FR2520885A1 - INFORMATION TRANSFER DEVICE IN A NON-LINEAR OPTICAL ENVIRONMENT - Google Patents

Abstract

THE INVENTION CONCERNS THE OPTICAL PROCESSING OF INFORMATION. THE DEVICE OF THE INVENTION IS INTENDED FOR THE TRANSFER OF OPTICALLY RECORDED INFORMATION, IN AN OPTICALLY NON-LINEAR MEDIUM, BETWEEN ADJACENT MEMORY ELEMENTS WHICH ARE DEFINED IN A FABRY-PEROT 4 RESONATOR WHICH IS LIT BY AT LEAST ONE LIGHT SOURCE AF. EACH MEMORY ELEMENT IS DEFINED BY ONE OR MORE SCREENS, POLARIZERS, FILTERS, PHASE LAYERS AND OR ELECTRODES, SO THAT THE INTENSITY, THE STATE OF POLARIZATION, THE WAVELENGTH AND WHERE THE PHASE OF THE LIGHT ARE INFLUENCED DIFFERENTLY TO THE COURSE OF LIGHT PROPAGATION TOWARDS ETOU THROUGH TWO ADJACENT MEMORY ELEMENTS. APPLICATION TO IMAGE PROCESSING DEVICES.

Description

The present invention relates to a device

  for transferring information recorded optically in an optically nonlinear medium between laterally positioned memory elements which are illuminated by at least one light source.

  U.S. Patent Application No. 363,598 discloses a disclosure

  positive for transforming information into form

  in optical form, or reverse

  in which the optical information is transferred, addressed or detected in the memory with the aid of circuits having an electro-optical reaction, these circuits being preferably integrated on a disk, to realize by

  example, a display device, a digitizer, a memory

  optical device or optical processing device

  Electro-optic reactions include optical modulators whose transmission of light depends on an electrical reaction signal. With the present technique, liquid crystals are the most practical devices as modulator because of their low

  energy consumption and their high level of modulation.

  However, for many applications such as fast optical processing devices and memories, liquid crystals are too slow, although it appears possible to obtain in the future time constants down to 1 ps Electro-optical modulators of the Fabry-Perot type have greater possibilities in

  speed, and the switching time of these modules.

  latters approaching 1 ns (see for example the article by P.W Smith and E H Turner entitled "A bistable Fabry-Perot

  resonator ", Appl Phys Letters, Vol 30, No. 16, March 15, 1977).

  These modulators make it possible to realize the devices

  described in the above-mentioned patent application, but problems

  appear to me because the time constants of the cir-

Electric cookware is limited.

  The invention aims to provide a solution to the problems

  aforementioned problems by using an "opto-optic" reaction to

  instead of an electro-optical reaction, which makes

  The invention is characterized in that it ensures that the light intensity, the state of polarization, the wavelength and / or

  the phase position of the light are influenced differently.

  during the propagation of light to and / or through two adjacent memory elements, by providing each memory element with one or more screens, polarizers, filters, phase shift layers and / or electrodes, and in that the medium above, receives light which, on at least one of the surfaces which limit the medium, does not have a normal incidence, in order to obtain an optical influence

  between the adjacent memory elements.

  If the interaction between light and electrons in a material is of such a nature that increased light intensity in a light intensity range produces a non-linear change in the absorption of light or

  of the refractive index, a strong relationship can be

  non-linear between the output light and the input light, if part of the output light from

  this matter is returned to the material.

  It was found in 1976 (H M Gibbs and Col Phys Rev.

  Lett 36, 1135) that, under given special conditions, this optical reaction could give a behavior

  bistable, that is to say a memory function Gibs et al.

  used a Fabry-Perot interferometer to obtain an optical reaction coupling, and used

  Na as an optically non-linear medium

  bistable behavior with resonances

  Fabry-P & rot, with several different types of optically nonlinear materials, such as for example C 02, SF 6, fluids with Kerr effect, ruby, In Sb and Ga As. The main nonlinear effect is due to variations of the refractive index, which, for the wavelength considered, modifies the length of the optical path and therefore

  the resonance conditions in the Fabry interferometer

Perot.

  According to the aforementioned patent application comprising circuits with electro-optical reaction, an opto-electrical interconnection of the circuits is made with a reaction

  electro-optical system, in order to be able to transfer information

  lateralization, which is necessary to write and read

  information and to perform spatial optical processing.

