IMPROVED OPTICAL ELEMENT WITH EXPANDING SUPPORT

Abstract

2 1 The invention 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 that surface is attached to thereto. 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, and / or the means is arranged to provide an output that is representative of the cover changing from the first cover contour profile to the further cover contour profile. According to the invention, the support is expandable, or a distance defined from the substrate to a plane spanning the support on a side of the cover locally varies.

Description

l IMPROVED OPTICALELEMENTWITHEXPANDING SUPPORT The current application relates to an optical element comprising, a cover having a rst surface and a second surface, a support, and ameans. The cover is orientated with the rst surface directed towards the support, a part ofthe rst surface is attached to the support, a spatial arrangement ofthe cover as seen in a cross section ofthe cover denes a cover contour prole, and the means is arranged to move the cover from a rst cover contour prole to a further cover contour prole which is different from the rst cover contour prole. An optical element is known from e.g.WO 2021 / 032752 Al andWO 2018 / 228671 Al. This document discloses optical devices ofspecic interest. The working principle is thatwhen a cover is provided that has some desired optical behaviour, e.g. reecting light, transmitting only some light, etc. the interaction ofincident light can be changed by changing the cover contour prole. To facilitate the cover changing shape to facilitate changing the optical behaviour ofthe optical device, the cover is made relatively thin, in terms ofWO 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, reection and / or interference behaviour can be used to turn a pixel on or offand / or vary its colour. This way, images can be generated and / or manipulated. Several principles ofoperation are available with such optical devices.A rst operational principle is shown in gures lA lC, which correspond to gures 9 ll ofWO 2021 / 032752 Al. These gures show respectively an optical device with a at cover, a convex cover, and a concave cover. Light incident on the at cover (g. 1A) is reected as ifhitting a smooth and straight surface, i.e. parallel incident rays remain parallel after reection. As such, specular reection takes place at the cover. In the convex and concave positions ofthe cover, parallel incident rays are no longer parallel after reection, thus causing diffuse reection. By changing the shape ofthe cover, it is thus possible to alternate between specular and diffuse reection. To suit this rst operational principle, the cover is sufciently reective towards the incident light. In this example, the light is incident on the second surface, whichmay also be called the outside ofthe optical device. Figures 2A 2C, which correspond to gures 12 l4ofWO 2021 / 032752 Al, show a second operational principle. Reference is rst made to the substrate which spans the support on an opposite side ofthe cover, in order to dene a cavity between the cover and the substrate. The substrate is partly reective and partly transmissive. The cover is relatively reecting. Light incident on the substrate is thus partly transmitted and partly reected. The transmitted light reects on the rst surface ofthe cover, i.e. coming from the inside, and is transmitted back through the substrate, where it interferes with the light reected by the substrate. Depending on the wavelength ofthe 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 ofthe optical device can be changed. Figures 8 and 9 show even otherways ofusing the changing cover contour prole. In the case ofgure 8, an optical element is shown with a substrate 106 that is relatively reective. The cover 101 in this case is relatively absorbing. Nevertheless, ofan incoming lightbeam 601, at least some lightmay be transmitted towards the substrate 106 as transmitted lightbeam 603. This reects back via the substrate 106 as reected light 604. Due to interference ofthe transmitted lightbeam 603 and the reected light 604, a pattern ofnodes and antinodes is present. The cover 101 can then be moved, e.g. by changing its cover contour prole 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 ormore intensity by controlling the cover. This principle is called interferometric absorption. Figure 9 shows the principle ofinterferometric reection, similar to g. 2, but with light 601 incident the cover. In this case, light is partially transmitted through the cover 101, and reected at the substrate 604, which for that purpose is reective. The cover 101 reects some light 605, but also transmits some light 603. After reecting 604 from the substrate 106, light passing through the cover 101 again interferes with the reected light 605. By controlling the position or cover contourprole ofthe cover 101, control is possible ofwavelengths oflight that do or do not interfere constructively. In both cases, light transmitted through the covermay actually be refracted. However, since the gures show a specic example oflight incident normal to the cover, the wording transmitting was used. The invention can however be applied, depending on the use-case, to non- normal light also. These principles have been described only briey herein, as the operational principles involved are in themselves known, and have been applied e.g. inWO 2018 / 228671 A1 (see gures 1 and 2). These principles thus show thatby varying the reectance and / or transmittance and / or absorbance ofthe cover and the substrate, and the direction atwhich 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 contourprole changes. There however exists a need to more accurately inuence the interaction between the optical device and incident light. It is an object ofthe invention to provide an optical element that allows more accurate control. In the current disclosure, two solutions are provided to this problem. The solutions are dened in the independent device claims. Firstly, an optical element