FR2863060A1 - Liquid crystal modulator incorporating an alternance of layers of polymerized material and liquid crystal material, notably for use as a polarizer - Google Patents

Abstract

A liquid crystal modulator incorporates at least one alternance of layers of polymerized material (2.0 to 2.n+1) and layers of liquid crystal material (1.0 to 1.n). Each layer of liquid crystal material is enclosed between two layers of polymerized material of which the surfaces in contact with the liquid crystal have a molecular structure oriented along a direction. Some wedges (4.00, 4.01) are distributed in the liquid crystal layer between the layers of polymerized material. The liquid crystal material has an index of ordinary refraction (n0) and an index of extraordinary refraction (ne) and the polymerized material has an index of refraction (n) with a value essentially equal to that of the index of ordinary refraction or the index of extraordinary refraction of the liquid crystal material. An independent claim is also included for the fabrication of this liquid crystal modulator.

Description

I

  The invention relates to a liquid crystal modulator and in particular a modulator having a non-rigid structure and therefore capable of deforming without substantially altering its operation, its manufacturing method, and its application to a polarizer.

  The well known technique of liquid crystal modulators consists in providing a layer of liquid crystal sandwiched between two glass slides with control electrodes arranged on the faces of the glass slides in contact with the liquid crystal. The thickness of the space between the two glass slides and containing the liquid crystal is a few micrometers or even a few tens of micrometers. A disadvantage of this technique is that the modulator only works in polarized light, polarizers are glued on the input and output faces. The incident light transmission generally unpolarized can not be greater than 50%.

  In addition, in order for the modulation by the liquid crystal layer to be effective over a broad spectrum (visible for example) and in a sufficient angular field (+ or - 45 for example), relatively complex special arrangements must be provided (use color filters, spiral liquid crystal alignment, rigorous thickness control, polarization compensating film ...).

  The invention provides a liquid crystal modulator and its manufacturing method that avoids these types of disadvantages.

  The invention therefore relates to a liquid crystal modulator comprising at least one alternating layers of polymerized material and layers of liquid crystal material. Each layer of liquid crystal material is sandwiched between two layers of polymerized material whose faces in contact with the liquid crystal have a molecular structure oriented in one direction. The alternating layer assembly is comprised between at least two control electrodes. The liquid crystal material has an ordinary refractive index n0 and an extraordinary refractive index ne, and the polymerized material has a refractive index of a value substantially equal to that of the ordinary refractive index or the extraordinary refractive index of the refractive index. liquid crystal material. Such a modulator advantageously comprises shims located in the layers of liquid crystal material between the layers of polymerized material.

  In addition, at least two control electrodes are arranged on either side of the alternation of layers.

  It is also possible to provide openings located in the layers of polymerized material and placing in communication the layers of liquid crystal material.

  According to an alternative embodiment of the invention, the modulator comprises a first layer alternation in which the faces of the layers of polymerized material in contact with a liquid crystal layer have a molecular structure oriented in a first direction. It also comprises a second alternation of layers in which the faces of the layers of polymerized material in contact with a liquid crystal layer have a molecular structure oriented in a second direction orthogonal to the first direction. The two alternations of layers are sandwiched between said electrodes.

  It is also possible to provide a plurality of alternations of layers, each alternating layers for modulating a particular range of wavelengths.

  The invention also relates to a method of manufacturing a liquid crystal modulator according to the invention. This method comprises the following steps: a) deposition of a volume of monomeric material on a face of a plate bearing at least a first electrode, b) polymerization in the volume of a monomeric material of several distinct layers, to obtain several layers of polymerised material of equivalent and regularly spaced optical thicknesses, c) drilling at least one hole through said layers of polymerised material, d) removing uncured material between said layers of polymerised material, e) filling spaces left free at the end of the preceding step between the layers of polymerized material using a liquid crystal material, f) closing said hole with a transparent plate or film carrying at least a second electrode which is applied against the upper face of the stack of layers.