  The invention thus relates to devices for carrying out a corresponding transfer of information by an intercom-

  "opto-optics" of the elements, with an optically

  In the same way as in the case of

  carrying an electro-optical reaction, a new technique must be introduced to obtain an information transfer

  which is well defined in time and space.

  The invention will be better understood on reading the

  description that will follow of embodiments and by

  Referring to the accompanying drawings in which: Figures la and lb show two examples of the relationship between the input light and the output light of a Fabry-Perot resonator which comprises an optical medium

non-linear.

  Figure 2 is a schematic representation

  of an assembly intended for measuring the corresponding characteristics

  laying in figures la, lb. Figures 3a and 3b show a configuration using no less than ten light sources, because

  the devices described in the invention require normal

  several light sources, rather than the light source

Figure 2.

  Figures 4 a-9 show that it is possible to transfer information laterally in different directions inside a Fabry-Perot

  medium of one or more light sources

  Figures 4a-4c and 5a, 5b show the transfer of information by switching light sources between different light levels in a specified sequence;

  FIGS. 6 a-6 c further show the use of a

  figuration of electrodes to obtain a well-defined transfer; Figure 7 shows the completion of a selection between

  different modulator elements with polarization filters

  tion; Figure 8 shows the completion of a selection with Fabry-Perot filters; and figure 9 shows

  the completion of a selection with phase shift filters

  ge. FIGS. 1a, 1b show the luminous intensity I at the output of a Fabry-Perot resonator comprising a non-linear optical medium, as a function of the intensity I of the incident light. Curves of the type shown on FIG.

  Figure la have been measured, inter alia, in

  rubies (see for example the article by T N C Venkate-

  san and S. McCall entitled "Optical bistability and diffe-

  rential gain between 85 and 296 K in a Fabry-Perot contai-

  ning ruby ", Applied Physics Letters, Vol 30, No. 6, Mar. 15, 1977), and curves such as that of Fig. 1b were obtained when measuring on In Sb (see for example the article by David AB Miller and column entitled "Optical Bistability in Semiconductors", IEEE Journal of

  Quantum Electronics, Vol. QE-17, No. 3, March 1981).

  FIG. 2 shows an assembly for measuring, in the laboratory, the relations between Ii and Io. A laser 1 emits a beam of parallel rays towards the Fabry-Perot resonator 4 (FP) which is housed inside a cryostat. 2 having two optical windows 3a and 3b The light I which passed through the Fabry-Perot resonator 4 is picked up by the

photodetector 5.

  In order to obtain appropriate light pulse sequences, according to the invention several

  laser light sources A-1 L (see FIGS. 3a, 3b).

  FIG. 3a is a representation of the mounting in a side view.

  Fig. 3b is a top view representation. With the arrangement according to Figs. 3a, 3b, time-multiplexed wavefronts having different angles can be applied to the Fabry-Perot resonator 4. impact,

  and the importance of this will appear in the following figures.

  The following is a description of the essential principle of

  tion with reference to Figure 4a, with the assistance of the

  The Fabry-Perot resonator itself

  two semi-transparent mirrors 7 and 8, between which is an optical medium my linear On both sides of the mirrors 7 and 8 are two additional semi-transparent mirrors 6 and 9, which carry a coating consisting of configuration of screens 10 that can be absorbent or reflective The screens 10 located on the mirror 6 have the function of stopping the light from A and B, and the screens 10 located on the mirror 9 have the function

  to stop the light coming from D and E With the configura-

  As shown in the drawings, an optical division of the Fabry-Perot resonator into a number of memory elements is now assumed. For memory element 1, Ii = I 2 (see FIG. la) and o = transmission (state B), for memory elements 2,

  , etc., where I and I for the other

  i 3 o M memory blocking (3, 5, 7, etc), Ii = I 2 and Io = Iblocage 'that is to say the state A If now we increase ID $ because of its angle of incidence, the light will be switched to the area of the resonator FP below, which is illuminated

  by B, and the luminous intensity Ii in this region of the reso-

  FP can thus reach the value I 4 (Figure la)

  fact that for the other elements, Io = 1 blocking 'one obtains

  will have a lower optical coupling coefficient to the IB illuminated elements below, so that these elements will not reach the value I 4 * When the second element, from the top, reaches Ii = I 4 , I Dest again reduced to a low value (ID = 0), whereby 2 one Itransmission and element 2 thus reaches the state B, if we now give Ii the value I 22 Then, we reduce IE during a short duration so as to have Ii = II for element 1, thanks to which Io = Iblocage '