is disclosed, with a coverhaving a rst surface and a second surface, a support, and ameans. The cover is orientated with the rst surface directed towards the support, a part ofthe rst surface is attached to the support, a spatial arrangement ofthe cover as seen in a cross section ofthe cover denes a cover contour prole, and the means is arranged to move the cover from a rst cover contourprole to a further cover contour prole which is different from the rst cover contour prole. As a rst solution disclosed herein, the support is expandable. It is noted that for any element that is described as being expandable in this application, and any similarterms used throughout this document, said expansionmay be reversible. As such, the supportmay also be contractible, retractable or collapsible. The support being expandablemay have several advantages. As a rst, it offers an additional tunable input to the position and shape ofthe cover. Since the cover is attached to the support, its position or shape can be changed by expanding the support. Further, ifthe support is expandable, itmay be used as an addition to the means, for instance to actuate the cover over a relatively precise or accurate distance, whereas the means may actuate the cover over larger distances or deviations. While the above can be achieved ifthe support is expandable in a direction in-plane with the cover, it is preferable ifthe support is expandable in a direction substantially normal to the cover. In this case, the height ofthe cover can be changed directly. The heightmay be dened for instance as the height ofa cavity below the cover, or from the cover to the opposite side ofthe support. The supportmay for instance comprise an expandable material. Using the expandable material, the support can be made to expand. An example, which is easily controlled, is any material that is expandable by application of electricity, such as a piezoelectric material, such as PZT. 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 ofthese materials being summarized as absorbing materials. As a particular example, a material containing spin-crossover particles is mentioned. In such a case, the material may be or comprise apolymer matrix. Such a material is described in e.g. Colossal expansion and fast motion in spin-crossover@polymer actuators by PiedrahitaBello et al. (http: / / dx.doi.org / 10.1039 / d1mh00966d). For a relatively large effect, the supportmay consist solely ofexpandable material. It is however also possible, for instance for precise control, ifthe support comprises an expandable portion and a non-expandable portion. Multiple expandable portionsmay also be used, for instance with different expansion-characteristics. As an alternative, or additionally, the substrate may be made (solely) ofan expandable material, whichmay ormay not be the same as the material ofthe substrate. The support is preferably controlled using a furthermeans comprised by the optical element. The furthermeans are congured to expand the support. Using the furthermeans it is possible to control the support, possibly independently from the cover. The furthermeans may be ofany suitable type, just like the earlier mentioned means. The furthermeans may be the same or different from the earlier mentioned means. As a preferred option, the furthermeans comprise at least one voltage and / or current source. Thismay facilitate easy control and / or production. The optical element described herein may comprise a substrate on a side ofthe support opposite the cover, the cover, substrate and support dening a cavity. The cavity can be used for instance to provide interferometric capacity to the optical element. Furthermore, the index ofrefraction ofsaid cavity can be ofinuence on the optical behaviour ofthe optical element. The index ofrefraction ofthe cavity can be inuenced by at least partially lling the cavity. To facilitate said lling the cavity may be enclosed by one ormore of the support, the cover and the substrate, ormay even be sealed entirely. Different llings ofthe cavity can lead to different refractive indices, and thus a different optical behaviour. The cavity may for this purpose be lled with a gas composition. Aside from a gas or gas mixture, the cavity may also be lled by a liquid (mixture) and / or liquid crystals, or even a solid lling, whichmay have a greater effect on the refractive index. Another option would be to instill avacuum inside of the cavity. Denition of, and lling ofthe cavity may also be done for other reasons than inuencing the index ofreection, i.e. to provide absorption, to provide structure rigidity, or other reasons. Moreover, the substance lling a cavity can be ofinuence on other than the optical behaviour ofthe optical element, including but not limited to the mechanical response ofthe cover and the electrical inuence ofthe means.A lled cavity can also be used to exert a pressure on the cover, in order to move it using pressure based means. The substrate may be at least locally expandable. By locally expanding the substrate, a distance from the substrate to the cover, which is dened as the local cavity height, can be inuenced. It for instance becomes possible to locally change the height ofthe substrate in correspondence with a cover shape. Accordingly, itbecomes possible to apply a relatively uniform cavity height overthe entire cavity even ifthe cover varies in height locally. Local expansion of the substrate can thus be used to at least partly compensate for deviation ofthe cover. Additionally or alternatively, locally expanding the substrate may also be used to directly inuence the optical characteristics ofthe optical element. It is for example possible to locally change the cavity heightby expanding a part ofthe substrate. When used as an interferometric modulator, this the interferometric behaviour is dependent on the cavity height, so that this behaviour can be inuenced by altering the substrates expansion. In non-interferometric settings, the expanding substrate can be used to change e.g. the