cover could be used to obtain a desired phase, whereas the absorbance could be used to further influence the amplitude. A non-limiting example of obtaining such a cover is providing it with a cover that has strain responsive optical properties. For this purpose the cover may be or may comprise a 2-dimensional material. The cover may be or may comprise a straintronic material, which may be the 2-dimensional material.

[0019] As yet another example, a cavity may be formed below the cover, optionally by the provision of a substrate on a side of the support away from the cover. Since the cavity may influence the optical properties of the device as a whole, changing the optical properties of the cavity may allow changing the phase or amplitude response, in addition to changing the position or shape of the cover. Optical properties of the cavity can for instance be changed by changing the composition of a gas, liquid, or liquid crystal contents of the cavity.

[0020] It is however also possible to change optical properties of the substrate instead or in addition. This could be done by providing a straintronic and / or 2-dimensional material at or in the substrate.

[0021] In particular, a straintronic material could be chosen that changes its refractive index in response to strain.

[0022] Similarly, the cover and / or the substrate may comprise a material which exhibits changing mechanical properties in response to e.g. temperature changes. Alternatively, a material could be chosen that changes its crystalline structure with temperature. Examples might be suitably chosen mechanical metamaterials, or sold-solid phase change materials.

[0023] Further, the cover and / or substrate may comprise a material with electrical properties that change in response to an applied torque, for instance a twisted bilayer of graphene, or suitably chosen other twistronic material.

[0024] In general, any material for the cover and / or substrate with changing properties in response to the application of a charge may also be used advantageously. Such a material could be a metasurface or could be structured as a tunable or photonic metamaterial. Alternatively, a photonic crystal could be used, with its response to an electric field changing with temperature.

[0025] These changing properties referred-to above could be used to provide a tunable property of the optical device, which can be tuned independently from the cover contour profile. As such, a larger variation of responses can be obtained, including those that allow selecting amplitude and phase responses at least almost independently from each other.

[0026] In any case, activation may be done using the means introduced earlier, or using separately provided means for influencing the cover and / or substrate and / or cavity respectively. Such separately provided means can operate based on any suitable principle (like the means introduced earlier). At this time, it is noted that regardless of the actuation method used, given a sufficiently small system, any one actuation method will often have some corresponding co-phenomenon in another domain as well. As such, at nano-scale, the actuation method and corresponding cophenomena usually pair up. Examples of such pairs, which may be used in the currently described invention for the separately provided means as a non-exclusive list of examples, are:

[0027] Thermo-electrical and electro-thermal actuation;

[0028] Thermo-optical and opto-thermal actuation;

[0029] Thermo-magnetic and magneto-thermal actuation;

[0030] Opto-electrical and electro-optic actuation; and Magneto-optic and opto-magnetic actuation.

[0031] At the same time, quantum and superconducting effects may also play a role. Accordingly, use can be made of such effects if desired.

[0032] In addition or as an alternative to affecting the amplitude and phase of light, materials could be chosen (for the cover and / or substrate and / or cavity) that exhibit a quantum -effect, in order to further change a state of the light.

[0033] Via temporal dithering, the optical element can be used to account for different sources and / or source strengths and / or sources of different spectral distributions. Accordingly, it is advantageous if the calculation is based in part on the intensity of light incident the optical element to facilitate said accounting. As an example, when the desired output is a relatively intense colour, e.g. a monochromatic colour, the method could include switching between a first cover contour profile which results in a high intensity output, and a further cover contour profile which results in a low intensity output. When the incident radiation is relatively strong (that is to say too strong), the residence time of the further cover contour profile may be lengthened as compared to the residence time of the first cover contour profile, in comparison with a situation in which the incident radiation is relatively weak, so that a desired intensity output is still achieved. The ratio of residence times can be changed in the other direction for relatively weak incident radiation.

[0034] Moreover, it is advantageous if the calculation is additionally or alternatively based at least in part on a spectral distribution of light incident the optical element. As an example, when the desired output is certain spectral distribution comprising e.g. a combination of two colours, the method could include switching between a first cover contour profile which results in a certain intensity output of a first colour of the two colours of said certain spectral distribution, and a further cover contour profile which results in another intensity output of a second colour of said spectral distribution. The ratio of residence times defines the desired output in colour and intensity, i.e. defines the spectral distribution that is output on average. When the incident radiation contains radiation of the first colour that is relatively strong (that is to say too strong), the residence time of the further cover contour profile may be lengthened as compared to the residence time of the first cover contour profile, in comparison with a situation in which the incident radiation contains radiation of the first colour that is relatively weak, so that a desired intensity output for that colour is still achieved. The ratio of residence times can be changed in the other direction for incident radiation that is relatively weak for the first colour.

[0035] Moreover, it is advantageous if the calculation is additionally or alternatively based at least in part on the state of quantized light incident the optical element. As an example, when the desired output concerns light with a certain light state comprising e.g. a combination of two polarization states, two quantum states (i.e., pure / mixed and / or coherent / incoherent states and / or squeeze states) or a combination of light with different states, the method could include switching between a first cover contour profile which results in a certain intensity output of a first state of the two states of said certain quantized light, and a further cover contour profile which results in another intensity output of a second state of said quantized light. The ratio of residence times defines the desired output in state and intensity and / or phase, i.e. defines the light state that is output on average. When the incident radiation contains radiation of the first state that is relatively strong (that is to say too strong), the residence time of the further cover contour profile may be lengthened as compared to the residence time of the first cover contour profile, in comparison with a situation in which the incident radiation contains radiation of the first state that is relatively weak, so that a desired intensity output for that state is still achieved. The ratio of residence times can be changed in the other direction for incident radiation that is relatively weak for the first state.

