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WO1998006002A1 - Composant pour la commutation de modeles optiques dans l'espace de microsecondes - Google Patents

Composant pour la commutation de modeles optiques dans l'espace de microsecondes Download PDF

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Publication number
WO1998006002A1
WO1998006002A1 PCT/EP1997/004263 EP9704263W WO9806002A1 WO 1998006002 A1 WO1998006002 A1 WO 1998006002A1 EP 9704263 W EP9704263 W EP 9704263W WO 9806002 A1 WO9806002 A1 WO 9806002A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical
component according
angle
switching
ferroelectric liquid
Prior art date
Application number
PCT/EP1997/004263
Other languages
German (de)
English (en)
Inventor
Wolfgang Dultz
Leonid Beresnev
Wolfgang Haase
Thomas Weyrauch
Original Assignee
Deutsche Telekom Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Deutsche Telekom Ag filed Critical Deutsche Telekom Ag
Publication of WO1998006002A1 publication Critical patent/WO1998006002A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
    • G02F1/31—Digital deflection, i.e. optical switching
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1347—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
    • G02F1/13471—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
    • G02F1/141—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent using ferroelectric liquid crystals

Definitions

  • the invention relates to a component for switching optical patterns or data with unpolarized light according to the preamble of claim 1.
  • a second element for parallel optical processing must enable the rapid switching of the optical patterns into a number of optical channels.
  • the usual way of switching the pattern or optical data into a number of channels is to record the image via a CCD video camera with subsequent transmission of the electrical signals and the regeneration of the images on the screen. This process is limited by the operating frequency of the computer, which does not exceed 10 9 bit / s.
  • the invention is therefore based on the object to alleviate the disadvantages described above and in particular to provide a component for switching optical patterns or data with unpolarized light according to the preamble of claim 1, which switch or process a large number of optical data or patterns very quickly in parallel can.
  • the device for switching patterns according to the invention operates much faster than the known methods and devices. It is possible to transmit any image with non-polarized light in a relatively wide wavelength range with the switching time of 3 to 5 ⁇ s and the operating frequency of 10 5 frames per second.
  • the transmission frequency can be up to 10 12 bits / s (ie terabits / s) for the example in which the optical pattern contains 10 7 pixels and the patterns are switched at a frequency before 10 5 frames / s.
  • the component according to the invention uses the division of the unpolarized light beam, based on the optical pattern, into two perpendicular polarized beams. This is achieved by a wide-angle polarization beam splitter, followed by rotating both polarizations by 90 ° using an electro-optical modulator and combining both polarized beams into one beam using a second beam splitter.
  • a suitable crystal such as LiNb0 3 can be used as the electro-optical modulator, as described in Storell in the published patent application DE 30 13 498 from April 8, 1980 "Optical modulator and laser engraving device with such a modulator".
  • the optical switch described here has disadvantages, such as a small aperture and a small angle of the control beam, high switching voltage on the order of a few 100 V, the wavelength dependence of the switching efficiency, due to optical dispersion and high prices for the electro-optical crystal.
  • This switch also appears to be usable only when using lasers. Cascading using this switch is difficult to accomplish.
  • Liquid crystals as an electro-optical medium were used by Coa, A.J.A. in EP-A-0 074 144 "Optical Switch", priority 07.09.1981, NL 8104 122, for switching unpolarized light from an optical fiber into different fiber channels. This was also described by K. Hirabayashi and T. Kurokawa in Liquid Crystals 14, pages 307-317 (1993) under the title "Liquid crystal devices for optical communication and information processing systems". In both works ne atic liquid crystals were used.
  • the optical circuit of a cell of a twisted nematic liquid crystal is as electro-optical modulator shown.
  • the orthogonally polarized light passes through the cell from the first polarizing beam splitter PBS 1, the polarization plane being rotated through 90 °.
  • the light After combining the two polarized beams in the second polarizing beam splitter PBS 2, the light enters the outgoing channel 1.
  • the liquid crystal is converted into the homeotropic alignment, both polarized beams pass through the rotary cell without to rotate the angle of the polarization planes. In this case, the light enters channel 2 after the polarized beams have been combined in the second polarizing beam splitter PBS 2.
  • the major disadvantage of the circuit using nematic liquid crystals is the low operating frequency of approximately 10 Hz. This means that the use of a nematic liquid crystal modulator for pattern transmission is slower than electronic video recording. In addition, gray level control of the light intensity between the optical channels is difficult.