volume ofthe cavity, orthe distance between the substrate and the cover, in order to inuence the way the covermove or to move the cover, so as to inuence its cover contour proles. The furthermeans may be further congured to expand the substrate. For this purpose, the furthermeans may be comprised oftwo separately controllable submeans, one for the substrate and one for the support, although this is not necessary. Eitherway, the furthermeans may be used to assume control over the expansion ofthe substrate, so as to dictate its behaviour. A particularly versatile optical element is achieved the furthermeans are congured to expand different parts ofthe substrate and optionally the supportby varying degrees. In this case, the substrate could be tuned to different shapes represented by the different parts ofthe substrate. As an example, the substrate could be made to correspond to at least some extend to the cover shape so as to keep a local cavity height uniform. In particular, the means and / or furthermeans may each, independent from one another, comprise any one ormore of: - an optical actuator, such as an optical tweezer or photonic circuitry, - ameans for applying or changing radiation incident on the cover, such as a radiation source. - ameans for inuencing a gas pressure acting on the cover, - a speaker or any other sound emitter, - a thermal actuator, operating viathermal expansion, and - an electromagnetic and / or superconducting actuator, for instance operating based on tunneling or eld emission. At this time, it is noted that regardless ofthe actuation method used, given a sufciently 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 co- phenomena usually pair up. Examples ofsuch pairs, whichmay be used in the currently described invention as a non-exclusive list ofexamples, are: - Thermo-electrical and electro-thermal actuation, - Thermo-optical and opto-thermal actuation, - Thermo-magnetic and magneto-thermal actuation, - Opto-electrical and electro-optic actuation, and - Magneto-optic and opto-magnetic actuation. At the same time, quantum and superconducting effects may also play a role. Accordingly, use can be made ofsuch effects ifdesired. More accurate control can also be achieved without expanding the support, as is disclosed below and claimed in the second independent device claim. In particular, in an optical element according to the preamble ofthe rst device claim, which also has a substrate on a side ofthe support opposite the cover, wherein the cover, substrate and support together dene a cavity. In such an element is it possible to achieve more accurate control ifa distance dened from the substrate to a plane spanning the support on a side ofthe cover locally varies. The local variationmay be both in time and / or in space. When the local variation is in space, the distance between said plane and the substrate varies across the substrate, i.e. throughout the cavity. As a result, the shape ofthe bottom ofthe cavity, dened by the substrate, need not be at. The shape could for instance be concave or convex, but need not be limited thereto. In any case, a shape could be chosen that corresponds to a deformed shape ofthe cover. For instance, in an optical device that is likely to have its cover pulled towards the substrate by the means, the substrate may be made concave.A cavity height, dened between substrate and cover, would therefore be relatively uniform as compared to a situation in which the substrate were at. Other use-cases are also possible for a non-at substrate, i.e. one in which the substrate heigh locally varies. In any case, the optical characteristics ofthe element are inuenced by said varying height, andmay therefore be suitable formore accurate control. It is however also possible, additionally or alternatively, that the substrate height locally varies in time, for instance due to actuation ofthe same. In that case, additional control possibilities are available, so that the characteristics ofthe element can be controlled more accurately. As an example, as the cover shape changes (due to the means), the substrate can be controlled to also change e.g. correspondingly. For providing the relevant change in shape, the substrate may be at least locally expandable. The expansion could for instance be provided by a piezoelectric material as was described above, such as PZT. Another kind ofmaterial that expands, such as one including spin- crossover particles as explained-above is also possible. As before, it is possible to actuate the substrate iffurthermeans are provided, which are congured to expand the substrate. The furthermeans may be individually controllable, i.e. independent from the means that control the cover. A high level ofcontrol can be obtained ifthe furthermeans are congured to expand different parts ofthe substrate by varying degrees. The locally expandable substrate can be combined with the expandable support thatwas described above. As such, in addition to the locally expandable substrate, the optical elementmay satisfy one ormore ofthe following: - the support is expandable, - the support is expandable in a direction substantially normal to the cover, - wherein the support comprises an expandable material, - the expandable material is a piezoelectric material, - the support consists solely ofexpandable material, or wherein the support comprises an expandable portion and a non-expandable portion, and - the optical element is according to claim 13, and the furthermeans are further congured to expand the support, wherein optionally the furthermeans comprise at least one voltage source. The above-mentioned advantages and examples apply similarly. The current disclosure also relates to amethod ofcontrolling an optical element as described herein. In particular, the methodmay comprise controlling the means and the furthermeans at the same time. The means and the furthermeans may be controlled at mutually different frequencies. In particular, one ofthe two may be controlled at a frequency that is at least 10 times