  Thus, the state A is reached. A transfer of

  formation into two adjacent memory elements, and this therefore necessitated a switching of the light source D and then a switching of the light sources B and E (see FIG. 3 A). In a corresponding manner, the information of the light source B is transferred. memory element 2 to the memory element 3 by first increasing somewhat IE 'and then switching A to a value IA large enough that the intensity I applied to the element 3 reaches I 4, then i 4 switching B so that the intensity I applied to the element i

  2 reaches I 1 or a lower value.

  line that the intensity Ii that is applied to the elements 1, 3, etc. is composed of both IE and the part of IE 3

  which is reflected at 6, and that the intensity Ii which is applied

  2, 4, etc., consists of both IB and the part of IB which is reflected at 9 When the intensity ID has been set, the intensity Ii applied to the elements 2, 4, etc., also includes the ID reflections falling on the elements 7 and 8, and when IA is added, the intensity Ii applied to the elements 3, 5, etc. also includes the reflections of IA falling on the elements 7 and 8 The coupling level between the elements, produced by ID and IA, depends on the reflectances of elements 6-9, the ID and IA indication angles, the characteristics of the nonlinear medium, the chosen wavelengths, etc., and can be optimize in this

  the speed and reliability of information transfer

  The speed is practically determined by the time

  recombination of the nonlinear medium, which often leads to

  at the completion of a transfer from state A to state B for a memory element faster (with a factor of 10-100) than a transfer from B to A This gives a

  memory function which makes it possible to operate in impulse

  light sources E and B, in addition to light sources

  A and D, with luminous intensity equal to zero at

  rest, which reduces the demands placed on light sources

  Neuses. In addition, light sources operating in

  pulses provide greater tolerances

  information transfer will be considered.

  In these conditions, the light source EA is first extinguished because of the recombination time, the element 1 will resonate for a duration tr after IE ppis the value O, while the elements 3, 5, 7 etc will not be in resonance If a pulse ID is generated during the duration M'r 'it can have an intensity corresponding to I 3, without the elements 3 , 5, 7, etc. do not leave the state I = Iblocage Because the element 1 is o blocking always in resonance, the light corresponding to Itransmis

  Sion will be switched to Element 2, which receives light

  re corresponding to a high switching margin, without

  elements 3, 5, 7 are brought to state B by ID.

  We can design different types of structures

  to implement the principle of transfer of information

  formation described above Thus, Figure 4b shows a structure in which the mirrors 6 and 9 have been inclined to allow the use of the same light beams IB and IE

  to maintain information and to transfer information

  This has the advantage of requiring fewer light sources

  but this simultaneously gives smaller margins

  for safe operation and, moreover, the information does not

  can be transferred only in one direction.

  In a Fabry-Perot resonator, the elec-

  transmitted tromagnetic is directly related to the internal field, by the boundary conditions in the initial mirror, so that we can in principle replace Io in the figures la, lb by intern without the relations represented are changed (RZE, in designating by E the field and internal O gr o by T the transmittance) This makes possible the use

  a simple Fabry-Perot structure with 10 screens

  forms in Figure 4c, which simplifies the manufacturing technique

  cation used in relation to structures conforming to the

Figures 4a and 4b.

  The information can be introduced into the Fabry-Perot resonator either optically or electrically.

  Figure 5a shows an example of the electrical introduction of

  In the demultiplexer 11, the input data is divided into a number of parallel channels which

  are connected by conductors 12 to trans-

  13 and 14 located on either side of the first element.

  memory in a row of memory elements

  so many screens 10 By mutual electro-optical influence on

  the refractive index of the Fabry-Pérot resonator, the first

  The first element can be brought into resonance for the wavelength of the light used. In accordance with the method described above, the passage of the information of a memory element

  another is blocked optically, and when the information is

  mation reaches the last element in a row, it is

  detected optically by the detector 15 which is connected

  multiplexer 16 for generating the data of scr-

  In FIG. 5b, two switched light rays are required from each side of the Fabry-Perot resonator. If three side-switched rays are used, and the screen configuration according to FIG. information to