  • the electro-optical circuit of the proposed embodiment uses for the first time an electro-optical modulator made up of several electrically controllable or controllable delay plates in series connection.
  • these switchable delay plates are based on ferroelectric liquid crystals (FLC's) for the first time.
  • FLC's ferroelectric liquid crystals
  • the great advantage of the switches according to the invention includes the high efficiency ( ⁇ 100%) of the optical circuit of the polarized light; low optical loss, which essentially results only from the reflection on the transparent solid surfaces such as quartz, glass or calcite.
  • the possibility of a light channel switch is given by cascading. Very fast switching and grayscale modulation of optical images every microsecond, - low switching voltage of approximately 25 V; Low dependence of the switching efficiency on the wavelength of the light and thus the perfect switching of any color image are also advantages of this component.
  • the low dependence on the angular distribution of the modulated light beam can be used for the rapid switching of the polarization plane of the light in compact stereo projectors, for which purpose only one lens is required.
  • the left and right eye images appear alternately on the screen at a frequency of 100 Hz or higher. This property is also ideal for realizing glasses with rapidly switchable polarization directions or for fast closures for viewing stereoscopic images using the polarization division or the time division of images for the left and right eyes.
  • 2 shows the principle of the conventional optical switching of non-polarized light, as described, for example, by RA Sorel in Optics Letters 5 (4), 147-149 (1980) under the title “Total switching of unpolarized fiber light with a fourport electro-optic liquid- crystal device "and Katsuhiko Hirabayashi and Takashi Kurokawa in Liquid Crystals 14 (2), 307-317 (1993) under the title “Liquid crystal devices for optical communication and information processing systems", where PBS refers to polarizing beam splitters and the twisted-nematic cell as electro-optical Switch of the polarization planes is shown
  • Fig. 4 the 2x2 cross switch according to the invention with two
  • Input and two output channels realized by using a number of at least two switchable uniaxial optical delay plates
  • Fig. 5 shows the electro-optical effect, based on the orientation of the inclination planes of the chiral inclined guest molecules, which were entered in the lamellar phase, in the given case in the smectic A phase, a) without an applied electric field, whereby a random orientation of the The planes of inclination of the chiral molecules result and the central optical axis n runs along the z-direction, which results in the local inclination of the chiral molecules at the angle ⁇ m , b) the electric field E runs parallel to the layers opposite to the viewing direction, the transverse ones molecular dipoles are oriented along the electric field and, due to the organization of the inclination planes of the inclined chiral molecules, the central optical axis ⁇ n> is rotated counterclockwise at an angle ⁇ > less than ⁇ m compared to case a), c) that electric field + E runs parallel to the layers in the direction of view, the middle re optical axis is rotated clockwise by
  • FIG. 7 shows the switching efficiency of the cross switch shown in FIG. 4 with an electroclinical double modulator using the ferroelectric liquid crystal FLC-392
  • FIG 8 shows an optical circuit diagram for the cascading of the optical switches according to the invention for switching optical patterns or data or of fiber channels from one input channel to 4 output channels.
  • a component according to the invention for the rapid switching of optical patterns is described below.
  • Each optical image 1 can be switched into two channels 2, 3 by means of unpolarized polychromatic light.
  • the component contains two polarizing beam splitters 4, 5 and prisms 6, 7 as well as an electro-optical modulator 8, which consists of at least two electrically controlled or controllable
  • the angle between the optical axes is 45 ° or 90 ° for switching in channel 1 or channel 2.
  • Capillary cells with ferroelectric liquid crystals in planar geometry can be used as switchable optical delay plates 9, 10.
  • SSFLC surface-stabilized ferroelectric liquid crystal
  • DHF ferroelectric helix
  • the modulator consists of four switchable delay plates 9, 10, 11, 12 and the electroclinic effect is applied, the required angle of inclination is only 5.625 °.
  • the response time is then correspondingly shorter and can be less than 1 microsecond.
  • the proposed fast optical switching element can be used for fiber channels 13, 14, 15 and as an active element in optical computers.
  • the operating speed for switching between the optical channels are in the order of several terabits / s.
  • the component can be cascaded, which enables the switching of patterns in any number of channels. Description of the principle of the component
  • Fig. 1 The general scheme of the proposed switch is shown in Fig. 1.