lowerthan the other. The lowest ofthe two frequencies may be substantially zero, i.e. one ofthe means may be controlled to be at a substantially constant expansion as compared to the other ofthe means and the further means. The furthermeans may be controlled at a lower frequency, or at a higher frequency. It is however alternatively possible forthe means and the furthermeans to be controlled at the same frequency. For some applications it can be ofadvantage that, as the cover shape changes (due to the means), the substrate can be controlled to also change correspondingly. Ifan element according to claim 14 is controlled, the methodmay comprise controlling the furthermeans so as to expand the different parts ofthe substrate in correspondence with the cover contour prole. Accordingly, a distance between cover and substrate can be kept relatively uniform. The substrate may have optical properties whichmay be relevant forthe element as a whole. These properties may change upon expansion ofthe substrate, be that locally or not. As such, it is advantageous ifthe control ofthe substrate is based on combined optical properties of the substrate and amedium between the cover and the substrate. Saidmedium could be a gas or gas mixture, a liquid or liquid mixture, or liquid crystals, or any other suitable medium. The medium would be chosen for inter alia its optical characteristics, but the choice ofmedium is outside ofthe scope ofthis application. In any case, an inert and transparent or translucent gas mixture could be used. As a nal remark, it is noted that mechanical properties or electrical properties ofthe medium are also ofimportance, as these may affectmovement or deformation of the cover. The optical element described herein can be ofany suitable type, and provide optical behaviour based on any number of suitable principles. As an example, the optical device can operate by reecting light using the cover. For that purpose, it is possible the cover has a relatively large reectance as compared to its transmittance. As an example, the value oftransmittance divided by reectance would be not more than 0.5, preferably notmore than 0.25, more preferably notmore than 0.1, most preferably not more than 0.01. The transmittance, reectance and absorbance dened herein may be measured at a wavelength X which varies from 10nm to 3000 um. In one aspect, most preferably 380 to 740 nm. In another aspect, more preferably from 10nm to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700nm to 2000 nm, most preferably from 850nm to 1550 nm. In another aspect, more preferably from 30 000nm to 3 000 000 nm. Ofcourse, absorptionmay 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 reectance. As an example, the value ofreectance divided by absorbance would be notmore than 0.5, preferably notmore than 0.25, more preferably notmore than 0.1, most preferably notmore than 0.01. The absorbance and reectance dened above may be measured at a wavelength X which varies from 10nm to 3000 um. In one aspect, most preferably 380 to 740 nm. In another aspect, more preferably from 10nm to 200 nm, most preferably from 13 nm to 193 nm. In another aspect, more preferably from 700nm to 2000 nm, most preferably from 850nm to 1550 nm. In another aspect, more preferably from 30 000nm to 3 000 000 nm. The optical elementmay be congured for reecting light incident on the second surface. In that case, the transmittance and reectance may be measured for light incident the second surface. Alternatively, the optical elementmay be congured for reecting light incident on the rst surface, in that case, the transmittance and reectance may be measured for light incident the rst surface. Besides using the cover for reection only or mainly, it is also possible to employ reective interference, taking place mainly between a reected lightbeam at the substrate (or cover) and a refracted lightbeam through the substrate (or the cover) that the cover (or substrate) reects, or absorbing interference, taking place mainly between a reected light bean with the incident lightbeam at the substrate (or cover) and its absorption at the cover (or substrate).An optical element congured for this purpose is called an interferometric optical device. The absorbance ofthe covermay accordingly also be relevant, as explained above. The interference may take place for light incident the second surface, or for light incident the rst surface. In the latter case, a substrate is needed below the cover, as is described further below. The substrate is congured for transmitting a part ofthe light and reecting a part ofthe light. The transmitted light is then reected on the cover, and transmitted back outthrough the surface. The egressing light interferes (constructively or destructively) with the directly reected light. Depending on the position ofthe cover with respect to the substrate, it is possible to change the interference-based behaviour ofthe optical element. Depending on the desired optical behaviour, it is ofcourse possible to use a cover with different ratios ofreectance, transmittance and absorbance, optionally in combination with e.g. a reective, transmissive or absorbing substrate, the terms reective, transmissive or absorbing being dened using the same ranges forthese respective quantities, and / orthe same ratios between them as is dened for the cover. In general, the optical properties for the substrate are chosen complimentary to the optical properties ofthe cover. using similar characteristics. The invention is not limited to any such combination, rather to inuencing the cover using the features described in the characterizing portions ofthe independent claims. Ofcourse, the substrate need not be square or rectangular. The substrates shape in general is not important, it is even possible for a single substrate to span multiple optical elements. More relevantmay be the shape dened within the support, as this denes the shape ofthe optical element in plan view. It is possible this shape is square or rectangular, to create a pixel-like