  both down and to the right, which allows

  to provide serial and parallel information

  is lying. The electro-optical effect, which is used on

  FIGS. 5a, 5b for the introduction of data in the reso-

  The Fabry-Perot numerator can also be used to sequence the transmission of information between different memory elements in the Fabry-Perot resonator, which is shown in FIGS. 6a-6c by alternately exciting the electrodes. 13 with respect to the electrodes 14 in FIG. 6a, it is possible to move the resonance conditions of the elements

  of memory so that their optical state, according to the

  res la, lb, can be switched between A and B and inversely

  For the transmission of information between the memory elements, it is possible to use directed rays, oblique mirrors or, as in FIG. 6 a, an electro-optically controlled Fabry-Perot blade 20, with a rear element 19

  absorbing light With the Fabry-Perot reflector con-

  form in Figure 6a, we can control the coefficient of

  coupling between the memory elements, which allows a

  range of memory elements with distinct pulses.

  Figure 6b shows the electrode configuration on the

  surfaces of the Fabry-Perot resonator 4 These electrodes con-

  are in a structure of interdigital networks with at least two distinct networks and with the fingers of each network interposed in the spaces of the other network.

  adjacent memory elements (in a perpendicular direction

  networks) are connected to configura-

  The Fabry-Perot resonator comprises on one side this interdigitated network structure and on the other side of the network, it is possible to apply separate electrical voltages (01 02) to two adjacent memory elements. electrode strips, perpendicular to the fingers of the gratings, or an interdigitated network structure which is more or less similar to the first interdigitated network structure and is rotated about 900 relative to the first network structure Electrical information is written, in parallel, at the top of FIG. 6b and then is shifted downwards synchronously with the aid of clock pulses 01 and 029 which are applied to one electrode 13 of two If several rays are used bright, we can transfer the information both in the

  direction x and in the y direction, using

  Cross-electrode electrodes according to Figure 6 c.

  The function of recording and transferring

  The training described is based on the feature that one out of two (or better, one on

  three), in a certain direction of the surface of the resonance

  Fabry-Perot can be excited (IB, EI) and enlightened

  obliquely (IA, Icy I Dy etc.) independently of other cellular

  In addition to the use of screens 10 and illumination in two directions, this lateral light multiplexing can also be performed with polarizers 21a and 21b, according to FIG. 7, which have directions. polarization directions corresponding respectively to the polarization directions of light sources B and Bo If the nonlinear effect in the Fabry-Perot resonator 4 is present in a certain wavelength range,

  may use wavelength multiplexing, in accordance with

  Figure 8 The filter placed in front of the resonator of

  Fabry-Pérot 4 here consists of another Fabry- resonator

  Perot, with separate resonance wavelengths for

  two adjacent memory elements can be obtained for example

  deny this by means of electrodes 24 which are excited for example by

  by means of a configuration such as that of the figure

  6 b Finally, mention should be made of the possibility of making a

  phase, in which case the Fabry-Perot resonator 4 is provided with a phase shift configuration 25 (FIG.

  get the different elements of memory.

  It goes without saying that many modifications can be made to the device described and shown,

  without departing from the scope of the invention.

he

Claims (14)

