Martin Marietta Corporation

Lockheed Martin Corporation

Other

Harvey L Wagner

Thomas William Karras

Vipulkumar K Patel

Prakash B Gothoskar

Kalpendu Shastri

Soham Pathak

Robert Keith Montgomery

Margaret Ghiron

Katherine A Yanushefski

David Piede

William H Meise

Michael S Margulis

A planar optical isolator is formed within the silicon surface layer of an SOI structure. A forward-directed signal is applied to an input waveguiding section of the isolator and thereafter propagates through a non-reciprocal waveguide coupling region into an output waveguide section. A rearward-directed signal enters via the output waveguide section and is thereafter coupled into the non-reciprocal waveguide structure, where the geometry of the structure functions to couple only a small amount of the reflected signal into the input waveguide section. In one embodiment, the non-reciprocal structure comprises an N-way directional coupler (with one output waveguide, one input waveguide and N&#x2212;1 isolating waveguides). In another embodiment, the non-reciprocal structure comprises a waveguide expansion region including a tapered, mode-matching portion coupled to the output waveguide and an enlarged, non-mode matching portion coupled to the input waveguide such that a majority of a reflected signal will be mismatched with respect to the input waveguide section. By cascading a number of such planar SOI-based structures, increased isolation can be achieved&#x2014;advantageously within a monolithic arrangement.

Planar waveguide optical isolator in thin silicon-on-isolator (SOI) structure

An optical fiber that transforms light of undesired polarization into light of desired polarization. In principle, the signal power of the non-preferred polarization is transformed into signal power of the preferred polarization, thereby actually transforming the polarization. The fiber can have a circular end for input of light having randomly phased polarization, and an elongated end for output of light having a single principal orientation component. A generally smooth transition from the circular end to the elongated end causes substantially all the light entering the fiber to exit from the fiber without losing light due to reflection or radiation. Alternatively, the fiber can have a lobed end, for input of light having first and second mutually orthogonal polarization components, and an elongated end, for output of light having a single principal orientation component. Alternatively, the fiber can be a combination of the two forms described above. That is, the fiber can have a circular section that transforms first into a lobed section with increasing distance from the input port, with the lobed section then transforms into an elongated (e.g., elliptical or ovoid) section with increasing distance from the input port.

Light polarization transformer

An eye protection arrangement for protection against multispectral laser threats includes goggles or spectacles with a tunable etalon optical filter. In one embodiment, the optical filter is fixed-tuned to a safe frequency. In another embodiment, light from the laser being used is sensed, and used to set the protective goggles to a different wavelength than the laser. In yet another embodiment of the invention, the protective optical filters have a comb response, and additional protection is provided by optically cascading two filters, each having a somewhat different comb response, so as to reduce the number of transmission spectra.

Wavelength-tunable eye protection

A color television camera includes a panchromatic light sensor such as a CCD imager. Light from a scene to be imaged is filtered by an electronically controlled light filter such as an etalon, which is scanned from color to color at the field rate, so that the image for each field is generated by a different color. The periodic spectral line or spectral band response of a single etalon is improved by a cascade of two etalons with different periodicity, which pass only a single spectral line or band. When an RGB color sequence is used, a complete color signal frame is generated in three fields. The imager may be operated at a field rate higher than the standard field rate, such as 90 Hz. for use with conventional 30 Hz. color frame rate, and a memory may be coupled to the output of the imager to store the three-field sequence of signals which occurs during each standard color frame, so that a complete color signal is available during each standard color frame. In the context of a spectrometer, the filter may be sequenced through a set of spectral responses which are characteristic of the light reflected from a particular material. A similar imager/filter combination may be used for spectrography as a 'tricorder'.

Color television camera using tunable optical filters

A Fabry-Perot etalon (310) has a cavity (12) occupied by an electric-field variable index of refraction material (22). The cavity is flanked by a pair of parallel mirrors (14), at least one of which is partially reflecting. At least one of the supporting substrates (18l) has deposited thereon a light polarizing field electrode (316l) which includes a plurality of mutually parallel, spaced apart electrical conductors (392) which define gaps (394). The electrical conductors are mutually interconnected by bus conductors (390), and may be connected by lead conductors (37) to an external voltage source, for generating the desired electric field across the cavity.

Etalon with optically polarizing field electrodes

An optical demultiplexer includes an electrooptic modulator (410) which modulates a beam of light (418) in response to frequency-multiplexed radio-frequency (RF) information signals, to produce diverging beamlets of light (420). The diverging beamlets are separated by a spatial separator arrangement (426), and each beamlet (420), including the information of its RF carrier, is coupled to a separate optical detector (428). The detector (428) can extract amplitude modulation from the signal. In order to reconstruct the RF signal as well as the amplitude modulator, an optical 'local oscillator' signal (OLO) is coupled to each detector together with its information signal. Signal loss due to vibration or misalignment is avoided, and heterodyne mixing efficiency is maximized in an embodiment of the invention, by propagating the OLO and information signals through a single-mode optical fiber to the detector. In a particular embodiment of the invention, the OLO signal is applied to a first fiber (622), the information signal is applied to a second fiber (610), and the first and second fibers are coupled together by a fiber-optic coupler (612). In another embodiment of the invention, the OLO signal results from generating an RF L.O. signal, and combining the RF L.O. local signal with the information signals before application to the electrooptic modulator, to generate an OLO beamlet (720) which is subject to the same vibration and misalignment as the signal beamlets.

Optical demultiplexer for optical/RF signals

A Fabry-Perot etalon 10 is located in the light path 30 between a light sourcesinks 40 and 44. The etalon is polarization insensitive, and its optical path length and transmission wavelength(s) is controlled by a bias source 60. When light at the desired wavelength is propagating from source 40, the bias is set to establish transmission through the etalon at that wavelength, whereupon the light propagates to the sink 44, and the switch is transmissive. By contrast, if the switch is to be nontransmissive, the bias sets the transmission wavelengths of the etalon on either side of the wavelength produced by source 40, whereupon the light from source 40 is reflected by the etalon, and does not reach sink 44. In a second embodiment, a third sourcesink 48 is coupled in a second light path 330a, for being coupled to the first sourcesink 40 when the etalon is set for reflection, to thereby form a single-pole, double-throw switch. In a third embodiment, a fourth sourcesink 68 is coupled in an extension maim of the second light path.

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Royersford, PA, United States of America

Harvey L Wagner