element, but circular optical elements are also envisaged. The invention may howeverbe applied to optical elements ofall shapes. This is true for all embodiments described herein, whether they do or do not have a substrate. It is noted that for some shapes ofoptical elements, the substrate is rigid and planar, while for others it is possible for it to be exible and / or curved. In such cases, the spacer and cover are adapted to the substrate, in such away that the second surface ofthe cover is approximately parallel to the substrate. In this case, the cover is preferably reective, for instance as expressed in the ratio above. The substrate is not as reective, for example having a ratio oftransmittance divided by reectance ofmore 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 ofthe substrate facing away from cover. The opposite direction is also possible, where the cover transmits and reects light, and the substrate reects the transmitted light. In this case, the coverwould be relatively transmissive, for example having a ratio oftransmittance divided by reectance ofmore 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 reective for light incident a surface ofthe substrate facing the cover. The reectance could be dened by a ratio oftransmittance divided by reectance ofnotmore than 0.5, preferably notmore than 0.25, more preferably notmore than 0.1, most preferably notmore than 0.01. Unless stated otherwise, transmittance and reectance are measured for light normal to the surface ofthe cover. In case a cover is used that is relatively reective, a value ofabsorbance divided by reectance ofthe cover can be less than 0.5, preferably notmore than 0.25, more preferably not more than 0.1, most preferably notmore than 0.01, for light incident the rst and / or second surface, depending on the desired optical behaviour. It is noted that in all cases, the position and shape ofthe cover inuences how the optical device interacts with incident light. Other operational principles which rely on the change ofthe cover position and shape can however also be applied, and the current invention is thus not limited to either reective 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 ofclaim 1, this can be realized by dening the spatial arrangement ofthe 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 ofthe coverwith respect to the support. As such, depending on the use, changing the position ofthe cover (without changing its shape) or changing the shape ofthe cover, thereby changing partially its position, could be used interchangeably. The covermay comprise a 2-dimensional portion. The 2-dimensional portion may be an extreme membrane. For the purpose ofthe invention in general however, it is sufcient ifthe 2- dimensional portion is sufciently thin to be deformed and / ormoved 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 ofthe cover, which could be or could comprise a metal or an additive. In that regard, reference is made toWO 2021 / 032752 A1 which explains multiple congurations ofthe cover. The skilled person is readily able to vary e.g. the thickness and material ofthe additional material to arrive at desired optical properties for the cover. In that regard, it is noted the 2-dimensional portionmay function as a carrier, whereas the additional material provides desired optical properties. The 2-dimensional portionmay be as dened in embodiment [39a] ofWO 2021 / 032752 A1. Accordingly, the 2-dimensional portionmay be one ormore ofthe following: a. One ormore 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 ormore selected from the group consisting of: graphene, one ormore graphitic layers and graphyne, preferably graphene. The preferredBN in this context is h-BN. The preferred P in this context is black phosphorus or phosphorene. The preferredB 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 ormore transition metal chalcogenides, each being a transition metal chalcogenide not listed in a., c. One ormore oxides, each being an oxide ofa species listed in a. or b., d. One ormore atomic intercalated variants, each being an atomic intercalated variant ofa species listed in a. or b., e. One ormore physically, chemically, mechanically and / or electromagnetically functionalised derivatives, each being a chemically functionalised derivative ofa 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 ofa voltage. In one aspect ofthis 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.. Specically, the 2-dimensional portionmay comprise or be graphene orboron 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 ofthis embodiment, the 2-dimensional portion comprises graphene, preferably is graphene. In one aspect ofthis embodiment, the 2-dimensional portion comprises boron nitride, preferably is boron nitride. As mentioned earlier, the thickness ofthe 2-dimensional portion is relatively small. For instance, 1mm or less, preferably 10 um or less, more preferably 1000nm or less, more preferably 100nm or less, more preferably 50nm or less. In one aspect ofthis embodiment, more preferably 10nm or less, more preferably 5 nm or less, most preferably 1 nm or less. A minimum thickness may be dened as 25 pm or more, preferably 69pm or more, more preferably 100pm or more. In one aspect ofthis embodiment, the thickness is 1 nm ormore, preferably 3 nm or more, more preferably 5 nm or more, more preferably still 10nm or more. In another aspect ofthis embodiment, the thickness is 15 nm or more, preferably 20nm or more, more preferably 30nm or more. Accordingly, the 2-dimensional portionmay be relatively light per unit area, such as 24 kg / m2 or less, preferably 2.4-10l kg / m2 or less, more preferably 2.4-102 kg / m2 or less, more preferably 2.4-103 kg / m2 or less, most preferably 1.2- 103 kg / m2 or less.A lower limit on the same weight per unit area is 1.7-109kg / m2 or more, preferably 3.4-108kg / m2 or more, more preferably 1.8-107kg / m2 or more. In one aspect ofthis embodiment, the mean density is 5- 107kg / m2 or more, preferably 1.5-106kg / m2 or more, more preferably 5.4-106kg / m2 or more, more preferably 5.7-105 kg / m2 or more. Various operational principles for the means are available, and have been identied 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, whichmay be identical, may be applied on the opposite side ofthe cover, e.g. in amirrored position with respect to the previously mentioned means, so that collectively control can be exerted in both ormore directions. While above an optical element has been described that has means congured 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 ofthe cover changing from the rst cover contour prole to the further cover contour prole. 