  The polymerization step is advantageously carried out by a two-photon interaction method using a focused light beam and by shifting the focal point of the beam within the monomer volume.

  It may also be provided before the step of producing the hole, a polymerization step shims thick between the layers of polymerized material.

  The step of removing the unpolymerized monomer material may be made using a solvent liquid specific for this monomer.

  The step of producing said hole may be made by drilling with the aid of a laser beam.

  According to a variant of the manufacturing method according to the invention, the polymerization step b) is done by holography using two light beams interfering in a layer of photosensitive monomeric material.

  Another variant of the method for manufacturing a modulator according to the invention provides the following steps: a) deposits, on a face of a plate carrying a first electrode, of a volume of monomer material, of alternating layers of monomers of a first type and a second type, each layer deposition being immediately followed by a polymerization of the layer and then a treatment of orientation of the surface of the polymerized layer, by friction or other means, to obtain several layers of polymerized material of a first type and a second type, b) drilling at least one hole through said layers of polymerized material, c) removal of the polymerized material of the second type located between the layers of polymerized material of the first type, d) filling the spaces left free at the end of the preceding step between the layers of material polymerized with a liquid crystal material, e) closing said hole, by a plate or a transparent film carrying at least a second electrode which is applied against the upper face of the stack of layers.

  According to another variant of the method of the invention, the realization of a stack of a first type and a second type of alternating layer of two different materials is done by producing a stack of layers of overall thickness of several hundred micrometers, then by extrusion of this stack to obtain a stack of thinned layers.

  The invention also relates to a liquid crystal modulator comprising at least one layer of liquid crystal material sandwiched between two layers of polymerized material, shims being distributed in the liquid crystal layer between the layers of polymerized material, and the at least one layer of polymerized material having holes having made it possible to fill the space between the two layers of polymerized material in liquid crystal.

  The invention also relates to an application to a modulator comprising at least one alternation of layers of polymerized material and liquid crystal material as described above.

  The various objects and characteristics of the invention will appear more clearly in the description which follows and in the appended figures which represent: FIGS. 1a to 1f, an embodiment of the liquid crystal modulator according to the invention, FIG. 2, an exemplary embodiment of the liquid crystal modulator according to the invention for modulating a non-polarized light, - Figures 3a and 3b, various means of encapsulation of the modulator according to the invention, - Figures 4a to 4d, different Other embodiments of the modulator according to the invention, - Figure 5, a system for manufacturing the modulator of the invention, - Figures 6a to 6g, different steps of a method of manufacturing a modulator according to 7a to 7d, a variant of the manufacturing method according to the invention - FIGS. 8a to 8c and FIG. 9, another variant of the manufacturing method according to the invention.

  Referring to FIG. 1, a simplified exemplary embodiment of a liquid crystal light spatial modulator according to the invention will first be described.

  This modulator comprises alternating layers of polymerized material and layers of liquid crystal material. Thus, the example of FIG. 1 represents layers of polymerized material 2.0, 2.1, 2.2, 2.n, 2.n + 1 alternated with layers of liquid crystal material 1. 0, 1.1, l.n. Each layer of liquid crystal material is sandwiched between two layers of polymerized material. The outer layers of polymerized material 2.0 and 2.n + 1 carry electrodes 3.0 and 3.1. These electrodes make it possible to apply one (or more) electric fields to the whole structure.

  The faces of the layers of polymerized material in contact with a liquid crystal layer, such as 2.0.1 and 2.1.0 for the layers 2.0 and 2.1, have been treated so as to orient their molecular structure in a direction such that the molecules of the liquid crystal in contact with these faces are oriented in this direction. The different faces 2.0.1 and 2.1.0 are treated in the same way. Thus, in the absence of an electric field applied to the structure, the liquid crystal molecules of the different layers 1.0 to 1n are oriented in the same direction.

  A light beam F thus sees layers of liquid crystal all having the same index, for example an ordinary index "nO" in the case where a maximum voltage is applied, or an extra-ordinary index "n" in the case where no electrical voltage is applied.