  1 Information transfer device, in a   optically nonlinear medium, between memory elements   positioned laterally which are illuminated by at least one light source, characterized in that the light from the light source (or light sources) is influenced differently with respect to the light intensity, state of polarization, the   wavelength and / or phase position, during its propagation   transmission to and / or through two memory elements placed one on top of the other, by taking each memory element from one or more screens, polarizers, filters, phase shift layers and / or electrodes, and in that the medium can be   subjected to the action of light which, on at least one of the   faces that limit the medium, does not have a normal incidence, in order to obtain an optical influence between elements of   memory positioned adjacently.   2 Device according to claim 1, characterized in that said medium is enclosed in a resonator of   Fabry-Pérot (4) which concerns one of its reflective surfaces   (7, 8) or both, and / or one or two reflections   external devices (6, 9), a configuration (10) for optically defining the memory elements, and that   this configuration is formed by variations of trans-   mittance, direction of polarization and / or phase shift,   and / or by the spectral dependence of these quantities.   3 Device according to claim 1, characterized in that the medium can be placed under conditions in which it has an optical bistable character, with a longer time constant for a passage of a transmission state of the high light (B) to a low light transmission state (A), than for the opposite direction (A-> B), and in that one or more of the light sources are switched with times that correspond to the first   aforementioned time constant, or are less than them.   4 Device according to claim 2, characterized in that the light source (s) (1) are designed to generate at least one light wavefront (IB, IE) perpendicular to one of the mirrors (7, 8 ) of the Fabry-Perot resonator, or both, and at least one light wavefront (IA, ID) that is not directed to the mirrors with   normal incidence, and that the intensity of   light source, polarization direction, length   wave and / or the phase position of these wave fronts.   Device according to claim 3, characterized in that the transmission state of the light of a memory element is transmitted to the adjacent memory element by applying a rapid intensity reduction to the light which holds the element of first mentioned memory in state B, after which the light which does not have normal incidence is emitted as a pulse for a period of time.   which corresponds to the aforementioned time constant.   Device according to claim 5, characterized in that said configuration (10) is applied to both reflective elements (7, 8 or 6, 9) and that these configurations are designed so that the wave fronts of light are influenced differently on their way to a memory element, depending on the reflective side   (7, 8 or 6, 9) on which fall Xe wave fronts.   7 Apparatus according to claim 6, characterized in that the Fabry-Perot resonator which is located on each reflective side 8 has light absorbing regions and / or light reflecting, in that each element of memory has such a region on one of its sides, and in that the memory elements placed adjacently include these regions on the sides   reflecting reflective (7, 8 or 6, 9).   8 Device according to claim 7, characterized in that the Fabry-Perot resonator is illuminated by each side with light having a normal incidence (IB, IE), as well as light having oblique incidence.   (IA, IC ID, IF, etc.), in that the light having an inci-   normal dence gives an intensity that maintains the character   bistable from an optical point of view, in that the state of an element   memory is transmitted to a memory element posi-   adjacent light by giving the light having an oblique incidence a sufficiently high value for the adjacently positioned memory element to be triggered, and in that the direction of the surface of the Fabry-Perot resonator located between the memory elements between which the state is to be transmitted, is determined by   the direction of light having oblique incidence.   9 Device according to claim 2, characterized in that the or the outer reflectors (6, 9) are inclined relative to the reflectors of the Fabry-Perot resonator so   to generate wave fronts that do not present an inci-   normal dence on these reflectors.   Device according to claim 9, characterized   in that the external reflector or reflectors consist of a   Fabry-Perot resonator electro-optically controlled.   11 Device according to claim 2, characterized   in that said configuration consists of a layer   polarization which is applied to one of the reflective   of the Fabry-Perot resonator, or both, in that this layer is divided into regions defining the memory elements, and in that the adjacent regions have different polarization directions, a difference of 900 between the directions of the polarization being chosen for   to obtain the greatest selectivity.   Device according to claim 2, characterized   in that said configuration is generated by one or two additional Fabry-Perot resonators of a c-tee or   two sides of the Fabry-Perot resonator mentioned previously   mnet, and in that the Fabry-Perot resonator which defines the configuration is coated on one side or on both sides of configurations in the form of electrically conductive and / or dielectric thin layers and optically acting on the phase. , so as to define regions with   distinct spectral transmission characteristics.   13 Apparatus according to claim 1, characterized   characterized in that said configurations consist of transparent and electrically conductive electrodes (13, 14) which can be controlled to generate electric field strengths of different value in adjacent memory elements, and in that the medium is electro-optically active at the wavelengths that are used for the non-linear effect (s).   Device according to claims 2 and 13,   characterized in that the electrodes consist of a structure   forming interdigital networks (13) with at least two distinct networks and with the fingers of each network interposed in the spaces of the other network, whereby adjacent memory elements (in a direction perpendicular to the network fingers) are connected to separate network configurations, which allows different voltage voltages (OV 02) to be applied to two memory elements adjacent.   Device according to claim 14, characterized   in that the Fabry-Perot resonator comprises, on one side, a structure of interdigitated networks and on the other side of the electrode strips perpendicular to the fingers of the networks, or an interdigital network structure which is more or less similar to the first interdigital network structure, and which has been rotated about 900 per   relation to the first structure of inverged networks.   Device according to claim 1, characterized   in that optical memory, consisting of   memory, receives electrical information from   means of electrodes which are placed on one or more   memory elements, in that said medium is electro-optically   that, and that an applied electrical voltage on the part and   else a memory element can change the optical state-   bistable element of this memory element.   Device according to claim 1, characterized   characterized in that the optically non-linear medium is placed in the ray path in an optical processing device in order to perform, in two dimensions, a filtering and / or correlation of an optical information, such as   images, which exists in two dimensions.