[0036] Of course, it is advantageous if the calculation is additionally or alternatively based at least in part on a combination of the intensity, phase and / or state of light incident the optical element. As an example, the optical element could receive light from two different sources: one LED or laser and one correlated or entangled photon-pair source. Such a setup allows for an improved use of the cover with two optical channels: one channel for optical transmission of classical data as part of a laser telecommunication system with the optical element modulating the amplitude and / or phase of light with visible / telecom wavelength, and another channel for secured transmission of quantum data as part of a system integrating a quantum communication protocol, such as Quantum Key Distribution and entanglement-based quantum communication, with the optical element modulating the amplitude, phase and / or state of quantized light.

[0037] Of course in these situations, a cover and / or substrate and / or cavity could be chosen that affects said quantum state differently upon operation.

[0038] Therefore, using a combination of amplitude, phase and / or state of light incident to the optical element allows for quantum-level security in classical data transmission, ensuring that sensitive information remains protected from eavesdropping, even by future quantum systems.

[0039] To facilitate control of both amplitude and phase, it is advantageous if the means comprise first means and further means. The first means may be configured to influence the amplitude of modulated light and the further means being configured to influence the phase of modulated light. Accordingly, light that is modulated by the optical element can be controlled by the two distinguishable means. If both means influence at least one other aspect of the modulated light (i.e. amplitude or phase), it becomes possible to collectively control phase and amplitude via both the means.

[0040] In this case, it is useful if the first means and further means are independently controlled. A controller may for instance be arranged to provide control signals for independent control.

[0041] The method may comprise receiving a desired phase and / or amplitude response. The method in general may be performed by a controller. The same controller can be used for multiple optical elements, so as to create an image using the multiple optical elements, such as a display or holographic display.

[0042] Other methods exist for controlling phase and amplitude. As an example, the support may be expandable, and the further means may be configured to expand the support.

[0043] It is noted that for any element that is described as being expandable in this application, and any similar terms used throughout this document, said expansion may be reversible. As such, the support may also be contractible, retractable or collapsible.

[0044] As the cover is attached to the support, expanding the support will provide different response for the cover. As such, an independent control method, that is independent from the means changing the cover contour profile, is available. The support can be made expandable for instance by manufacturing it from a piezoelectric material, such as PZT.

[0045] Another option is to use a material that is expandable, e.g. by absorption. In general materials that can change their thickness by absorbing something, such as light, heat, charge, etc. can be used, all of these materials being summarized as “absorbing materials”. As a particular example, a material containing spin crossover particles is mentioned. These particles are described in e.g. “Colossal expansion and fast motion in spin-crossover@polymer actuators” by Piedrahita- Bello et al. (http: / / dx.doi.org / 10.1039 / dlmh00966d).

[0046] Another way to influence the optical behaviour besides using the first means is to change the index of refraction of the cavity. The cavity may for this purpose be filled with a gas composition which may be altered to change its refractive index. The further means may therefore be configured to influence a gas composition in the cavity. Aside from a gas, the cavity may also be filled by a liquid (mixture) and / or liquid crystals, which may have a greater effect on the refractive index. In such a case, the further means may be configured to influence the respective composition of the liquid and / or liquid crystals in the cavity.

[0047] Also disclosed herein is an accumulating optical element. Various aspects of the accumulating optical element are discussed below. Clauses are also presented below, which additionally describe the accumulating optical element. It is noted the optical element may have certain characteristics in common with the element used for amplitude and phase control these common characteristics will be described further below. However first, the accumulating element is described.

[0048] ACCUMULATING ELEMENT

[0049] It is observed that there are some limits as to how the optical element of WO 2021 / 032752 Al can be used in optical systems. The application therefore has as its object to provide a more versatile optical system. More specifically, the optical element of WO 2021 / 032752 Al, and that of clause 1, need relatively specific light conditions in order to work optimally. While it is possible to provide such conditions using a collimated light source, this limits the application of the optical system as a whole. Consequently, a need exists to provide an optical system with less such limitations.

[0050] The object is achieved by an optical system according to the preamble, which is characterized in that it further comprises an accumulator. Said accumulator can accumulate light from an external source of light, such as a source of diffused light.

[0051] As a result, an optical system is obtained that can use a broader range of light inputs. In particular, it is possible to use diffused light as a source. One such example is ambient light such as daylight. This severely reduces the amount of power needed to operate the optical system. Other sources of ambient light can also be used the same way, including when the illumination is direct, indirect, or both. For example, light used to illuminate a room, e.g. from an artificial light source and / or the Sun, can be used accordingly. Ambient light herein is thus defined as contrasting with purpose-specific light, that would be generated specifically for illuminating the optical element. As an example of purpose-specific light, laser light is envisioned. One another example is any purpose-specific light with direct or indirect illumination including but not limited to light emitted from sources such as laser diodes, light emitting diodes and broadband lamps. In principle, all type of sources of incandescence, luminescence or indirect illumination could be used as source in this invention.

[0052] At this time, it is noted that optically relevant elements, such as the diffusor, condenser, collimator, beam splitter, lens, polarizer, filter, mirror, referred to in this application may be provided as an array of micro -elements having the required properties. As an example, a diffusor may be provided as an array of micro-diffusors. Typically, but not necessarily, the array would be provided as a film material comprising the micro elements. The same is true for the other optically relevant elements. On the other hand, and as an alternative, the traditional variants of the optically relevant element could be used. In case of the diffusor, this could be called a macro diffusor, macro in this case meaning that a single element performs the optical function as opposed to many micro variants of the same element. This can also be true for the other optically relevant elements mentioned above.