  Moreover, the polymerized material of the layers 2.0 to 2.n + 1 was chosen to have a refractive index substantially equal to the ordinary index or the extraordinary index of the liquid crystal layers 1.0 to 1.n.

  For example, if the polymerized material has an index substantially equal to the ordinary index "nO" of the liquid crystal, when an electric field of a sufficient value is applied to the structure by applying a potential difference to the electrodes 3.0 and 3.1, a light beam F incident on one of the main faces of the structure, will see a stack of layers all of the same index. The light will pass through the stack of layers without being substantially disturbed.

  On the other hand, if no electric field is applied to the structure, the molecules of the liquid crystal retain their original orientation. The index of the liquid crystal then has a value equal to the extraordinary index "ne". The structure will be in the form of alternating layers of different indices "nO" and "ne" and it will behave like a dielectric mirror for at least one polarization of light. The corresponding light of the beam F will be reflected successively by the stack of layers E, as shown schematically in Figure 1c, in the form of the beam FR.

  The operation of such a mirror is described on the theoretical level by the formalism of Abeles. The structure is assumed to consist of a quarter-wave thin film stack at an operating wavelength λ 0. As shown in FIG. 1f, each layer of polymerized material is characterized by a thickness d1 and an index n0 such that dl.n0 = (2k + 1) Xo / 4 and each liquid crystal layer is characterized by a thickness d2 and by an index such as d2.ne = (2k + 1) Ao / 4. The integer k corresponds to the order of the quarter-wave layers.

  The reflection coefficient R of such a dielectric mirror is expressed as a function of the indices n0, ne and of the number N of layer periods, that is to say the number of pairs of layers of polymerized material and layers of liquid crystal material. . We have: R = [(l - (n0 / ne) 2N) / (1 + (n0 / ne) 2N)] 2 The table below gives some examples of values of this reflection coefficient R as a function of the number of N periods of the structure with indices n0 = 1.5 and n = 1.7, and the corresponding total thicknesses d.

  % In A = 636 nm 31 58 72 91 97 99 d (order 0) in pm 1 2 2 3 4 5 d (order 1) in pm 3 5 6 8 11 14 The thicknesses d 1 and d2 respectively layers of polymerized material and layers of liquid crystal material and the thickness d of the entire structure depend on the nominal wavelength 1 \ o of operation to form a stack of quarter wave blades . The table below gives the thicknesses of a structure as a function of the nominal wavelength Xo for N = 20 periods with the same index values (n0 = 1.5 and n = 1.7) as before, to obtain a reflection coefficient R of 97%.

  Wavelength Ao in nm 450 500 550 600 670 dl (order 0) in nm 75 83 92 100 112 dl (order 1) in nm 66 74 81 88 98 Total thickness d in pm 3 3 3 4 4 Spectral width n ( nm) 47 53 59 64 72 Angular field oe () 65 65 65 65 65 dl (order 0) in nm 225 250 275 300 335 dl (order 1) in nm 199 221 243 265 295 Total thickness d in pm 8 9 10 11 12 Spectral Width AA (nm) 15 17 19 21 24 Angular field e () 35 35 35 35 35 35 It emerges that in order to reflect light at one of these wavelengths with a reflection coefficient of substantially 97%, the total thickness d of the structure should be 3 to 4 micrometers. But this can be difficult to achieve because the thickness of each layer must be less than one hundred nanometers. On the other hand, the structure in the order 1 is easier to achieve with layers of thickness 200 to 300 nanometers and a total thickness d of 10 micrometers.

  Moreover, it is shown that the spectral width AA of a stack of layers is substantially proportional to 1 / (2k + 1). It is therefore not necessary to use structures with an order that is too high to maintain a sufficient spectral width. Thus, referring to the table above, it is found that it is necessary to stack five structures of order 0 period (LÀ50nm) or fifteen structures of order 1 (LA-20nm) to obtain substantially the same result.

  In addition, the angular aperture of such a structure also depends on the order of the layers of the structure. The table below gives indications on the evolution of the angular opening LO at mid-height as a function of the order k.