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. Ifa predetermined and externally applied electrical charge is applied to the cover, the electrodes could be used to measure deformation ofthe coverby capacitive means, for instance as a result ofincoming radiation or pressure. An electrode or other type ofsensing means would be necessary to measure the changing electric eld as the charged covermoves. In these circumstances, the element described herein need not be described as an optical element per se. 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 ofwhether or not the characterizing portion of the claims is applied. In this novel way ofusing the device, a substrate opposite the cover is necessary, so that a cavity is formed between the cover and the substrate. The device is congured to allow entry ofelectromagnetic radiation, such as (visible) light, into the cavity between the support and the substrate, and to allow egress ofthe 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 rst or second surface), the lightnow travel 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 covers rst surface and optionally for material to ll the cavity with, so thatwaves are inuenced by the cover. This inuence could for example result in a change in amplitude, phase or the state ofthe light. Suitably chosen characteristics, such as optical characteristics, ofthe cover allow interaction with light passing through the cavity. By changing the contour shape ofthe cover, orby changing its position, the waveguide formed in the cavity can be altered. The changing inuence ofthe 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 strainmay be altered for instilling different optical properties. The invention will be further elucidated with reference to the attached drawings, in which: Figures 1A, 1B and 1C show schematically interaction oflight with an optical element known in the state ofthe art, Figures 2A, 2B and 2C show schematically interference interaction oflight with an optical elementknown in the state ofthe art, Figures 3A, 3B, 3C and 3D show schematically changes in cover contour shape for a support that is expandable, Figures 4A and 4B show schematically a support comprising multiple portions that can be expanded in varying degrees, Figure 5 shows schematically changes in cover contour shape for a substrate that is expandable, Figures 6A and 6B show schematically changes in cover contour shape for a substrate comprising multiple parts that are expandable in varying degrees, Figure 7 shows schematically a device with a stack ofexpandable portions ofthe support, Figures 8 and 9 show schematically an optical element for different interferometric effects, and Figure 10 shows schematically in perspective view anotherway ofusing the optical element. Figure 1A shows interaction oflight with ofa at cover 101, which is supported by supports 104. The parallel rays 601 and 602 are both deected by the same angle and remain parallel after interaction with the cover 101. This constitutes specular reection. Figure 1B shows interaction oflight with a convex cover. Due to the rounded convex cover contour prole, a rst ray 601 is deected by almost 180° and the second ray 602 is only deected by a small angle. The rays 601 and 602 are no longer parallel after reection at the cover. This constitutes diffuse reection. Figure 1C shows interaction oflight with a concave cover. Due to the rounded concave cover contour prole, a rst ray 601 is deected by an angle less than 90° and the second ray 602 is deected by almost 180°. The rays 601 and 602 are no longer parallel after reection at the cover. This constitutes diffuse reection. Figure 2A shows interference interaction with a at cover. Aside from the supports 104, a substrate 106 is also present in this example ofthe state ofthe art, which lies on the bottom ofthe optical element. The support 104, cover 101 and substrate 106 dene a cavity having a depth 205. The substrate 106 is transmissive and absorbing to an extent and the cover 101 is reective, such that an incoming ray 601 undergoes interference which is dependent on the depth 205. Figure 2B shows interference interaction with a convex cover. The cover 101 ofthe optical element ofgure 12 has been deformed into a convex shape (cover contour prole). This was brought aboutby ameans pushing the cover 101 upwards. This increases the depth 205 and the interference behaviour ofincoming light 601 is altered. Figure 2C shows interference interaction with a concave cover. The cover 101 ofthe optical element ofgure 12 has been deformed into a concave shape (cover contour prole). This was brought aboutby the means pushing the cover 101 downwards. This decreases the depth 205 and the interference behaviour ofincoming light 601 is altered. Now rst referring to gures 8 and 9, it is noted that depending on the optical properties of the cover 101 and the substrate 106, different operational principles are also usable for inuencing incident light. Figure 8 for instance, shows an optical element similar to that ofgures 1 and 2, but with a cover 101 that is relatively absorbing, and a substrate 106 that that is relatively reective. As a result, incident light 601 transmitted 602 through the cover 101 interacts with light reected 604 from the substrate to form a pattern ofnodes 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 ofexiting light 605 