  • SRP's series-connected optical delay plates
  • Two or more ferroelectric liquid crystalline layers connected in series result in the excellent properties of the optical switch such as:
  • the resulting deviation in the plane of polarization after passing through two of these plates is then 90 °, as described by G. Andersson, I. Dahl, L. Komitov, S.T. Lagerwall, K. Skarp, and B. Stebler in J. Appl. Phys. 66 (10), 4983-4995 (1989) under the title "Device physics of the soft-mode electro-optic effect".
  • the response time can be of the order of a microsecond or less, due to the small value of the induced tilt angle. This means that the working frequency can be around 10 5 - 10 6 Hz.
  • the intrinsic grayscale scale of the electroclinic and the DHF effect means that the controlled distribution of the intensity of the optical patterns in two channels can be achieved regardless of the possibility of the overall circuit.
  • This property can be used for effective amplitude modulation of the non-polarized light with very high transmission close to 100% in the open state.
  • An application for this is e.g. in fast optically limiting components or for the automatic control or control of the light intensity when using a photodetector in the corresponding output and the feedback to the voltage that is applied to the switchable delay plates.
  • the switch proposed according to the invention is able to switch two incoming optical beams symmetrically into two outgoing channels, as can be seen in FIG. 4.
  • the plane of the deviation of the optical axis is perpendicular to the field direction and the size of the deviation angle is proportional to the amplitude of the electrical field in the case of the electroclinic and DHF effect.
  • the resulting is
  • All three mentioned electro-optical modes can be used to implement a component, ie for Rotation of the polarization plane and thus as a basic element of the switchable delay plate of the proposed optical switch.
  • the inventors use a new electroclinic material that requires only a very low switching voltage.
  • Mixtures which consist of a lamellar matrix (for example of a smectic A or smectic C * phase) and chiral guest molecules which are inclined in the layer at a certain angle ⁇ m , as shown in FIG. 5a.
  • the hindrance of these molecules when rotating about the longitudinal axis is due to the monoclinic local environment, which is caused by the inclination of the chiral molecules in the layer. Because of this handicap, the short axis of these molecules is oriented in the direction of the layer and perpendicular to the plane of inclination.
  • the transverse dipole moment which is connected to the short axis, can be oriented in this direction.
  • the tilt planes of the chiral tilted molecules are statistically distributed.
  • An external electric field applied along the layers, orients the dipole moments of the separated molecules and correspondingly their planes of inclination, as shown in FIGS. 5b and c.
  • the mean optical refractive index index deviates by the mean angle ⁇ >, which is smaller than ⁇ m , in the plane that is perpendicular to the applied electric field.
  • the value of the deviation of the mean optical indicatrix depends on the concentration of the chiral guest molecules, their angle of inclination ⁇ m and the optical transition moment of the matrix and the guest molecules.
  • the expected response time is shorter than with collective switching in the chiral smectic C "phase.
  • the electroclinic material used according to the invention with the lamellar phase and the inclined chiral molecules dissolved therein allows switching in a very short response time.
  • FIG. 6 shows the temperature dependence of the switching time and the induced inclination angle ⁇ of an electroclinic material FLC-392 according to the invention at a switching voltage of ⁇ 10 V. It can be seen that the response times are on the order of a few microseconds and drop in the range of 1.5-2 microseconds at higher temperatures.
  • FIG. 7 shows the efficiency of switching the switch according to the invention in accordance with the configuration shown in FIG. 4.
  • the transmission of a few percent of the light intensity which is still present in the case of the blocking state is due to the wavelength dispersion of the polarizing beam splitter used and the optical non-uniformity of the electroclinic modulators.
  • the DHF materials can be used for electro-optical switching, where fractions of a millisecond are required as switching time in connection with very small switching voltages of 1 - 2 volts. You could e.g. are used in glasses to be operated with low switching voltages for stereoscopic TV systems.
  • the transmission speed can reach many terabits / s and is only limited by the resolution of the optical standard elements, such as lenses, prisms, etc.
  • optical switch according to the invention can be used in optical limiting components, e.g. in fast shutters in video cameras or to protect the eye, or to control or control the light intensity when using the feedback of the photo receiver via an amplifier.
  • the proposed switch can also be used for the overall switching of depolarized light in optical fibers.
  • FIG. 8 shows the optical circuit diagram for a possible cascading which contains 4 output channels.