  Order k 0 1 2 3 Angular aperture 32 17 13 11 00 in degrees It is concluded that a periodic multi-layer layer liquid crystal-polymer at order 1 with elementary layers of 200 to 300 nanometers thick and consisting of 15 stacks of 10 micrometers each allow to modulate the intensity and color of a polarized light beam with an efficiency of about 97%. The total angular field (2L0) is about 35.

  As will be seen with reference to FIG. 2, to modulate an unpolarized light, it is necessary to double the structure and it is necessary, under the same conditions, a structure comprising 30 stacks of layers.

  As can be seen in FIG. 1a, the liquid crystal layers comprise shims 4.00 to 4.nl located between the different layers of polymerized material. Preferably, these shims are made of the same material as the layers of polymerized material.

  Also, it can be seen in Fig. 1a that holes 5.0 to 5.n through the layers of polymerized material and communicate the liquid crystal layers therebetween. These holes are not mandatory but they may be useful in the context of manufacturing as will be described later in the description of a manufacturing method of the modulator according to the invention.

  Figure 1d shows an enlarged view of a portion of the layers. The thicknesses d1 and d2 of the polymerized material and liquid crystal layers will, as previously described, preferably be between 0.2 and 0.5 micrometers.

  Figure lb shows an enlarged view of a shim. By way of example, the width L1 of such a wedge will be about one micrometer.

  Figure ic represents an enlarged view of a communication hole between two liquid crystal layers. The width L2 of such a hole may be, for example, a micrometer.

  If we consider that the dielectric constant Ep of the polymerized material has the value Ep = 2 and that the dielectric constant EXL of the liquid crystal material has the value EXL = 5, the impedance ZXL of a liquid crystal layer measured according to FIG. thickness of the layer will be two and a half times lower than the impedance Zp of a layer of polymerized material assuming that these layers are of the same thicknesses.

  Furthermore, assuming that the switching threshold voltage VXL of the liquid crystal is 1.5 volts, the voltage required for the switching of a stack of n liquid crystal layers will be: Vo = n VXL (ZXL + Zp ) / ZXL For layers of liquid crystal and polymerized material of substantially equivalent thicknesses, this relation can be written: ## EQU1 ## For a structure having a number n = 10 of layers Therefore, for the above examples of dielectric constant and threshold voltage values VxL, it will be necessary to have a voltage Vo to be applied to the electrodes 3. 0 and 3.1 of about VO = 52.5 volts. It can thus be seen that the modulator will operate easily under the control of a voltage of a hundred volts. To reduce this control voltage, it is possible to interdigitate several pairs of electrodes (3.0, 3.1) as will be described in connection with Figure 4d.

  Figure 2 shows a structure for modulating unpolarized light. In this figure, there are two stacks of EO and El layers each similar to the stack of layers of Figure la. The electrodes 3.0 and 3.1 are located on either side of the two stacks of layers. The layer 20.n + 1 is common to both stacks of layers.

  In the stack E0, the faces of the layers of polymerized material 20.0 to 20.n + 1 in contact with the liquid crystal layers 10.0 to 10.sub.n have been treated so that their molecular structure is oriented in a first direction. determined as previously described.

  On the other hand, in the stack E1, the faces of the layers of polymerized material 20.n + 1 to 21.n + 1 in contact with the liquid crystal layers 11.0 to 11n have been treated in such a way that their structure molecular is oriented in a second determined direction perpendicular to the first direction. Such a structure thus makes it possible to modulate the two polarizations of a non-polarized light beam.

  According to one embodiment of the invention shown in FIG. 3a, the stack of layers of FIG. 1 or the stacks of layers of FIG. 2 are sandwiched between two supports 6.0 and 6.1. These supports can be rigid or semi-rigid. The electrodes 3.0 and 3.1 are preferably located between these supports and the stack or the stacks of layers.