[0053] An example of an optically relevant element for which the same can apply, is a light source. E.g. in case of an artificial light source, this may be present as a macro light source, such as an incandescent bulb, iridescent tube, etc. of course, a LED lamp can also be used, in all cases possibly being composed of several sub-sources. These are contrasted however to an array of micro-sources, possibly present as a film comprising said sources. As an example, an array of micro-LEDs is envisioned. It is noted that the skilled person is readily able to distinguish between sources with several large-scale LEDs and micro-LEDs. Nevertheless, micro LEDs are likely to be no bigger than 10 times the optical element, whereas macro LEDs are likely over 100 times bigger.

[0054] The accumulator may comprise a diffusing device, which could for example be a diffusor or a film comprising an array of diffusors. A diffusing device can be used to make sure that at least some of the incident light, regardless of its angle of incidence or collimation, reaches the optical elements under optimal conditions. The diffusing device is particularly useful for instance to input indirect illumination from the Sun or artificial light into the system, e.g. input ambient light into the system.

[0055] The accumulator may comprise, additionally or alternatively, a condensing device, which could for example be a condenser or a film comprising an array of condensers. The use of a condensing device may be particularly useful to focus or collimate an otherwise diverging source of light, such as that produced by a purpose-specific light source. When the system includes a condensing device, many external light sources readily available could be used as light source, whereas previously only specifically provided light sources for the purpose were suitable.

[0056] The accumulator may comprise a collimating device, which could for example be a collimator, arranged to direct light towards the at least one optical element. The collimating device may be used to enlarge the portion of incident light that is usable for modulation by the optical element(s).

[0057] It is also possible to include a source of light in the system, so that the system becomes stand alone, or can be used in the dark. Said source would thus be a purpose-specific source of light, contrasting to ambient light sources. If the source is a source of non-collimated light, the optical system may comprise a collimating device (e.g. as part of the accumulator explained above).

[0058] Preferably, the collimating device is arranged to direct the light normal to the at least one optical element. The normal direction may be defined as normal to a plane spanning the support at a side thereof corresponding to the cover.

[0059] Additionally or alternatively a condenser could be used for the same or similar purpose. Normal incident light may be modulated relatively effectively by the optical element. The system may further comprise a beam splitting device, which could for example be a beam splitter, arranged between the accumulator and the at least one optical element.

[0060] Using the beam splitting device allows to take in light from the accumulator at the optical element(s), which may then reflect light back to a user through the beamsplitter. Accordingly, a user would see an image formed by the optical element(s), and the optical element(s) and accumulator themselves can be hidden from view.

[0061] The beam splitter may be provided as a film material. In particular, in combination with an accumulator provided as a film material, wherein both could be integrated in the optical element, as opposed to the accumulator and the at least one optical element being arranged on mutually perpendicular ports of the beam splitting device, described herein. Instead of a beamsplitter, it is also possible in this case to include a light guide plate, which could for instance allow edgelighting the element via the light guide plate. As yet another alternative, a system of gratings connected to waveguides could be used to direct light from a front light illumination system onto the optical element.

[0062] Instead of, or additional to, the beam splitting device, other optical components may also be used, such as polarizing devices and (colour) fdtering devices. These may provide an efficiency benefit. At least one lensing device may be provided for forming an image. A lensing device may be a lens.

[0063] In particular, the accumulator and the at least one optical element are arranged on mutually perpendicular ports of the beam splitting device, and the at least one lensing device is arranged on a port of the beam splitting device directly opposite the at least one optical element.

[0064] As was explained above, the lensing device may be provided as an array of microlenses, e.g. in a film form. Such an array may allow tuning accurately the optical properties of each lens to obtain a resulting image specifically suitable for the optical system of clause 1.

[0065] The system may comprise an array of optical elements, e.g. to form collectively an image or to create a large effective area.

[0066] Using an array of optical elements, several configurations can be made. As an example, a beam splitter may be used together with an array of microlenses, to allow input from an accumulator to reach the optical elements, and to then be output to a user. Each microlense may be integrated in each optical element. Alternatively, and to make maximum use of each optical element, the array of optical elements and the array of microlenses may be aligned. In general, when an array of optical elements is used, and an array of micro-elements as described above, it is advantageous if these are aligned.

[0067] The beam splitter may however also be present as a fdm material comprising micro-beam splitters. Additionally or alternatively, the micro beam splitters may be integrated with each optical element. In any case, the micro beam splitters can be aligned with the optical elements. A lens can be used at a collective output port of the micro beam splitters, or an array of microlenses can be used, as a fdm material or integrated in the optical elements.

[0068] The invention also relates to a use of an optical system as described hereabove, to display an image using ambient light, optionally sunlight, and / or purpose-specific light, optionally laserbased light, as a light source. As was described before, the accumulator allows using ambient light as an input. Before, it was only possible to form images using a specifically provided light source, which would provide light at a specific angle of incidence or with predefined collimation. Alternative uses are to project an image or video into an eye, into a conventional combiner, into a waveguide combiner, into a projector screen or into a wall using ambient light, optionally sunlight, and / or purpose-specific light, optionally laser-based light, as the light source.

[0069] The invention also relates to a use of an optical system according to any of the clauses, to communicate using modulated light, with ambient light, optionally sunlight, and / or purpose - specific light, optionally laser-based light, as a light source. Since the optical element can modulate light, it can be used to transfer information, for instance in communication. Using the accumulator, communication is made possible with a large variety of sources, such as natural light. Another variety of sources that can be used is a light emissive diode or a lamp, both of which could be used as an input to the optical element, which can then be used to influence the light, e.g. for communication.

[0070] COMMON CHARACTERISTICS

[0071] The following disclosure can apply to the accumulating element as well as the control of amplitude and phase.

[0072] The optical element described herein can be of any suitable type, and provides optical behaviour based on any number of suitable principles.