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Liquid Crystal (AREA)

Abstract

L'invention concerne un composant pour la commutation des modèles ou données optiques à l'aide d'une lumière non polarisée. Ce composant comprend deux séparateurs (4, 5) de faisceau polarisants, au centre desquels est implanté au moins un modulateur (8) électro-optique. La modification de la polarité et de l'amplitude de la tension électrique appliquée au modulateur provoque une rotation de 0 à 90° du plan de polarisation de la lumière qui provient du premier séparateur de faisceau polarisant puis traverse le modulateur. Pour pouvoir rapidement commuter parallèlement et traiter un grand nombre de données ou modèles optiques, le modulateur (8) comprend au moins deux plaques (9,10) de retard optiques à connexion et à commande électrique. Ces plaques contiennent des cristaux liquides ferroélectriques.
PCT/EP1997/004263 1996-08-05 1997-08-05 Composant pour la commutation de modeles optiques dans l'espace de microsecondes WO1998006002A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19631644.8 1996-08-05
DE19631644 1996-08-05

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WO1998006002A1 true WO1998006002A1 (fr) 1998-02-12

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6331910B1 (en) 1997-07-19 2001-12-18 Deutsche Telekom Ag Arrangement and method for electrically controlling the intensity of unpolarized light
EP1212640A4 (fr) * 1999-09-15 2003-01-22 Spectraswitch Inc Dispositif optique birefringent
EP1315026A1 (fr) * 2001-10-25 2003-05-28 Corvis France R&D Dispositif optique à routage de polarisation
WO2003048854A1 (fr) * 2001-08-22 2003-06-12 Innovative Technology Licensing, Llc Commutateur optique a duplex integral independant de la polarisation
US6735016B1 (en) 1999-09-15 2004-05-11 Spectraswitch, Inc. Electro-optically controllable polarization insensitive optical device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0624812A1 (fr) * 1993-05-11 1994-11-17 Mitsui Petrochemical Industries, Ltd. Dispositif de modulation de la lumière à cristal liquide
JPH0777699A (ja) * 1993-09-07 1995-03-20 Fujitsu Ltd 偏光制御器
WO1996007951A1 (fr) * 1994-09-08 1996-03-14 British Telecommunications Plc Modulation de polarisation

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0624812A1 (fr) * 1993-05-11 1994-11-17 Mitsui Petrochemical Industries, Ltd. Dispositif de modulation de la lumière à cristal liquide
JPH0777699A (ja) * 1993-09-07 1995-03-20 Fujitsu Ltd 偏光制御器
WO1996007951A1 (fr) * 1994-09-08 1996-03-14 British Telecommunications Plc Modulation de polarisation

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
ANDERSSON G ET AL: "Device physics of the soft-mode electro-optic effect", JOURNAL OF APPLIED PHYSICS, 15 NOV. 1989, USA, vol. 66, no. 10, ISSN 0021-8979, pages 4983 - 4995, XP000105101 *
PATENT ABSTRACTS OF JAPAN vol. 095, no. 006 31 July 1995 (1995-07-31) *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6331910B1 (en) 1997-07-19 2001-12-18 Deutsche Telekom Ag Arrangement and method for electrically controlling the intensity of unpolarized light
EP1212640A4 (fr) * 1999-09-15 2003-01-22 Spectraswitch Inc Dispositif optique birefringent
US6594063B1 (en) 1999-09-15 2003-07-15 Spectraswitch, Inc. Birefringent optical device
US6735016B1 (en) 1999-09-15 2004-05-11 Spectraswitch, Inc. Electro-optically controllable polarization insensitive optical device
WO2003048854A1 (fr) * 2001-08-22 2003-06-12 Innovative Technology Licensing, Llc Commutateur optique a duplex integral independant de la polarisation
EP1315026A1 (fr) * 2001-10-25 2003-05-28 Corvis France R&D Dispositif optique à routage de polarisation

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