Abstract: A digital watermark which is incorporated, perceptibly or imperceptibly, into a diffractive device such as a hologram. When applied to protect and/or authenticate a document of value or a product, the device provides an increased degree of overt and covert security, and permits tracking of the sale, use or other parameters associated with the product and/or document of value.

Abstract: A method for monitoring laser light launched into a core of a single mode fiber includes launching a portion of light directly into the cladding about the core. The cladding launched light is a known fraction of the core launched light and can be monitored by placing a detector about the cladding. Detected light including light that was launched into the cladding and has leaked through the cladding is used as a known fraction of light in the core and can be used to control the laser light source. This can be done with a straight section of single mode optical fiber and does not require bending the fiber. Advantageously, most of the core launched light remains in the core as guided light.

Abstract: A novel approach for providing temperature compensation for semiconductor lasers is disclosed. This approach utilizes reflectivity characteristics in the at least one of the mirrors of the semiconductor laser to provide temperature compensation to the device.

Abstract: A Mach-Zehnder (MZ) interferometer modulator structure for fiberoptic telecommunications is disclosed in which drift of the operating point can be monitored with a reduced phase tracking error. One or more components of free-space light radiated into the substrate of the MZ modulator are selectively detected with one or more photodetectors. Suitable summing circuits are described for nulling out undesired photocurrent contributions in the photodetector(s) from on-state and off-state light radiated from the MZ.

Abstract: An achromatic converter of spatial distribution of polarization from a first to a second pre-defined distribution of polarization is described. The converter comprises a plurality of photo-aligned quarter-wave or half-wave liquid crystal polymer layers, wherein the patterns of alignment of the layers are correlated with each other so as to make polarization conversion achromatic. Achromatic polarization vortices can be formed. The polarization conversion efficiencies over 97% have been demonstrated over most of the visible spectrum of light. The polarization converters can be used in imaging, photolithography, optical tweezers, micromachining, and other applications.

Abstract: The present invention provides a front-illuminated avalanche photodiode (APD) with improved intrinsic responsivity, as well as a method of fabricating such a front-illuminated APD. The front-illuminated APD comprises an APD body of semiconductor material, which includes a substrate and a layer stack disposed on a front surface of the substrate. The layer stack includes an absorption layer, a multiplication layer, and a field-control layer. Advantageously, a back surface of the APD body is mechanically and chemically polished, and a reflector having a reflectance of greater than 90% at the absorption wavelength band is disposed on the back surface of the APD body. Thus, incident light that is not absorbed in a first pass through the absorption layer is reflected by the reflector for a second pass through the absorption layer, increasing the intrinsic responsivity of the front-illuminated APD.

Abstract: The invention relates to an electro-optic modulator structure containing an additional set of bias electrodes buried within the device for applying bias to set the operating point. Thus the RF electrodes used to modulate incoming optical signals can be operated with zero DC bias, reducing electrode corrosion by electro-migration and other effects that can be present in non-hermetic packages. The bias electrodes include an upper split portion and an optically transparent lower portion. The optically transparent lower layer improves modulation frequency and reduces optical loss.

Abstract: The present invention provides a transceiver housing comprising: an opening at a proximal end thereof for receiving a optical receptacle; an electrical contact for engaging the optical receptacle and retaining the optical receptacle in the housing body; and a first side and a second side, each of the first side and the second side including mountings for mounting a printed wire assembly within the housing. In a preferred embodiment, the transceiver housing of the present invention has a uni-body construction.

Abstract: A method of generating a variable demetallized pattern in a holographic web and a security device using such method. A holographic microstructure pattern is imparted to an oligomer disposed on a surface of a substrate. A metal layer, such as aluminum, is deposited to the holographic microstructure pattern of the substrate and then covered with a variable resist pattern. The variable demetallized pattern in the holographic web is then generated by removing the metal layer not covered by said variable resist pattern.

Abstract: A compact variable optical attenuator having optical-tap functionality is described comprising a planar waveguide attenuator, a lens, and a photodetector. Input and output waveguides are located close to the optical axis of the lens, which reduces optical aberrations and insertion loss. The waveguide attenuator works by light absorption with virtually no scattered light present, which improves fidelity of measurements of the tapped optical power by the photodetector. The entire tap-attenuator assembly is packaged into a small form pluggable (SFP) package having two optical connectors.

Abstract: The invention relates to an electro-optic directional coupler suitable for use as a variable optical attenuator at reduced voltages compared to those known in the prior art. The present invention has found that by careful selection of an asymmetric directional coupler geometry, the transfer function of the device can be shifted so that it has an operating point between maximum and minimum transmission. Signal electrodes driven in push pull configuration advantageously use this operating point to achieve significant reduction in operating voltages for switching to maximum or minimum transmission. Asymmetry is created in the directional coupler by forming the waveguides to have different propagation constants by a difference in waveguide width, depth, index of refraction or index profile.