[0073] As an example, the optical device can operate by reflecting light using the cover. For that purpose, it is possible the cover has a relatively large reflectance as compared to its transmittance. As an example, the value of transmittance divided by reflectance would be not more than 0.5, preferably not more than 0.25, more preferably not more than 0.1, most preferably not more than 0.01.

[0074] The transmittance, reflectance and absorbance defined herein may be measured at a wavelength X which varies from 10 run to 3000 pm. In one aspect, most preferably 380 to 740 run. In another aspect, more preferably from 10 run to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700 nm to 2000 nm, most preferably from 850 nm to 1550 nm. In another aspect, more preferably from 30 000 nm to 3 000 000 nm. Of course, absorption may also be considered. As an example, the optical device can operate by absorbing light using the cover. For that purpose, it is possible the cover has a relatively large absorbance as compared to its reflectance. As an example, the value of reflectance divided by absorbance would be not more than 0.5, preferably not more than 0.25, more preferably not more than 0.1, most preferably not more than 0.01.

[0075] The absorbance and reflectance defined above may be measured at a wavelength X which varies from 10 nm to 3000 pm. In one aspect, most preferably 380 to 740 nm. In another aspect, more preferably from 10 nm to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700 nm to 2000 nm, most preferably from 850 nm to 1550 nm. In another aspect, more preferably from 30 000 nm to 3 000 000 nm.

[0076] The optical element may be configured for reflecting light incident on the second surface. In that case, the transmittance and reflectance may be measured for light incident the second surface.

[0077] Alternatively, the optical element may be configured for reflecting light incident on the first surface, in that case, the transmittance and reflectance may be measured for light incident the first surface.

[0078] Besides using the cover for reflection only or mainly, it is also possible to employ reflective interference, taking place mainly between a reflected light beam at the substrate (or cover) and a refracted light beam through the substrate (or the cover) that the cover (or substrate) reflects, or absorbing interference, taking place mainly between a reflected light bean with the incident light beam at the substrate (or cover) and its absorption at the cover (or substrate). An optical element configured for this purpose is called an interferometric optical device. The absorbance of the cover may accordingly also be relevant, as explained above.

[0079] The interference may take place for light incident the second surface, or for light incident the first surface. In the latter case, a substrate is needed below the cover, as is described further below. The substrate is configured for transmitting a part of the light and reflecting a part of the light. The transmitted light is then reflected on the cover, and transmitted back out through the surface. The egressing light interferes (constructively or destructively) with the directly reflected light. Depending on the position of the cover with respect to the substrate, it is possible to change the interference-based behaviour of the optical element.

[0080] Depending on the desired optical behaviour, it is of course possible to use a cover with different ratios of reflectance, transmittance and absorbance, optionally in combination with e.g. a reflective, transmissive or absorbing substrate, the terms reflective, transmissive or absorbing being defined using the same ranges for these respective quantities, and / or the same ratio’s between them as is defined for the cover. In general, the optical properties for the substrate are chosen complimentary to the optical properties of the cover. The invention is not limited to any such combination, rather to improving movement of the cover using amplitude and phase modulation. The disclosure relating to the accumulating element is also not limited to the same, but tot the subject matter defined in clause 1.

[0081] In any case, and of course, the substrate need not be square or rectangular. The substrate’s shape in general is not important, it is even possible for a single substrate to span multiple optical elements. More relevant may be the shape defined within the support, as this defines the shape of the optical element in plan view. It is possible this shape is square or rectangular, to create a pixellike element, but circular optical elements are also envisaged. The invention may however be applied to optical elements of all shapes. This is true for all embodiments described herein, whether they do or do not have a substrate.

[0082] It is noted that for some shapes of optical elements, the substrate is rigid and planar, while for others it is possible for it to be flexible and / or curved. In such cases, the spacer and cover are adapted to the substrate, in such a way that the second surface of the cover is approximately parallel to the substrate.

[0083] In this case, the cover is preferably reflective, for instance as expressed in the ratio above. The substrate is not as reflective, for example having a ratio of transmittance divided by reflectance of more than 0.5, more than 0.75, more than 0.9 or even more than 0.99, or even more than 1, preferably for light incident from a surface of the substrate facing away from cover.

[0084] The opposite direction is also possible, where the cover transmits and reflects light, and the substrate reflects the transmitted light. In this case, the cover would be relatively transmissive, for example having a ratio of transmittance divided by reflectance of more than 1, for light incident the second surface, so that it is relatively transmissive. Said ratio could for instance be between 1 and 3, such as between 1.5 and 2.5, such as around 2. The absorbance could in this case be relatively high. The substrate would preferably be reflective for light incident a surface of the substrate facing the cover. The reflectance could be defined by a ratio of transmittance divided by reflectance of not more than 0.5, preferably not more than 0.25, more preferably not more than 0.1, most preferably not more than 0.01.

[0085] Unless stated otherwise, transmittance and reflectance are measured for light normal to the surface of the cover.

[0086] In case a cover is used that is relatively reflective, a value of absorbance divided by reflectance of the cover can be less than 0.5, preferably not more than 0.25, more preferably not more than 0.1, most preferably not more than 0.01, for light incident the first and / or second surface, depending on the desired optical behaviour.

[0087] It is noted that in all cases, the position and shape of the cover influences how the optical device interacts with incident light. Other operational principles which rely on the change of the cover position and shape can however also be applied, and the current invention is thus not limited to either reflective or interferometric operational principles. In any case, the invention is not limited solely to a cover with a changing shape or a changing cover. In terms of claim 1, this can be realized by defining the spatial arrangement of the cover with respect to the support. After all, a cover that has not changed in shape but is at a different position with respect to the support, still has a different spatial arrangement as seen in cross section of the cover with respect to the support. As such, depending on the use, changing the position of the cover (without changing its shape) or changing the shape of the cover, thereby changing partially its position, could be used interchangeably.

