Chiral Photonics, Inc.

Exxon Research and Engineering Company

Azriel Zelig Genack

Victor Il'ich Kopp

Bruce N Perry

Guoyin Zhang

Zhao-Qing Zhang

A chiral fiber grating for reflecting, scattering or polarizing an optical signal, or for forming a fiber laser feedback structure is disclosed. The chiral fiber grating is fabricated by fusing and then twisting/drawing two tapered optical fibers in accordance with a predetermined fabrication protocol. In one embodiment of the invention, the chiral fiber grating includes two single helix structure end-regions, with a double helix structure therebetween, providing the grating with apodizing properties. In another embodiment of invention, the pitch profile along a portion of the grating is configured to produce desired chiral fiber grating properties. In yet another embodiment of the invention, the chiral fiber grating, comprising two single helix end regions and a middle double helix region, may be separated into two or more portions after fabrication, for example to provide one or more single helix chiral fiber gratings and one or more double helix chiral fiber gratings. In an alternate embodiment of the invention, a double helix structure chiral fiber grating is provided by twisting two parallel optical fibers around a longitudinal central axis positioned therebetween.

Chiral fiber grating device and method of fabrication thereof

Lasing at the edge of the reflection band or at a defect state within the reflection band of a thin one-dimensional feedback structure is used to create a large-area, thin-film laser source with transverse dimensions that can be much greater than the film thickness. Angular confinement of radiation propagating perpendicular to the layers leads to a spreading of the beam inside the medium which is much greater than the diffraction divergence. This enhances the spatial extent of correlation at the output surface of the thin film. When a pump source induces gain at the lasing threshold in a wide region, a spatially coherent monochromatic light beam is emitted perpendicular to the film surface from the entire gain region. Alternate embodiments of the present invention include a passive spatial filter and an active amplifier.

Thin-film large-area coherent light source, filter and amplifier apparatus and method

A chiral structure having an advantageous extended chiral defect that provides an enhanced energy distribution characteristic therein. This is accomplished by configuring a central portion of the chiral structure with a pitch different from the rest of the structure. This may be envisioned as a distributed chiral twist with a predefined angle over a portion of a chiral structure. With the distributed defect, the photonic stop band remains wide, allowing for the substantial increase in the lifetime of the mode in which lasing occurs, while the extent of the high intensity region of the mode is large. The extended chiral defect structure may also be implemented as a thin-film chiral structure, for example using cholesteric liquid crystal or sculptured thin films.

Extended chiral defect structure apparatus and method

A chiral structure having an expanded adjustable reflection band to provide broadband tunability is provided. In the preferred embodiment, the chiral structure is implemented as a chiral fiber structure and comprises two or more sequential chiral fiber elements of different pitches, each having a tunable chiral defect generator. The pitches are selected such that the individual photonic band gaps of the elements are formed into one expanded reflection band such that at least one defect state can be formed and moved within the expanded reflection band by selectively activating and adjusting one or more of the tunable chiral defect generator. The tunable chiral defect generators may generate and control defect state(s) in the structure's spectral response by introducing chiral twists and/or spacing between the chiral elements, with the length of the spacings and angles of chiral twists being proportional to the position of the defect state(s) within the reflection band of the structure.

Chiral boardband tuning apparatus and method

An add-drop filter, utilizing chiral couplers, that enables a new signal to be added at a particular vacuum wavelength &#x3bb;'to a fiber optic line carrying n signal channels over a band of wavelengths encompassing &#x3bb;. . . &#x3bb;, &#x3bb;, &#x3bb;. . . &#x3bb;, while an existing signal, &#x3bb;, is simultaneously dropped from the signal group.

Configurable add-drop filter utilizing chiral fiber gratings

A a chiral fiber grating mimicking a cholesteric liquid crystal structure to achieve fiber Bragg grating properties, is provided. The chiral fiber grating includes a first and a second helical structures disposed along its central longitudinal axis, where the second helical structure is identical in orientation to the first helical structure but is shifted by one half of the structure's pitch forward. In another embodiment of the invention, only a single helical structure is disposed along the fiber to create an optically resonant chiral fiber.

Chiral fiber grating

A chiral fiber sensor implemented in a chiral fiber is provided that mimics advantageous optical properties of a cholesteric liquid crystal structure. In a passive sensor embodiment the chiral fiber sensor of the present invention includes a chiral fiber element configured to shift its reflection band in response to a change in a particular external condition (such as temperature, pressure and axial twist). The chiral fiber element is subjected to a broadband emission while monitoring its refection or the transmission spectrum. Changes in the monitored spectrum indicate changes in the particular external condition. In an active sensor embodiment, the chiral fiber element is configured as an optically pumped chiral laser having a lasing wavelength that shifts in response to a change in a particular external condition (such as temperature, pressure and axial twist). The lasing wavelength is monitored and shifts in the wavelength indicate changes in the particular external condition.

Chiral fiber sensor apparatus and method

An add-drop filter, utilizing chiral elements, that enables a new signal to be added at a particular vacuum wavelength &lgr;&prime; to a fiber optic line carrying n signal channels over a band of wavelengths encompassing &lgr; . . . &lgr; , &lgr; , &lgr; . . . &lgr; , while an existing signal, &lgr; , is simultaneously dropped from the signal group.

