Abstract: A method and device for coherent addition of semiconductor laser emission, in particular for use in telecommunications. Individual emitters are coupled, each emitter to some extent experiencing some of the emission of all the others. Rather than all emitting independently of one another, the emitters are arranged in a common resonator. Using an optimization method, e.g., the simulated annealing method, the shape of the resonator mirror may be optimized until it optimally fulfils a preassigned set of mathematical requirements which constitute a set criterion. The individual emitters in the form of individual diodes, a diode matrix or a diode bar are arranged between two or more mirrors. At least one of these mirrors has a special, non-spherical surface that forms an internal correction element. Alternatively, the mirrors may be spherical-shaped with at least one non-spherical phase plate arranged in the resonator beam path.

Abstract: A method and device for reducing the distortion of optical pulses caused by the polarization mode dispersion in optical communication systems is provided. When an optical pulse having any polarization is transmitted through an optical communication system, which is optically anisotropic, at least in sections, the optical pulse may become distorted due to the different velocities of the various polarization components. This distortion of the optical pulses may reduces the maximum transmission rate of the system. A method is provided for functioning in response to the detected transmission quality of the communication system where a polarization-controlling device for setting the polarization of the optical pulse is driven in such a way that the transmission quality is maximized. An optical communication system, including an optical transmission medium, involves a device for determining the transmission quality of the communication system, a regulating device, and a polarization-controlling device.

Abstract: A method and a device for reducing speckle formation on a projection display when working with a coherent light source. In this context, the light coming from the light source, before the projection, may strike an electrically controllable optical element having a spatially inhomogeneous refractive index, passing through the same, the refractive index being varied over time within the projection period. This may lead to an averaging out of the speckle pattern on the projection screen. For purposes of illumination, a multimode light source may be used, and/or the light coming from the light source is separated into a plurality of spatial modes, thereby reinforcing the effect. As an optical element, one may employ a liquid crystal element composed of at least two liquid crystal layers, to which a spatially dependent voltage is applied to generate a spatially dependent refractive index. Its birefringence may be compensated by orientating the layers to one another in appropriate fashion.

Abstract: A method and arrangement for producing a hologram of an object uses light, having photon packets, to illuminate the object and to serve as a reference light. Each photon packet includes a plurality of photons correlated in a quantum-mechanical manner and jointly form a multi-photon Fock state. Some of the photon packets may be used for illuminating the object, and some may be used as a reference light. Photon packets arriving from the object may be made to interfere with the reference light in an interference field, and the brightness distribution in the interference field or a part thereof may be registered by a detector. A light source emitting a plurality of mutually coherent rays of photon packets may be used for generating the packets, some of the rays being used for illuminating the object, and some of the rays being used as a reference light or for forming same.

Abstract: A device for generating, adding and subtracting digital sequences of optical pulses and a method for the secure transmission of information. An interferometer having at least one electro-optical switch or electro-optical modulator positioned in one of its branch sections is used so that binary optical pulse sequences may be added and/or subtracted in the context of an electro-optical device and a method for the secure transmission of information using optical signals.

Abstract: An intensity-dependent light modulating device and method involves light successively passing through a polarizer, a first phase retardation plate and a first light modulator. The light then strikes a mirror and then passes once again through the light modulator and the phase retardation plate in the opposite direction, and then strikes an analyzer that is crossed relative to the polarizer. The light modulator and the phase retardation plate are respectively located in an electric field in which the indicatrices of the light modulator and the phase retardation plate are deflected, wherein the deflection of the indicatrix of the light modulator is intensity-dependent. Due to the passage of light through the phase retardation plate and the light modulator, an intensity-dependent rotation of the direction of polarization occurs in such a way that higher intensity light is filtered in the analyzer while lower intensity light is transmitted.

Abstract: An intensity-dependent light modulating device or method for providing same, involves light successively passing through a polarizer, a first phase retardation plate and a first light modulator. The light then strikes a mirror and from there on, it passes once again through the light modulator and the phase retardation plate in the opposite direction and then strikes an analyzer that is crossed relative to the polarizer. The light modulator and the phase retardation plate are respectively located in an electric field in which the indicatrices of the light modulator and the phase retardation plate are deflected, wherein the deflection of the indicatrix of the light modulator is intensity-dependent. Due to the passage of light through the phase retardation plate and the light modulator, an intensity-dependent rotation of the direction of polarization occurs in such a way that higher intensity light is filtered in the analyzer while lower intensity light is transmitted.

Abstract: An intensity-dependent light modulating device involves a light successively passing through a polarizer, a first phase retardation plate and a first light modulator. The light then strikes a mirror and passes one again through the light modulator and the phase retardation plate in the opposite direction. The light then strikes an analyzer that is crossed relative to the polarizer. The light modulator and the phase retardation plate are respectively located in an electric field in which the indicatrices of the light modulator and the phase retardation plate are deflected, the deflection of the indicatrix of the light modulator being intensity-dependent. Due to the passage of light through the phase retardation plate and the light modulator, an intensity-dependent rotation of the direction of polarization occurs in such a way that higher intensity light is filtered in the analyzer while lower intensity light is transmitted.

Abstract: A method and system for the secure transmission of messages between at least two users of a telecommunications network, using a secret, random binary encryption key, which is used once for encryption. The key is generated in a key generator recorded on at least two portable data media, such as CDs, and then output in this form to the users, each of whom receives one data medium containing the recorded key. The key is not stored in any other location. The users insert the recorded key media into reading devices, which are respectively assigned to telecommunications equipment, e.g., telephones, fax machines, or PCs, employed by the users. When a connection is established, logistics devices, which are also assigned to the telecommunications equipment, check whether the keys were entered properly and whether they correspond to each other. The logistics devices also synchronize the entered keys, or at least portions of the keys, when the information to be transmitted is encrypted and decrypted.