[0088] The cover may comprise a 2-dimensional portion. The 2-dimensional portion may be an extreme membrane. For the purpose of the invention in general however, it is sufficient if the 2- dimensional portion is sufficiently thin to be deformed and / or moved using the applicable means. In general, it is not necessary, however possible, that the 2-dimensional portion has favourable optical properties in and of itself. Instead, it is possible to provide the desired optical properties using additional material, such as an additional layer or an amorphous portion of the cover, which could be or could comprise a metal or an additive. In that regard, reference is made to WO 2021 / 032752 Al which explains multiple configurations of the cover. The skilled person is readily able to vary e.g. the thickness and material of the additional material to arrive at desired optical properties for the cover. In that regard, it is noted the 2-dimensional portion may function as a carrier, whereas the additional material provides desired optical properties.

[0089] The 2-dimensional portion may be as defined in embodiment [39a] of WO 2021 / 032752 Al . Accordingly, the 2 -dimensional portion may be one or more of the following: a. One or more selected from the group consisting of: C, BN, P, MoS2, MoSe2 , MoTe2, WS2, WSe2, WTe2, NbS2, NbSe2, NbTe2, TaS2, TaSe2, TaTe2, TiSe2, VSe2, CrS2, CrSe2, B, Ge, Si, Si2BN, Sn, Pb, P, Sb, Bi. The preferred C in this context is one or more selected from the group consisting of: graphene, one or more graphitic layers and graphyne; preferably graphene. The preferred BN in this context is h-BN. The preferred P in this context is black phosphorus or phosphorene. The preferred B in this context is borophene. The preferred Ge in this context is germanene. The preferred Si in this context is silicene. The preferred Sn in this context is stanene. The preferred Pb in this context is plumbene. The preferred Sb in this context is antimonene. The preferred Bi in this context is bismuthine; b. One or more transition metal chalcogenides, each being a transition metal chalcogenide not listed in a.; c. One or more oxides, each being an oxide of a species listed in a. or b.; d. One or more atomic intercalated variants, each being an atomic intercalated variant of a species listed in a. or b.; e. One or more physically, chemically, mechanically and / or electromagnetically functionalised derivatives, each being a chemically functionalised derivative of a species listed in a. or b.. A preferred physical functionalisation is perforation or atomic barrage treatment. A preferred mechanical functionalisation is stretching or stressing. A preferred electromagnetic functionalisation is application of a voltage.

[0090] In one aspect of this embodiment, the 2-dimensional portion is a combination selected from the group consisting of: a., b., c., d., e., a.+b., a.+c., a.+d., a.+e., b.+c., b.+d., b.+e., c.+d., c.+e., d.+e., a.+b.+c., a.+b.+d., a.+b.+e., a.+c.+d., a.+c.+e., a.+d.+e., b.+c.+d., b.+c.+e., b.+d.+e., c.+d.+e., b.+c.+d. +e., a.+c.+d.+e., a.+b.+d. +e., a.+b.+c. +e., a.+b.+c.+d. and a.+b.+c.+d.+e..

[0091] Specifically, the 2-dimensional portion may comprise or be graphene or boron nitride or both. A preferred boron nitride is hexagonal boron nitride. Graphene is preferably chemical vapour deposited. Boron nitride is preferably chemical vapour deposited. In one aspect of this embodiment, the 2-dimensional portion comprises graphene, preferably is graphene. In one aspect of this embodiment, the 2-dimensional portion comprises boron nitride, preferably is boron nitride.

[0092] As mentioned earlier, the thickness of the 2-dimensional portion is relatively small. For instance, 1 mm or less, preferably 10 pm or less, more preferably 1000 nm or less, more preferably 100 nm or less, more preferably 50 nm or less. In one aspect of this embodiment, more preferably 10 nm or less, more preferably 5 nm or less, most preferably 1 nm or less.

[0093] A minimum thickness may be defined as 25 pm or more, preferably 69 pm or more, more preferably 100 pm or more. In one aspect of this embodiment, the thickness is 1 nm or more, preferably 3 nm or more, more preferably 5 nm or more, more preferably still 10 nm or more. In another aspect of this embodiment, the thickness is 15 nm or more, preferably 20 nm or more, more preferably 30 nm or more.

[0094] Accordingly, the 2-dimensional portion may be relatively light per unit area, such as 24 kg / m2or less, preferably 2.4- 101kg / m2or less, more preferably 2.4- 102kg / m2or less, more preferably 2.4- 103kg / m2or less, most preferably 1.2- 103kg / m2or less. A lower limit on the same weight per unit area is 1.7- 109kg / m2or more, preferably 3.4- 108kg / m2or more, more preferably 1.8 - 107kg / m2or more. In one aspect of this embodiment, the mean density is 5 • 107kg / m2or more, preferably 1.5- 106kg / m2or more, more preferably 5.4-106kg / m2or more, more preferably 5.7- 105kg / m2or more.

[0095] Various operational principles for the means are available, and have been identified throughout the previous paragraphs. It is noted that some operational principles may allow exerting a force on the cover only in one direction, whereas for others the same means can be used to exert forces in opposing or even various directions on the cover. In case the operational principle only allows forces in a single direction, further means, which may be identical, may be applied on the opposite side of the cover, e.g. in a mirrored position with respect to the previously mentioned means, so that collectively control can be exerted in both or more directions.

[0096] While above an optical element has been described that has means configured to affect the cover, the inverse is also possible and envisaged. Accordingly, the means may alternatively or additionally be arranged to provide an output that is representative of the cover changing from the first cover contour profile to the further cover contour profile.