Add-drop filter utilizing chiral elements

A apodized chiral fiber grating consists of a chiral fiber with a variable effective grating strength along different regions of its length, such that the effective grating strength gradually increases from one end of the chiral fiber until a peak effective grating strength is reached and then gradually decreases at the same rate towards the other end of the fiber. Optionally, the effective grating strength remains stable for a portion of the fiber before decreasing. Other forms of grating strength variations in different regions of the chiral fiber are also contemplated. The effective grating strength variation produces an apodized chiral fiber that possesses desirable characteristics that greatly reduce or eliminate the sidelobes in the fiber's spectral response. The effective grating strength is varied by modulating the pitch of the apodized chiral fiber along different regions of its length in accordance with a mathematical expression, such as for example: linear, polynomial, sinusoidal or quasi-sinusoidal function. Advantageously, the inventive apodized chiral fiber is customizable to any application by selectively controlling the pitch variation along the different regions.

Customizable apodized chiral fiber grating apparatus and method

A chiral in-fiber tunable polarizer implemented in a chiral fiber structure is provided. The chiral fiber is selected with a predetermined handedness and scatters (by reflecting, coupling into the fiber core or otherwise) the circularly polarized light matching its handedness while transmitting circularly polarized light of opposite handedness. By combining the chiral fiber with another fiber component having a non-cylindrical core, the inventive apparatus produces a linearly polarized wave with a predetermined orientation. The orientation may be adjusted by rotating the fiber component around its central axis. The chiral fiber structure may be configured as a long period chiral fiber grating. Optionally, the chiral fiber structure may be configured with a variable pitch along its length, such as a chirped fiber grating, an apodized fiber grating, or a set of multiple sequential chiral polarizer elements with different pitches. This variable pitch arrangement results in output light having a configurable polarization spectrum of a predetermined shape.

Chiral in-fiber adjustable polarizer apparatus and method

The inventive chiral laser achieves lasing by placing an electro-luminescent emitting layer with quarter wave plate properties and a layer of cholesteric liquid crystal (CLC) between two electrodes. The electrode connected to the emitting layer is highly reflective and serves as a source of electrons, while the second electrode, connected to the hole-transporting CLC, serves as a source of holes. The recombination of electrons and holes in the emitting layer produces luminescence. If a right handed CLC structure is used, then right circularly polarized emission is reflected from the CLC as right circularly polarized light, and then converted to linear polarized light by passing through quarter wave plate emitting layer. It is then reflected by the electrode and converted again into the right circularly polarized light in a second pass through the quarter wave plate emitting layer. The emitted and reflected light emissions are incrementally amplified on each pass through the emitting layer and thus a laser cavity is formed. Once a predefined lasing threshold is reached, lasing occurs perpendicular to the CLC layer. Because the laser cavity is formed only for right circularly polarized light, polarized laser emission will occur.

Chiral laser utilizing a quarter wave plate

A chiral fiber laser implemented in a fiber Bragg grating mimicking the advantageous optical properties of a cholesteric liquid crystal structure is provided. The dopant, the pitch, the core cross section and dimensions thereof, of the inventive chiral fiber laser as well as the core and cladding materials used in construction thereof, may be advantageously selected and configured to enable the inventive chiral fiber laser to produce lasing at a desirable wavelength. In another embodiment of the inventive chiral fiber laser, a tunable defect is introduced to provide tunable lasing corresponding to the wavelength at the defect mode. Multiple embodiments using coupled fiber optical pumping as well as direct optical pumping for excitation of the inventive chiral fiber laser are provided.

Chiral fiber laser apparatus and method

The present invention advantageously enables single-mode lasing at higher pump power and further enables general reduction of the lasing radiation bandwidth. This is accomplished by producing an appropriate spatial gain distribution inside the laser medium. The present invention further enables advantageous selection of a particular photonic mode for lasing at that mode in a periodic laser by varying spatial gain distribution within the periodic laser medium. Photonic mode selection by varying gain distribution within the laser medium is accomplished in accordance with various embodiments of the present invention.

Apparatus and method for mode selection in a photonic band edge laser

A chiral laser apparatus comprises a layered structure configured to produce a photonic stop band, the layered structure including a upper chiral material layer, a middle excitable light-emitting layer, and a lower chiral material layer and an excitation source that, when applied to the layered structure, causes the middle light-emitting layer to emit electromagnetic radiation, such that polarized lasing at a lasing wavelength occurs in a direction perpendicular to the layered structure. The middle light-emitting layer may be configured to produce a defect such that lasing advantageously occurs at a wavelength corresponding to a localized photonic state within the photonic stop band. The excitation source may be an electrical power source connected to the layered structure via two or more electrodes. In another embodiment of the invention, the layered structure is replaced with a homogeneous chiral material doped with a light-emitting material. Excitation sufficient to cause lasing is provided by the electrical power source via a pair of electrodes connected to the chiral material. In yet another embodiment of the invention, the excitation source may be an electromagnetic wave source that applies an electromagnetic wave to the middle light-emitting layer to excite the middle layer sufficiently to cause lasing.

Chiral laser apparatus and method

A defect causing a localized state is induced in a chiral structure composed of multiple chiral elements by twisting one element of the chiral structure with respect to the other elements along a common longitudinal axis such that directors of the element molecular layers that are in contact with one another are disposed at a particular &ldquo;twist&rdquo; angle therebetween, the twist angle being greater than a shift angle between directors of consecutive layers. The chiral twist structure may be utilized in a variety of applications such as filters, lasers and detectors. The defect caused by the twist may be made tunable by providing a tuning device for ly rotating one or more of the chiral elements with respect to one another to vary the twist angle and thus vary the position of the induced defect within a photonic stop band. Tunable defects may be advantageously utilized to construct wavelength tunable chiral filters, detectors and lasers.

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New York, NY, United States of America

Azriel Zelig Genack