  FIG. 3b shows an embodiment in which the stack of layers E is made on a support plate 6. An encapsulation membrane 7 covers the assembly. The electrodes 3.0 and 3.1 are also preferably situated, on the one hand, between the support plate 6 and the stack E and, on the other hand, between the membrane 7 and the stack E. The supports 6.0, 6.1 and the support plate 6 can be made of glass or plastic depending on the application that is being considered. The encapsulation film 7 may be a plastic film.

  FIG. 4a represents an embodiment of the invention in which the modulator makes it possible to modulate an unpolarized light in a wide range of wavelengths. It comprises a first ECO stack for modulating the polarized light in a first direction. This stack itself comprises several stacks of layers E0.1d_, EO.A2, E0.3 each capable of modulating a particular range of wavelengths. They are designed so that they can modulate, for example, the light of the visible spectrum. A second stack EC1 makes it possible to modulate the polarized light in a second direction perpendicular to the first direction. This stack also includes several stacks E1. A1, E1. X2, E1.2 \ .3 for modulating different ranges of wavelengths. Preferably, the ECO stack is of identical structure or almost identical to the structure of the stack EC1 with the exception of the orientation of the faces of the layers of polymerized material which are in contact with the liquid crystal layers, these orientations being perpendicular from an ECO stack to a stack EC1.

  FIG. 4b represents an embodiment variant in which each stack of layers making it possible to modulate a range of wavelengths such that EO.A1 is sandwiched between two electrodes such as 3.00 and 3.01 and is controlled by these electrodes. We can therefore independently modulate each range of wavelengths and each polarization.

  FIG. 4c represents an alternative embodiment comprising three stacks E.X1, E.2 \ 2 and E.X3 each making it possible to modulate a range of wavelengths of unpolarized light. Each of these stacks comprises two stacks such as EO.X1 and E1.X1 for E.X1. These two stacks are of almost identical characteristics to be able to modulate the same wavelengths; they differ only in their orientations so that each of them modulates a polarization of light. In FIG. 4c, if the electrodes 3.01, 3.03 and 3.05 are not used, control of the other electrodes will allow color modulation on unpolarized light.

  FIG. 4d shows an embodiment in which interdigitated electrodes 3.e0 and 3.el have been provided for controlling the structure with smaller voltages.

  Referring to FIGS. 5 and 6a to 6f, an embodiment of a modulator according to the invention will now be described.

  A monomer M is deposited on a plane P of a support piece 60. Advantageously, this plane P has been previously covered or provided with at least one transparent conductive layer corresponding to the electrode 3.0 of FIGS. 1a and 2. known in the art this conductive layer is made of ITO.

  An illumination system S makes it possible to focus a light beam F1 in the thickness of the monomer layer M. It is known to make a photo inscription of a point zone inside a volume of a photo-polymerizable material without changing the surrounding matter. For this purpose, a two-photon photo-polymerization type nonlinear interaction is used as described in the following document, Stephen M. Kuebler et al., Journal of Photochemistry, "Design and Application of High-sensitivity Two-photon Initiators for Threedimensional Microfabrication". and Photobiology A: Chemistry, Volume 158, Issues 2-3, June 2, 2003, Pages 163-170.

  According to this document, the material to be treated is a monomeric material in the liquid or quasi-liquid phase. The composition of this material is known from the state of the art (for example, Novel nonlinear optical organic materials: Dithienylethylenes, B.Sahraoui, IVKityk, I.Fuks, B.Paci, P.Baldeck, J.-M Nunzi, P.Frere, and J. Roncali, PP 6179-6184, The Journal of Chemical Physics, V 115, No. 13, October 2001).

  The invention applies this technique to polymerize the layers of material in the volume of monomeric material.