[0097] In this manner, the optical element can be used as a sensor responsive to any phenomenon, not necessarily optical, that changes the cover shape. For instance, incident radiation, pressure, sound waves, an electrical charge, temperature, etc. could all be sensed using suitable means. As an example, an electrode could be used to sense a changing electrical charge, e.g. changing in response to a charged cover moving. If a predetermined and externally applied electrical charge is applied to the cover, the electrodes could be used to measure deformation of the cover by capacitive means, for instance as a result of incoming radiation or pressure. An electrode or other type of sensing means would be necessary to measure the changing electric field as the charged cover moves.

[0098] In these circumstances, the element described herein need not be described as an optical element per se.

[0099] In particular, the means and / or further means may each, independent from one another, comprise any one or more of:

[0100] - an optical actuator, such as an optical tweezer or photonic circuitry;

[0101] - a means for applying or changing radiation incident on the cover, such as a radiation source.

[0102] - a means for influencing a gas pressure acting on the cover;

[0103] - a speaker or any other sound emitter;

[0104] - a thermal actuator, operating via thermal expansion; and

[0105] - an electromagnetic and / or superconducting actuator, for instance operating based on tunneling or field emission.

[0106] At this time, it is noted that regardless of the actuation method used, given a sufficiently small system, any one actuation method will often have some corresponding co-phenomenon in another domain as well. As such, at nano-scale, the actuation method and corresponding cophenomena usually pair up. Examples of such pairs, which may be used in the currently described invention as a non-exclusive list of examples, are:

[0107] Thermo-electrical and electro-thermal actuation;

[0108] Thermo-optical and opto-thermal actuation;

[0109] Thermo-magnetic and magneto-thermal actuation;

[0110] Opto-electrical and electro-optic actuation; and Magneto-optic and opto-magnetic actuation.

[0111] At the same time, quantum and superconducting effects may also play a role. Accordingly, use can be made of such effects if desired.

[0112] It is noted that the substrate may be used to define a cavity below the cover. The index of refraction of said cavity can be of influence on the optical behaviour of the optical element. The index of refraction of the cavity can be influenced by at least partially filling the cavity. To facilitate said filling the cavity may be enclosed by one or more of the support, the cover and the substrate, or may even be sealed entirely. If the cavity is indeed sealed, it can be filled with a substance. Different fillings of the cavity can lead to different refractive indices, and thus a different optical behaviour. The cavity may for this purpose be filled with a gas composition. Aside from a gas or gas mixture, the cavity may also be filled by a liquid (mixture) and / or liquid crystals, or even a solid filling, which may have a greater effect on the refractive index. Another option would be to instill a vacuum inside of the cavity. Definition of, and filling of the cavity may also be done for other reasons than influencing the index of reflection, i.e. to provide absorption, to provide structure rigidity, or other reasons.

[0113] Moreover, the substance filling a cavity can be of influence on other than the optical behaviour of the optical element, including but not limited to the mechanical response of the cover and the electrical influence of the means. A filled cavity can also be used to exert a pressure on the cover, in order to move it using pressure based means.

[0114] As a further remark, it is noted that the structure described herein as optical element can be used in a different and novel way as well, regardless of whether or not the characterizing portion of the claims is applied. In this novel way of using the device, a substrate opposite the cover is necessary, so that a cavity is formed between the cover and the substrate. The device is configured to allow entry of electromagnetic radiation, such as (visible) light, into the cavity between the support and the substrate, and to allow egress of the same, also between the support and the substrate. In contrast to the principles shown above, in which light interacts by being incident the cover (either from the first or second surface), the light now travels substantially parallel to the cover, through the cavity. In this case, the cavity acts like a waveguide. To form a waveguide, the skilled person is able to choose suitable materials for the support, the substrate and the material at the cover’s first surface and optionally for material to fill the cavity with, so that the light is influenced by the cover. This influence could for example result in a change in amplitude, phase or the state of the light. Suitably chosen characteristics, such as optical characteristics, of the cover allow interaction with light passing through the cavity. By changing the contour shape of the cover, or by changing its position, the waveguide formed in the cavity can be altered. The changing influence of the cover on waves passing through can be used to modulate the light. It is noted that the cover need not actually move or change shape in order to affect the passing light differently. For instance, its strain may be altered for instilling different optical properties.

[0115] The invention and the accumulating element will be further elucidated with reference to the attached drawings, in which:

[0116] Figures 1A, IB and 1C show schematically interaction of light with an optical element known in the state of the art;

[0117] Figures 2A, 2B and 2C show schematically interference interaction of light with an optical element known in the state of the art;

[0118] Figures 3A and 3B show different configurations of an optical element, with its cover in different positions;

[0119] Figures 4 and 5 show schematically an optical element for different interferometric effects; and

[0120] Figure 6 shows schematically in perspective view another way of using the optical element.

[0121] Figure 7 shows schematically a device with multiple optical elements;

[0122] Figure 8 shows schematically a system with the device of figure 3;

[0123] Figure 9 shows schematically a different embodiment of an optical system comprising the device of figure 7;

[0124] In these figures, figures 1A - 1C, 2A - 2C, and 4 - 5 are common to the invention and to the accumulating element disclosed herein. Figures 3A - 3B are specifically relevant for the invention. Figures 7 - 9 are specifically relevant for the accumulating element.

[0125] Figure 1A shows interaction of light with of a flat cover 101, which is supported by supports 104. The parallel rays 601 and 602 are both deflected by the same angle and remain parallel after interaction with the cover 101. This constitutes specular reflection.

[0126] Figure IB shows interaction of light with a convex cover. Due to the rounded convex cover contour profile, a first ray 601 is deflected by almost 180° and the second ray 602 is only deflected by a small angle. The rays 601 and 602 are no longer parallel after reflection at the cover. This constitutes diffused reflection.

