In this letter, we present a source of quantum-correlated photon pairs based on parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550-nm fiber-optic communication band and detected with InGaAs-InP avalanche photodiodes operating in a gated Geiger mode. A generation rate > 10/sup 3/ pairs/s is observed, which is limited by the detection electronics at present. We also demonstrate the nonclassical nature of the photon correlations in the pairs. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks.

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All-fiber photon-pair source for quantum communications

A method for converting electromagnetic (EM) energy between guided modes of a photonic crystal waveguide (800) having a waveguide axis (810), the method including: (i) providing the photonic crystal waveguide (800) with a mode coupling segment (820) comprising at least one bend (830) in the waveguide axis (810), wherein during operation the mode coupling segment (820) converts EM energy in a first guided mode to a second guided mode; (ii) providing EM energy in the first guided mode of the photonic crystal waveguide (800); and (iii) allowing the EM energy in the first guided mode to encounter the mode coupling segment to convert at least some of the EM energy in the first guided mode to EM energy in the second guided mode.

Electromagnetic mode conversion in photonic crystal multimode waveguides

A planar laser illumination and imaging (PLIIM) based system employing wavefront control methods for reducing the power of speckle-pattern noise within digital images acquired by the system. The system comprises a housing having a first light transmission aperture, a second light transmission aperture, and a third light transmission aperture, wherein the first and second light transmission apertures are optically isolated from said third light transmission aperture spatially aligned on opposite sides thereof. A pair of planar laser illumination arrays (PLIAs) are mounted within the housing, for producing and projecting a first and second planar laser illumination beams (PLIBS) through the first and second light transmission apertures respectively, thereby producing a composite planar laser illumination beam (PLIB) outside of the housing, and illuminating an object therewith as the object is transported past the first, second and third light transmission apertures. An image formation and detection (IFD) module is mounted within the housing, and has a linear image detection array and imaging forming optics for providing the linear image detection array with a field of view (FOV) which is projected through the third light transmission aperture, and along which digital images of illuminated portions of the object can be detected. Notably, digital images contain speckle-pattern noise, and the PLIB and FOV are arranged in a coplanar relationship along the working range of the PLIIM based system so that the composite PLIB illuminates primarily within the FOV of the IFD module. A wavefront control mechanism is mounted within said housing, for controlling one or more characteristics of the wavefront of the composite PLIB so as to reduce either the spatial and/or temporal coherence of the composite PLIB prior to its illumination of a selected portion of the object, so that time-varying different speckle-noise patterns are present in the digital images detected at the linear image detection array. These time-varying different speckle patterns are temporally averaged at the linear image detection array during the photo-integration time period thereof so that the power of speckle-pattern noise at the linear image detection array is substantially reduced.

Planar laser illumination and imaging (PLIIM) system employing wavefront control methods for reducing the power of speckle-pattern noise digital images acquired by said system

An all-digital display system includes an electronic processor that is operable to receive an internet protocol video packet and to generate a control signal based at least in part on the internet protocol video packet. In one particular embodiment, the electronic processor includes at least a header processor, a CPU electronic processor, and a display processor unit. The all-digital display system also includes one or more light sources capable of generating one or more optical signals and one or more light modulating chips. The one or more light modulating chips are operable to receive the one or more optical signals and to modulate the one or more optical signals based at least in part on the control signal. The all-digital display system further comprises one or more display screens operable to receive the modulated signals communicated from the light modulating chips.

Packet-based digital display system

A planar laser illumination and imaging (PLLIM) based camera system capable of producing digital images with reduced levels of speckle-pattern noise. The PLIIM based camera system comprises a planar laser illumination array (PLIA) including a plurality of laser diodes for producing and projecting a planar laser illumination beam (PLIB), so as to illuminate an object as it is moving past said PLIIM based camera system. An image formation and detection (IFD) module is provided having a image detection array and imaging forming optics for providing the image detection array with a field of view (FOV). The PLIB and FOV are arranged in a coplanar relationship along the working range of the PLIIM based camera system so that the PLIB illuminates primarily within the FOV of the IFD module. A speckle-pattern noise reduction subsystem is integrated with the PLIA, for reducing the temporal-coherence of said planar laser illumination beam (PLIB) before the PLIB illuminates a target object. The speckle-pattern noise reduction subsystem carries out a temporal phase modulation technique during the transmission of the PLIB towards the target, so that the object is illuminate with a temporally coherent-reduced planar laser illumination beam (PLIB) and numerous substantially different time-varying speckle-noise patterns are produced at the image detection array over the photo-integration time period thereof. The numerous substantially different time-varying speckle-noise patterns are detected at the image detection array over the photo-integration time period, and the detected speckle-noise patterns are temporally averaged at said image detection array during the photo-integration time period thereof. As a result of such temporal averaging, the RMS power of observable speckle-noise patterns is reduced at the image detection array. By virtue of the present invention, it is now possible to enjoy the benefits of using laser-based illumination during high-speed imaging operations, without the adverse effects associated with speckle-pattern noise.