  Preferably, the light beam is a beam at the wavelength of the visible or near infrared. It is transmitted in the form of very short pulses (a few tens of femtoseconds), the duration of which is, for example, 150 femtoseconds, with an average power of 1.5W at a wavelength of 800 nm, a repetition rate of 1 to 5 kHz, a peak power of the order of 10GW. Under these conditions, as described in the aforementioned document, the treated material is the seat, at the focusing point of the light beam, of a two-photon interaction corresponding to the appearance of photons of wavelength divided by two (2 IR photons at 800nm equivalent to one photon at 400nm). The two-photon interaction thus produces a polymerization of the monomer material at the point of focus of the beam. It turns out that the polymerized zone is well defined in the volume. When a zone has been polymerized, the focus point of the beam F1 in the monomer material is shifted to polymerize a neighboring point situated in the same plane and so on until an entire plane of the monomer has been polymerized.

  Since the diameter of a focusing point is of the order of a few tenths of a micrometer and two to three times more for its length, several juxtaposed planes can be polymerized so as to obtain a first layer of polymerized material such as layer 2.0. of Figure 1.

  Then, by moving the monomer volume in a direction parallel to the direction of the beam F1, polymerized areas limited to the dimensions of the shims 4.00 and 4.01 according to the same technique.

  Then, the polymerization of several juxtaposed planes is carried out again so as to obtain a next layer, 2.1 for example, of polymerized material, and so on.

  The structure shown in FIG. 6a is thus obtained with polymerized zones represented in hatching and unpolymerized zones represented in dashed lines.

  In a second step, shown in FIG. 6b, holes are made in the structure such as the hole 5 which makes it possible to place all the uncured zones in communication with the outside of the structure. These holes can also be made during the first step.

  In a third step shown in FIG. 6c, the hole thus formed is used to remove the unpolymerized material using a suitable solvent.

  In a fourth step shown in Figure 6d, is filled through the hole 5, the structure that has been emptied of the unpolymerized material. It should be noted that, according to a known technique, the third and fourth steps are performed in the same chamber and are successively by circulation of a solvent in the chamber followed immediately by the circulation of a liquid crystal. According to another variant and according to the nature of the solvent and the liquid crystal, it is also possible, as is also known, to perform these two steps in one by providing for circulation in the chamber of a mixture evolving from the solvent to the liquid crystal.

  During a fifth step shown in FIG. 6e, the hole 5 is closed using, for example, a polymer material.

  During a sixth step, at least one control electrode 3.1 is produced on the upper face of the stack of layers (FIG. 6f).

  According to an alternative embodiment, the fifth and sixth preceding steps can be replaced by a step in which is applied to the upper face fl of the structure of Figure 6d, a transparent plate 6.1 carrying an electrode 3.1 which thus closes the hole 5. The electrode 3.1 will cooperate with the electrode 3.0 to apply an electric field to the structure.

  Instead of applying a plate 6.1 it is also possible to apply a transparent film 7 carrying an electrode 3.1 to obtain the embodiment shown in FIG. 3b.

  Finally, a treatment step will advantageously be provided for orienting the molecular structures of the faces of the layers of polymerized material that are in contact with a liquid crystal layer. This step can be done using a spot such as f1 (Figure 5) or a flat light beam that is moved on each surface to be treated. To achieve a structure for modulating a non-polarized light, such as the structure of Figure 2, the displacement of the light beam will be in a first direction for the faces of a portion of the polymerized material layers and in a second perpendicular direction in the first direction for the other layers of polymerized material of the structure.

  Referring to Figures 7a to 7d, a variant of the manufacturing method according to the invention will be described.

  The step of producing a stack of layers of polymerized material and unpolymerized material is done by holography by interfering two light beams H1 and H2 in a layer of uncured material (see Figure 7a). P0.1 to p0.n + 1 layers of polymerized material and layers p1.1 to pl.n of unpolymerized material are thus obtained. Then, the shims such as 4.00 and 4.01 are made (FIG. 6b) either by laser irradiation or also by direct exposure through a mask delimiting the edges of the shims.

  Then, the second and third steps of making an access such as 5 in the stack of layers and extracting, through this access, the unpolymerized material of the layers pl.l to pl.n (FIG. 7c) are carried out.

  The spaces thus free are then filled with liquid crystal material (FIG. 7d). The rest of the process proceeds as described above.

  Figures 8a to 8c show a variant of the method according to the invention.