[0127] Figure 1C shows interaction of light with a concave cover. Due to the rounded concave cover contour profile, a first ray 601 is deflected by an angle less than 90° and the second ray 602 is deflected by almost 180°. The rays 601 and 602 are no longer parallel after reflection at the cover. This constitutes diffused reflection. Figure 2A shows interference interaction with a flat cover. Aside from the supports 104, a substrate 106 is also present in this example of the state of the art, which lies on the bottom of the optical element. The support 104, cover 101 and substrate 106 define a cavity having a depth 205. The substrate 106 is transmissive and absorbing to an extent and the cover 101 is reflective, such that an incoming ray 601 undergoes interference which is dependent on the depth 205.

[0128] Figure 2B shows interference interaction with a convex cover. The cover 101 of the optical element of figure 12 has been deformed into a convex shape (cover contour profile). This was brought about by a means pushing the cover 101 upwards. This increases the depth 205 and the interference behaviour of incoming light 601 is altered.

[0129] Figure 2C shows interference interaction with a concave cover. The cover 101 of the optical element of figure 12 has been deformed into a concave shape (cover contour profile). This was brought about by the means pushing the cover 101 downwards. This decreases the depth 205 and the interference behaviour of incoming light 601 is altered.

[0130] Now first referring to figures 4 and 5, it is noted that depending on the optical properties of the cover 101 and the substrate 106, different operational principles are also usable for influencing incident light. Figure 4 for instance, shows an optical element similar to that of figures 1 and 2, but with a cover 101 that is relatively absorbing, and a substrate 106 that that is relatively reflective. As a result, incident light 601 transmitted 602 through the cover 101 interacts with light reflected 604 from the substrate to form a pattern of nodes and antinodes. The cover can be controlled by means (not shown) to be placed at or away from a node or antinode, to accordingly absorb strongly or less strongly light, so that the intensity of exiting light 605 can be controlled. In figure 75 a cover 101 is present that is both transmissive and reflective, and a substrate that is reflective. Accordingly, use can be made of interferometric reflection, similar to figures 2A - 2C, however now the optical element is configured for light incident the cover 101. Otherwise, the optical element may be identical to that described above.

[0131] Figures 3A and 3B show an optical element 99 with a support 4 and a cover 1. The cover 1 is attached to the support 4 as described in claim 1. A substrate 6 is present, with a means 7 to control the cover contour profile. A controller 12 is attached to the means 7 to power it. Although the means in this case are shown as an electrode, other types of means 7 are not excluded. The support 4 also includes an expandable portion 18, so that the support 4 is expandable. The expandable portion can be expanded using further means which are not shown, and could be controlled by e.g. the same controller.

[0132] In figure 3A, the cover 1 is shown in two positions, each with its own resulting optical response in terms of amplitude Ai, A2 and phase 0i, 02.

[0133] In figure 3B, the support 4 is expanded using the expandable portions 18. Accordingly, a different structure defines the optical properties of the optical element. As a result, the means 7 can be used to control the cover to provide an amplitude response Ai, A2 similar or identical to that with unexpanded portions 18 in figure 3 A, but which will now have a different phase 0 04. Accordingly, it is clear that at least to some extent, amplitude and phase can be controlled independently, which can be used to provide a wider range of optical responses using the optical element.

[0134] Further, reference is made to figure 6, which shows a perspective view of a device, such as an optical element, similar to that described herein. Like before, the device has a substrate 106 and support 104, which in this case are monolithic. The support 104 defines a cavity C that is of longitudinal shape in this example. Cover 101 held by the support 104 spans the cavity C. Materials for the support 104, the substrate 106, the material at the cover’s first surface and material with which the cavity C is filled are chosen so that the cavity C acts as a waveguide. Incident waves 601, such as light, can therefore pass through from one side to another, and egress as exited light 602. Via means 107, in this case presented on top of the support 104, although not strictly necessary, the cover 101 can be moved, or its cover contour profile changed. As a result, the cover 101 at least locally influences the light passing through the cavity C in order to modulate it.

[0135] Figure 7 shows a device 98 with several optical elements 99 arranged in an array of 3x3. Each optical element 99 comprises a cover 1 having a first surface and a second surface, a support, and a means. The cover is orientated with the first surface directed towards the support, a part of the first surface is attached to the support. A spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile, and the means is arranged to move the cover from a first cover contour profile to a further cover contour profile which is different from the first cover contour profile. The optical elements 99 are seen in plan view, i.e. normal to their cover 1.

[0136] Figure 8 shows how such a device 98 can be used in a system 97 having multiple optical elements 99 and an accumulator 23. The accumulator 23 is, in the example of figure 4, a collimating device 23. A source 24 of non -collimated light, this case sunlight, is shown. The collimating device 23 collimates the lights and directs it to the device 98. For the sake of clarity, the light in figure 4 is shown parallel to the optical elements 99, but it is preferable if the light is directed normal to the optical elements 99. The optical elements 99 modulate the light for a user 25 to see.

[0137] Another system 97 is shown in figure 9. This system includes a source 24 of light, which is fed through a condensing device 26 and a beam splitting device 27 to reach the device 98. After modulation, the light is emitted / reflected / refracted back through the beam splitting device 27 and finally to a user 25 after passing through a lens 28 in order to form an image.

[0138] Another exemplary arrangement of the optical system is depicted in figure 5, this time using a purpose-specific light source rather than an ambient light source, such as sunlight. It is noted that terms like “preferably”, “generally” and “typically” are not utilized herein to limit the scope of the claims or to imply that certain features are critical, essential, or even important to the structure or function of the claims. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present disclosure. Likewise, for the purposes of describing and defining the present disclosure, it is noted that the terms “substantially” and “approximately” and their variants are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement or other representation, as well as to represent the degree by which a quantitative representation may vary without resulting in a change in the basic function of the subject matter at issue.