Abstract: The invention relates to an optical waveguide device that includes a waveguide phase modulator (WPM). A waveguide monitoring structure is coupled optically in parallel with the WPM so as to form a Mach-Zehnder interferometer therewith for producing monitor light indicative of a phase shift imparted by the WPM. The waveguide monitoring structure includes a first optical tap for tapping off a fraction of light entering the first WPM for providing first tapped-off light, a second optical tap for tapping off a fraction of light exiting the first WPM for providing second tapped off light, and an ancillary phase modulator for modulating the optical phase of the first or second tapped-off light so as to modulate the intensity of the monitor light in dependence upon the first phase shift. A feedback circuit controls the phase shift imparted by the WPM based on a modulation index of the monitor light.

Abstract: Apparatus and related methods align magnetic flakes in a carrier, such as an ink vehicle or a paint vehicle to create optically variable images in a high-speed, linear printing operation. Images can provide security features on high-value documents, such as bank notes. Magnetic flakes in the ink are aligned using magnets in a linear printing operation. Selected orientation of the magnetic pigment flakes can achieve a variety of illusive optical effects that are useful for decorative or security applications.

Abstract: The invention relates to a fiber laser and harmonic frequency conversion module incorporating a 90 degree Polarization Maintaining (PM) fiber fusion splice therebetween for providing temperature insensitive power stabilization. The present invention has found that incorporating at least one 90 degree splice of the transmission axes of the PM fiber, coupling a fast axis to a slow axis, to create substantially equal optical path lengths of the two transmission axes of the fiber coupling can nearly eliminate output amplitude fluctuation within a practical operating temperature range.

Abstract: The invention relates to an external optical modulator comprising a Mach-Zehnder having a signal electrode including at least four sections of unequal length to one another positioned over an alternating domain structure in an electrooptic substrate, and including a center section, or center pair of sections disposed asymmetrically between pairs surrounding sections. The surrounding pairs, comprise the two sections adjacent the center section or pair of sections, and each two sections adjacent the previous pair of sections, moving outwardly from the center to the final outermost pair, L1 and LN at the RF input 2 and RF output 4. In each pair, the section lengths are equal, or the section closer to the RF output 4 has a longer length than the section closer to the RF input 2. The surrounding pairs have lengths that decrease from the innermost pair to the outermost pair. For a zero chirp structure, the section lengths are selected to maintain an equivalent length for the inverted and uninverted domain sections.

Abstract: A change in loading conditions of fiber amplifiers in an optical communications network causes rapid variations in the gain profile of the amplifiers due to spectral hole burning and stimulated Raman scattering. An apparatus for reducing such gain profile variations is described which monitors optical signal perturbations and reacts by adjusting pump powers of the amplifiers and, or fast variable optical attenuator according to a predetermined function stored in the form of constants in controller's memory. The optical signal is monitored as total power, and the power of light after passing through one or more optical filters. The light detection is relatively fast, whereby the gain profile variations are compensated by fast controlled variable optical attenuator and pump power adjustment upon the change in loading conditions.

Abstract: The invention relates to phase matched optical gratings for performing signal multiplexing and demultiplexing in optical communications networks. In prior art gratings there is a phase linearity error between the grating line and the outputs on the focal line, comparing the center output to the surrounding outputs. This corresponds to a relative phase difference between each output which limits the passband. In the case of the AWG this degradation comes primarily from field aberrations in the output star coupler. The present invention has found that if the grating line of the optical grating is disposed on a ellipse instead of a circular arc, while the focal line of outputs defines a substantially circular arc, an optimum can be found where the phase linearity error is substantially eliminated, and all outputs have substantially the same phase. As a result, this creates substantially uniform passbands across the WDM spectrum.

Abstract: The invention provides a fiber pigtail assembly wherein a polarization maintaining fiber is soldered directly to a mounting pad without a sleeve or a ferrule therebetween. A portion of the polarization maintaining fiber near a fiber end is embedded in a vertical slow axis orientation within an asymmetrical solder ball having a flat portion for adhering to the mounting pad. The vertical slow axis orientation of the polarization maintaining fiber within the solder ball enhances power stability and polarization extinction ratio properties of optical modules utilizing the invention.

Abstract: The invention relates to a wafer scale process for the manufacture of optical waveguide devices, and particularly for the manufacture of ridge waveguide devices, and the improved waveguides made thereby. The present invention has found a process for achieving sub-micron control of an optical waveguiding layer thickness by providing a dimensionally stable wafer assembly into which adhesive can be introduced without altering the planar relationship between a carrier wafer and an optically transmissive wafer in wafer scale manufacture. This process permits wafer scale manufacture of optical waveguide devices including thin optically transmissive layers. A pattern of spacer pedestals is created by a deposition and etch back, or by a surface etch process to precisely reference surface information from a master surface to a carrier wafer to a thin optically transmissive wafer. The tolerance achievable in accordance with this process provides consistent yield across the wafer.

Abstract: The reinforced opaque glitter particles have a substantially uniform shape and size. Each of the particles includes a reflective core supported by a transparent organic substrate and one or more robustness-improving layers for providing rigidity to the particle. Optionally, the particles have lacquer layers at a surface of the particle. One example of a robustness-improving layer is an inorganic transparent protective layer having a thickness of at least 20 nm adjacent directly to the aluminum layer. Another example is an adhesion promoting layer directly adjacent to the transparent organic substrate.