can be controlled. In gure 9 a cover 101 is present that is both transmissive and reective, and a substrate that is reective. Accordingly, use can be made ofinterferometric reection, similar to gures 2A 2C, however now the optical element is congured for light incident the cover 101. Otherwise, the optical elementmay be identical to that described above. Figures 3A 3D show an optical element 99 with support 4 and a cover 1. The cover 1 exhibiting a rst cover contourprole is shown in solid lines, whilst a further cover contour prole is shown in dotted lines. In this further prole, the covermay be deformed and / or displaced. The support 4 in each case is expandable. The cover 1 has a rst surface and a second surface.A means is also present, but not shown. The cover 1 is orientated with the rst surface directed towards the support 4, a part ofthe rst surface is attached to the support 4, a spatial arrangement ofthe cover 1 as seen in a cross section ofthe cover denes a cover contour prole, the means is arranged to move the cover from a rst cover contour prole to a further cover contour prole which is different from the rst cover contour prole, and / orthe means is arranged to provide an output that is representative ofthe cover changing from the rst cover contour prole to the further cover contour prole. In gure 3A, it can be seen how expanding the support 4 on both sides equally, results in higher supports 4awith an elevated cover 1a. Figure 3B shows that it is also possible to operate the means (not shown) simultaneously, to create a constructive effect (gure 3B) or a counteractive effect (gure 3C). In gure 3D, only a part ofthe support 4 has been expanded, to create an asymmetric cover shape. The example device shown in gures 4A and 4B differs from that in gure 3 in thatthe support 4 comprises an expandable portion 18a. The rest ofthe support 4 may not be expandable in this case. In gure 4B it can be seen how the cover 1 can be moved from its initial position (gure 4A, or gure 4B dashed lines), to a higher position (gure 4B, solid lines) ifthe expandable portion 18a is expanded. It is noted that the expandable portion 18a shown here may be placed anywhere in the support, such as at the top or bottom. For this reason, the expandable portion 18 has been shown on the left ofgure 4B on the bottom, whereas it has been drawn on top in the right. Figure 5 shows the alternative solution also presented herein. In this case, protrusions 6a are provided as part ofa substrate 6. Due to the protrusions, a distance between a plane spanning the support 4, here shown as the at cover 1 in solid lines, and the substrate 6 including the protrusions 6a locally varies. Accordingly, said local distance may be kept relatively constant ifthe cover is pulled towards the substrate 6 as is shown in dashed lines. As shown in gures 6A and 6B, the substrate 6may be locally expandable. This may or may not include the earlier mentioned protrusions 6a. In any case, the substrate 6 can be expanded locally, as shown in gure 6A, in this example by expanding the protrusions 6a. The bent-down shape ofthe cover in gure 6A is accommodated forby the resulting shape ofthe substrate 6 with its protrusions 6a. In an unexpanded state ofthe substrate 6, here shown in gure 6B with unexpanded protrusions 6b, the surface ofthe substrate 6 with its protrusions 6b is substantially at to accommodate a substantially at cover 1. To facilitate control ofthe expansion locally, means 7 are provided. In this case, the means 7 comprise several separate means that affect different parts ofthe substrate 6 and support 4 differently due to their location in relation to the substrate 6 and support 4. Figure 7 shows an example device similar to that ofgure 4A. Only differences are described herein. Instead ofa single expandable portion 18, the support 4 now comprises two expandable portions 18, 19, although even more could be used. As such, a stack ofexpandable portions 18, 19 could be part of, or could form the entire support 4. It is noted that the expandable portions 18, 19 can differ in nature, type or size, to have mutually different characteristics.A more versatile device may be obtained as such. Finally, reference is made to gure 10, which shows a perspective view ofa 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 denes 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 covers rst surface and material with which the cavity C is lled are chosen so that the cavity C acts as a waveguide. Incidentwaves 601, such as light, can therefore pass through from one side to another, and egress as exited light 602. Viameans 107, in this case presented on top ofthe support 104, although not strictly necessary, the cover 101 can be moved, or its cover contour prole changed. As a result, the cover 101 at least locally inuences the light passing through the cavity C in order to modulate it. It is noted thatterms like preferably, generally and typically are not utilized herein to limit the scope ofthe claims or to imply that certain features are critical, essential, or even important to the structure or function ofthe claims. Rather, these terms are merely intended to highlight alternative or additional features thatmay ormay not be utilized in a particular embodiment ofthe present disclosure. Likewise, forthe purposes ofdescribing and dening the present disclosure, it is noted that the terms substantially and approximately and their variants tilized herein to represent the inherent degree ofuncertainty thatmay be attributed to any itative comparison, value, measurement or other representation, as well as to represent the ee by which a quantitative representationmay vary without resulting in a change in the basic tion ofthe subject matter at issue. While certain representative embodiments and details have been shown forpurposes of trating the present disclosure, it will be apparent to those skilled in the art that various changes be made without departing from the scope ofthe disclosure, which is dened in the appended s.