Abstract: A method and arrangement for generating binary sequences of random numbers uses the principle of random selection of the path of photons on a beam splitter and generating a random number by using two detectors (D10, D21) downstream from a beam splitter (ST2). To generate photons, a light source (L) of a low power is used, and an additional beam splitter (ST1) is connected upstream from the beam splitter (ST2). The photons emitted by the light source (L) during a predefined measurement time are split by the beam splitters (ST1, ST2) arranged one after the other in the beam path of the light source (L). The random sequence is generated when the splitting of the photons matches a predefined photon scheme.

Abstract: The invention relates to an optical waveguide (optical fiber) based on quartz glass having reduced internal mechanical stresses. In prior art optical waveguides, the internal mechanical stresses are primarily due to the production process, namely due to the difference of the linear thermal coefficients of expansion of the core and sheathing material during the cooling of the fiber and due to the drawing itself. In an inventive optical waveguide, the difference of the linear thermal coefficients of expansion of the core and/or sheathing material is selected by means of an appropriate doping of the core and sheathing material. This selection is made so that the internal mechanical stresses, which are caused by the cooling during the production process, are significantly reduced or eliminated and/or they counteract the stresses caused by the drawing.

Abstract: The present invention relates to a method and a device for forming the intensity profile of a laser beam, in particular for producing a homogeneous intensity profile. In an embodiment of the present invention, the laser beam can strike an optically addressable spatial light-modular (OASLM), whose local transmission or reflection properties depend in nonlinear fashion on the local illumination intensity.

Abstract: To provide a phase modulator for introducing a topological phase, which is designed to produce any desired phase shift between zero and 360°, the phase modulator has means, at least one double-refractive, electrooptical delay element having a rotatable indicatrix, which is/are used to direct the polarization of the light, during transmission through the modulator, over at the light one closed path on the Poincaré sphere, the indicatrix rotating in accordance with the predefined phase shift, and the total encircled surface on Poincaré sphere being equal in terms of absolute value to ?.

Abstract: To provide directionally dependent attenuation for an optical information transmission link using simple means without the use of an active component, it is proposed to couple two optical waveguides (1, 2) having different core diameters to one another, the core diameter of the second fiber (2) being at least six times greater than the core diameter of the first fiber (1). In this manner, it is achieved that the conduction of light signals in a predefined direction is attenuated by at least the factor 30, while, on the other hand, the light propagating in the reverse direction, is attenuated very slightly.

Abstract: An electrically drivable light modulator having liquid crystal layers, which are disposed one behind the other and are enclosed between transparent plates having a surface anisotropy that orients the molecules of the liquid crystals and having electrodes for generating an electric field in the liquid crystals, at least two layers of helical, smectic, ferroelectric liquid crystals are situated one behind the other in the path of rays of a light beam to be modulated. The directions of the fast and slow axes of the individual layers are rotated relatively to each other so that the polarization of the light beam is the same upstream and downstream from the modulator. An adaptive, optical device has a field of light modulators configured in a raster-type array, in which the modulators are situated in the path of rays of the device, each individual light modulator being able to be driven to compensate for unsharpness occurring on a point-by-point basis in an image to be processed.

Abstract: In order to substantially reduce temperature-dependent influences and attendant long switching times in the case of an optical liquid crystal modulator having at least one ferroelectric liquid crystal and in a method for operating an optical liquid crystal modulator, the ferroelectric liquid crystals are provided to have a DHF mode and to exhibit an operating range of an electric field of more than 20 V/?m at the location of the liquid crystal.

Abstract: A method is provided for changing the polarization of at least one of the photons emitted from a photon pair source into various partial ray paths using an electro-optical modulator (EOM), which is positioned in the particular partial ray path being traversed by the photon to be influenced and which, in the activated state, is able to alter the polarization of a photon, the modulator being activated as a function of time such that the probability that the photon is found in the region of the electro-optical modulator in the activated state is at a maximum.

Abstract: The present invention provides an optical communications link having at least one optical fiber, in particular for communications transmission, where the optical fiber is repeatedly bent. The fiber sections having a right-hand and left-hand curvature are distributed in such a way over the communications link that the average torsion of the fiber is approximately zero. The communications link in accordance with the present invention is compact, flexible, and variable in length. In addition, it reduces the sensitivity of the polarization state of the optical signal to changes in the form of the communications link.

Abstract: The invention relates to an intensity-dependent light modulating device, wherein said light successively passes through a polarizer, a first phase retardation plate and a first light modulator; the light then strikes a mirror and from there on, it passes once again through the light modulator and the phase retardation plate in the opposite direction and then strikes an analyzer that is crossed relative to the polarizer. The light modulator and the phase retardation plate are respectively located in an electric field in which the indicatrices of the light modulator and the phase retardation plate are deflected, wherein the deflection of the indicatrix of the light modulator is intensity-dependent. Due to the passage of light through the phase retardation plate and the light modulator, an intensity-dependent rotation of the direction of polarization occurs in such a way that higher intensity light is filtered in the analyzer while lower intensity light is transmitted.

Abstract: The present invention is directed to an optical system for coupling light from a light source into a medium, in particular into an optical fiber. The optical system has at least one light-deflecting surface, which directs the light by reflection or refraction into the medium. The form of the light-deflecting surface is such that the light source is not sharply imaged in the medium or on its surface. The optical system according to the present invention can advantageously be used for coupling light of a very high intensity into the medium without the risk of a too high, local luminous density producing non-linear optical effects or resulting in material damage.