[0139] While certain representative embodiments and details have been shown for purposes of illustrating the present disclosure, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the disclosure, which is defined in the appended claims. .

[0140] The accumulating optical element disclosed herein is also described by the following clauses:

[0141] 1. Optical system, comprising at least one optical element which comprises: a. a cover having a first surface and a second surface, b. a support, and c. a means; wherein: the cover is orientated with the first surface directed towards the support; a part of the first surface is attached to the support; a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile; the means is arranged to move the cover from a first cover contour profile to a further cover contour profile which is different from the first cover contour profile; characterized by the optical system further comprising an accumulator that accumulates light from a source of light, such as a source of diffused light.

[0142] 2. Optical system according to the previous clause, wherein the accumulator comprises a diffusing device. 3. Optical system according to any of the preceding clauses, wherein the accumulator comprises a condensing device.

[0143] 4. Optical system according to any of the preceding clauses, wherein the accumulator comprises a collimating device arranged to direct light towards the at least one optical element.

[0144] 5. Optical system according to any of the preceding clauses, further including a source of light.

[0145] 6. Optical system according to the previous clause, the source being a source of noncollimated light, and the optical system further comprising a collimating device to collimate the light.

[0146] 7. Optical system according to the previous clause, wherein the collimating device is arranged to direct the light normal to the at least one optical element.

[0147] 8. Optical system according to any of the preceding clauses, further comprising a beam splitting device arranged between the accumulator and the at least one optical element.

[0148] 9. Optical system according to any of the preceding clauses, further comprising at least one lensing device for forming an image.

[0149] 10. Optical system according to at least clauses 7 and 9, wherein the accumulator and the at least one optical element are arranged on mutually perpendicular ports of the beam splitting device, and the at least one lensing device is arranged on a port of the beam splitting device directly opposite the at least one optical element.

[0150] 11. Optical system according to any of clauses 9 - 10, wherein the lensing device is provided as an array of microlenses, optionally arranged between the accumulator and the at least one optical element.

[0151] 12. Optical system according to any of the preceding clauses, comprising an array of optical elements.

[0152] 13. Optical system according to at least clauses 11 and 12, wherein the array of optical elements and the array of microlenses are aligned. 14. Use of an optical system according to any of the preceding clauses, to display an image using ambient light, optionally natural light, as a light source. 15. Use of an optical system according to any of the preceding clauses, to communicate using modulated light, with ambient light, optionally sunlight, and / or purpose-specific illumination, optionally laser-based light, as the light source.

Claims

24Claims1. Method of operating an optical element, the optical element comprising a. a cover having a first surface and a second surface, b. a support, and c. a means; wherein: the cover is orientated with the first surface directed towards the support; a part of the first surface is attached to the support; a spatial arrangement of the cover as seen in a cross section of the cover defines a cover contour profile; the means is arranged to move the cover from a first cover contour profile to a further cover contour profile which is different from the first cover contour profile; wherein the optical element further comprises a substrate on a side of the support opposite the cover, a cavity being defined between the cover and the substrate, with a cavity height defined as a distance from the substrate to the cover, characterized in that the method is characterized by:- based on a desired phase response for the optical element and a desired amplitude response, control the means to cause the optical element to exhibit a response corresponding to the desired phase response and the desired amplitude response.

2. Method according to the previous claim, wherein the means comprise first means and further means, wherein the first means is configured to influence the amplitude of modulated light and the further means is configured to influence the phase of the modulated light.

3. Method according to the previous claim, wherein the first means and the further means are controlled independently.

4. Method according to any of the previous claims, comprising receiving a desired phase response and a desired amplitude response, optionally further including receiving a desired wavelength response.

5. Method according to any of the preceding claims, wherein the support is expandable, and the further means are configured to expand the support.

6. Method according to any one or more of the preceding claims, wherein the cover and / or substrate and / or cavity exhibits changeable properties, such as optical or mechanical properties, and the method comprises changing these properties.

7. Method of fabricating an optical element according to the previous claim or method according to the previous claim, wherein the cover and / or the substrate comprise a material configured to change its optical properties, e.g. by applying strain to a material whose refractive index changes with strain, and wherein the method comprises changing the optical properties of the cover and / or the substrate.

8. Method according to any one or more of claims 6-7, wherein the cover and / or the substrate comprises a material configured to change its mechanical properties, e.g. by applying temperature to a mechanical metamaterial or a material whose crystalline structure changes with temperature, and wherein the method comprises changing the optical and / or mechanical properties of the cover and / or the substrate.

9. Method according to any one or more of claims 6-8, wherein the cover and / or the substrate comprises a material configured to change its electrical properties, e.g. by applying a torque to part of the crystalline structure of a material whose electronic behavior changes with rotational angle, and wherein the method comprises changing the electrical properties of the cover and / or the substrate.

10. Method according to any one or more of claims 6-9, wherein the cover and / or the substrate comprises a material configured to change any of its properties, e.g. by applying charge to a material containing metasurfaces or structured as a tunable / photonic metamaterial or photonic crystal whose response to electric and magnetic fields changes with temperature, and the method comprises changing such properties.

11. Method according to any one or more of claims 6-10, wherein the cavity is filled with a substance whose refractive index can be changed, e.g. by changing a gas composition in the cavity, and the method comprises changing the refractive index of the cavity.

12. Method according to any one or more of claims 6-11, wherein the cover and / or the substrate comprises a material configured to change the light state of the modulated light, optionally to a certain polarization state, a certain quantum state or a combination of different states.

13. Method, preferably of operating an optical element, according to the previous claim, comprising receiving a desired light state response.

14. Use of an optical element according to the previous claim, for communicating using modulated light that is secure.

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