Abstract: A single helix chiral fiber grating of a predetermined grating strength is provided that is operable to control light transmission in a predetermined wavelength range. The novel fiber grating comprises a first optical fiber with a first interface portion at a first end, a second interface portion at a second end, and a middle portion therebetween. The first optical fiber is configured with at least one fiber core, surrounded by a corresponding at least one cladding, with a first longitudinal section disposed within the first interface portion, a second longitudinal section disposed within the second interface portion, and also includes a longitudinal helical section, disposed therebetween within the middle portion, that comprises a longitudinal helix structure of a single predetermined handedness, having a predetermined pitch profile, and having a predetermined helix diameter profile selected and configured to produce the predetermined grating strength.

Abstract: A distributed elongated optical fiber detection system is provided, having at least one sensitive region, and being capable of detecting the occurrence and location(s) of one or more events along its length that cause one or more perturbations in the at least one sensitive region. In one embodiment of the invention, the novel detection system includes, at its first end, an optical signal source capable of launching a signal in a first signal mode through an optical fiber waveguide comprising at least one sensitive region along its length, and configured for transmitting at least two signal modes therethrough, toward its second end. A reflecting device, capable of reflecting only signals in a second signal mode, is positioned at the second end of the waveguide.

Abstract: The present invention provides an optical in-fiber chiral fiber isolator, capable of transmitting a signal of a predetermined optical polarization in a forward direction therethrough, while rejecting all signals traveling in a backward direction therethrough, and a method of fabrication thereof.

Abstract: An optical fiber mode coupling device, capable of being readily connected to a conventional optical fiber with a high degree of ruggedness, is provided. The inventive mode coupling device only allows transmission of at least one supported fiber mode therethrough, and is preferably configured to maximize the coupling, of at least one desired fiber mode, to the at least one supported fiber mode. Advantageously, the inventive mode coupling device is capable of performing the functions of a mode filter for the signal entering its first end, or serving as a mode conditioner for the signal entering its opposite second end.

Abstract: 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.

Abstract: An optical fiber coupler capable of providing a low loss, high coupling coefficient interface between conventional optical fibers and optical waveguide devices is provided. The novel coupler, which may be polarization maintaining, if a polarization maintaining preform is used in its fabrication includes a core, a cladding, a first end for interfacing with an optical fiber and a second end for interfacing with an optical waveguide device. The sizes of the core and cladding are gradually reduced from the first end to the second end in accordance with a predetermined reduction profile. Various parameters, such as refractive indices and sizes of the core and cladding and the reduction profile are selected to produce a low numerical aperture at the first end and a high numerical aperture at the second end, while advantageously minimizing insertion loss and maximizing the coupling coefficient at each end.

Abstract: 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.

Abstract: 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.

Abstract: A chiral in-fiber polarizer implemented in a chiral fiber structure having a core and a cladding surrounding the core, is provided. The chiral polarizer includes an entry end for receiving incident light and an exit end for outputting polarized light, as well as a pitch variation along its length between the entry and exit ends in accordance with a predetermined desirable pitch profile, wherein in one embodiment of the inventive polarizer, the inverse value of the chiral structure's pitch at the exit end is less than at the entry end, and preferably substantially equal to zero. The pitch profile may be advantageously selected to correspond to one or more predetermined pitch configurations, may be determined in accordance with one or more mathematical functions, or may be random.

Abstract: 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.

Abstract: A long period chiral fiber grating (“LPCFG”) that has a number of advantageous properties that can be readily utilized in a number of different applications is provided. The inventive LPCFG is a fiber grating having a pitch that exceeds the wavelength of light propagating therethrough. The LPCFG includes a number of dips in its transmission spectrum, but does not reflect any portion of the signal passing therethrough. The LPCFG is sensitive to changes in the refractive index of its external environment (or in the refractive index of a coating covering the LPCFG cladding). In response to changes in the external refractive index, the transmission dips shift proportionally to changes in the index, thus enabling the use of LPCFG as a fiber sensor element. In addition, the LPCFG is polarization sensitive—one circular polarized wave of one handedness is coupled to the cladding mode stronger than the wave of the other polarization handedness.

Abstract: An add-drop filter, utilizing chiral couplers, that enables a new signal to be added at a particular vacuum wavelength ??k to a fiber optic line carrying n signal channels over a band of wavelengths encompassing ?1 . . . ?k?1, ?k, ?k+1 . . . ?n, while an existing signal, ?k, is simultaneously dropped from the signal group.

Abstract: An apparatus and method for fabricating a thin layer periodic structure by successively depositing alternating uniform layers of two or more different dielectric materials on a substrate utilizing centrifugal force in a novel spin coating technique. In an alternate embodiment of the present invention, the novel spin-coating technique is configured for fabricating chiral media by successively depositing layers of one or more anisotropic materials, while rotating the substrate by a predetermined angle between deposition of each layer. In both embodiments of the inventive apparatus, a defect layer may be introduced by depositing a defect material in a desired position in the media.

Abstract: 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.

Abstract: 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.

Abstract: An add-drop filter, utilizing chiral elements, that enables a new signal to be added at a particular vacuum wavelength &lgr;′k to a fiber optic line carrying n signal channels over a band of wavelengths encompassing &lgr;1 . . . &lgr;k−1, &lgr;k, &lgr;k+1 . . . &lgr;n, while an existing signal, &lgr;k, is simultaneously dropped from the signal group.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.