Claims

1. Optical element comprising: a. a covering with a first and a second surface, b. a support, and c. a means; whereby: - the cover is oriented with the first surface facing the support; - a part of the first surface is attached to the support; - a spatial arrangement of the deck considered in a cross-section of the cover defines a cover contour profile; - the device is designed to move the cover from a first cover contour profile to a further cover contour profile that differs from the first covering contour profile, and / or the device is designed to provide an output that is representative of changing the cover of the first cover contour profile to the further cover contour profile; with the characteristic that the support is expandable.

2. Optical element according to the previous conclusion, where the support is expandable in a direction that is essentially perpendicular to the cover.

3. Optical element according to one of the preceding claims, where the support is a includes expandable material.

4. Optical element according to the previous conclusion, where the expandable material is expandable through the application of electricity, such as a piezoelectric material, like PZT or a material that has spin-crossover particles.

5. Optical element in accordance with one of the preceding claims, where the support is local is expandable.

6. Optical element in accordance with one of the preceding claims, where the support consists exclusively of expandable material exists, or where the support is an expandable part and a includes non-expandable part.

7. Optical element according to one of the preceding claims, further comprising a further means, whereby the further means is designed to expand the support.

8. Optical element according to the previous claim, whereby the further ground of appeal has at least one includes a voltage and / or current source.

9. Optical element pursuant to one of the preceding claims, further comprising a substrate on one side of the support opposite the cover, where the cover, substrate and support a define cavity.

10. Optical element according to the previous conclusion, where the substrate is at least locally is expandable.

11. Optical element according to the previous conclusion, whereby the further remedy is structured is to expand the substrate.

12. Optical element according to the previous conclusion, whereby the further remedy is structured to to expand different parts of the substrate and possibly the support to varying degrees.

13. Optical element comprising: a. a covering with a first and a second surface, b. a support, and c. a means; whereby: - the cover is oriented with the first surface facing the support; - a part of the first surface is attached to the support; - a spatial arrangement of the deck considered in a cross-section of the cover defines a cover contour profile; - the device is designed to move the cover from a first cover contour profile to a further cover contour profile that differs from the first covering contour profile, and / or the device is designed to provide an output that is representative of changing the cover of the first cover contour profile to the further cover contour profile; where the optical element further forms a substrate on one side of the support opposite the cover includes, where the cover, substrate, and support define a cavity, with the characteristic that a distance defined from the substrate to a plane extending over the support on one side of the cover varies locally.

14. Optical element according to the previous claim, where the substrate is at least locally is expandable.

15. Optical element according to the previous claim, comprising a further remedy, arranged is to expand the substrate.

16. Optical element according to the previous conclusion, whereby the further remedy is structured to to expand different parts of the substrate to varying degrees.

17. Optical element according to one of claims 13–16, where one or more of: - the support is expandable; - the support is expandable in a direction substantially perpendicular to the cover stands; - where the support comprises an expandable material; - the expandable material contains a piezoelectric material; - the support consists exclusively of expandable material, or where the support is a comprises an expandable part and a non-expandable part; and - the optical element according to claim 15 is, and the remainder of the plea further is designed to expand the support, whereby the further means, if applicable, at least one includes voltage source 18. Procedure for operating an optical element in accordance with one of claims 15 – 17, the method comprising operating the further means in such a way to the various to expand parts of the substrate in accordance with the covering contour profile.

19. Method of operation according to the previous conclusion, whereby operation is performed on the basis of combined optical properties of the substrate and a support between the cover and the substrate.

20. Use of an optical element pursuant to one of claims 1–17 for image formation with screens, spatial light modulators, optical systems and / or photonic integrated circuits

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