  On a support plate 6.0 carrying an electrode 3.0, a first monomer layer of a first type is produced which is polymerized and the upper surface of which is treated by friction in order to orient the surface. A second monomer layer of a second type is then produced which is polymerized and the upper surface of which is also treated by friction. In the same way, alternating layers of polymer of a first type and layers of polymer of a second type are produced. Thus, as shown in FIG. 8a, a stack of layers 2.0, 2.1, etc. is obtained. alternate with layers 1.0, 1.1, etc. Then, holes are drilled perpendicularly to the plane of the structure which are filled with a monomer material of the first type and which is polymerized. This gives elements such as 4.0 and 4.1 (Figure 8b) that will serve as wedges for the structure.

  Then holes are drilled such that the hole 5 (Figure 8c) to access all the polymer layers of the second type. By these accesses is carried out, using a solvent, the dissolution of the polymer of the second type and its replacement with liquid crystal. The process then continues as previously described.

  As is shown in FIG. 8c, a stack of layers 2.0 to 2.n + 1 of a polymer material of the first type alternating with layers 1.0 to 1.n of a liquid crystal material is obtained.

  According to a variant of this embodiment method, the stack of layers 2.0 to 2.n + 1 and 1.0 to ln of FIG. 8c can be made in the form of a stack of relatively thick layers D1 several hundred micrometers thick. thickness for example to provide a stack of layers D2 of a few tens of micrometers thick. This operation can be carried out by extrusion of the structure of FIG. 8b between two rolls R1 and R2 as shown in FIG. 9. The replacement of the type 2 polymer with liquid crystal is as before.

  The modulator of the invention has very thin liquid crystal layers which gives it the advantage of being very insensitive to the angle of incidence of the light beam to be modulated. In addition, the fact that the liquid crystal layers are thin allows for rapid switching of the device.

  Moreover, by providing, as shown in FIG. 2, at least two stacks of layers whose faces of the layers of polymerized material have been oriented in two orthogonal directions, the modulator of the invention makes it possible to modulate unpolarized light. without the need for polarizers. Under these conditions, the modulator according to the invention does not absorb light and is therefore not subject to heating which allows it to modulate significant optical powers. This particularity is especially interesting for the UV spectral band (350-400nm) where it is very difficult to find effective polarizing films.

  The invention is applicable to the production of a polarizer. Such a polarizer comprises at least one stack of layers as shown in FIG. It does not necessarily then need to provide the electrodes 3.0, 3.1 of Figure la, unless it is desired to achieve an electrically controllable polarizer. It is also possible, similarly to the structures shown in Figures la to 1c, to provide several stacks of layers to polarize the light of several wavelength ranges. In this case also, the control electrodes are not necessarily necessary unless one wants to achieve an electrically controllable polarizer.

  The invention is applicable in the production of: - active glass electro-optical modulators for controlling the flow and / or color of a UV, visible or infrared non-polarized light beam.

  - large display system (image walls) - electronic paper - luminous flux projectors - high efficiency polarizer

Claims (14)