Method of speckle-noise pattern reduction and apparatus therefor based on reducing the spatial-coherence of the planar laser illumination beam before it illuminates the target object by applying spatial intensity modulation techniques during the transmission of the PLIB towards the target

The invention relates to a method and a device for reducing the speckle that is formed on a projection display when a coherent light source (1) is used. Before being projected, the light coming from the light source strikes an electrically controllable optical element (4) with a spatially inhomogeneous index of refraction and penetrates said optical element, whereby the index of refraction within the period of projection is temporally altered. This leads to the averaging out of the speckle pattern on the projection screen (6). A multimode light source is preferably used for illumination and/or the light coming from the light source is split into several spatial modes in order to increase the effect. The light from the light source is preferably split by being coupled into a multimode light-conducting fibre. Said optical element is advantageously a liquid crystal element consisting of at least two liquid crystal layers, to which a position-dependent voltage is applied in order to produce a position-dependent index of refraction and whose birefringence is compensated by the appropriate alignment of the layers in relation to each other.

Method and device for reducing the formation of speckle on a projection screen

The invention relates to a method for producing a choice of either single photons or pairs of photons in an optical channel (16, 17), comprising the following steps: establishing a two-photon state (photon pair); physically separating said photon pair and obtaining the quantum mechanical correlation in the event that the photons are emitted collinearly; coupling each photon into one optical channel (14, 14', 14') respectively, one channel (15, 15', 15') containing an interferometer (7-13) with a variable difference in optical paths δ1F-δ1S and the other channel containing an optical retardation route (19) of optical length δ1; physically bringing the two channels together with a beam splitter (18, 31-36); matching the values δ1F, δ1S and δ1 in such a way that the probability K of coincidences between the outputs (16, 17) of the beam splitter can be either approximately K=0 or approximately K=1 or approximately a predetermined intermediate value, K=0 corresponding to a photon pair in one of the output channels (16, 17) of the beam splitter and K=1 corresponding to two single photons in the two output channels of the beam splitter. The invention provides a means of producing an optical separating filter or gate for either single photons or photon pairs which can be used in quantum cryptography and as a basic element of a quantum optical calculating machine.

Method and device for producing a choice of either single photons or pairs of photons in an optical channel

The aim of the invention is to provide an inexpensive method and an arrangement for generating binary sequences of random numbers. The invention should also be easy to integrate onto a chip card. The inventive method is based on the principle of the random path selection of photons in a beam splitter and the generation of a random numbers by means of two detectors (D10; D21) situated downstream of a beam splitter (ST2). According to the invention, a low-power light source (L) is used to produce the photons and an additional beam splitter (ST1) is arranged upstream of the original beam splitter (ST2). The photons emitted by the light source (L) for a set measuring period are split up by the beams 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 up of the photons is matched with a predetermined photon model. The invention provides an inexpensive random-check generator which is easy to integrate onto a chip card, especially because of the light source (L) used.

Method and arrangement for generating binary sequences of random numbers

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.

Method and device for reducing speckle formation on a projection screen

Die Erfindung betrifft ein Verfahren zur Erzeugung von wahlweise Einzelphotonen oder Photonenpaaren in einem optischen Kanal (16, 17) mit folgenden Schritten: Erzeugen eines Zweiphotonenzustandes (Photonenpaar); raumliches Auftrennen des Photonenpaars unter Erhalt der quantenmechanischen Korrelation, falls die Photonen kollinear emittiert werden; Einkoppeln jeweils eines Photons in jeweils einen optischen Kanal (14, 14', 14''), wobei der eine Kanal (15, 15', 15'') ein Interferometer (7-13) mit veranderlicher optischer Weglangendifferenz delta 1F - delta 1S und der andere Kanal eine optische Verzogerungsstrecke (19) der optischen Lange delta 1 enthalt; raumliches Zusammenfuhren beider Kanale durch einen Strahlteiler (18, 31-36); Abstimmen der Grossen delta 1F, delta 1S und delta 1 derart, dass die Wahrscheinlichkeit K fur Koinzidenzen zwischen den Ausgangen (16, 17) des Strahlteilers wahlweise etwa K = 0 oder etwa K = 1 oder etwa einen vorbestimmten Zwischenwert betragt, wobei K = 0 einem Photonenpaar in einem der Ausgangskanale (16, 17) des Strahlteilers und K = 1 zwei Einzelphotonen in beiden Ausgangskanalen des Strahlteilers entspricht. Mit der Erfindung kann eine optische Weiche bzw. Gatter fur wahlweise Ein- oder Zweiphotonenzustande realisiert werden, welches in der Quantenkryptographie und als Grundelement einer quantenoptischen Rechenmaschine verwendbar ist.

Gisela Dultz

Papers

Method and device for reducing the formation of speckle on a projection screen

Method and device for producing a choice of either single photons or pairs of photons in an optical channel

Method and arrangement for generating binary sequences of random numbers

Method and device for reducing speckle formation on a projection screen

Verfahren und vorrichtung zur erzeugung von wahlweise einzelphotonen oder photonenpaaren in einem optischen kanal