  1. Liquid crystal modulator characterized in that it comprises at least one alternating layers of polymerized material (2.0 to 2.n + 1) and layers of liquid crystal material (1.0 to 1.n), each layer of material liquid crystal being sandwiched between two layers of polymerized material whose faces in contact with the liquid crystal have a molecular structure oriented in one direction, shims (4.00, 4.01) being distributed in the liquid crystal layer between the layers of polymerized material, the liquid crystal material having an ordinary refractive index n0 and an extraordinary refractive index ne, and the polymerized material having a refractive index (n) of a value substantially equal to that of the ordinary refractive index or the refractive index. extraordinary refractive index of the liquid crystal material.   2. Liquid crystal modulator according to claim 1, characterized in that it comprises at least two control electrodes (3.0, 3.1) disposed on either side of the alternation of layers.   3. Liquid crystal modulator according to claim 1, characterized in that it comprises communication ports (5.0, 5.n) located in the layers of polymerized material (2.0 to 2.n + 1) and placing in communication the layers of liquid crystal material (1.0 to 1.n).   4. Liquid crystal modulator according to claim 2, characterized in that it comprises a first layer alternation in which the faces of the layers of polymerized material (20.0 to 20.n + 1) in contact with a layer of liquid crystal ( 10.0 to 10n) have a molecular structure oriented in a first direction, and a second alternation of layers in which the faces of the layers of polymerized material (20.n + 1 above, 21.1 to 21.n + 1) in contact with a liquid crystal layer (11.0 to 11.n) have a molecular structure oriented in a second direction orthogonal to the first direction, the set of layers being sandwiched between said electrodes.   5. Liquid crystal modulator according to one of claims 2 to 4, characterized in that it comprises a plurality of alternating layers, each alternating layers for modulating a range of wavelengths.   6. A method of manufacturing a liquid crystal modulator, characterized in that it comprises the following steps: c) depositing a volume of monomeric material (M) on a face of a plate (6.0) bearing at least a first electrode (3.0), d) polymerization in the volume of a monomeric material (M) of several distinct layers, to obtain several layers of polymerized material (20.0 to 20.n + 1) of equivalent optical thicknesses and regularly e) piercing at least one hole (5) passing through said layers of polymerized material, f) removing the unpolymerized material between said layers of polymerized material, g) filling the spaces left free at the end of said polymerized material; preceding step between the layers of material polymerized with a liquid crystal material, h) closing said hole (5) by a plate (6.1) or a transparent film (7) carrying at least a second electrode (3.1) which is applied cont re the upper face (fi) of the stack of layers.   7. A method of manufacturing a liquid crystal modulator according to claim 6, characterized in that the polymerization step is performed by a two-photon interaction method using a focused light beam and moving the point of focus of the beam within the monomer volume (M).   8. A method of manufacturing a liquid crystal modulator according to claim 6, characterized in that it comprises before the step of producing the access (5), a step of polymerization realization of shims thick between the layers of polymerized material.   9. A method of manufacturing a liquid crystal modulator according to claim 6, characterized in that the step of removing the unpolymerized material is done with a solvent liquid.   10. A method of manufacturing a liquid crystal modulator according to claim 6, characterized in that the polymerization step b) is by holography with the aid of two light beams interfering in a layer of photosensitive monomeric material.   11. A method of manufacturing a liquid crystal modulator, characterized in that it comprises the following steps: i) deposits, on one side of a plate (6.0) carrying a first electrode (3.0), a monomer material volume (M), alternating monomer layers of a first type and a second type, each layer deposition being immediately followed by a polymerization of the layer and then a treatment of orientation of the surface of the polymerized layer by friction or other means, to obtain several layers of polymerized material of a first type and a second type, j) drilling of at least one hole (5) which passes through said layers of polymerized material, k) removal of the polymerized material of the second type located between the layers of polymerized material of the first type, 1) filling of the spaces left free at the end of the preceding step between the layers of polymerized material using a crystal materialLiquid, m) closing said hole (5) by a plate (6.1) or a transparent film (7) carrying at least a second electrode (3.1) which is applied against the upper face (fi) of the stack of layers.   12. A method of manufacturing a liquid crystal modulator according to claim 11, characterized in that the realization of a stack of alternating layers of two different materials of a first type and a second type is done by producing a stack of layers with an overall thickness greater than several hundred micrometers, then by extrusion of this stack (D2) to obtain a stack of layers (D1) thinned.   13. Liquid crystal modulator characterized in that it comprises at least one layer of liquid crystal material (1.0 to 1.n) sandwiched between two layers of polymerized material (2.0 to 2.n + 1), shims thick (4.00, 4.01) being distributed in the liquid crystal layer between the layers of polymerized material, and at least one layer of polymerized material having holes having made it possible to fill the space between the two layers of liquid crystal with liquid crystal. polymerized material.   14. Application of the modulator according to claim 1, characterized in that it comprises at least one alternating layers of polymerized material and liquid crystal material according to claim 1.